AN INTRODUCTION

to COASTAL HABITATS

and BIOLOGICAL RESOURCES

for OIL SPILL RESPONSE

Report No. HMRAD 92-4

Prepared by

Hazardous Materials Response and Assessment Division

National Oceanic and Atmospheric Administration

7600 Sand Point Way NE

Seattle, Washington 98115
Contributing Authors 

Miles O. Hayes1 

Rebecca Hoff2 

Jacqueline Michel1 

Debra Scholz1 

Gary Shigenaka2 

1Research Planning, P.O. Box 328, Columbia, South Carolina 29202 

2National Oceanic and Atmospheric Administration, 7600 Sand Point Way N.E., Seattle, 

Washington 98115 
An Introduction 

to Coastal Habitats and Biological Resources 

Page
 

Introduction............................................................................................i
 

1 The Coastal Environment............................................................1-1
 

2 Oil Behavior and Toxicity.............................................................2-1
 

3 Sensitivity of Coastal Environments to Oil.....................3-1
 

4 Biological Resources........................................................................4-1
 

5 Oil Spill Response and Cleanup Techniques....................5-1
 

6 Field Methods for Oil-Spill Response....................................6-1
 

7 Monitoring/Sampling.....................................................................7-1
 

8 The Archetypical Environmental Sensitivity Index 8-1
 

9 Glossary...................................................................................................9-1
 

10 Appendices........................................................................................10-1
 
Introduction 

We will discuss the physical, geological, and biological considerations 

relevant to oil behavior and oil spill response and cleanup. The questions 

which we will address include: 

•	 How does the physical environment affect the impacts of an oil spill on 

a shoreline? 

•	 What factors affect the behavior and toxicity of oil? 

•	 What kinds of shorelines are most at risk from an oil spill, and why? 

•	 What are the effects of oil exposure on biological resources? 

•	 What kinds of techniques are available for treatment of oil spills? 

•	 How are the impacts of oil and cleanup assessed and monitored? 

•	 What are the tools that are available for assisting response personnel in 

evaluating resource impacts? 

•	 What are the important lessons from previous spills? 

The response and cleanup techniques that we will discuss have, as their 

ultimate goal, the minimization of impacts from oil spills. To realize this 

goal, it is important to have a basic understanding of how each of the 

components covered in this course interrelate. It is our intent that readers 

understand the role that each set of considerations—physical, chemical, 

geological, and biological—plays in determining both the route and degree to 

which the goal is attained. We will try to pass on the lessons of previous 

experience and research, and to provide a foundation on which insights and 

knowledge can be added as time goes on. Ultimately, we hope that this will 

contribute to an informed and effective oil spill response in coastal waters. 

i 
1 The Coastal Environment 

Miles O. Hayes1 

Page 

Introduction.....................................................................................................1-1
 

Coastal Morphology.....................................................................................1-1
 

Global Tectonics........................................................................................1-2
 

Hydrodynamic Regime.............................................................................1-4
 

Wave-dominated coasts.....................................................................1-6
 

Tide-dominated coasts........................................................................1-6
 

Mixed-energy coasts............................................................................1-7
 

Sediment Supply and Sources............................................................1-7
 

River deltas.................................................................................................1-9
 

Climate............................................................................................................1-13
 

Local geological history and sea-level changes.................1-14
 

Dynamic Coastal Processes.....................................................................1-18
 

Winds...............................................................................................................1-18
 

Waves..............................................................................................................1-18
 

Tides..................................................................................................................1-21
 

Currents........................................................................................................1-23
 

Coastal storms...........................................................................................1-29
 

The three-dimensional beach........................................................1-31
 

Coastal Sediments.........................................................................................1-34
 

Sediment texture....................................................................................1-34
 

Composition of beach sediments..................................................1-34
 

Estuaries—Bays—Lagoons.........................................................................1-36
 

Relationship to tidal range...............................................................1-37
 

Water circulation and mixing.........................................................1-39
 

References.........................................................................................................1-42
 

1 Research Planning, Inc., P.O. Box 328, Columbia, South Carolina 29202 
Chapter 1.
 

The Coastal Environment
 

Introduction 

This chapter presents the physical controls and attributes of coastal habitats as 

preparatory material for understanding how they may be impacted by an oil spill. 

The discussion begins with a brief review of the geological forces, such as plate 

tectonics and continental glaciation, that have shaped the primary framework of the 

coastal systems. Also given is an introduction to the dynamic coastal processes that 

shape the detailed configurations of the habitats, as well as a description of the 

origin and nature of sediment types and water/sediment (and potentially oil) 

interactions in certain specific environments, such as estuaries and sand beaches. 

Coastal Morphology 

Introduction 

The morphology of a coastline provides the basic framework to which other 

relevant factors, such as biological habitat and physical processes, are tied. 

Therefore, a general knowledge of the coastal morphology of the spill site is of 

primary importance in planning the response to a spill. For example, a young 

mountain range coast backed by cliffs in bedrock with beaches of coarse gravel 

presents an entirely different set of problems than does a low-lying coastal plain 

shoreline with abundant mud flats and salt marshes. The morphology of coastlines 

is determined by five primary controlling factors: 

1) Global tectonic crustal movements 

2) Hydrodynamic regime 

3) Sediment supply and sources 

4) Climate 

5) Local geological history and sea-level changes 

Each of these controls will be considered separately. 
Global Tectonics 

A most important aspect of any coastal region is whether it is rising, sinking, 

or essentially stable—that is, its tectonic setting. In a study of the widths and slopes 

of continental shelves, Hayes (1964) classified the shorelines of the world into the 

categories given below: 

Class Tectonism Examples 

A) Tectonic coasts 

1) young mountain range 

coasts 

- Rapid uplift - California; Alaska; 

western South America 

2) glacial rebound coasts - Rapid uplift - Eastern Canada; Norway 

B) Plateau-shield coasts - Relatively stable - India; West Africa; 

central Brazil 

C) Depositional coasts - Downwarp - Gulf and East Coasts 

of the United States 

Definitions of these shoreline classes follow: 

Young mountain range coasts: Coastal zone made up of high mountains 

(maximum elevations greater than 5,000 feet) related to Cenozoic orogenic activity 

(<±50,000,000 years ago). Bedrock of variable age but principally Tertiary sediments 

and volcanic rocks. Active tectonic uplift. Mostly short, high-gradient rivers 

emptying into the sea. 

Plateau-shield coasts: Coastal zone made up of plateaus and moderate mountain 

ranges related largely to pre-Cenozoic orogenic activity. Bedrock composed of 

ancient basement complexes of granite and gneiss (in shield areas) and Paleozoic, 

Mesozoic, and Tertiary sediments (in plateau areas). Plateaus formed on complex 

suites of volcanic rocks are also present and the area is tectonically stable (relative to 

young mountain range and depositional coasts). Numerous moderately long rivers 

may be present, depending on climate. 
Depositional coasts: Coastal zone made up chiefly of broad coastal and deltaic plains. 

Bedrock generally Tertiary and Quaternary sediments. Tectonically subsiding area. 

Many long, large rivers emptying into the sea. 

Glacial rebound coasts: Coastlines undergoing uplift because of isostatic 

readjustment of the earth’s crust after removal of the load of the continental ice 

sheets at the end of the last major glaciation (Wisconsin, 10,000-14,000 years Before 

Present [B.P.]). 

Genetically, these shoreline types are closely related to plate tectonics. The simplest 

distinction, on the basis of plate tectonics, is between leading edge and trailing edge 

coasts (Fig. 1-1). Leading edge, or collision, coasts have roughly the same 

characteristics as young mountain range coasts (as defined above), whereas trailing 

Figure 1-1. Diagrammatic representation of a section through collision and trailing 

edge coasts. Arrows indicate the direction of movement of crustal plates. (After 

Inman and Nordstrom, 1971; Fig. 2.) 
edge coasts usually have the characteristics of depositional coasts. Inman and 

Nordstrom (1971) treated this subject in considerable detail and proposed the 

following major classes: 

1) Collision coasts—formed where two plates converge. 

a) Continental collision coasts—where a continental margin is located along the 

zone of convergence. 

b) Island arc collision coasts—where no continental margin is located along the 

zone of convergence. 

2) Trailing edge coasts—where a plate-imbedded coast faces a spreading zone. 

a) Neo-trailing edge coasts—where a new zone of spreading is separating a land 

mass. 

b) Afro-trailing edge coasts—where the opposite continental coast is also trailing. 

c) Amero-trailing edge coasts—where the opposite continental coast is a
 

collision coast.
 

3) Marginal sea coasts—where a plate-imbedded coast faces an island arc. 

As a general rule, the collision coasts are characterized by steep, rocky shores and 

coarse-grained sediments. Wave energy is usually high. Neo- and Afro-trailing 

edge coasts are of the plateau-shield variety, usually being very complicated 

shorelines with scattered pocket beaches, some cliffed shorelines, and a variety of 

other features. Amero-trailing edge coasts and marginal sea coasts are usually 

dominated by coastal plain shorelines composed of river deltas and barrier islands. 

Most of the East and Gulf coasts of the USA shoreline fall in the Amero-trailing 

edge category. The coasts of Washington, Oregon, California, and the south coast of 

Alaska are continental collision coasts. Much of the rest of the Alaskan coast is a 

complex marginal sea coast. 

Hydrodynamic Regime 

Introduction 

Following the pioneer work of W.A. Price (1955), we have concluded that the most 

important control of the morphology of coastal plain shorelines (primarily found 

on trailing edge and marginal sea coasts) is the type and amount of hydrodynamic 

energy expended within an area; furthermore, with some exceptions, the two energy 

factors of most significance, wave energy flux and tidal energy flux, can be related 
directly to tidal range. Davies (1964) and Hayes (1965) classified shorelines, as 

follows, on the basis of tidal range: 

Class Tidal Range* 

Microtidal coasts 0-2 m 

Mesotidal coasts 2-4 m 

Macrotidal coasts >4 m 

*To be exact, Davies’ boundaries were 0-6 ft, 6-12 ft, and >12 ft, and Hayes’ were 0-5 ft, 5-10 ft, 

and >10 ft. We have rounded off these numbers to the nearest whole metric unit. On the basis of study 

of details of coastal morphology on the coast of North America, we feel there is much justification for 

considering changing the mesotidal boundaries or perhaps splitting the mesotidal class into two 

categories; however, the boundaries proposed above will be maintained in these notes. 

Generally speaking, coastal plain shorelines with small tidal ranges (microtidal) are 

dominated by wave energy, and coastal plain shorelines with large tidal ranges 

(macrotidal) are dominated by tidal currents and tidal-level fluctuations. 

The reasons for this emphasis on tidal range is the fact that the effectiveness of wave 

action diminishes (i.e., waves cannot break in a concentrated area for a long period 

of time), and tidal current activity increases as the vertical tidal range increases. Of 

course, a small tidal range does not insure high wave energy, inasmuch as wave 

energy varies according to the fetch, average velocity, and duration of onshore 

winds in an area, as well as the incident swell. 

On the basis of a study of coastal charts of the world (conducted at the Defense 

Research Laboratory, University of Texas), Hayes has compiled the distribution of 

coastal features versus tidal range. The distribution patterns of seven coastal 

features are shown in Figure 1-2. Note that river deltas and barrier islands are best 

developed in microtidal regions, whereas offshore linear sand ridges (built by tidal 

currents), tidal flats, and salt marshes are most abundant in macrotidal regions. 

Tidal deltas and tidal inlets are most abundant on mesotidal coasts. Further 

generalizations can be made about the interaction of wave parameters and tidal 

range. In fact, it is possible to designate three coastal plain shoreline types [(1) wavedominated coasts, (2) mixed-energy coasts, and (3) tide-dominated coasts] on the 

basis of this interaction. Usually, wave-dominated coasts are microtidal; tidedominated coasts are macrotidal; and mixed-energy coasts are mesotidal. There are 
Figure 1-2. Variation of morphology of coastal plain shorelines with respect to 

differences in tidal range. (From Hayes, 1975; Fig. 1.) 

exceptions. For example, a microtidal coast with smaller than normal waves may 

have the morphology of the typical mixed-energy coast (e.g., west coast of Florida). 

Therefore, it is the ratio of wave-energy flux to tidal-energy flux that ultimately 

determines the morphology of coastal plain shorelines. 

Wave-dominated Coasts 

River deltas with smooth, outer margins made up of sandy beaches occur at 

the mouths of major rivers on wave-dominated coasts. Between major rivers, long 

uninterrupted barrier islands are commonplace. Examples of coasts of this type 

include the Gulf Coast of the United States, the southern Baltic, southern Australia, 

and many other areas located on enclosed tideless seas, such as the Baltic and 

Mediterranean. These coasts are usually of the “barred coast” type; that is, a series of 

break-point bars parallel the beach. Sediment patterns of this model show a simple 

gradation in grain size from coarse to fine away from shore as a result of decreasing 

bottom agitation by waves with increasing water depth. 

Tide-dominated Coasts 

Along coasts occurring at the tide-dominated extreme of the hydrodynamic 

spectrum, the morphology at major river mouths consists mostly of open-mouthed 

estuaries. Deltas and barrier islands are inhibited in areas with large tidal ranges 

because of the tremendous erosive and transporting capacity of currents generated 
by the tides. Where deltas are present, they are usually of the multilobate type (e.g., 

Ganges-Brahmaputra Delta). Between major rivers, the coast is occupied by 

extensive salt marshes and tidal flats. Barrier islands are completely absent. 

Examples of this coastal type occur in northeast Australia, western Korea, the upper 

Bay of Bengal, the northern end of the Gulf of California, Cook Inlet, Alaska, the 

Wash (England), and at many other localities with tidal ranges greater than 4 m. 

Generally speaking, sediment patterns on coasts of this type are exactly opposite to 

those on wave-dominated coasts, inasmuch as finest sediments occur on mud flats 

of the upper intertidal zone, and coarsest sediments occur further offshore in zones 

where tidal currents prevail. 

Mixed-energy Coasts 

The intermediate type of coast on the hydrodynamic spectrum, where tidal 

energy flux and wave-energy flux are relatively equal, is the most complex of the 

three models. Modern examples include the South Carolina/Georgia coasts of the 

United States and the Wadden Sea coast of northwest Europe. Deltas are less well 

developed in this setting than on wave-dominated coasts. Between rivers, the 

barrier islands are short (“stunted”), and inlets are wide to allow for the large water 

exchange through the tidal cycle. Tidal deltas are large and numerous due to the 

occurrence of both strong tidal currents and wide inlets between the barrier islands. 

Sediment patterns are very complex, being controlled by the combination of wave 

action and tidal currents. The general model for this type of coastline is illustrated 

in Figure. 1-3. 

Sediment Supply and Sources 

Introduction 

The nature of the beaches on many coastlines is highly dependent upon the volume 

and composition of sediments supplied to that shoreline. Where sediments are in 

abundance, beaches tend to accrete, building seaward, but where they are in short 

supply, beaches tend to erode, commonly causing damage to man-made structures 

built along the beach. Therefore, the zone of sediment supply is an important 

component of the coastal environment, and any change in it would greatly effect the 

evolution of the coastline. In most areas, the dominant source of sediments within 
Figure 1-3. Characteristic morphology developed on a coastal plain shoreline 

(between major rivers) that has a mesotidal range (2-4 m) and average wave 

conditions, a mixed-energy coast. (From Hayes and Sexton, 1989; Fig. 44.) 

the zone of sediment supply is the drainage network that carries sediments from the 

land areas to the shoreline. Other possible sources include: (a) material brought to 

the beach from remote segments of the coastline by longshore sediment transport; 

(b) erosion of rocky headlands or other portions of the shoreline adjacent to the 

beach; and (c) offshore marine sources, such as coral reefs, chemical precipitates, and 

shell-bearing organisms. Any of these potential sediment sources can be impacted 
by the activities of man. Studies on the coasts of California (Inman and Frautschy, 

1966), Japan (Watanabe and Horikawa, 1983), and South Carolina (Hayes and Sexton, 

1989) show that dams constructed along rivers that supply sediments to the 

shoreline have trapped large volumes of sand, causing severe beach erosion in 

those areas. Natural changes frequently impact the zone of sediment supply, as 

well, as the following two examples illustrate. 

Mississippi River delta. - The character of the shoreline around the 

Mississippi river delta complex varies considerably, dependent upon 

nearness to the major distributaries of the river. Today, the main 

channel of the river is building a large birdfoot delta out onto the 

continental shelf. At positions formerly occupied by the major 

distributaries, however, the abandoned delta lobe is subsiding and the 

shoreline is eroding at rates exceeding 10’s of meters per year (Penland 

and Suter, 1983), and a system of barrier islands is forming. There are 

several abandoned lobes on the delta, each of which continues to erode. 

Therefore, whole environmental complexes come and go at the whim 

of the shifting distributaries of the delta. 

Icy Bay, Alaska. - Our field work in Alaska indicates that the 

shoreline west of Icy Bay is undergoing rapid erosion (over 1,000 m 

between 1900 and 1970; Hayes et al., 1973). This is presumably the result 

of the fact that a large glacier system, the terminus of which formerly 

occupied a position parallel to the present shoreline, had retreated over 

40 km up inside the bay between 1900 and 1970. The whole character of 

the shoreline was altered dramatically as a result of this abrupt change 

in sediment supply. The termini of glaciers are a rich source of coastal 

sediments in southeastern Alaska. 

River Deltas 

The most striking manifestation of the impact of the zone of sediment supply 

upon shorelines is where a major river delta forms at a river mouth. This irregular 

progradation of the shoreline at the mouth of a sediment-laden stream may or may 

not conform to the “classic” shapes defined by such river deltas as the Nile and the 

Mississippi, depending on how the sediment mass is modified by marine processes. 

In order for the prograding delta form to have been developed on the modern ocean 
shoreline, the alluvial valley eroded during periods of lowered sea level during the 

ice ages must be aggraded to above sea level beyond the present shoreline. Where 

this has not happened, coastal water bodies referred to as estuaries, bays, or lagoons 

occupy the drowned river valleys. This type of valley flooding is primarily the 

result of insufficient sediment load of the river, but the process may be aided by 

tectonic downwarp or strong tidal flow that transports the river sediments offshore. 

In their classic summary paper on marine deltas, Coleman and Wright (1975) 

discussed over 50 parameters that have an impact on river delta morphology. 

Factors such as characteristics of the drainage basin, river slope, tectonic setting, and 

coastal climate were acknowledged. Most present-day workers, however, following 

the original ideas of Price (1955) and Bernard (1965), try to simplify matters by 

focusing on three basic factors—sediment supply, wave energy, and tidal current 

energy—in their attempts to define the morphological character of deltas. The ratio 

of constructive (i.e., sediment supply) to destructive (i.e., waves and tidal currents) 

processes was used by Fisher et al. (1969) to classify deltas. Galloway (1975) placed 

this concept on a ternary diagram, with sediment supply, wave-energy flux, and 

tidal-energy flux comprising the three end members. 

Galloway’s (1975) classification of river deltas in the marine environment is given 

in Figure 1-4. River-dominated deltas are characterized by lobate protrusions into 

the offshore area, such as the modern “birdfoot” delta of the Mississippi River. At 

river mouths where the sediment output is overwhelmed by the hydrodynamic 

processes at the shoreline, entirely different delta configurations result. Tidedominated deltas, such as the Colorado River and Ganges/Bramaputra River deltas, 

have a characteristic funnel shape, with multiple estuarine channels at the river 

mouths. Wave-dominated deltas, such as the Nile River and Rhone River deltas, 

have smooth, arcuate to cuspate, sandy outer margins. In some areas, particularly 

on young mountain range and arid shorelines, steep gradient streams build alluvial 

fans into coastal waters, creating another type of delta called a fan delta. The 

nearshore zones of these deltas are characteristically steep and the beaches are 

usually coarse-grained sand and gravel. 

The zone where the river’s waters and suspended sediment load enters the marine 

environment is characterized by complex flow and mixing patterns. Oil spilled into 

this zone is usually subject to mixing with the water mass and interaction with the 

suspended sediments (see discussion of Santa Barbara spill in Appendix A). An 

example of one of the many ways riverine and ocean waters mix at river mouths is 

given in Figure 1-5. The type of mixing illustrated in this diagram, usually occurs at 
a major river mouth in a microtidal, relatively low wave-energy setting (e.g., one of 

the distributary mouths of the Mississippi River). The term buoyant effluent is 

applied to this type of river outflow. Wright (1985; p. 28-29) described the process 

Figure 1-4. Classification of river deltas in the marine environment on the basis of 

sediment input, wave-energy flux, and tidal-energy flux. (From Galloway, 1975; Fig. 

3.) 
Figure 1-5. Spreading, mixing, deceleration, and secondary flow patterns of buoyant 

river-mouth effluents. Based on the Mississippi River mouth model. (From 

Wright, 1977a.) 

as follows: 

“Visually dramatic and important features of buoyant effluents are 

pronounced frontal boundaries and related three-dimensional internal 

circulation patterns. ...Plume fronts are exceptionally sharp. ...Flow (V) 

divergence from the centerline of the buoyant effluent near the surface 

converges at the frontal boundaries with inward-directed saltwater 

transport from outside that plunges beneath the sloping pycnocline*. 

(Fig. 1-5) Flow in the lower part of the buoyant effluent is also directed 

inward. The net result of the combination of flow divergence near the 

surface and flow convergence near the pycnocline is the development 

of the dual helical cells illustrated qualitatively”... in Figure 1-5. 

*Boundary marking a sharp change in water density, as at a fresh-water/salt-water 

interface. 
Figure 1-6. Major world wave environments. (From Davies, 1973; Fig. 27.) 

Climate 

Climate is an important factor in the shaping of coastal environments in that wave 

conditions, the occurrence of storms, and certain aspects of sediment production and 

supply can be related to it. Wave climate is controlled principally by global wind 

and storm patterns (see Fig. 1-6). Needless to say, the production of carbonate 

materials in the tropics and ice impingement on the shorelines of polar regions are 

also important climatic considerations. Vegetation type, also primarily related to 

climate, has an important effect on coastal sedimentation in some areas. 
The role of climate in sediment production and supply for the continental shelf, and 

concurrently in the nearshore coastal zone, was investigated by Hayes (1967). It was 

found that: 

1) Mud is most abundant off areas with high temperature and high rainfall 

(humid tropics). 

2) Sand is everywhere abundant and increases to a maximum in 

intermediate zones of moderate temperature and rainfall and in arid areas 

of all, except extremely cold, temperatures. 

3) Coral is most common off areas with high temperatures. 

4) Gravel is most common off areas of low temperatures (subpolar and 

polar). 

5) Rocky bottoms are generally more abundant in cold areas, but their 

distributions correlate strongly with tectonism of the adjacent land mass. 

6) Shell distribution is not diagnostic with regard to climate. 

Three primary climatic factors are thought to be responsible for these patterns. The 

type of weathering (chemical or mechanical) taking place in the source areas is of 

major importance in that it determines the availability of sediment types to streams 

(e.g., mud is most abundant off areas with intense chemical weathering). The 

presence or absence of major rivers (controlled by amount of precipitation) 

determines the volume of Holocene sediments being carried onto the shelf; hence 

sand is dominant on the inner shelves of arid areas due to the absence of rivertransported mud. Deposition of coarse (gravel) sediments is virtually restricted to 

polar and subpolar areas, where they are deposited as the result of glaciation and icerafting. Other factors, such as source stream gradient and hydrodynamic energy, 

exert strong local influence, but are thought to be less important than the above 

climatic factors in determining world-wide, sediment distribution patterns. 

Local Geological History and Sea-level Changes 

The aspect of local geological history of shorelines related to plate tectonics was 

discussed above. When responding to an oil spill, the detailed local geological 

history of the spill site should be considered carefully. For example, areas that were 

glaciated during the Pleistocene, such as the coastlines of New England, Puget 

Sound, and the Great Lakes, have complex local configurations related to the 

passage of the ice. Shorelines produced by erosion of glacial till deposits differ 

markedly from flooded glacial scours, eroded outwash shorelines usually are 

associated with extensive sand-beach systems, and so on. Local faulting and 
earthquake history also leave an indelible mark on leading-edge coasts such as 

California and Alaska. The Exxon Valdez spill impacted some shorelines that had 

been uplifted (as much as 10 m) and some that had been downdropped (as much as 2 

m) during the Good Friday earthquake of 1964. Several differences in spill behavior 

were noted on the opposite sides of the fault zone (Michel and Hayes, 1991). 

Another important historical factor is the changes in sea level that have occurred 

relative to the last ice ages. It is generally conceded that sea-level dropped more 

than 100 m during the Wisconsin glaciation (Milliman and Emery, 1968). 

Beginning around 17,000 BP (Laville and Renault-Miskovsky, 1977), sea level 

probably rose rapidly to near its present level around 6,000 BP. A generalized sealevel curve for that time period is given in Figure 1-7. Details on the more minor 

variations in sea level that have occurred during the relative stillstand of the past 

6,000 years have been greatly refined by excellent collaborative efforts by 

archeologists and geologists (e.g., DePratter and Howard, 1980; Colquhoun et al., 

1981). The sea-level curve that has been derived for this time period on the South 

Carolina coast is given in Figure 1-8. 

Figure 1-7. Proposed sea-level changes during the last 20,000 years for the Gulf Coast 

area. (From Fisher, et al., 1973; Fig. 5C.) 
Figure 1-8. Changes in sea level on the South Carolina coast over the past 6,000 

years, based on detailed, combined archeological and stratigraphical research. 

(Modified after Colquhoun et al., 1981 and Colquhoun and Brooks, 1986.) 
Dynamic Coastal Processes 

This section is a brief introduction to the important dynamic coastal processes that 

affect an oil spill site, including winds, waves, tides, and currents. 

Winds 

Probably the most important factor in dispersal of an oil spill is the effect of the 

wind. The importance of this factor was clearly illustrated during the spills of the 

Amoco Cadiz, Florida, Bouchard No. 65, and Puerto Rican, among others. During 

the Amoco Cadiz spill, consistent westerly winds over 20 km/hr accounted for a 

west-to-east dispersal of the oil and an initial uniform coating of the westwardfacing shore during the first two weeks after the spill. The wind changed on 2 April 

and blew consistently from the northeast until 10 April. It was these northeast 

winds, aided by tidal currents, that dispersed the oil to the west and south, polluting 

previously unaffected eastward-facing coasts (Gundlach and Hayes, 1979). 

Waves 

Introduction 

Waves are important at an oil spill site in that they: 

1) May inhibit cleanup activities by creating rough seas. 

2) Disrupt or inhibit booming activities. 

3) Mix oil into the water column. 

4) Erode the beach. 

5) Cleanse beach sediments of oil. 

The occurrence of wave environments on a worldwide basis is given in Figure 1-6. 

The highest wave energy is found in the storm-wave environments. High-tomedium wave energy is experienced on west coasts of continents in swell 

environments; wave energy varies from low to medium-high on east coasts of 

continents in swell environments. In major enclosed seas and along Arctic and 

Antarctic coasts, mean wave energy levels are low (Davies, 1973). 

Most of the wave energy arriving at the shoreline is contained in progressive waves 

generated by winds blowing over the water. They are termed progressive waves 
because they move in the general direction the wind is blowing. These waves have 

two common forms: seas and swell. 

Seas 

Seas are highly irregular waves with pointed crests which are produced and 

influenced directly by the wind blowing over the water. They generally include a 

wide range of wave lengths and periods, making it difficult to describe the average 

wave. The height of waves at a given water depth depends on three factors: wind 

velocity, fetch (the waterway distance over which the wind blows), and wind 

duration (length of time a given wind velocity occurs). As each of these factors 

increases, wave heights increase. 

Swell 

When the wind stops blowing, seas become more rounded and smooth in 

appearance, approaching a sinusoidal shape. Such waves are called swell. Because 

the velocity depends on the period or wave length, swell waves tend to sort 

themselves out naturally at sea, traveling in groups with approximately equal 

velocity. Typically, the sea surface contains a complex pattern of locally generated 

seas interacting with swell from another part of the ocean. 

Waves at the Shoreline 

Seas and swell are transformed as they approach the coast because of the effect 

of friction as the depth of water decreases. If waves approach at an angle to the 

shore, they will bend (refract) toward the shore. Also, they will generally decrease in 

height because of shoaling and friction with the sea floor. Waves break when the 

depth of water is approximately equal to the height of the wave. Thus, a wave one 

meter high will usually break in about one meter of water. 

Breaking Wave Types 

There are three basic types of breakers which occur on beaches, mainly 

depending on beach slope (Fig. 1-9). Along gently sloping beaches, spilling waves 

are most common. These waves have a broad foam area at the wave crest as they 
Figure 1-9. The three principal types of breaking waves that occur on the beach. 

(From Komar, 1976; Fig. 4-17.) 

approach the beach, expending their energy over a relatively wide surf zone. As a 

rule, they tend to move sand onto the beach. Plunging waves occur as beach slope 

increases. They have curling breakers which entrain a vortex of air as they break. 

They are more violent than spilling waves and expend their energy rapidly over a 

narrow width of the surf zone. As a rule, they entrain more sediment than spilling 
waves and commonly tend to move beach sand offshore to the limit of the outer 

breaker line. Surging waves occur on steep slopes and are characterized by sloshing 

up and down the beach. 

Wave Erosion 

Steep, plunging waves generally cause shoreline erosion and retreat. A 

schematic representation of storm waves eroding a beach is given in Figure 1-10. 

Beaches typically erode during storms and recover to near-original profiles during 

intervening periods. In a few areas, such as the southern California coast and the 

monsoon-impacted coast of Oman, a seasonal beach cycle is present (winter erosion 

in California and summer erosion in Oman!). 

Local Variations in Wave Energy 

Wave energy is not distributed evenly along some shorelines. Usually, this is 

the result of wave refraction around an offshore island or rocks, over submerged 

bathymetric highs or lows, or as the result of a variable orientation of the coast. 

The uneven distribution of wave energy along local shorelines (scale of a few 

kilometers) has been demonstrated in many areas. Two well-known examples, the 

coast of southern California and the Delmarva Peninsula, illustrate this principle. 

In southern California, submarine canyons occur close to the shoreline. Waves 

tend to refract away from the canyon openings, creating areas of decreased wave 

energy at the shoreline adjacent to the canyon heads. On the Delmarva Peninsula, 

submerged linear ridges project away from shore in a northeasterly direction. 

Waves passing over these ridges are focused by wave refraction near the points of 

intersection of the ridges with the shoreface. In both regions, beach erosion is most 

critical in areas where wave energy is focused by wave refraction. 

Tides 

The importance of tides in shaping coastal morphology is discussed above. Tides are 

also important at oil spills in that they: (1) generate currents that disperse the oil 

and (2) alternately expose and cover intertidal areas impacted by the oil. 
Figure 1-10. Schematic diagram of storm wave attack on beaches. (From CERC 1973; 

Fig. 1-7.) 
The largest tides in the United States are experienced on the coast of Maine and in 

parts of Alaska (e.g., Cook Inlet and Bristol Bay). Small tides occur along the Gulf 

and Arctic coasts; medium tides occur along the rest of the U.S. shoreline. 

The tides follow a cycle which is controlled by the position of the sun and moon 

relative to the earth. When the sun and moon are in syzygy (i.e., in line with each 

other), the tidal range is greatest (spring tides), and when they are in quadrative (i.e., 

at right angles to each other), the tidal range is least (neap tides). Spring and neap 

tides occur twice each lunar month. 

The most severe erosion of the beach occurs at high tide. During spring tides, 

higher levels of the beach are exposed to wave action than during neaps, so erosion 

is at a maximum. This is an important consideration when predicting oil removal 

from sand beaches by natural processes. 

Observations on the east coast of the U.S. by university researchers and the U.S. 

Army Corps of Engineers show that storms do their greatest damage when they 

cross the coast during a high spring tide. Observations on the southeastern U.S. 

coast show that the beach may be erosional during spring tides and depositional 

during neap tides under similar wave conditions. Erosion occurs at spring tide 

because (1) the dune ridge is exposed to wave action, and (2) the beach sediment is 

water-saturated because of the higher level of the sea. 

It is important that careful attention be paid to the tides during a spill response, 

through repeated reference to the daily tidal curves, such as the ones shown in 

Figure 1-11. Reference must be made to the tidal data in order to: a) plan field 

surveys in order to utilize the times of maximum exposure of the intertidal zone; b) 

predict future impacts of exceptionally high or low tides; c) predict possible beach 

cycle changes; and d) anticipate changes in tidal current velocity and direction. 

Currents 

Importance at Oil Spills 

Large oceanic current systems, such as the Gulf Stream, usually have little 

effect on coastal-zone oil spills. An exception occurred during the Exxon Valdez 

spill, when the Alaska coastal current carried oil from the spill hundreds of 
Figure 1-11. Tidal curves for the Monterey Bay, California area. A) The curve for a 

full week. Note the strong diurnal inequality. B) Curve for a 24-hour period. 
kilometers along the coast. The current systems which are usually most important 

during spills are those induced locally by rivers, tides, winds, and waves. 

River-induced currents are almost entirely confined to deltaic and estuarine 

situations and vary geographically with factors affecting the amount and seasonality 

of discharge (Davies, 1973; p. 52). During periods of high runoff, these currents 

would generally tend to keep the oil offshore, but the potential for mixing of oil into 

the water column should always be considered (e.g., see Fig. 1-5). 

Tide-induced currents vary with tidal type and range, tending to be most powerful 

with semidiurnal tides of large range and least powerful with diurnal tides of small 

range. Further details were given by Davies (1973; p. 53). 

“Although tidal currents are reversing, inequalities between flood and 

ebb streams may often be significant in terms of net transport, and on 

coasts with mixed tides, the normal sequence of highs and lows may be 

of especial importance in producing such inequalities. Thus, if the 

sequence is low low water, low high water, high low water, high high 

water, the two flood currents are essentially equal in magnitude and 

duration, but the two ebb currents are unequal so that velocities in the 

great ebb between high high water and low low water may be much 

greater than at either of the flood stages. Conversely, a sequence of 

high high, high low, low high, low low gives one exceptionally strong 

flood current between low low and high high water. 

In coastal inlets, the size, and particularly the length, of the inlet may 

affect the phase relationship between tidal stage and current velocities. 

Normally, the highest velocities occur at mid-tide, but in long 

estuaries, there may be considerable divergence so that, near the 

mouth, low tide may be associated with the fastest ebb and high tide 

with the fastest flood. This may have a morphologic effect by 

influencing the height at which strongest currents operate.” 

In short, these currents can be very complex, thus site specific data are usually 

required. 
Wind-induced currents are highly variable; thus, a constant monitoring of wind 

conditions at the spill site is necessary for prediction of oil-slick motion. 

Wave-induced currents are produced by wave setup along the shore and are 

basically divisible into longshore currents, resulting from oblique wave approach 

and running more or less parallel to the shore in the surf zone, and rip currents that 

move outward from the shore. These types of currents are important in 

transporting oil and oiled sediments once oil from the spill impacts the beach where 

it may be either resuspended into the surf zone or become incorporated as part of 

the sediment mass. 

All of the above types of currents combine and interact to produce very complicated 

current systems in the nearshore zone, as is illustrated for the La Jolla, California 

area in Figure 1-12. Detailed site-specific data and continued monitoring of wind 

and tidal conditions are almost always required to accurately predict oil trajectories 

in the nearshore zone. 

Importance to Coastal Sedimentation 

Of the different types of currents present, wave-generated currents have the most 

important influence on open coast beaches. Tidal currents are important in 

modifying sediment transport near inlets, but have little effect on uninterrupted 

straight shorelines, except in areas with very large tidal ranges (greater than 4 m). 

Ocean currents only rarely affect nearshore sediment transport. A notable exception 

is the Guyana Current, a branch of the North Equatorial Current, which moves large 

quantities of fine-grained sediment discharged from the Amazon River along the 

shoreline of northeastern South America (Fig. 1-13). 

Wave-generated currents include longshore currents and rip currents. Longshore 

currents are discussed in Chapter 3. Rip currents flow from the beach seaward and 

are generally part of a well-defined nearshore cell circulation such as is illustrated in 

Figure 1-14. The most commonly held theory for the origin of rip currents is that 

they result from interactions between incoming waves and edge waves trapped 

within the nearshore system (Komar, 1976). Edge waves are free-wave motions 

introduced by a coast in its interaction with surges or lower-period oscillations 

(Bowen and Inman, 1971). They are generally standing waves with crests normal to 

the shoreline and wave lengths from crest to crest parallel to the shoreline (Komar, 
1976; p. 176). Bowen and Inman (1969) demonstrated that longshore variations in 

wave setup caused by periodic longshore variation in wave height generate lateral 

flow, with rip currents flowing seaward at the positions of lowest wave heights. 

Figure 1-12. Nearshore current sytem near La Jolla Canyon, California on 2 

December 1948. (From Shepard and Inman, 1950.) 
Figure 1-13. Surface currents over the Amazon Delta front. (Based on data of Gibbs, 

1980; from Wright, 1985; Fig. 1-28.) 
Figure 1-14. Illustration of nearshore rip currents. Note the positioning of the 

currents where the breaker height is smallest—that is, where edge waves and 

incoming waves are 180 degress out of phase. (From Komar, 1976; Fig. 7-8.) 

Wave heights are least where the edge wave and incoming wave are 180 degrees out 

of phase (see Fig. I-14; from Komar, 1976). Rip currents carry sediments off the beach 

during erosional events. The authors have observed rip currents carrying 

significant quantities of oil offshore during a spill at Cape Hatteras, North Carolina 

and at the Peck Slip spill in Puerto Rico. 

Coastal Storms 

The most dramatic changes of shorelines occur during major storms, which usually 

result from the passage of tropical or extratropical cyclones. Much of the eastern and 

southern shoreline of the United States is affected by a tropical cyclone, or hurricane, 
every few years (Fig. 1-15). Most of these storms result in extensive coastal flooding, 

severe beach erosion, and loss of property and lives. A tropical cyclone that occurred 

on the Texas coast in September 1979 removed much of the oil that had 

accumulated on the beach as a result of the Ixtoc 1 spill (discussed further in Chapter 

3). 

Figure 1-15. Computer plot showing the tracks of a selected number of Atlantic 

tropical cyclones, 1886 through 1969. (From Neumann and Hill, 1976.) 

Extratropical cyclones are the dominant force in initiating beach cycles on the east 

coast of North America (discussed in Chapter 3). The effectiveness of these storms, 

which occur several times a year, is determined by: (1) size of storm; (2) speed of 

storm movement; (3) tidal phase and stage; (4) storm path; and (5) time interval 

between storms (Hayes and Boothroyd, 1969). Both hurricanes and extratropical 

cyclones breach barrier islands and create new tidal inlets, a process of concern 
during a spill response because the new inlets provide an avenue for oil from an 

offshore spill to reach sensitive lagoonal or estuarine habitats. 

The Three-Dimensional Beach 

The beach is a three-dimensional body of sediment made from material carried to 

the site by wave-generated currents which flow both parallel and perpendicular to 

the shore. On many sandy shorelines, a type of rhythmic beach topography (Homma and Sonu, 1962) develops. This topography has been described for the coasts of 

the Netherlands (Bruun, 1954), North Carolina (Dolan, 1971), the Great Lakes 

(Evans, 1939), Cape Cod (Goldsmith and Colonell, 1970), and several other localities. 

Sonu (1968), who termed the features “cusp-type sand waves”, discussed them in 

detail. He stated (p. 383) that Evans (1939) was probably the first to describe their 

formation. The total system of rhythmic topography migrates parallel with the 

shore in the direction of longshore drift at different rates, depending upon the size 

of the features, the local wave climate, and probably the grain size of the sediment. 

In the process of formation of rhythmic topography, depositional berms assume 

cusp-like shapes; however, these cuspate forms are considerably larger than normal 

beach cusps. The wave lengths of most of the cusp-type sand waves at Cape 

Hatteras, North Carolina, ranged between 500 and 600 m, and they migrated at rates 

averaging between 100 and 200 m per month (Dolan, 1971; p. 177). The most 

important implication of the recognition of the abundance of rhythmic topography, 

according to Dolan (1971; p. 178), is the fact that “sand beaches cannot be considered 

in terms of stationary straight lines or simple angles, but must be treated as 

nonstationary sinuous forms.” A sketch of the type of rhythmic topography 

described by Sonu (1968; 1973) is given in Figure 1-16. 

Studies in recent years on the microtidal, sandy beaches of the swell-dominated 

southeastern coast of Australia have provided a more detailed accounting of the 

three-dimensional variability of high-energy beaches (Short, 1978; Wright et al., 

1979). 

The combined work of Short, Wright, and their colleagues on the southeastern coast 

of Australia gave birth to the concept of morphodynamics, which is defined as the 

“combination of beach-surfzone morphology and wave-current dynamics” (Short, 

1979; p. 553). Short (1979; p. 567) stated that “breaker wave power provides energy to 
Figure 1-16. Rhythmic beach topography as described by Sonu (1973). The shoreline 

bulges move in the direction of longshore sediment transport at rates of up to 

hundreds of meters per year. 

move a beach through various beach stages”. Wright et al. (1979) placed emphasis 

on the reflective and dissipative nature of beaches, based on extensive field 

measurements of surf and inshore current spectra and inshore circulation patterns. 

According to Wright et al. (1979; p. 105), reflective sandy beaches are characterized by 

steep, linear beach faces, well-developed berms and beach cusps, and surging 

breakers with high runup and minimum setup; rip cells and associated threedimensional inshore topography are absent. Dissipative sandy beaches are typically 

found on open coasts and are characterized by concave-upward nearshore profiles 

and wide, flat surf zones which may contain multiple bars. Waves break tens of 

meters seaward of the beach and dissipate much of their energy before reaching it. 

Typical reflective and dissipative beach profiles are shown in Figure 1-17. 
Figure 1-17. Typical cross-sectional profiles of reflective (A) and dissipative (B) 

sandy beach profiles. (From Wright et al., 1979; Figs. 3 and 6.) 
Coastal Sediments 

Introduction 

The characteristics of the coastal sediments at the spill site are of primary 

importance. All cleanup programs must be attuned to the nature of the 

oil/sediment interactions. For example, oil does not penetrate fine-grained sand 

beaches but may percolate down to several tens of centimeters in gravel beaches. 

Sediment Texture 

Coastal sediments are classified according to the dominant size of the individual 

clasts into three general categories: 1) gravel, mean size greater than 2.0 mm; 2) 

sand, mean size between 0.0625 and 2.0 mm; and 3) mud, mean size less than 0.0625 

mm. As shown in Figure 1-18, the general classes may be subdivided further. 

The Wentworth (1922) classification of grain size is the one used most widely by 

engineers and geologists. It is a logarithmic scale in that each class limit is twice as 

large as the next smaller class limit (Fig. 1-18). The property of having class limits so 

defined led Krumbein (1936) to propose a phi unit scale based on the following 

definition: phi units (F) = -log2 (diameter in mm). The phi scale of Krumbein, 

which is shown in Figure 1-18, is used to calculate statistical parameters of sediment 

grain-size populations. 

The grain size of mud is measured by pipette analysis and that of sand with sieves or 

a settling tube. Gravel sizes are determined by measurements of the long, 

intermediate, and short axes of individual clasts. Ratios of the different clasts of 

gravel occurring on a beach (i.e., granule, pebble, cobble, boulder) can be estimated 

visually by comparing the beach sediment with the chart shown in Figure 3-14. 

Composition of Beach Sediments 

Sediments on beaches range from coarse-grained fragments of rocks, usually derived 

from local rock outcrops, to fine-grained sand, derived from 10’s to hundreds of 

miles away. Quartz sand is the most common constituent of beach sediments 

because of its relative abundance in the earth’s crust, as well as its chemical stability 

and resistance to abrasion. Carbonate sand beaches are common in tropical regions. 
A summary of the generalized global occurrence of beach sediment, with regard to 

its composition, is given in Table 1-1. 

Figure 1-18. Grain-size scale. (From CERC, 1973; Fig. 4-7.) Phi unit scale is indicated 

by writing ø or phi after the numerical value. 
Table 1-1. Generalized global occurrence of beach sediment. 

Tropical regions Carbonate sand composed of coral and algal fragments, 

shell, and carbonate precipitates abundant; quartz and rock 

fragments common in sand, especially in areas of eroding 

bedrock and near river mouths 

Temperate regions Quartz sand dominant; rock fragments and feldspar 

abundant in sand near river mouths and along coasts 

with eroding bedrock 

Subpolar and polar 

regions 

Gravel beaches of highly variable composition abundant; 

pure sand present on long, exposed beaches; quartz and 

rock fragments common in sand 

Oceanic islands Volcanic sands (normally black in color) and carbonate 

sands common 

Estuaries—Bays—Lagoons 

Introduction 

Semi-enclosed water bodies of relatively small dimensions that separate the land 

from the sea are termed estuaries, bays, or lagoons, depending upon configuration 

and their hydrographic characteristics. On coastal plain shorelines, many of these 

water bodies are sheltered behind barrier islands. Drowned river valleys, such as 

Chesapeake Bay and Delaware Bay, are also common. The classic definition of the 

term “estuary” was given by Pritchard (1967) as follows: 

“a semi-enclosed coastal body of water which has a free connection 

with the open sea and within which sea water is measurably diluted by 

fresh water derived from land drainage”. 

Patterns of sedimentation in the “classic” estuaries are very complex, owing to the 

interaction of tidal currents, waves, and biogenic processes. Coarsest sediments 

occur in the inlets, on the tidal deltas, and in the larger tidal channels, whereas 

finest sediments occur on the tidal flats and in the salt marshes. 
Relationship to Tidal Range 

Hayes (1975) pointed out that the distribution of coastal habitats and sediments 

within semi-enclosed coastal water bodies is controlled largely by the tides. The 

coastal water bodies were grouped and discussed, as follows, into the three major 

tidal classes. General models for the three classes are given in Figure 1-19. 

Microtidal Systems 

The processes that dominate in microtidal systems are created by wind and 

wave effects. Wind tides are commonly generated and extensive wind-tidal flats 

may develop. The wave-formed features include aligned bay beaches, recurved 

spits, and cuspate spits. Tidal currents generated by the astronomical tide are 

important only at the inlet throat. In some instances, however, large intertidal 

shoals (flood-tidal deltas) can develop on the landward sides of the inlets. 

Mesotidal Systems 

These systems differ from those of microtidal areas in that sediments 

deposited by tidal currents begin to predominate. The barrier islands themselves are 

short and stubby, and the tidal deltas are large and conspicuous. Meandering tidal 

channels occur behind the barriers; point-bar deposits containing bedforms 

generated by tidal currents usually predominate in these channels. The principal 

sand deposits in mesotidal estuaries are the tidal deltas. Hayes (1969) proposed the 

following terminology for the two major sand deposits associated with tidal inlets: 

(a) ebb-tidal delta—sediment accumulation seaward of a tidal inlet, deposited 

primarily by ebb-tidal currents and modified by waves, and (b) flood-tidal delta— 

sediment accumulation formed on the landward side of an inlet by flood-tidal 

currents. The general morphological model for a tidal inlet is given in Figure 1-20. 

Macrotidal Systems 

The most prominent feature of this type of coastal water body is the 

overwhelming dominance of tidal currents. Such systems are usually 

broadmouthed and funnel-shaped. Sand deposition is normally concentrated in the 

center of the water body, away from shore, which is usually dominated by broad, 

muddy tidal flats. The sand bodies are long linear features oriented parallel with the 

tidal currents. 
Figure 1-19. Variations of coastal estuaries, bays, and lagoons in response to 

differences in the tides. (After Hayes, 1975; TR = tidal range.) 
Figure 1-20. General model showing the morphological components of a tidal inlet. 

Water Circulation and Mixing 

As can be seen from the plan-view map of a group of Georgia estuaries (mesotidal) 

in Figure 1-21 and a hypothetical cross-section of a Chesapeake Bay-type estuary in 

Figure 1-22, oil spilled in either the entrance or the interior of a major estuary will 

be subjected to complex circulation and mixing patterns. Water circulation at the 

entrances to the Georgia estuaries is controlled by ebb- and flood-tidal currents, 

which are commonly both horizontally and vertically segregated, and complex 
wave-generated currents created by wave-refraction around the shoals at the estuary 

entrances (ebb-tidal deltas). The circulation pattern of both water masses and their 

suspended sediment loads inside major estuaries, which is illustrated in Figure 1-22, 

makes estuaries very effective traps for fine-grained, suspended sediments. The 

flocculation and entrapment of the sediments occurs predominantly in the zone of 

mixing between the fresh and salt water. This zone is sometimes referred to as the 

“turbidity maximum”, because of the overabundance of suspended sediments in 

that zone. Oil from the Amoco Cadiz spill was entrapped in the bottom sediments 

of some of the estuaries in Brittany, France probably as a result of getting caught up 

in this type of circulation pattern. 

Figure 1-21. Water circulation and sedimentation patterns at the mouths of Georgia 

estuaries. (From Stanley and Swift, 1976; after Oertel, 1972.) 
Figure 1-22. Conceptual model of sediment dispersal zones and circulation patterns 

in a hypothetical, Chesapeake Bay-type estuary. Note presence of zone of turbidity 

maximum and zone of suspended sediment entrapment in the area where salt and 

fresh waters mix (cross-section C). (From Nichols and Biggs, 1985; Fig. 2-48.) 
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Stanley, D.J. and D.J.P. Swift. 1976. Marine Sediment Transport and Environmental 

Management. New York: John Wiley and Sons. 602 pp. 

Watanabe, A. and K. Horikawa. 1983. Review of coastal stabilization works in Japan: 

in Proc. Intl. Conf. on Coastal Port Eng. in Dev. Countries, V.I., Colombo, Sri Lanka, 

pp. 186-200. 

Wentworth, W.C. 1922. Grade and class terms for clastic sediments. Jour. Geol.(30): 

377-392. 
Wright, L.D. 1977. Sediment transport and deposition at river mouths: a synthesis. 

Geol. Soc. Amer. Bull. (88):857-868. 

Wright, L.D. 1985. River deltas: in R.A. Davis, Jr. (Ed.), Coastal Sedimentary 

Environments (2nd revised ed.). New York: Springer-Verlag. pp. 1-76. 

Wright, L.D., J. Chappell, B.G. Thom, M.P. Bradshaw, and P. Cowell. 1979. 

Morphodynamics of reflective and dissipative beach and inshore systems: 

southeastern Australia. Mar. Geol.(32):105-140. 
2 Oil Behavior and Toxicity 

Jacqueline Michel1 

Page 

Composition of Crude Oils........................................................................2-1
 

Weathering Processes at Oil Spills.....................................................2-3
 

Evaporation.................................................................................................2-3
 

Dissolution....................................................................................................2-5
 

Emulsification.............................................................................................2-6
 

General spill types and behaviors..............................................2-7
 

References.........................................................................................................2-9
 

1 Research Planning, Inc., P.O. Box 328, Columbia, South Carolina 29202 
Chapter 2.
 

Oil Behavior and Toxicity
 

Composition of Crude Oils 

Crude oils are complex mixtures which vary widely in composition. However, they 

can be divided into three broad groups of compounds which help the responder 

assess the initial impacts and fate of the oil. These groups are very simple: 

1) Light-weight components 

2) Medium-weight components 

3) Heavy-weight components 

We use compositional data on crude oils to characterize them as to the amounts of 

each group present in the oil, and thus predict the behavior of the oil and the risk 

the oil poses to natural resources of concern. 

Light-weight components are characterized by: 

•	 Hydrocarbon compounds containing up to ten carbon atoms 

•	 A boiling range up to 150 degrees C 

•	 Rapid and complete evaporation, usually within a day 

•	 High water solubility; usually contributes >95% of water-soluble fraction 

•	 High acute toxicity because they contain the monoaromatic hydrocarbons 

(benzene, toluene, xylene) which are soluble and toxic 

•	 No potential for bioaccumulation (they evaporate instead) 

•	 Mostly composed of alkanes and cycloalkanes which have relatively low 

solubility (and thus low acute toxicity potential) 

These light ends evaporate so quickly that they do not persist in the environment. 

Even though individual aromatic compounds have solubilities of over 1,000 mg/L, 

they are rapidly removed from solution by evaporation. One important exception 

to this general rule is when the dissolved fraction is rapidly mixed into the water 

column under cold conditions, as occurred during the Ashland spill of over 1 

2-1
 
million gallons of No. 2 fuel oil into the Monongahela River on 2 January 1988. To 

make conditions even worse, the spill flowed over numerous locks and dams, 

which caused the oil to mix throughout the water column as it plunged over the 

dams. Dissolved and dispersed oil was detected in the river for hundreds of miles 

downstream. 

Medium-weight components are characterized by: 

•	 Hydrocarbon compounds containing between 10 and 22 carbon atoms 

•	 A boiling range from about 150 to 400 degrees C 

•	 Evaporation rates of up to several days, although there will be some 

residue which does not evaporate at ambient temperatures 

•	 Low water-soluble fraction (at most a few mg/L) 

•	 Moderate acute toxicity because they contain diaromatic hydrocarbons 

(naphthalenes) which are toxic in spite of their low solubilities 

•	 Moderate potential for bioaccumulation and chronic toxicities associated 

with the diaromatic hydrocarbons 

•	 Alkanes which are readily degraded 

These medium-weight components pose the greatest environmental risks to 

organisms because the compounds are more persistent, they are biologically 

available, and the PAHs have high toxicities. The alkanes (aliphatic hydrocarbons) 

are readily biodegraded under the right conditions. In fact, chemists monitor the 

distribution of these compounds over time to show the process of degradation of a 

spill. 

The heavy-weight components are characterized by: 

•	 Hydrocarbon compounds containing more than 20 carbon atoms 

•	 Almost no loss by evaporation 

•	 Almost no water-soluble fraction 

2-2 
•	 Potential for bioaccumulation, via sorption onto sediments, otherwise not 

highly bioavailable 

•	 Potential for chronic toxicity, because they contain polynuclear aromatic 

hydrocarbons (phenanthrene, anthracene, etc.) 

•	 Most of the components are waxes, asphaltenes, and polar compounds 

which do not have any significant bioavailabilites or toxicities 

•	 Long-term persistence in sediments, as tar balls, or asphalt pavements 

These heavier components pose little acute toxicity risks, except that due to 

smothering, because of the very low solubilities of the individual compounds. 

Animals have to be exposed via a sediment pathway or through the food chain. 

However, these are the most persistent components of an oil, and degradation rates 

will be very slow. 

Refined petroleum products, in contrast to crude oil, have only a very narrow range 

of components, and they are characterized according to boiling range fractions. 

Weathering Processes at Oil Spills as Applied to Resources at Risk, Oil 

Persistence, and Cleanup 

Evaporation 

Evaporation is the single most important weathering process in the first several 

days of an oil spill (Fig. 2-1). For light, refined products such as gasoline, 

evaporation will remove 100 percent of the spill within a very short time. For 

heavy refined products such as No. 6 fuel oil or Bunker C, evaporation will only 

remove 5-10 percent of the spill. For crude oils, the amount of the spill lost to 

evaporation can range from 20 to 60 percent. For spills of medium crude oils, a rule 

of thumb is that 20-30 percent of the oil is lost to evaporation within the first 24 

hours! 

2-3
 
Figure 2-1. Schematic showing the relative importance of weathering processes of 

an oil slick over time. The width of the line shows the relative magnitude of the 

process in relation to other contemporary processes. 

Payne et al. (1983) have developed an oil-weathering model which has a good 

evaporation sub-model in it. It uses the true boiling point distillation temperatures 

and the volume percent of the oil for each of these boiling point ranges, 

information which is usually available from the owner or shipper. This model is 

available for use on microcomputers, and it is relatively easy to use. The differences 

in the rate of evaporation for various oils can be shown by running the model for 

two different spills: the Exxon Valdez spill of Prudhoe Bay crude, a medium-heavy 

oil, spilled under cold conditions (March 1989), where 10 percent was calculated to 

have evaporated within the first 24 hours; and the Mega Borg spill of Angola crude, 

a light oil, spilled in June 1990, where 45 percent was calculated to have evaporated 

within the first 24 hours. 

Environmental factors which affect the rate of evaporation are: 

• Area of slick exposed, which changes rapidly 

• Wind speed and water surface roughness 

• Air temperature and solar radiation 

• Formation of emulsions, which dramatically slows evaporation 

2-4
 
Windy, sunny days and currents which rapidly spread the slicks speed evaporation. 

Evaporation even removes dissolved hydrocarbons from the water column. Figure 

2-2 shows the concentration of the volatile aromatic hydrocarbons in the watersoluble fraction of Prudhoe Bay crude over time as measured in laboratory tests. 

These compounds are lost via evaporation from the water. 

Figure 2-2. Plot of the concentrations of volatile aromatic hydrocarbons in the 

water-soluble fraction of Prudhoe Bay crude oil over time. Note the rapid loss of 

these compounds by evaporation (Payne et al., 1983). 

Dissolution 

Dissolution of petroleum hydrocarbons into the water column poses risks to aquatic 

organisms because of the acute toxicity of the compounds that have significant water 

solubility. Figure 2-3 shows the solubility of normal alkanes, cycloalkanes, and 

aromatic hydrocarbons in fresh water. It should be noted that solubilities in sea 

water are lower, by about 70 percent (Sutton and Calder, 1974). Compounds with 

2-5
 
Figure 2-3. Water solubility of the major components of crude oil, for three groups 

of compounds, plotted by carbon number. (McAuliffe, 1983) 

carbon numbers less than four are gases at ambient temperatures, so they are not of 

concern. The monoaromatics have the highest solubilities, by a factor of 50, than 

similar weight alkanes. Benzene has the highest solubility, at 1,750 mg/L, with 

toluene at 515 mg/L, and xylene less than 100 mg/L. McAuliffe (1987) reported the 

water-soluble fraction of six oils equilibrated with saline water, ranging from 20 to 40 

ppm total dissolved hydrocarbons. Benzene plus toluene constituted from 70-85 

percent of the aromatic fraction, and total aromatics constituted 35-80 percent of the 

total dissolved hydrocarbons. Of the higher PAHs, naphthalene is the most watersoluble, contributing 0.12 ppm to the water-soluble fraction of south Louisiana crude 

and 0.02 ppm for Kuwait crude (McAuliffe, 1987). The amount of the next heavier 

PAHs in the water-soluble fraction is 100 times lower than the naphthalenes. 

Emulsification 

Formation of emulsions affects the behavior of an oil spill in many ways. First, 

weathering rates are much slower. The oil is more viscous and sticky. The volume 

of “oil” is increased by a factor of 2-3, because the emulsion is up to 70 percent water. 

Most recovery equipment works very poorly on mousse. Tendency to emulsify and 

emulsion stability is very closely related to the asphaltene content. Predicting the 

2-6
 
formation and stability of emulsion is important. Based on laboratory and field 

experience, stable emulsions are likely to form for: 

•	 Heavy crudes with high viscosities 

•	 Crudes and refined products with high asphaltene content 

• Crudes with high NSO compound content 

Emulsification almost never occurs during spills of: 

•	 Gasoline 

•	 Kerosene 

•	 Diesel fuels (except under VERY cold conditions) 

General Spill Types and Behaviors 

Based on all the properties of spilled oil, there are four types of oil for which a 

general assessment of the behavior and fate can be made: 

Type 1—Very Light Oils (Jet Fuels, Gasoline) 

•	 Highly volatile (should all evaporate within 1-2 days). 

•	 High concentrations of toxic (soluble) compounds. 

•	 Result: Localized, severe impacts to water column and intertidal 

resources. 

•	 Duration of impact is a function of the resource recovery rate. 

•	 No dispersion necessary. 

•	 No cleanup necessary. 

Type 2—Light Oils (Diesel, No. 2 Fuel Oil, Light Crudes) 

•	 Moderately volatile; will leave residue (up to one-third of spill amount) 

after a few days. 

•	 Moderate concentrations of toxic (soluble) compounds, especially 

distilled products. 

•	 Will "oil" intertidal resources with long-term contamination potential. 

2-7
 
•	 Has potential for subtidal impacts (dissolution, mixing, sorption onto 

suspended sediments). 

•	 No dispersion necessary. 

•	 Cleanup can be very effective. 

Type 3—Medium Oils (Most Crude Oils) 

•	 About one-third will evaporate within 24 hours. 

•	 Maximum water-soluble fraction 10-100 ppm. 

•	 Oil contamination of intertidal areas can be severe and long-term. 

•	 Oil impacts to waterfowl and fur-bearing mammals can be severe. 

•	 Chemical dispersion is an option within 1-2 days. 

•	 Cleanup most effective if conducted quickly. 

Type 4—Heavy Oils (Heavy Crude Oils, No. 6 Fuel Oil, Bunker C) 

•	 Heavy oils with little or no evaporation or dissolution. 

•	 Water-soluble fraction is less than 10 ppm. 

•	 Heavy contamination of intertidal areas likely. 

•	 Severe impacts to waterfowl and fur-bearing mammals (coating and 

ingestion). 

•	 Long-term contamination of sediments possible. 

•	 Weathers very slowly. 

•	 Chemical dispersion seldom effective. 

•	 Shoreline cleanup difficult under all conditions. 

2-8
 
References 

McAuliffe, C.D. 1987. Organism exposure to volatile/soluble hydrocarbons from 

crude oil spills–a field and laboratory comparison. Proceedings of the 1987 Oil Spill 

Conference, April 6-9, 1987, Baltimore, Maryland, pp. 275-288. 

Payne, J.R., B.E. Kirstein, G.D. McNabb, Jr., J.L. Lambach, C. de Oliveria, R.E. Jordan, 

and W. Hom. 1983. Multivariate analysis of petroleum hydrocarbon weathering in 

the subarctic marine environment. Proceedings of the 1983 Oil Spill Conference, 

February 28-March 3, 1983, San Antonio, Texas, pp. 423-434. 

Sutton, C. and J.A. Calder, 1974, Solubility of higher-molecular-weight n-paraffins in 

distilled water and seawater. Environ. Science Tech.(8):320-322. 

2-9
 
3 Sensitivity of Coastal Environments to Oil 

Jacqueline Michel and Miles O. Hayes1 

Page 

Introduction.....................................................................................................3-1
 

Exposed Rocky Coasts.................................................................................3-2
 

Wave-cut cliffs..........................................................................................3-2
 

Wave-cut platforms..............................................................................3-3
 

Sand Beaches...................................................................................................3-6
 

Morphology and Sediment Transport............................................3-7
 

Fine-grained sand beaches..............................................................3-10
 

Coarse-grained sand beaches........................................................3-17
 

Gravel Beaches...............................................................................................3-23
 

Introduction...............................................................................................3-23
 

Pure gravel beaches.............................................................................3-25
 

Mixed sand and gravel beaches....................................................3-32
 

Tidal Flats............................................................................................................3-37
 

Origin and sedimentation patterns............................................3-37
 

Exposed tidal flats....................................................................................3-41
 

Sheltered tidal flats...............................................................................3-43
 

Sheltered Rocky Coasts............................................................................3-44
 

Marshes................................................................................................................3-52
 

Marshes of the southeastern USA.............................................3-52
 

Marshes of California............................................................................3-56
 

Behavior of oil in marshes...............................................................3-60
 

Factors affecting the impacts of oil on marshes................3-61
 

Impacts by oil type................................................................................3-58
 

1Research Planning, Inc., P.O. Box 328, Columbia, South Carolina 29202 
Page 

Mangroves and Coral Reef Comunities..........................................3-65
 

Mangroves...................................................................................................3-66
 

Coral reefs....................................................................................................3-73
 

References.........................................................................................................3-77
 
Chapter 3.
 

Sensitivity of Coastal Environments to Oil
 

Introduction 

Intertidal habitats are at risk during spills because of the high likelihood of being 

directly oiled when floating slicks impact the shoreline. Oil fate and effects vary 

significantly by shoreline type, and many cleanup methods are shoreline-specific. 

The concept of mapping coastal environments and ranking them on a scale of 

relative sensitivity was originally developed in 1976 for lower Cook Inlet (Michel et 

al., 1978). Since that time, the ranking system has been refined and expanded to 

cover shoreline types for all of North America, including the Great Lakes and 

riverine environments. 

Prediction of the behavior of oil on intertidal habitats is based on an understanding 

of the coastal environment, not just the substrate type and grain size. The 

sensitivity of a particular intertidal habitat is an integration of the: 

1) Shoreline type (substrate, grain size, tidal elevation, origin), 

2) Exposure to wave and tidal energy, 

3) Analysis of the natural persistence of the oil on the shoreline, 

4) Biological productivity and sensitivity, and 

5) Ease of cleanup without causing more harm. 

All of these factors are used to determine the relative sensitivity of shorelines. Key 

to the sensitivity ranking is an understanding of the relationships between physical 

processes and substrate which produce specific geomorphic shoreline types and 

predictable patterns in oil behavior and sediment transport patterns. In the 

following sections, the definition, morphology and processes, and oil behavior for 

six general coastal environments are summarized. 

3-1
 
Exposed Rocky Coasts 

Although exposed rocky coasts can be highly variable in elevation, slope, exposure, 

crenulation, and biological utilization, they can be divided into two broad types, 

based on the behavior and persistence of oil: wave-cut cliffs and wave-cut rock 

platforms. Both types are characterized by strong waves which wash across the 

intertidal zone and, except where very large waves occur, a rich biological 

community. In general, oil persistence is low because the oil does not penetrate the 

substrate and so it is available for rapid removal by wave action. But, both types can 

have complex micro-environments in the form of sheltered crevices and waveshadow pockets behind large boulders or offshore rocks. They differ in the slope and 

width of the intertidal zone, the presence of sediments, and wave reflection 

patterns. Each type is discussed below. 

Wave-cut Cliffs 

This shoreline type has a steep intertidal zone with very little width. The rock 

surface can be highly irregular, with numerous cracks and crevices. Sediment 

accumulations (gravel- to boulder-sized material) are uncommon and usually 

ephemeral, since waves remove the debris of mass wasting as the sea cliffs retreat. 

Wave-cut cliffs are found interspersed with other shoreline types, particularly wavecut platforms. 

The narrowness of the intertidal zone limits to some degree the extent of biological 

colonization, which must also be able to survive the intense wave action. There is 

strong vertical zonation of biological communities, with animals dominating the 

mid- to upper intertidal zone, and algae dominating the lower intertidal zone. 

Offshore, large kelp beds can occur, providing habitat for a wide range of organisms. 

The ruggedness and isolation of rocky headlands make them important as nesting 

sites for seabirds. 

Observations at many oil spills have shown that: 

•	 Oil is held offshore by waves reflecting off the steep cliffs 

•	 Any oil that is deposited is rapidly removed from exposed faces 

•	 The most resistant oil would remain as a patchy band at or above the hightide line 

•	 Impacts to intertidal communities are expected to be of short duration 

3-2
 
•	 An exception would be where heavy concentrations of a light refined 

product (e.g., No.2 fuel oil) came ashore very quickly 

•	 Greatest impacts are likely to be to birds when present at nesting colonies 

or feeding in nearshore waters 

Because of the low potential for oil accumulation and high degree of natural 

cleansing, wave-cut cliffs have been ranked as having the lowest sensitivity of all 

natural intertidal habitats. 

Wave-Cut Platforms 

Where erosion has formed a flat rock bench within the intertidal zone, it is referred 

to as a wave-cut platform (or shore platform). The width of platforms can range 

from a few meters to nearly a kilometer. Somewhat surprisingly, there is no 

consensus as to how they are formed; studies have proposed, in addition to wave 

action, ice scouring during either or both glacial and modern periods, salt 

weathering, mechanical fracture by freeze and thaw action, and biological 

weakening of the rock. However, it has been shown that many platforms are very 

young, maybe taking only up to a thousand or a few thousand years to form. (How 

else could the present platforms keep up with sea-level rise?) 

Wave-cut platforms can be characterized as follows: 

•	 They are composed of a rock bench, of highly variable width 

•	 The shoreline may be backed by a steep scarp or low bluff 

•	 There may be a narrow, perched beach of gravel- to boulder-sized 

sediments at the base of the scarp 

•	 The platform surface is irregular and tidal pools are common 

•	 Small accumulations of gravel can be found in the tidal pools and crevices 

•	 Pockets of sandy "tidal flats" can occur on the platform in less exposed 

settings 

•	 These habitats can support large populations of encrusting animals and 

plants, with rich tidal pool communities 

•	 They can be used as haulouts by marine mammals 

Even though they are exposed to high wave energy, there are two factors which 

make wave-cut platforms more sensitive to oil spill impacts than wave-cut cliffs. 

3-3
 
First, oil may penetrate and persist longer in the beach sediments, if present. This 

oil would be removed only when large waves reworked the sediments. There can 

be a wide variability in the rate of reworking along a shoreline segment, depending 

upon the width of the platform, fetch, shoreline orientation, and the presence of 

offshore rocks which refract waves. The latter condition can result in accumulation 

and persistence of oil due to what we term the tombolo effect, which is illustrated in 

Figure 3-1. A tombolo is a spit-like projection of unconsolidated sediment that 

forms behind an offshore island or bedrock outcrop. The tombolo is the 

accumulation of sediment which forms as a result of wave refraction bending 

around the island or bedrock outcrop, where the refracted waves meet in the lee of 

the offshore obstruction. The important point is that wave energy is lower in the 

lee of the tombolo, and any stranded oil tends to persist much longer there. For 

example, Figure 3-1 shows that oil from the Exxon Valdez oil spill in Alaska 

remained over one year in a very high energy setting as a result of the protection 

(from wave attack) afforded by the offshore rock outcrops on the wave-cut platform. 

The second factor which increases the sensitivity of wave-cut platforms is the 

potential for greater impacts to intertidal communities. Although oil does not 

adhere to the wet rock surfaces, heavy accumulations of oil can temporarily cover 

the intertidal zone during falling tides. Tidal pool organisms can be killed by 

smothering or exposure to the toxic fractions of fresh oil or refined products. Also, 

marine mammals using the platforms as haulouts can be directly oiled. 

Oil behavior on wave-cut platforms can be summarized as follows: 

•	 Oil will not adhere to the rock platform, but rather be transported across 

the platform and accumulate along the high-tide line 

•	 Oil can penetrate and persist in the beach sediments, if present 

•	 Persistence of oiled sediments is usually short-term, except in wave 

shadows or larger sediment accumulations 

3-4
 
Figure 3-1. Example of the tombolo effect at the Exxon Valdez spill site. (From 

Hayes et al., 1990; Fig. 4.) 

3-5
 
Sand Beaches 

Introduction 

A beach is an accumulation of unconsolidated sediment that is transported and 

molded into characteristic forms by wave-generated water motion. Beaches will 

form virtually anywhere sediment is available and there is a site for sediment 

accumulation. Inherent to sand beaches is change, over timescales ranging from 

seconds to years. Knowing the patterns of change enables us to better predict the 

behavior of oil spills and the persistence of oiled sediments. Sand beaches vary 

widely in their grain size, width, slope, origin, exposure to waves, and sediment 

transport patterns, and geologists and engineers have devised many types and 

models to describe them. In contrast, biologists seldom differentiate among sand 

beaches and consider them to have simple biological communities. 

Figure 3-2 shows a typical beach profile and common terminology. Starting at the 

water level (WL), a low-tide terrace forms a flat, hard-packed, and water-saturated 

surface. Over this surface, sand which was eroded from the beach by storm waves 

migrates in the form of intertidal bars (ridges) up to 1 meter in height. The 

depression in front of the ridge is called a runnel. Eventually, the ridge welds onto 

the beach, forming a berm at the high-tide line. Note that the berm top slopes gently 

landward, forming a berm runnel. During the depositional stages on a beach, 

multiple berms can form. It should also be noted that deposition of the berm can 

build up to 2 meters of sand over a period of weeks to months. The beachface 

extends from the berm crest to the low-tide terrace and is steeply inclined toward the 

sea. 

From the perspective of oil behavior on beaches, there are three basic factors: 

1) The depth of oil penetration into the sediments 

2) The potential for burial of oiled layers by clean sediments 

3) The ability of the sediment to support equipment 

3-6
 
Figure 3-2. Three of the more common types of beach profiles occurring on sand 

beaches. Examples from Plum Island, Massachusetts. The upper profile, a 

constructional profile, occurs when beach is recovering from an erosional episode. 

The intertidal bar migrates landward, accretes to the beach, and a major accretional 

berm (mature profile; one labeled 10 Sept. 1967) results. The flat, post-storm profile 

(labeled 22 June 1967) occurred after a brief summer storm. (After Hayes and 

Boothroyd, 1969; Figs. 4 and 5.) 

Morphology and Sediment Transport 

The grain size of a beach shows a distinct relationship to the slope of the beachface– 

the coarser the sand, the steeper the beachface. The beach slope is also controlled by 

wave activity in that eroding beaches tend to flatten and accreting beach steepen. 

Figure 3-3 illustrates the relationship of beach slope to grain size and degree of 

exposure. Knowledge of the sediment transport patterns for sand beaches is 

important for understanding how oil behaves on them. 

3-7
 
Figure 3-3. Relationship of beach grain size to beachface slope on the east and west 

coasts of North America. The more exposed beaches of the west coast tend to have 

flatter slopes because of the large volumes of backwash produced by the larger 

waves. Halfmoon Bay, California, is partially sheltered by a headland, so its data 

points fall between the two extremes. (From Komar, 1976, Fig. 11-8; based on data of 

Bascom, 1951 and Wiegel, 1946.) 

Sand is moved alongshore on beaches by two mechanisms. Under oblique wave 

approach, the paths of moving sand grains on the beachface follow a saw-tooth 

pattern as the wave uprush pushes the grains obliquely up the beach and they roll 

straight down the slope as gravity pulls back the backwash. Also, the continuous 

action of the oblique waves induces a longshore current which carries sediment 

parallel to shore. Both processes are simply illustrated in Figure 3-4, although 

complex sediment circulation patterns can form complicated bar and rip systems. 

3-8
 
Figure 3-4. Longshore motion of beach sediment produced by wave swash and 

wave-generated current action when waves approach the shoreline at an angle. 

(From Bird, 1968.) 

The erosion and deposition of sand on beaches is known as the beach cycle. The 

concept of the cyclical change of beaches from a flat, erosional profile in winter to a 

wide, depositional berm in summer is well ingrained in both the popular and 

scientific literature. The concept originated from detailed studies on the west coast 

of the United States (Shepard, 1950; Bascom, 1954). Generally speaking, storm waves 

which erode sand from the beach are more common in the winter, whereas flatter, 

depositional swell waves are more common in the summer on the California coast– 

hence the terms summer and winter profiles. Figure 3-5 shows the deposition at 

Carmel, California during the summer and the subsequent erosion triggered by big 

winter storms. However, this strong seasonal storm pattern is not present along 

other coasts, and the more appropriate terminology is to refer to the beach profile as 

the post-storm, constructional, or mature (fully accretional) profile. 

3-9
 
Figure 3-5. Growth and retreat of beach berm at Carmel, California between 14 April 

1946 and 21 February 1947 (after Bascom, 1954). These and other observations on the 

California coast gave birth to the concept of winter and summer beach profiles. 

The stage of the beach cycle determines the rate and amount of sediment 

accumulation on beaches, and hence the potential for burial of oiled layers by clean 

sand or removal of oiled sediment by erosion. For oil spill analysis, sand beaches 

can be divided into two basic types, fine-grained and coarse-grained, which are 

compared and contrasted in the following sections. 

Fine-grained Sand Beaches 

The grain size of sediment on fine-grained sand beaches ranges between 0.0625 and 

0.25 millimeters (mm). The compact sediments prevent deep penetration of oil. On 

exposed shorelines, the beaches are generally flat, wide, and hard-packed. Along 

more sheltered bays and lagoons, the beaches are still flat but much narrower and 

commonly fronted by tidal flats. Because of this flat profile, they change very slowly 

in response to changing wave and tidal conditions. The importance of this 

characteristic is best exemplified by observations at the Urquiola oil spill in Spain in 

1976, shown by sequential beach profiles of a heavily oiled fine-grained sand beach 

in Figure 3-6 and described by Gundlach et al. (1978). 

3-10
 
Figure 3-6. Beach profiles at the Urquiola oil-spill site, Plaza de Raso, Spain, plotted 

at 5:1 vertical exaggeration. Note the relatively shallow depths of oil penetration 

and burial on this fine-grained sand beach. Trenches are not drawn to scale. Circled 

numbers refer to the chronological sequence of depositional events (see text). (After 

Gundlach et al., 1978; Fig. 7.) 

“Initially, 1-3 cm of oil covered the entire intertidal zone. The oil coating was 

strictly superficial owing to the close packing of the sediment. Comparison of 

the profiles taken on May 19 and June 9 (Fig. 3-6) illustrates minor, though 

important, variations in the morphology of the beach. During this time, the 

lower beachface lost 2 cm of sediment and oil, while the upper portions 

gained an equal amount of clean sediment. As a result of these subtle 

changes, oil was removed from 60 m of shore and buried along 23 m. 

“Trenches dug in the oiled zone yield substantial information concerning the 

depositional history of the beach during and after initial oil impact. 

Interpreted trenches, illustrated in Figure 3-6, indicate the following 

3-11 
depositional sequence: (1) burial of the oil deposited on the beachface before 

measurement of the first profile on May 19, (2) deposition of 3 cm of clean 

sand on the berm, (3) deposition of the thin surficial oil layer visible on the 

May 19 profile, and (4) deposition of clean sand over the oiled layers along the 

upper portion of the beach. Oil that was placed on the berm during the high 

spring tides of mid-May remained undisturbed throughout the study period.” 

The most important of these observations are that oil penetration was limited to a 

few centimeters and maximum burial of oil anywhere on the beach was about 10 

cm. Measurements of oil penetration and burial were made at 19 heavily oiled 

beaches at the Urquiola oil spill, and the results are plotted in Figure 3-7. There is a 

good correlation between oil penetration and burial with grain size. Maximum 

penetration in fine-grained sand beaches was less than 10 cm and maximum burial 

over a three-week period was less than 20 cm. 

Similar results have been observed at many other spills. Since most of the oil 

remains on or near the surface on fine-grained sand beaches, natural removal 

processes can be very effective, depending upon the frequency of storms. Usually, 

the first moderate storm will remove a significant amount of the oil. For example, 

oil from the Ixtoc 1 well blowout accumulated on Texas beaches for nearly 30 days, 

until a tropical depression passed through, generating 1-2 m waves. After the storm, 

surveys showed that over 90 percent of the oil on the shoreline had been removed 

(Fig. 3-8), with no buried oil found on any of the fine-grained sand beaches. Only 

the mixed sand and shell beaches retained a significant amount of oil (Gundlach et 

al., 1981). Figure 3-9 shows the comparison of the changes in beach profile and oil 

distribution on fine-grained versus coarse-grained sand and shell hash beaches at 

the Ixtoc 1 site. The storm completely reworked the fine-grained sand and removed 

all of the oil except for a light accumulation of tarballs at the landward limit of wave 

swash. On the coarse-grained beach, the storm eroded the beachface but deposited a 

0.5m thick layer of sediments mixed with tarballs high on the backbeach. 

At the Amoco Cadiz oil spill in France (March, 1978), most of the fine-grained sand 

beaches went from being heavily oiled to having a light oil coverage, usually with 

only a minor oiled swash line, within about a month (Gundlach and Hayes, 1978). 

By mid-summer, four months later, the fine-grained sand beaches were generally 

free of oil. However, in some localities, some discontinuous, oiled-sediment layers 

3-12
 
 

Figure 3-7. Relationship of thickness of oiled sediment layers and oil burial to 

sediment grain size at 19 oiled beaches at the Urquiola oil-spill site. The oil-layer 

thickness, a function of oil penetration, capillary forces and mixing of sediment and 

oil by wave action, clearly increases with an increase in grain size (upper curve; 

correlation coefficient [r2] = 0.71). Depth of oil burial also increases with increasing 

grain size (lower curve). (From Gundlach et al., 1978; Fig. 6.) 

3-13
 
Figure 3-8. Oil coverage along the beach of Padre Island, Texas in August and 

September 1979 as result of Ixtoc 1 spill. Note rapid cleaning of the beaches by wave 

action (1-2 m waves) resulting from passage of a tropical storm on 13 September. 

(From Gundlach et al., 1981; Fig. 3.) 

3-14
 
Figure 3-9. Beach profiles of two south Texas beaches that were oiled during the 

Ixtoc 1 spill. The changes shown, brought about by the passage of a tropical storm, 

resulted in oil burial up to 70 cm on the coarse-sand/shell-hash beach and removal 

of most of the oil from the fine-grained sand beach. (From Gundlach et al., 1981; Fig. 

6.) 

persisted along the upper beachface until November 1978. All of the fine-grained 

sand beaches were located along the outer coast, in relatively exposed settings. 

In more sheltered settings, oil will persist longer, but burial is less likely because of 

the low wave energy. Therefore, asphalt pavements may form in such areas if they 

are heavily oiled. In Saudi Arabia and Bahrain, there are asphalt pavements on 

sheltered sand beaches from spills up to ten years old. Because these types of beaches 

are narrow, the pavement can cover nearly the entire beachface. Once a pavement 

forms, it stabilizes the beach sediments to the degree that only very large, infrequent 

waves can slowly erode them. 

3-15
 
Biological utilization of fine-grained sand beaches is usually low because of the lack 

of a stable, solid surface and the abrasive action of the moving sand. Epibiota are 

absent to rare, and infauna are found seasonally in low to moderate densities with a 

low diversity. Of the small, burrowing species, bivalves, polychaete worms, and 

crustaceans make up significant portions of the infaunal community on exposed 

beaches. At certain times of the year, large numbers of shorebirds may be present, 

feeding on these infauna. 

The behavior and short-term impacts of oil on fine-grained sand beaches can be 

summarized as follows: 

On exposed beaches: 

•	 During small spills, oil will concentrate in a band along the high-tide line 

•	 Under heavy accumulations, oil can cover the entire intertidal areas, 

although the oil will be lifted off the lower part of the beach with the 

rising tide 

•	 Maximum penetration of oil into fine-grained sand will be less than 10 cm 

•	 Burial of oiled layers by clean sand within the first few weeks after the spill 

will be limited usually to less than 30 cm along the upper beachface 

•	 Deeper burial is possible if the oil is deposited at the beginning of an 

accretionary period 

•	 Much of the oil will be removed during the next storm 

•	 Biological impacts include temporary declines in infaunal populations, 

which can also affect feeding shorebirds 

•	 The usually hard, compact sediments will support pedestrian and 

vehicular traffic 

On sheltered beaches: 

•	 More of the beachface can be covered because it is narrow 

•	 Even less oil penetration occurs because the sediments are finer and can 

contain small amounts of silt and clay 

•	 There is little to no likelihood of burial, except by wind-blown sand 

•	 Depending on the degree of exposure to any waves, oil persistence can 

increase to months or years 

3-16
 
•	 A moderately rich biological community can be supported 

•	 Asphalt pavements can form under heavy accumulations; pavements 

will change nature and stability of the substrate and thus its biological 

utilization 

Coarse-grained Sand Beaches 

The grain size of sediment on coarse-grained sand beaches ranges between 0.25 and 2 

mm. The more porous sediments allow penetration of oil up to 25 cm (Fig. 3-7). On 

exposed shorelines, the beaches are steeper and softer than fine-grained sand 

beaches, and the width is highly variable. Along more sheltered bays and lagoons, 

the beaches are steep but much narrower and commonly fronted by tidal flats. 

Coarse-grained sand beaches change rapidly in response to changing tidal and wave 

conditions, again as observed first at the Urquiola oil spill. 

The processes are shown in Figure 3-10 and discussed by Gundlach et al. (1978), as 

follows: 

"As oil first came ashore on May 17 or 18, the runnel behind the spring berm 

acted as a trap for incoming oil. Pools of oil several centimeters thick 

remained in the berm runnel for several weeks. As inferred from the 

trenches illustrated in Figure 3-10, the following sequence of events probably 

occurred during and after initial oil impact. Alternative clean and oiled 

layers along the upper portion of the beach indicate that: (1) Oil slicks came 

ashore and were stranded during an accreting stage of spring berm 

development. Oil continued to come onshore as the tidal stage regressed 

toward neap. The neap berm formed as a result of constructional wave 

activity during this tidal stage. (2) Oil deposited at the time rapidly became 

incorporated into the accreting neap berm. (3) Oil pools formed in the neap 

berm runnel as more oil slicks came ashore. As the tidal cycle once again 

advanced toward spring conditions, after neap tides on May 20-23, the neap 

berm was partially destroyed and its sand distributed higher on the beach. (4) 

Oil previously deposited in the runnel of the neap berm was buried during 

this process. Remnants of this deposit are visible as discontinuous layers 

intersecting the beachface at high angles. During all stages, oiled sediment 

3-17
 
was continuously reworked so the main portions of the beach still appeared 

heavily oiled on June 9, almost four weeks after the grounding." 

Figure 3-10. Burial of oil as result of beach-profile changes on a moderately oiled 

medium- to coarse-grained sand beach at the Urquiola spill site (Playa de Doñinos, 

Spain). Numbers refer to chronological sequence of depositional events (discussed 

in text). Trenches are not drawn to scale. (From Gundlach et al., 1978; Fig. 9.) 

Coarse-grained sand beaches pose much greater oil persistence and cleanup 

problems than fine-grained sand beaches because of the deeper penetration and 

rapid burial. The stage of the beach cycle at the time of oil deposition will greatly 

3-18
 
affect the total potential depth of burial. If the oil strands just after a major storm, 

when the beach is at its erosional maximum, rapid depostion of clean sand can bury 

the oil until the next storm or perhaps the next storm season (e.g., in California). 

Figure 3-11 shows sequential profiles from a coarse-grained sand beach at the Amoco 

Cadiz oil spill. Continued deposition of clean sand from March to November 

resulted in burial up to 82 cm. During the Ixtoc 1 spill in Texas, coarse-grained sand 

and shell beaches had a much greater amounts of buried oil than the fine-grained 

beaches (90 percent versus 37 percent, Fig. 3-12). In California, where there is strong 

storm seasonality, oil deposited on beaches in March or April could be buried by 

several meters of clean sediment and re-exposed 6-9 months later, causing re-oiling 

problems for the shoreline and wildlife. 

There is a second mechanism by which oiled layers can be buried by clean sand, 

namely, migrating rhythmic topography. Figure 3-13 shows the process by which 

stranded oil could be buried by this alongshore erosional and depositional pattern. 

This shoreline pattern is most common on beaches with a sustained oblique wave 

approach. 

Because of the mobility of coarse-grained sand beaches, they do not generally 

support a rich biological community. Some animals may be found in association 

with beach wrack, mostly amphipods and insects. Burrowing animals can be 

seasonally low to moderate in densities, but with low diversity and consisting of 

bivalves, crustaceans, and polychaetes. These beaches can be important resting and 

feeding habitat for shorebirds and coastal diving birds. 

3-19
 
Figure 3-11. Burial of oil as result of beach-profile changes on an oiled sand beach at 

the Amoco Cadiz spill site (Brittany, France). The upper diagram shows loss of sand 

from the upper part of the profile in late March. Deposition of new sand on the 

beach between 31 March and 22 April resulted in deep (25 cm) oil burial. The beach 

continued to accrete, and the oiled zone was buried by 82 cm of sand by November. 

(After Gundlach and Hayes, 1978.) 

3-20
 
Figure 3-12. Oil occurrence on coarse-sand/shell-hash versus fine-grained sand 

beaches in South Texas as result of Ixtoc 1 spill. Note predominance of buried oil in 

the coarser-grained beaches Based on examination of 16 stations on 3-6 September 

1979. (After Gundlach et al., 1981.) 

Figure 3-13. Process of oil burial on a beach containing alongshore migrating 

rhythmic topography. This process was observed at both the Metula and Exxon 

Valdez oil-spill sites. (After Hayes and Gundlach, 1975.) 

3-21
 
The behavior and short-term impacts of oil on coarse-grained sand beaches can be 

summarized as follows: 

On exposed beaches: 

•	 During small spills, oil will concentrate in a band along the high-tide line 

•	 Under heavy accumulations, oil can cover the entire intertidal zone, 

although the oil will be lifted off the lower part of the beach with the 

rising tide 

•	 Large amounts of oil can accumulate in the berm runnel where it is 

unable to drain off the beach at low tide 

•	 Penetration of oil into coarse-grained sand can reach 25 cm 

•	 Burial of oiled layers by clean sand within the first few weeks after the spill 

can be rapid, and up to 60 cm or more 

•	 Burial over 1 m is possible if the oil is deposited at the beginning of an 

accretionary period 

•	 Persistence of deeply buried oil could be long, depending upon the season 

of year and beach cycle 

•	 Biological impacts include temporary declines in infaunal populations, 

which can also affect feeding shorebirds 

•	 The sediment can be very soft, making vehicular access difficult 

On sheltered beaches: 

•	 More of the beachface can be covered because it is narrow 

•	 Oil penetration will be less where the sediments are finer and more poorly 

sorted 

•	 Depending on the degree of exposure to any waves, oil persistence can 

increase to months to years 

•	 Burial by clean sand is still significant but less than exposed beaches 

•	 Asphalt pavements can form under heavy accumulations; pavements 

will change nature and stability of the substrate and thus its biological 

utilization 

3-22
 
Gravel Beaches 

Introduction 

Gravel beaches are less well studied than sand beaches and present special problems 

with regard to the behavior and fate of spilled oil that reaches them. The term 

gravel refers to a wide range of grain sizes and is further divided into classes as 

follows: 

Class Size Range 

granule 2 - 4 mm 

pebble 4 - 64 mm 

cobble 64-256 mm 

boulder > 256 mm 

Figure 3-14 is a visual estimate chart which shows the gravel classes. The term 

"rock" is commonly used at spills to refer to gravel, but we recommend that this 

term be restricted to bedrock or possibly large rubble at the base of cliffs. 

Gravel beaches are most common along two types of coastlines–glaciated coasts and 

rocky, mountainous coasts. Coasts now subject to glaciation, such as the southcentral coast of Alaska, typically have gravel beaches along up to 50 percent of their 

lengths. Areas subject to Pleistocene glaciation, including much of the temperate to 

subpolar regime of the Northern Hemisphere, also have abundant gravel beaches 

where the relict glacial deposits are eroding. Erosion of rocky, mountainous coasts, 

such as those that occur on parts of the outer coasts of Washington, Oregon, and 

California, also tends to produce gravel beaches. 

Gravel beaches are complex features. Research on sediment transport on gravel 

beaches is quite limited in comparison with work on sand beaches. Sediment 

transport patterns on gravel beaches are different from those of sand beaches, with 

gravel being transported landward during storms, forming high berms called storm 

berms, rather than being eroded and deposited offshore. Gravel beaches occur in a 

very wide range of energy regimes, with complex geologic and topographic settings. 

Bedrock headlands are usually present, separating isolated gravel beaches. Some 

gravel beaches are located on straight, open shorelines where they are constantly 

subjected to large waves. However, many gravel beaches are exposed to significant 

3-23
 

wave activity only seasonally, and then only when waves approach from a specific 

direction. Under these conditions, 1-2 seasons might pass between mobilizing storm 

events. 

Pure Gravel Beaches 

Controls of Nature of Gravel Beaches. The internal character of waves is one 

of the most important determinants of the nature of gravel beaches. Hayes et al. 

(1991) classified gravel beaches as reflective or dissipative, according to the types of 

predominant wave conditions (Fig. 3-15). Reflective waves break close to the beach 

and are characterized by surging breakers with high run-up and minimum set-up. 

Reflective gravel beaches show clear evidence of size and shape sorting on steep 

beachfaces, have multiple cuspate berms, and a narrow directional width of 

incoming wave angle, which is always shore-normal. Oil deposited on reflective 

gravel beaches could be buried under the developing berms. In contrast, dissipative 

waves typically break tens of meters seaward of the beach and dissipate their energy 

before reaching it. Gravel beaches we classify as dissipate show strong evidence of 

longshore transport, frequent shifts in wave conditions, and limited swell effects. 

Where beaches are host to both wave conditions, dissipative waves are more 

common during storms, with reflective waves more common during calmer 

periods (Fig. 3-15). During dissipative storm wave conditions, spilled oil may be 

carried high into the storm berm environment and penetrate into the coarse 

material above the elevation of normal reworking. 

Morphology and Sediments. Figure 3-16 shows a typical profile for a gravel 

beach exposed to large waves. Note the large, multiple pebble and cobble berms at 

the upper part of the profile and the eroded, wave-cut platform of the lower part, 

which is covered with boulders up to a meter in diameter. The grain-size 

distribution shows the very coarsest material on the outer platform and finer 

material on the depositional berms, with the storm berm being slightly coarser than 

the lower-level berms accreted on its seaward face. 

On some gravel beaches, a stable armor of coarse material develops over the surface 

of the middle and lower portions of the beachface (Michel and Hayes, 1991), as 

illustrated in Figures 3-17 and 18. On a beach which typically has constantly 

changing current velocities, threshold transport conditions for different particle 

sizes are frequently achieved. Also, smaller particles are shielded by larger particles. 

3-25
 
These factors combine to allow intermediate-sized particles to be removed and a 

coarse armor to develop over the finer particles, as shown in Figure 3-17. Once 

armoring is achieved on gravel bars in rivers, a process known as structural 

strengthening occurs (White and Day, 1979), such that a stronger current is required 

to transport the material available (at least one-fourth greater). It is assumed that 

the same type of structural strengthening occurs on armored beaches. 

Figure 3-15. Examples of types of changes in morphology at the same gravel beach 

during dissipative and reflective wave conditions. Dissipative waves prevail during 

storms, and reflective waves are present during calmer periods on gravel beaches of 

this type. Note sites of potential oil burial at base of post-storm, constructional 

berms, a process observed at the Exxon Valdez spill site. (From Hayes et al., 1991; 

Fig. 2.) 

3-26
 
Figure 3-16. Beach profile and distribution of surface sediments for profile PB-1, on 

the outer coast of Montague Island, Alaska. This profile, measured at low tide on 24 

June 1990, is typical of exposed, high-energy gravel beaches in an eroding, retreating 

setting. This area, which was subject to more than three meters of uplift in the 

March 1964 earthquake, has readjusted rapidly because of the constant reworking of 

the beach by large waves. (From Hayes et al., 1991; Fig. 3.) 

3-27
 
Figure 3-17. Process involved in the development of an armored surface of coarse 

material on a gravel beach. The particles of size A are too large to be removed by 

prevailing currents, those of size B are readily transportable, and those of size C are 

sheltered by the larger particles and are not picked up by the current. The C particles 

are on the order of 1 1/2 to 3 times smaller than the A particles. (From Hayes et al., 

1991; Fig. 7.) 

3-28
 
Figure 3-18. Examples of armoring on the beach at Point Helen, Prince William 

Sound, Alaska, on 24 May 1990. Oil from the Exxon Valdez spill occurred 

underneath the armor in trenches A and B. (From Hayes et al., 1991; Fig. 8.) 

Many of the beaches in Alaska are armored, especially on the platforms. The 

trenches illustrated in Figure 3-18 for an armored beach oiled by the Exxon Valdez 

spill demonstrate how subsurface oil is protected below the coarse armor. The 

surface sediments, mostly cobbles, are clean, but the pebble-dominated subsurface 

sediments were still oiled, over a year after the spill. Oil beneath an armored surface 
would tend to remain for a longer period of time than oil buried on an unarmored 

beach, because of the higher velocities required to mobilize the armor. Thus, the 

stable armor shelters subsurface oil from natural removal. For example, on a wellarmored Alaskan gravel beach, sediments at depths greater than 25 cm contained 

10,000 to 18,000 ppm total petroleum hydrocarbons (TPH) in January 1991, nearly two 

years after the Exxon Valdez oil spill (Michel and Hayes, 1991). 

Oil Behavior on Gravel Beaches. A number of special features of gravel 

beaches enhance oil accumulation and preservation during an oil spill. The major 

ones are: 

1) They have high porosity and permeability that allow deep penetration 

from the surface. At the Urquiola spill, fresh oil readily penetrated up to 65 cm in 

gravel beaches (Fig. 3-7). At the Exxon Valdez spill, the oil had formed a thick 

mousse which piled up heavily on the beaches at first, when the cold temperatures 

kept the viscosity high. However, as the days warmed, the oil, which had been 

pooled in places on the surface, literally melted into the beach. The deepest 

penetration observed was 125 cm along the banks of a small stream, although the 

average depth of penetration was around 50 cm. After such oil penetration, the 

issue becomes one of predicting if and when natural processes will remove the 

subsurface oil. 

2) They have a high potential for oil burial by accretional features. Gravel 

tends to be highly mobilized during peak and waning periods of storm activity. The 

finer gravel classes, such as granules, pebbles, and small cobbles, are readily moved 

by normal wave activity. The gravel may be moved onto the beach, in the form of 

berms or swash bars (Figs. 3-15B and 19A), or parallel to the beach, in the form of 

rhythmic topography (Fig. 3-19B). One of the biggest cleanup issues of the second 

year of the Exxon Valdez spill was what to do about deeply buried oil on the Barren 

Islands, where large seabird nesting colonies occur. Berm accretion had buried a 

layer of oil over a meter deep in a gravel beach hundreds of meters long. Later 

erosion would surely release the oil, but no one could be sure when and under what 

conditions. 
Figure 3-19. Two types of potential oil burial at permanently dissipative gravel 

beaches. In both examples, a mass of sediment in motion buries oil deposited at an 

earlier time. Oil burial by migrating rhythmic topography (B) was observed at the 

Metula spill site, and oil burial by migrating swash bars (A) was observed at the 

Exxon Valdez spill site. (From Hayes et al., 1991; Fig. 1.) 

3) The formation of asphalt pavements in sheltered areas is likely where 

accumulations are heavy. Shorelines with gravel beaches tend to be irregular in 

outline, and sheltering from wave action is common. Even on generally exposed 

beaches, there can be microenvironments where oil tends to accumulate, persist, 

and form pavements: in the lee of larger boulders, on tombolos, and in the wave 

shadow of exposed headlands. At the Arrow spill site in Chedabucto Bay, Nova 
Scotia, stranded bunker C oil remained as scattered patches of pavement 20 years 

later (David Kennedy, pers. comm.). During the 1991 multi-agency shoreline survey 

of the Exxon Valdez spill site, small amounts of asphalt pavement could be found 

on nearly every gravel beach in Prince William Sound that had been heavily oiled. 

Because of these factors, gravel beaches pose very difficult cleanup problems. The 

rate of replenishment of gravel is usually very slow, and therefore cleanup by gravel 

removal can increase beach and cliff erosion where it is already a problem. Owens 

(1971) plotted multiple beach profiles at sites in Chedabucto Bay (the Arrow spill) 

where machinery was used to excavate oiled layers in gravel beaches over 1.5 m 

deep. He showed that, on beaches of limited sediment supply, removal of sediment 

caused erosion which was not replenished before the beginning of winter storms. 

Mixed Sand and Gravel Beaches 

As might be expected, mixed sand and gravel beaches have properties of both sand 

and pure gravel beaches. Because of the mixed sediment sizes, there can be distinct 

zones of sand, pebbles, or cobbles. For example, the berm is frequently composed of 

pebbles, surficial patches or stringers of sand can develop on the middle beachface, 

and cobbles usually dominate the lower beachface. The sand fraction can be quite 

mobile, and oil behavior is much like on a sand beach if the sand fraction exceeds 

about 40 percent. 

Mixed sand and gravel beaches are irregular in outline, with rocky points or eroding 

cliffs forming headlands which provide the gravel clasts. Thus, the wave angle can 

be highly variable and rhythmic topography is common, with the associated 

potential for burial of oil by alongshore sediment movement. The gravel 

component can range widely in size and mobility, from highly mobile pebbles which 

form multiple berms, to large cobbles and boulders, which have very low sediment 

mobility and form a stable substrate over which the finer materials migrate. 

Exposure of mixed sand and gravel beaches to significant wave activity can be 

episodic, particularly in places like Puget Sound where narrow channels and 

complex local topography limit fetch and wave height. Persistence of oil on these 

more sheltered beaches will be higher and natural removal processes will be less 

effective. 

Because of sediment mobility and dessication, biological communities in mixed 

sand and gravel beaches are usually depauperate. The lower intertidal zone has the 

most epifauna (on the larger cobbles and boulders) and infauna. 
The degree of oil penetration in mixed beaches is less than in gravel beaches, because 

the finer fractions fill the spaces between the gravel to some degree, although this is 

highly variable. Burial of oil is more likely on mixed beaches, and this oil can 

remain buried for long periods, up to years. One of the best examples of oil 

persistence in mixed beaches was observed at the Metula spill, which occurred in 

1974 in the Strait of Magellan (Hayes and Gundlach, 1975; Blount, 1978; Gundlach et 

al., 1982; Owens et al., 1987). The majority of the shoreline impacted by the Metula 

consisted of mixed sand and gravel beaches, including a wide range of grain sizes 

and wave exposure. There was no cleanup of any shoreline. 

Table 3-1 summarizes the observations made 1-2 years and then 6.5 years post-spill at 

selected locations at the Metula spill site. Within 1-2 years after the spill, exposed 

beaches still retained oil in two areas: 

1) A band of both surface and subsurface oil along the upper beachface and 

above the highest berm crest 

2) A layer of asphalted sediments on the low-tide terrace 

The middle section of the beachface was free of oil on all exposed beaches. The 

subsurface oil remained soft and mousse-like in consistency. On the low-tide 

terrace, thick asphalted sediments ranged in width from 10-100 m. By 6.5 years, oil 

along the upper beachface had been reduced to a few layers, and oil on the low-tide 

terrace had been eroded from all but two stations, which had high currents but low 

wave activity. Figure 3-20 shows comparative profiles of a heavily oiled, mixed sand 

and gravel beach, where oil remained on the upper beachface. After 12 years, 

pavements 0.5 - 1 m in width and 50 to 100 m in length remained on the highest 

parts of the beaches. The consistency of the pavements ranged from soft to hard. 

The persistence of oil on sheltered mixed sand and gravel beaches at the Metula site 

was much different. One to two years after the spill, field teams observed that: 

1) Extensive pavements of asphalted sediments (up to 100 m wide and 700 m 

long) extended from the high-tide line to the toe of the beach 
Table 3-1. Summary of observations at stations revisited during the 1981 survey of 

the Metula spill site. Oil was most prevalent at stations 3, 4, and 6—all located along 

the more sheltered First Narrows area. (From Gundlach et al., 1982.) 
Figure 3-20. Changes in the oil distribution on a sand and gravel beach at the Metula 

spill site between 1976 and 1981 (Strait of Magellan, Chile). The surface oil present in 

1976 was buried by 1981. Wave action had reworked much of the middle beachface 

area, removing the subsurface oil from that zone. However, 6.2 m of the original 19 

m zone of oiled-sediment layers remained in place, seven years after the spill. (After 

Gundlach et al., 1982; Fig. 3A.) 

2) Discontinuous bands and pieces of asphalted sediments were scattered 

throughout the intertidal zone 

3) Most of the oil remained on the surface 

By 6.5 years later, the extensive pavements showed only minor evidence of erosion 

along the upper edge of the pavement. After 12 years, there was still little change. 

Owens et al. (1987) reported that, at the most heavily oiled and sheltered site: 

“...oil is present: (1) in very large volumes (more than 100 m3 in total); (2) 

over the entire area, which includes marsh, sheltered beach and exposed 

beach environments; (3) in all sections of the beach from the low-water level 

to the spring high-water level; and (4) generally as an apparently fresh deposit 

below a weathered surface crust.” 
The behavior and short-term impacts of oil on mixed sand and gravel beaches can be 

summarized as follows: 

On exposed beaches: 

•	 During small spills, oil will be deposited along and above the high-tide 

swash 

•	 Large spills will spread across the entire intertidal area 

•	 Oil penetration into the beach sediments may be up to 50 cm 

•	 Burial of oil may be deep at and above the high-tide berm, where oil tends 

to persist 

•	 Oil can be stranded on low-tide terraces composed of gravel, particularly if 

the oil is weathered or emulsified 

On sheltered beaches: 

•	 Pavements are likely to form wherever heavy accumulations of oil can fill 

the voids between the sediments 

•	 Once formed, these pavements are very stable and can persist for many 

years 

•	 Any oil stranded above the high-tide line will be highly persistant 
Tidal Flats 

Intertidal flats are deposits of sand and/or mud of very low slope that are exposed at 

low tide. The width of the flat is dependent on the tidal range and sediment supply; 

very wide flats are found mostly in macrotidal (TR > 4 m) areas. Tidal flats occur 

along shorelines sheltered from direct attack by large waves, although highly mobile 

sand shoals are common at the mouths of inlets. Thus, compared to beaches, tidal 

flats have slow deposition and erosion patterns. 

Origin and Sedimentation Patterns 

Much of the original work on the sedimentology of tidal flats was done on the 

shoreline of the North Sea, first by Van Straaten in the Wadden Sea, The 

Netherlands, and then by Reineck and colleagues on the tidal flats of Germany. Van 

Straaten published several summary articles (1951; 1954), and Reineck’s work is 

summarized by Reineck and Singh (1975) and several later papers. 

Through a series of detailed studies, van Straaten determined that the Wadden Sea 

can be subdivided into three distinct environments: the marsh (above mean high 

water level), the tidal flat (intertidal zone), and the tide channel (below mean low 

water level). He further subdivided the tidal flat in high flats (between mean high 

water and half tide levels) and low flats (between mean half tide and low water 

levels). The sediments of the high flats are intensely bioturbared, whereas those of 

the lower flats contain mostly physical sedimentary structures, such as ripple marks. 

These environments are illustrated in Figure 3-21, which indicates that the main 

trends in grain-size distribution in the Wadden Sea show a systematic decrease of 

mean size of sand and silt particles and an increase in clay content from the tidal 

inlets toward the estuary shores. The coarsest sediments are thus found on the 

bottom of the largest tidal inlets and the finest on the highest reaches of the tidal 

flats. The same pattern occurs on many other coastlines of the world, for example 

the mesotidal components of the coasts of South Carolina/Georgia, Alaska, 

California, and Puget Sound. 

The problem of why large quantities of mud accumulate on the upper reaches of the 

tidal flat is an interesting one. Van Straaten and Kuenen (1957) indicated that much 

of this mud is deposited at ebb just before water is drawn away. Postma (1967) 

proposed that a combination of settling lag and scour lag moves fine-grained 
Figure 3-21. Sheltered tidal flat region of the Wadden Sea, The Netherlands. (After 

Van Straaten, 1951.) 

sediments up into the estuary. These processes, which are shown diagrammatically 

in Figure 3-22, were described as follows by Nichols and Biggs (1985; p. 138): 

“Settling lag effect. The diagram ..(in Fig. 1-22).. shows the velocities with 

which different water masses move with the tides at each point along a 

section through a tidal inlet (left) to the shore (right). Although the tide at 

fixed points is assumed to be symmetrical, the distance-velocity curves are 

asymmetrical. A water mass moves in and out along one such curve. The 

tangent (P) represents the maximum current velocity in each point and meets 

each curve at a point attained by the water mass at half tide. The curves apply 

only to idealized average conditions, and scour lag is neglected. 

A particle at point 1 is taken into suspension by a flood current (water 

mass at A) of increasing velocity and starts to settle toward the bottom at point 

C, when the current still has a velocity equal to 2. While settling, the particle 

is carried farther inland by the still flooding currents and reaches the bottom 

at point 5 while the water has a velocity at point 4. 
Scour lag effect. After the turn of the tide, the particle cannot be eroded by 

the same water mass (AA’) because this water parcel attains the required 

velocity later at a point beyond the particle toward the inlet. The sediment 

particle is therefore eroded by a more landward water mass (B’) and is 

transported toward the inlet to point B. At 7, it starts to drop out of 

suspension and reaches the bottom at point 9. During one tidal cycle, the 

particle has therefore been transported landward from point 1 to 9. After a 

number of these landward transport cycles, the particle may reach a point 

where it cannot be entrained by subsequent ebb flow currents because of the 

landward decrease of the average velocity of the tidal current (after Postma, 

1967, and Van Straaten and Kuenen, 1957).” 

Figure 3-22. Diagram of the settling lag and scour lag effect in estuaries as described 

by Postma. (From Nichols and Biggs, 1985; Fig. 2-39.) 

Eventually, the fine sediments reach the tidal flats. 

Flocculation and aggregation of suspended silts and clays is another process that aids 

in the buildup of muddy sediments in estuaries (and ultimately on tidal flats). 

Examples of sizes and groups of flocculated particles are given in Figure 3-23. 

In order for flocculation to occur, the suspended particles must be brought together 

(i.e., collide) and stay together (i.e., cohere). Collision is enhanced in waters with 

large volumes of suspended sediments, and the natural forces that tend to repluse 

fine particles from each other are destabilized by high concentrations of cations, 
Figure 3-23. Schematic sequence of typical structures and size of flocculated fine 

sediments (flocs) and groups of flocs. (From Nichols and Biggs, 1985; Fig. 2-41.) 

such as Ca++, Mg++, and Na+ (Nichols and Biggs, 1985). Both of these conditions 

are met in estuaries, where sediment-laden stream waters mix with the “salt wedge” 

of marine water that moves into the estuary on a rising tide. 

Once the mud is deposited on a tidal flat, it tends to remain there because: 

1) The mud dries out. 

2) Burrowing organisms tend to stabilize the mud. 

3) Diatoms move up through the mud and deposit slime. 

4) Much higher velocities are required to erode consolidated mud than those 

at which it was deposited, as illustrated by the diagram in Figure 3-24. 

In some instances, mud is trapped between plants on the flat. Another factor of 

prime importance to mud deposition is the super-abundance of the suspensionfeeding organisms on the flats, such as oysters and clams. During the filtering 

process, these organisms compress the finely divided clay particles and bind them 

together in their intestines as fecal pellets. Another part of the suspended matter is 
Figure 3-24. Sediment erosion, transport, and deposition regimes for mean current 

velocities versus grain size. Solid lines represent critical velocities required for 

erosion, transport, and deposition of bed sediment while dashed lines represent 

extrapolated trends. Lines A-C are critical velocities for various stages of 

consolidation represented by decreasing water content. Adapted from Hjulstrom 

(1939) and Postma (1967); by Nichols and Biggs (1985; Fig. 2-17). 

coagulated in their gills and pushed back into the water as pseudo-feces. These feces 

and pseudo-feces are easily deposited, even in comparatively turbulent water (Van 

Straaten and Keunen, 1957). This process of mud accumulation is clearly evident 

around the oyster mounds on the tidal flats of the South Carolina coast (Hayes and 

Sexton, 1989). 

For oil-spill planning, tidal flats are divided into two types: exposed and sheltered. 

Exposed Tidal Flats 

Exposed tidal flats can be characterized as follows: 

•	 They are composed primarily of sand and mud (silt and clay), though in 

Alaska they can have a large gravel component 
•	 The presence of sand indicates that tidal or wind-driven currents and 

waves are strong enough to mobilize the substrate 

•	 They are always associated with another shoreline type on the landward 

side of the flat 

•	 There may be low sand ridges slowly migrating over the flat surface 

•	 The sediments are water-saturated, with only the topographically higher 

ridges and bedforms drying out during low tide 

•	 The sediments are compact and may support pedestrian and vehicular 

traffic in some areas 

•	 Biological utilization can be very high, with varying numbers of bivalves, 

macroinvertebrates, and polychaetes 

•	 Birds utilize exposed flats as roosting and foraging areas 

The behavior of oil on exposed tidal flats has been studied at several major spills. At 

the Metula site, oil slicks moved across wide flats (up to 10 km wide) and 

accumulated only at the landward edge of the flat (Blount, 1978). The oil remained 

on the surface, penetrating only a few centimeters, and there was no burial after 1.5 

years. Because the wide flats attenuate nearly all the wave energy, the oil eventually 

formed into a thin pavement or crust which remained unchanged for 6.5 years. At 

the Urquiola spill, oil was observed to pass over the flats and accumulate on the 

adjoining beach. At low tide, heavy oil slicks covered the flat, but the rising tide 

would lift the oil off and push it across the flat. No long-term deposition of oil on 

the flats was observed, although the surface sediments were lightly stained early in 

the spill. Biological impacts were significant, with over 70 percent mortality of 

cockles. At the Amoco Cadiz spill, heavy oil slicks passed across the flats; oiled 

sediments occurred on the tidal flats only where cleanup crews had dug trenches 

and pits for oil collection. Where high densities of bivalves occupied the flats, there 

were mass mortalities. 

The only spill where significant contamination of exposed tidal flats has been 

reported is along the Saudi Arabian coast where the Gulf oil spill innudated the 

shoreline for 500 km. The oil coverage on the tidal flats was nearly 100 percent, as of 

May 1991. This spill was unique in that onshore winds kept extremely large slicks 

piled up against the shoreline for months. Eventually, the oil adhered to the 

intertidal sediments. But, the oil did not penetrate the sediments very deeply; in 
most cases, the oil was less than 5 cm deep, with a thin surface oil crust (Michel, 

1991). Also, the oil did not completely fill the pore spaces, a condition that tends to 

result in formation of asphalt pavements, which would slow natural removal rates. 

Instead, the oiled sandy sediments showed permeability to water, which should 

speed removal by flushing and weathering by degradation. The surface crust had 

been ripped up and flipped over in some places, indicating that the flats were being 

exposed to tidal current energy. Tidal currents draining off the wide flats were 

generating enough energy to lift the oil crust and mobilize the sediments, providing 

an important "self-cleansing" mechanism. 

Based on observations at many spills, the behavior of oil on exposed tidal flats can be 

summarized as follows: 

•	 Oil does not usually adhere to the surface of exposed tidal flats, but rather 

moves across the flat and accumulates at the high-tide line 

•	 Heavy accumulations will cover the flat at low tide 

•	 Oil does not penetrate the water-saturated sediments 

•	 Biological impacts can be severe, primarily to infauna, thereby reducing 

food sources for birds and other predators 

Sheltered Tidal Flats 

Sheltered tidal flats can be characterized as follows: 

•	 They are composed primarily of silt and clay 

•	 The sediments are very soft and cannot support even light foot traffic 

•	 Wave energy is very low, although there may be strong tidal currents 

active on parts of the flat and in channels across the flat 

•	 They are usually fronted by marshes 

•	 They have a dense and diverse infauna, which is highly utilized by birds 

Sedimentation on sheltered tidal flats results from deposition of sediment from 

suspension, which occurs primarily during periods of slack high water. The upper 

tidal flat is a zone of higher rates of accumulation of finer-grained material due to 

"differential time of inundation and submergence ...during a tidal cycle, associated 

changes in bottom-current velocities of tidal currents during a tidal cycle (being 
therefore concentrated over the low-tidal flats), and the dominance of suspension 

processes near the time of high tide and slack water, which favors preservation of 

mud in high-tidal flats." (Klein, 1985). The processes of flocculation and 

scour/settling lag, described above, are also important in the partitioning of 

sediment sizes along sheltered tidal flats. 

Sheltered tidal flats become contaminated by direct contact with oil slicks and by 

deposition of contaminated suspended sediments. During the Amoco Cadiz spill, 

large waves dispersed the oil into the water column, both as the oil exited the ship 

and when storm waves eroded the oil from exposed beaches. During the first three 

weeks, about 20,000 metric tons of oil were estimated to be incorporated into the 

water column (Gundlach et al., 1983). This oil sorbed onto suspended sediments 

which were then deposited onto sheltered tidal flats; oiled intertidal sediments were 

found in sheltered bays which never received any surface slicks. Oil removal and 

weathering rates were slowest in very fine-grained sediments. 

Based on observations at many spills, the behavior of oil on sheltered tidal flats can 

be summarized as follows: 

•	 Oil does not usually adhere to the surface of sheltered tidal flats, but rather 

moves across the flat and accumulates at the high-tide line 

•	 Very heavy accumulations will cover the flat at low tide 

•	 Oil will not penetrate the water-saturated sediments at all 

•	 In areas of high suspended sediments, sorption of oil can result in 

contaminated sediments that can be deposited on the flats 

•	 When sediments are contaminated, oil will persist for years 

•	 Biological impacts can be severe 

Sheltered Rocky Coasts 

Sheltered rocky coasts encompass many types and sizes of substrates. Included in 

this general class are: 

•	 Vertical bedrock cliffs, such as along fjords 

•	 Wide, rocky ledges which may be strewn with boulders 
•	 Rocky, rubble slopes which are formed by passive accumulation of sand to 

boulder-sized talus on bedrock slopes 

The only common factors among these diverse shoreline types are a hard substrate 

and the absence of significant wave or tidal energy. Otherwise, there can be wide 

variations in the width of the intertidal zone and the degree of "permeability" of the 

rocky substrate. Because of the low wave energy, there is little sorting of sediments, 

so the substrate is a jumbled mix of grain sizes, from boulders to clay. This poorly 

sorted mixture usually does not allow deep penetration of oil into the subsurface. 

But, then, where is the “surface” on a shoreline with boulder- and cobble-sized 

rubble layer overlying an irregular bedrock platform with patches of muddy sand 

and granules? 

Without substrate mobility, the hard, rocky surface can be heavily colonized by a 

rich epifaunal community in the mid to lower intertidal zone, including algae, 

mollusks, and snails. On steep, sheltered bedrock shores, the intertidal zone can be 

nearly vertical; zonation patterns for attached epifauna have sharp boundaries 

because of the lack of waves to smear the zones over a wider area. Tidal pool 

communities are uncommon and small. Concrete seawalls are the man-made 

equivalents of this shoreline type. 

Oil tends to readily adhere to the dry rock surface, particularly along the high-tide 

line where there are little to no attached organisms and the rock dries for longer 

periods. During the Exxon Valdez spill, many miles of sheltered vertical bedrock 

shores were heavily oiled in this manner. Only infrequently did oiling of the mid to 

lower intertidal zone occur. It seems that oil did not adhere to the wetter, heavily 

colonized surface of the lower half of the intertidal zone, but rather the oil lifted off 

these surfaces with the rising tide. 

On sheltered, vertical rocky shores, oil will: 

•	 Adhere readily to the rough rocky surface, particularly along the high tide, 

forming a distinct oil band 

•	 The lower half of the rock face usually stays wet enough to prevent oil 

from adhering and remaining 

•	 Heavy oils and weathered oils can cover with upper zone with little 

impacts to the rich biological communities of the lower zone 
•	 Fresh oil and light refined products have high acute toxicities which can 

affect attached organisms after even short exposures 

On sheltered, bedrock ledges, the intertidal zone can be very wide. The surface can 

be covered with a wide range of grain sizes, but the bedrock ledge is the dominant 

substrate type. There can be some evidence of sorting of the sediment veneer, 

especially at the high-tide line where a small mixed sand and gravel beach can form. 

But the frequency of wave action is very low, at the most 1-2 times per year. In very 

sheltered settings, the rock ledge can be covered by a thin layer of weathering residue 

that fills in the cracks and crevices on the uneven rock surface. 

Oil stranding on this shoreline type can coat the surface and penetrate this surface 

residue. Oil penetration will be limited by the depth of the intact bedrock surface. 

But it should be noted that rock fractures can be 10-20 cm deep and are common sites 

of oil pooling and persistence. Figure 3-25 shows a sketch, profile, and grain-size 

cover for a typical sheltered rocky ledge in Alaska. Note that the surface is covered 

by a thick layer of angular debris. The oil on this shoreline eventually formed a 

patchy asphalt pavement covering the upper one-third of the ledge. This specific 

site was not cleaned, as part of a research program to monitor the effectiveness of 

different treatment techniques versus natural recovery. Without any cleanup, 

heavy patches of oil have remained and formed pavements three years post-spill. 

The oil coating on the rock surfaces has dried, started to crack, and has been reduced 

by about 50 percent in 2.5 years. However, oil in the rock crevices and below the 

surface boulders has not changed at all and remains relatively fresh. 

The biological utilization of these rocky ledges can be very high, with dense growth 

of algae and associated epifauna. Tidal pools can be common, and there can be a rich 

underrock community. When heavily oiled, the lower intertidal areas can be 

covered by oil trapped in low areas and pools on the irregular rock surface during 

the falling tide. If the oil is weathered and sticky, it can eventually strand, 

penetrating into the small accumulations of sediments on the rock surface. Seldom 

have we seen oil adhering to bedrock on the lower intertidal zone; the surface stays 

too wet and the oil is lifted off with the rising tide. 
Figure 3-25. Example of a sheltered rocky ledge oiled during the Exxon Valdez spill, NOAA’s 

station N-6 in the Bay of Isles, Prince William Sound. A) Beach sketch. A permanent 

topographic profile was run down a small draw between two bedrock highs. Note barnacle and 

mussel zones on lower half of the rock face. 
Figure 3-25. Continued. B) Topographic profile, illustrating the 

steepness of the profile. C) Surface sediment distribution pattern 

based on grain size estimates at eight of the survey points along the 

profile (circles shown in B). Note slight increase in size down the 

slope. This surficial debris is angular and poorly sorted, which 

indicates little transport by wave action. 
On wide, rocky ledges, oil will: 

•	 Adhere readily to the rough rocky surface, particularly along the high tide, 

forming a distinct oil band 

•	 If a beach is present, the oil will penetrate the sediments, with long-term 

persistence very likely 

•	 Fractures in the bedrock surface are sites of oil pooling and persistence 

•	 Even for wide ledges, the lower intertidal zone usually stays wet enough to 

prevent oil from adhering to the rock surface 

•	 Heavy oils and weathered oils can persist on the lower intertidal zone by 

penetrating surficial sediments 

•	 Fresh oil and light refined products have high acute toxicities which can 

affect attached organisms after even short exposures 

Sheltered rocky rubble slopes have the greatest potential for long-term persistence of 

oil. These shoreline types are relatively steep and short. The bedrock surface can be 

covered with a thick veneer of poorly sorted materials, which can vary greatly in 

degree of permeability. Figure 3-26 shows a sketch, profile, and surface oil coverage 

for a rubble slope from Prince William Sound, which was set aside and never 

cleaned. Note that the oil stranded only on the upper zone, with 100 percent 

coverage in September 1989, six months after the spill. By September 1990, surface 

oiling had been reduced to a maximum of 30 percent coverage. Again, most of the 

oil on the undersides of the rubble remained. 

Most of the time, the subsurface is very tightly packed and the oil penetrates only the 

top few centimeters. Without oil removal, pavements are formed. However, on 

this surface can be large boulders, and oil will be deposited in the open spaces 

between the boulders and at the base. It is nearly impossible to cleanup this oil and 

natural removal rates are extremely slow. 

Another problem area on these rubble slopes is where they are covered with a loose 

assemblage of debris, which can be very permeable. Oil pooled on these slopes can 

penetrate deeply, up to 50 cm. At the site shown in Figure 3-26, fresh-looking oil 

remained at depths of 30 cm as of September 1991, 2.5 years later. Detailed chemical 

analysis of the oil showed that it had weathered very little. 
Figure 3-26. Example of a sheltered rubble slope that was oiled by the Exxon Valdez spill, 

NOAA’s station N-13 in Herring Bay, Prince William Sound. A) Field sketch. The 

contrasting sediment types and slopes of the two subdivisions of the profile, angular taluslike material on the steep rubble slope and finer material on the flatter bay bottom, are 

evident. Oil cover as high as 50 percent was still present on the upper portion of the 

rubble slope on 27 May 1990, over one year after the spill. 
Figure 3-26. Continued. B) Topographic profile, illustrating the clear 

break between the rubble slope and the raised bay bottom. The 

distribution of oil coating (in percent) is also shown. C) Plot of the 

distribution of surface oil coverage between September 1989 and 

September 1990, based on visual estimates. 
On sheltered rubble slopes, oil will: 

•	 Adhere readily to the rough rocky surface, particularly along the high tide 

line, forming a distinct oil band 

•	 Penetrate into the crevices formed by the surface rubble and pool at the 

contact of the rubble and the surface 

•	 Form pools and eventually pavements under heavy oiling 

•	 Penetrate deeply into loosely packed rubble, causing long-term 

contamination of the subsurface sediments 

Marshes 

Depositional shorelines sheltered from wave action have a range of intertidal and 

supratidal environments, from barren saline flats (sabkhahs) to mangrove forests, 

depending mainly on the coastal climate. Some examples are given in Figure 3-27. 

This discussion is limited to marshes, which, as defined here, are restricted to 

wetlands containing emergent, herbaceous vegetation. Thus, they include salt, 

brackish, and freshwater marshes. But, the emphasis in this section is on marshes 

bordering water bodies such as estuaries, bays, lakes, and rivers, where floating oil 

slicks can impact the vegetation. 

Marshes of the Southeastern USA 

The estuaries on the coasts of South Carolina and Georgia are host to one of the 

most extensive developments of salt, brackish, and freshwater marsh systems in the 

USA. Many excellent, detailed studies of these marshes allow them to be used as a 

general model of marsh ecology and sedimentation. These marshes are well 

documented as being the primary food source for the coastal and nearshore 

ecosystem of the region. The importance of protecting these systems during oil 

spills, both in the southeastern USA and elsewhere, cannot be overemphasized. 

Brackish and salt marshes originate as tidal flats that are sites of relatively quiet 

water deposition at the high-tide line. As the flat is built up to or slightly above man 

sea level, marsh grasses take root. Once grasses grow on the flat, the sedimentation 

process is accelerated because of the baffling effect of the plants. 
Figure 3-27. Relationship of coastal vegetation zones to geomorphic zones in a 

variety of climatic and physical settings. Profiles are diagrammatic and not to scale. 

(From Davies, 1973; Fig. 125.) 
These marshes are, in effect, intertidal flats well-vegetated with halophytes (a plant 

that grows in salty soil; Basan and Frey, 1977). Marshes can prograde very rapidly, up 

to several cm/year, if the slope is flat and sediments are abundant. 

For purposes of description, estuaries are usually subdivided into upper, middle, 

and lower zones. Freshwater marshes are most common in the upper estuary, 

where there are tides but very low salinities; brackish marshes occur in the middle 

estuary, where salinities generally average less than 15 parts per thousand (ppt); and 

salt marshes occur in the lower estuary, where salinities range from 15 ppt to the 

low 30s. 

Lateral salinity changes up and down the estuary have a striking impact on the plant 

communities. Giant cordgrass (Spartina cynosuroides) is a conspicuous plant along 

the banks of the channels in both the upper and middle estuaries. Black needlerush 

(Juncus roemerianus) is by far the most common plant in the middle estuary, 

covering many thousands of acres in each estuary, and smooth cordgrass (Spartina 

alterniflora) dominates the lower estuary. See Figure 3-28 for a delineation of the 

distribution of the more conspicuous plants throughout estuaries of Georgia and 

South Carolina. 

The lower reaches of the estuaries and landward margins of barrier islands of 

Georgia and South Carolina are bordered by salt marshes dominated by smooth 

cordgrass (Spartina alterniflora). The typical marsh profile found throughout the 

area is given in Figure 3-29. Most experts agree that plant distribution in the 

marshes is controlled by depth and duration of flooding (Barry, 1980); therefore, it is 

convenient to divide these marshes into a regularly flooded low marsh, the zone 

between mid-tide and neap high tide, and an irregularly flooded high marsh, which 

occurs roughly between neap and spring high tides. 

Spartina alterniflora is the only plant that normally occurs in the low marsh zone, 

which is flooded 2-14 hours/day and has soil salt concentrations of 0.5-3.2 percent 

(Barry, 1980). The Spartina is usually quite tall (2-3 m at full growth) in the lower 

half of the profile (e.g., on creek banks and levees), but becomes dwarfed (10-50 cm) 

in the higher areas (e.g., between drainage creeks; behind levees). The reason for 

these differences in height is still a matter of conjecture. 
Figure 3-28. Occurrence of the most conspicuous plants in the marshes of the upper 

(fresh), middle (brackish), and lower (saline) parts of the estuaries of South Carolina 

and Georgia. (Modified after Stalter, 1974.) 

Figure 3-29. Typical profile of the salt marshes of South Carolina and Georgia. 

(Modified after Teal, 1958.) The “Minax marsh” zone is named after the dominant 

species of fiddler crab found there, Uca minax. The dominant plant is extremely 

short Spartina alterniflora. 
At the lower elevations of the high marsh, zones of glasswort, or pickleweed 

(Salicornia virginica), sea oxeye (Borichia frutescens), and saltgrasses (Distichlis 

spicata) grow in soils with salt concentrations of 0.3-3.0 percent that are usually 

flooded daily. The upper high marsh, which is flooded mostly by spring tides, may 

be populated by Juncus roemerianus, in areas of lower salinity, and plants such as 

marshay cordgrass (Spartina patens), marsh elder (Iva frutescens), or sea myrtle 

(Baccharis sp.), in more saline areas. 

Sediments in these marshes are typically muddy, and grain size decreases from the 

tidal channels to the highest portions of the marsh, except where runoff washes 

sand from adjacent sandy barrier islands or beach ridges onto the upper marsh 

(Edwards and Frey, 1977). Marsh sediments are always highly bioturbated, frequently 

being riddled with crab burrows (e.g., fiddler crabs; Uca sp.), having much the 

appearance of Swiss cheese. 

The marsh sediments are commonly rich in organic matter, but they should not be 

referred to as “peat” unless the organic matter exceeds 70 percent of the sediment (by 

weight). Bona fide peat deposits rarely occur along tidal channels at the outer fringe 

of the marsh, where oil-spill impacts more often occur. Where peat does occur in 

estuarine marshes of the southeastern USA, it is usually found in the remotest, 

most freshwater portion of the marsh (e.g., in Snuggedy Swamp, South Carolina; 

Hayes and Sexton, 1989). 

Marshes of California 

In California, coastal wetlands are highly variable, depending upon the amount and 

frequency of freshwater influence. Southern California marshes are confined to 

narrow stream outlets with freshwater contribution only during the brief winter wet 

season (which can be completely missed during droughts). Thus, hypersaline 

conditions and salt-tolerant species dominate. Figure 3-30 shows a checklist of 

species within southern California salt marshes and Figure 3-31 shows the 

distribution of the most common halophytes by elevation. Soil salinity is the most 

important factor affecting salt marsh vegetation in Southern California (Zedler, 

1982). Figure 3-32 shows a vegetation-succession model for Southern California 

marshes. The mature vegetation has Spartina foliosa restricted to the lower marsh, 

with the more salt-tolerant and opportunistic Salicornia virginica dominating the 

upper marsh. 
 

Figure 3-30. Check list of species within salt marshes of southern California wetlands. Data 

are cumulative lists from a variety of sources, including observations of W. Ferrens (UCSB 

Herbarium) and J. Zedler. Wetlands with a history of good tidal flushing are boxed on the 

right-hand column. (From Zedler, 1982.) 
Figure 3-31. Distribution of the most common halophytes by elevation, at Tijuana 

Estuary. Data from Anaheim Bay were used to extend the ranges of species beyond 

the 3- to 12-dm MSL range observed at Tijuana Estuary. (From Zedler, 1982.) 
Figure 3-32. Conceptual model of species establishment and spread in southern 

California salt marshes. (From Zedler, 1982.) 
San Francisco Bay and the Sacramento-San Joaquin River Delta have a diverse and 

variable salt marsh community, with about 125 species of vascular plants reported in 

the area. The following summary of the distribution of species is from Atwater et al. 

(1979). 

Common pickleweed (Salicornia pacifica) and California cordgrass dominate the 

tidal-marsh vegetation of the Bay, with common pickleweed monopolizing the 

vegetation at elevations near and about MHHW. Other common plants include salt 

grass (Distichlis spicata), marsh Grindelia (Grindelia humilis), halberd-leaved 

saltbush (Atriplex patula), alkali heath (Frankenia grandifolia), and fleshy Jaumea 

(Jaumea carnosa). California cordgrass fringes tidal-marsh plains where they 

descend into mudflats; near MTL it forms pure stands. Common tule (Scirpus 

acutus), Olney’s bulrush (Scirpus olneyi), common reed (Phragmites communis), 

and cat-tails (Typha sp.) dominate islands of pristine marsh in the Delta. The tidal 

marshes of San Pablo Bay, Carquinez Strait, and Suisun Bay represent complex 

transition communities, which are even more complex because of long-term 

changes in salinity from water diversions and multi-year droughts. There can be 

gradual changes in soil salinities during droughts which favor or discourage certain 

species. 

Behavior of Oil in Marshes 

Most of our experience comes from the study of spills affecting vegetation under 

tidal influence in coastal estuaries. And most of the studies have been of marshes 

dominated by Spartina, sp. Based on the available data, there are significant 

differences among species assemblages. 

When oil comes in contact with a marsh in a tidal setting, it generally behaves in 

the following manner: 

•	 Oil adheres readily to the vegetation; in fact, marsh vegetation is a very 

effective oil sorbent. 

•	 The band of coating will vary widely, depending upon the tidal stage at the 

time that the oil slicks are in the vegetation. There can be multiple bands. 

•	 Large slicks will persist through multiple tidal cycles and coat the entire 

stem from the high-tide line to the base. 
•	 Fresh crudes and heavy oils will tend to “slide” down the stem over time 

in warmer weather and pool on the sediments at the base of the plant. 

•	 Weathered oils do not “slide” as much; the oil stays on the vegetation. 

•	 If the vegetation is thick, heavy oil contamination can be restricted to the 

outer fringe, with penetration and lighter oiling up to a 10 m width. 

•	 Lighter oils (light refined, fresh crudes) can penetrate deeply, to the limit of 

tidal influence. 

•	 Medium to heavy oils do not readily adhere to or penetrate the wet, 

muddy sediments, but they can pool on the surface and in burrows. 

•	 Light oils can penetrate the top few cm of sediment and deeply into 

burrows and cracks (up to 100 cm). 

Factors Affecting the Impacts of Oil on Marshes 

Although every spill is a unique combination of events, there are several factors 

which affect the behavior and impact of the oil on the marsh ecosystem: 

1) Oil type 

2) Extent of contamination of the vegetation 

3) Degree of contamination of the sediments 

4) Exposure to currents and waves which effects the speed of natural removal 

5) Time of year of the spill 

6) Species sensitivity 

7) Damages associated with cleanup activities 

Impacts by Oil Type 

It has been shown that light refined products have the greatest acute toxicity to 

marsh vegetation, when compared to other types of oil. 

Spill/Experiment	 Observations 

Florida barge, No. 2 fuel oil Spartina killed; no regrowth after 16 mo. where 

(Burns and Teal, 1979) sediments had > 2,000 ppm fuel oil 
Bouchard No. 65 barge, No. 2 fuel Total mortality of Spartina and Salicornia; no 

oil, Buzzards Bay, MA reseeding or rhiozome growth in 3 yrs in zone 

(Hampson and Moul, 1978) heavily oiled; 2-4x slower growth elsewhere. 

Erosion rates were 24x greater in oiled areas. 

Four oil types tested on Spartina All oils caused mortality within 3 weeks; after 5 

(Alexander and Webb, 1983) mo., only plots with No. 2 fuel oil had reduced 

growth of plants, compared with 2 crudes and 

No. 6 fuel oil. 

In contrast, observations of spills of crude oils and heavy refined products show 

mostly short-term impacts, and recovery within 1-3 years (Baker, 1971; Baca et al., 

1985; 1977; Bender et al., 1980; Michel, 1989). There are even studies which show that 

an increase in standing crop of the marsh grass occurs following some spills 

(Hershner and Moore, 1977). Crude oils contain nitrogen, and when nitrogen is 

limiting, there can be growth simulation under some conditions (Leendertse and 

Scholten, 1987). However, the net impact is always negative. 

Extent of Vegetation Contamination 

The extent of vegetation contamination is another very important factor. Many 

plants can survive partial oiling; few survive when all or most of the stem is coated. 

Examples from the literature are: 

Spill/Experiment Observations 

Cape Fear River, NC, No 6 fuel After 5 mos., lightly oiled Spartina had 

oil (Baca et al., 1983) recovered; heavily oiled areas showed reduced 

no. of plants/m2 and sediment oiling. 

Four oil types tested on Spartina Highest mortality was observed in plots 

(Alexander and Webb, 1983) where oil was applied to entire plant surface, 

compared to on the sediment and lower plant 

Field oiling with crude oil on No initial mortality or difference in aboveSpartina stems, not leaves ground biomass or stem density for 2 growing 

(DeLaune et al., 1979) periods. 

Degree of Sediment Contamination 

The degree of contamination of sediments is another very important factor, which 

can prolong impacts to marsh ecosystems for many years, compared with the initial 

loss of oiled vegetation. Slower recolonization rates are frequently related to 
hydrocarbon levels in the sediments, though it should be noted that the 

composition of the oil is as important as the total petroleum content. That is, 

fresher oil and refined products have higher percentages of the more toxic fractions 

in oil, whereas heavy oils have lower initial and long-term toxicities. Examples are: 

•	 5,000-50,000 ppm of a light crude slowed growth of Spartina for 18 months 

in field oiling experiments. Growth was unaffected at lower 

concentrations (Alexander and Webb, 1987). 

•	 No regrowth of Spartina in sediment with >2,000 ppm No. 2 fuel oil 

following the Florida spill (Burns and Teal, 1979). 

•	 In 2-year studies of restoration through sediment stripping following a No. 

6 fuel oil spill in the Potomac River, Krebs and Tanner (1981) found: 

-Little impacts to vegetation at concentrations <2,000 ppm 

-Rhizome death and no regrowth at concentrations >10,000 ppm. 

Exposure 

The physical setting of the oiled marsh, relative to exposure to waves and currents, 

is one of the most important factors controlling the persistence of oiled vegetation 

and overall rate of recovery. Exposure can work to speed recovery, but, in some 

cases, it can also work to increase erosion after plant roots die and before new growth 

can occur. 

Oil deposited along the outer fringe is removed as the vegetation dies back and is 

exported. There are many examples of oiled vegetation along tidal rivers where, 

after one season, there is no visual evidence of oiled vegetation or sediments. Boat 

wakes, river currents, and tidal flushing are important natural removal processes, 

and they are usually much more effective than any man-made cleanup. In contrast, 

oil spilled in interior settings, such as from pipelines crossing wide marsh or swamp 

areas, have no physical removal mechanisms, and the oil can only weather in place 

or be removed by cleanup efforts. 

Seasonal Effects 

The timing of an oil spill, relative to the plant’s growing season, can affect the 

nature and duration of the spill impact. In general, oiling during the dormant 

winter season has the lowest impact, whereas oiling of vegetation during the 

summer growing season had longer effects. The mechanisms responsible for the 

slower recoveries from a spill during the growing season have not been adequately 
studied, but probably are related to plant stress at a time when the plant’s resources 

are being fully expended. For example, oiled plants rarely flower and oiled flowers 

do not produce seed (Baker, 1979), resulting in loss of the year’s seed production. 

Alexander and Webb (1985) found that, in experimental plots, the time of year the 

oil was applied did not influence the response of Spartina to oil when it was applied 

to sediments and the lower portions of the plants; however, when the entire plant 

surface was oiled, impacts were greater for a May versus a November oiling. 

If oil persists, then there can be delayed impacts to marshes. Thomas (1977) reported 

delayed toxicity of heavy surface oiling by No 6 fuel oil to Spartina the second year 

after the Arrow spill in Chedabucto Bay. 

Species Sensitivities 

There are some known variations in sensitivity among species, however, very little 

else is known about other species. In general: 

•	 Annuals are less resistant than perennials, which have large roots systems 

that allow them to regrow after damage to aerial portions (Getter et al., 

1984); for example, the annual Salicornia is less resistant than other 

species, such as Spartina, to oil spills (Baker, 1971) 

•	 Juncus is more resistant than Spartina to chronic spills (Lytle and Lytle, 

1987) 

Impact of cleanup 

Sometimes, the greatest impact of an oil spill on a marsh is a result of the cleanup 

efforts. The greatest damages derive from: 

•	 Destruction of the root system by trampling 

•	 Mixing oil deeper into the sediments, slowing weathering and removal 

•	 Removal of surface sediments suitable for supporting new growth 

•	 Smothering of vegetation by mobilized sediments 

•	 Exposure of the interior of the plant to toxic substances in the oil 

Nowadays, responders are very sensitive to causing more harm during cleanup than 

what will result from the oil alone. Most of the time, very little cleanup is 

conducted in marshes, other than passive collection of oil onto sorbents. However, 

there are two conditions where cleanup can be warranted: 1) when heavy oil has 

pooled in a marsh sheltered from natural removal processes, and 2) when other 

uses or resources present are at risk from leaving the oil in place. The biggest 
controversy is over cutting of the oiled vegetation. Again, most all of the experience 

is vegetation cutting is of Spartina along the east and Gulf coasts. The literature is 

summarized below. 

Spill/Experiment Observations 

Cape Fear River, NC, No 6 fuel After 15 mos., uncut Spartina, Scirpus, and 

oil (Baca et al., 1985) Phragmites showed good recovery; cut Spartina 

showed no recovery. 

Four oil types tested on Spartina Clipped plots showed regeneration by growth of 

(Alexander and Webb, 1983) new stems and seedlings, but No. 2 fuel oil and 

Light Arabian crude inhibited stem emergence. 

Crude oil spill, TX into sheltered 6 mos. later, only heavily oiled vegetation 

Spartina marsh showed impacts; clipped areas showed slightly 

(Holt at al., 1978) better recovery than non-cleaned, except where 

physical damage to roots occurred. 

Nepco 140 barge, No. 6 fuel oil Cattails were cut below water level in June 1976. 

in St. Lawrence River Next spring growth was normal but no 

(Alexander et al., 1981) flowering occurred. 

Light Arabian crude in Neches Cut S. patens showed no or minimal growth, 

River, TX in January 1979 whereas leave-alone plots showed normal 

(McCauley and Harrel, 1981) growth through next growing season. 

Louisiana crude applied to Cutting of vegetation reduced plant growth and 

sediment surface of plots slowed rate of recovery, compared with oiled 

(DeLaune at al., 1984) only and unoiled plots. 

Mangroves and Coral Reef Communities 

The dominant estuarine and nearshore coastal communities in tropical and some 

subtropical regions are mangroves and corals. These environments are very 

important to the ecological balance of many of the marine ecosystems in the tropics. 

Like the salt marshes of the temperate zones, mangroves and coral serve as nursery 

habitats and have a high diversity and density of animal and plant species. 

Mangrove photosynthetic activity provides the base for secondary productivity, in 

the form of leaf detritus, that supports important commercial and recreational 

fisheries. They provide habitat for endemic and endangered species. 
The impacts to these environments from spilled oil is dependent on the amount 

and type of oil spilled, extent of weathering of the oil prior to landfall, and the 

physical characteristics of the impacted area (water depth, exposure to waves, 

nearshore and intertidal topography, sediments, etc.). Each of these factors will be 

discussed as they determine the sensitivity of coral and mangrove ecosystems to oil 

spills. 

Mangroves 

The two most common species of mangroves found in the United States are the red 

mangrove (Rhizophora mangle) and the black mangrove (Avicennia germinans). 

The red mangroves have gracefully curving prop roots which extend a meter or 

more above ground and are covered with small pores, called lenticels, through 

which oxygen diffuses when exposed to the air at low tide. Because mangroves grow 

in anaerobic soils, they obtain most of the oxygen needed from the atmosphere. 

Black mangroves uptake oxygen through small roots, called pnematophores, which 

extend 20-30 centimeters straight up above the soil from an underground root 

system. Where both species exist, red mangroves occur in the low- to mid-intertidal 

zones, whereas black mangroves are more common in the upper intertidal and 

supratidal zones. Black mangroves are less tolerant of high salinities, so they grow 

better where there is less exposure to salt water inundation and some fresh 

groundwater influence. The white or buttonwood mangrove (Laguncularia 

racemosa) occurs primarily seaward of the black mangrove. 

Where mangrove forests occur, water depths are very shallow and most of the forest 

is exposed during low tide on a regular basis. They are frequently fronted by shallow 

seagrass or reef flats. Topographic elevations in the forest control the location and 

extent of oiling from floating slicks. Figure 3-33 depicts four types of physical 

impacts likely to occur during oil spills (Getter et al., 1981). 

Inner fringe impacts occur when there is a berm behind mangroves growing in the 

subtidal or low intertidal areas. The oil passes through the open network of prop 

roots and collects at the front of the berm, causing defoliation and mortality of both 

seedling and adult trees at the inner stand of mangroves. The prop roots of the 

outer mangroves are oiled, but only as a thin band. Greatest impacts occur where 

the oil is concentrated in the sediments and wrack is piled on top of the berm. This 
 

Figure 3-33. Four models of the distribution of oil spill effects in mangroves. 
interior berm is either inherited topography or built by the accumulation of 

sediment and debris carried into the forest by storm waves. The berm serves to 

prevent the transport of oil deeper into the forest, so where present, the berms are 

the de facto interior limit of oil penetration. The natural rate of flushing of oil from 

these inner berms is highly variable. Large amounts of debris may be indicative of 

accumulation zones with slow removal rates. Heavy debris also acts as a natural 

sorbent for oil, with the potential as a long-term leaching source. 

Outer fringe impacts are likely along relatively steep intertidal zones where red 

mangroves commonly occur in a narrow band. Because of the narrow intertidal 

zone, there can be heavy oiling of the sediments and any accumulated debris. The 

steepness of the intertidal zone may be due to a wave-built sand beach or a steep 

rocky shore. The presence of a sand beach indicates exposure to waves and the 

potential for removal of stranded oil by natural processes. A rocky substrate may 

indicate wave exposure, but is not as diagnostic as a depositional beach. There may 

be very sheltered bays where mangroves have been established on a rocky substrate. 

However, oil is less likely to contaminate and persist in the rocky substrate than in 

fine-grained sediments. 

Inner basin impacts occur where there is a low overwash berm in front of a shallow 

depression or interior basin. Oil gets washed over the low berm and is trapped in 

the basin. Although the oil can spread over a large area, the oil is less likely to be 

concentrated in a narrow band, thus partial defoliation as shown on Figure 3-33 

often occurs. Persistence of the oil can be long term, depending on the degree of 

natural flushing in the basin. In more exposed areas, oil can be removed from the 

system within several months, particularly for refined products and light crudes. 

Heavy oils are always more persistent because of their higher viscosities. In 

sheltered areas, oil persistence of years is likely. 

Riverine impact is very similar to outer fringe impact, however, it occurs only on 

river point bars, and it can be more extensive than outer fringe impacts. Of course, if 

the spill occurs during unusually high water levels, the oil can be carried over the 

bars and river levees, into the interior basin forests. Riverine environments are, 

however, relatively high energy, being exposed to both riverine and tidal currents 

which are effective in natural removal of the oil. 
The type of oil greatly affects the nature and degree of impacts to mangrove 

ecosystems. Refined petroleum hydrocarbons with large amounts of the watersoluble aromatic compounds (e.g., jet fuels, gasoline) are more acutely toxic to 

mangroves at lower concentrations than are crude oils and heavy refined products. 

The best example of the high acute toxicity of light refined products is the 1986 spill 

of 60,000 gallons of JP-5 from the Roosevelt Roads Naval Station in Puerto Rico 

(RPI, 1987). The oil had a low viscosity so there was no smothering and the only 

impacts were due to direct exposure and poisoning via absorption through the 

pneumatophores and prop roots. An estimated 70 percent of the oil evaporated 

within 24 hours, however, a thin slick was blown across a small bay and was quickly 

deposited in a tidal mixed species assemblage of red, black, and white mangroves, 

with reds dominating the seaward zone and blacks dominating the landward zone. 

Trees exhibited stress in 10 days, and within 5 months, 5.5 hectares of trees were 

dead. This acreage of mortality is disproportionately large for the number of gallons 

spilled, compared to heavier oils. 

It was interesting to note that seedlings survived more than adult trees because the 

seedling roots were buried in sediments and avoided acute exposure. Seedling 

mortality for the period 6-9 months post-spill averaged 30 percent, which not 

different from non-oiled sites. Chemical analysis showed no residual oil in the 

sediments, so natural recovery was predicted to occur unimpeded by contaminated 

sediments. Natural recovery depends on adequate supply of seeds and growing 

conditions, including regular flushing by clean seawater, which provides stabilized 

surface and interstitial water salinities, brings in nutrients, and increases 

colonization rates by transport of seeds into the area. Following this incident, a 

restoration plan was developed to open selected channels to increase the level of 

circulation in parts of the forest which had low flushing rates. 

Heavier oils (Bunker C and medium to heavy crudes) lead to chronic exposure and 

chronic impacts to the mangrove ecosystem. Oil impacts to the trees are related to 

the physical coating of the roots, which prevent gas exchange, and from chronic 

exposure to oil-contaminated sediments. Such exposure can result in slow 

defoliation and death over a period of time. If mortality does not occur, signs of 

severe stress will be manifested, such as partial defoliation, low survival of 
propagules, leaf deformities, reduced leaf size, and increased insect infestation 

(Lewis, 1983). 

Seedling and propagules die when they are coated with oil, even when the oil has 

weathered for a few days before stranding. It should be noted that where defoliation 

and death of adult trees occurs following a spill, seedling density increases 

significantly. Because of the newly opened canopy, more light reaches the seedlings 

and they have higher sprouting rates. However, where the sediments remain 

contaminated, long-term seedling survival is lower. Even eight years after the Zoe 

Colocotronis oil spill in Puerto Rico, seedlings in heavily oiled sediment appeared 

chlorotic, stunted, and insect damaged (Cintron et al., 1981). After the 1986 Texaco 

spill of 50,000 barrels of a medium-light crude oil in Panama, sediments were toxic 

to planted seedlings for the first six months post-spill, but after twelve months 

survival was the same for control and oiled sites (Teas et al., 1989). 

Impacts to the associated fauna and flora can be severe. Red mangrove prop roots 

support a dense community of attached algae, mussels, oysters, and barnacles, which 

are frequently directly killed under moderate to heavy oil coating. Crabs are 

particularly hard hit, whereas gastropods appear to be able to shift to less 

contaminated areas, if present (Getter et al., 1980; Jernalov et al., 1976). 

Laboratory studies have shown wide variability in the relative toxicity of different 

types of oil in sediments on seedling survival. Table 3-2 summarizes the results of 

experiments by Getter et al. (1984). No. 2 fuel oil was shown to be the most toxic, 

compared to Bunker C and two crude oils. Bunker C was the least toxic oil tested. 

Black mangroves exhibited higher mortalities and sublethal stress effects than red 

mangroves at the same dosages and were found to be especially sensitive to aromatic 

compounds. Similar results were reported from studies conducted at the Universiti 

Sains Malaysia (Lai and Feng, 1984). 

Extensive laboratory and field studies were conducted in the 1980s to determine the 

relative toxicity of oil versus dispersed oil. In fact, the previously mentioned 

laboratory studies were the oil-only controls for comparison with dispersed-oil 

treatments. These studies have been conducted by RPI (Getter et al., 1984; Ballou et 

al., 1985) and researchers at Universiti Sains Malaysia (Lai and Feng, 1984). The 

results of these studies include: 
Table 3-2. Concentrations of different types of petroleum hydrocarbons and 

observed toxic effects from laboratory experiments (Getter et al., 1984). 

CONCENTRATION FUEL TYPE TOXIC EFFECTS 

(in ppm) 

100 Diesel Growth alteration 

300 No. 2 92% mortality; survivors with 

no new leaves 

300 Bunker C 24% mortality; survivors with 

fewer new leaves 

300 South 20% mortality; survivors with 

Louisiana fewer new leaves 

crude 

300 Kuwait crude No mortalities; increased 

number of new leaves 

1,000 Diesel Growth deformities 

10,000 Diesel Lethal 

38,600 Bunker C Fewer new leaves; depressed 

No. 2 weight gain 

Kuwait crude 

100,000	 Diesel Lethal 

•	 Dispersed Bunker C was less toxic than undispersed Bunker C. 

•	 Dispersed light Arabian crude and No. 2 fuel oil resulted in increased 

defoliation. 

•	 Toxicity can result from oil entering roots and being drawn up the stems 

and leaves by transpiration. 

•	 In field experiments, dispersed oil had minor effects on mangroves 

whereas untreated oil caused extensive defoliation and death to adult 

trees, lower survival rates of planted propagules, and long-term sediment 

contamination. 

•	 Black mangroves are more sensitive to oils, both dispersed and untreated. 
Based on both laboratory and field studies of oil spills in mangroves, the following 

comments and recommendations are made: 

Light Oils (Gasoline, Jet Fuel, No. 2 Fuel Oil) 

•	 Fresh spills will have acute, toxic impacts to both trees and intertidal biota. 

•	 Sunny, windy weather will speed evaporation which will lessen watercolumn and intertidal impacts. 

•	 These light products will penetrate deeply into the forests, stopping only at 

the high-tide line. Highest concentrations will occur at the high-tide line 

and in detrital material. 

•	 Persistence of oil in sediments should not be great, unless there has been 

physical mixing into the substrate by wave or cleanup efforts. 

•	 No. 2 fuel oil will have the greatest persistence; it can persist and remain 

toxic for many years if it penetrates burrows and prop root cavities. 

•	 It is generally impossible to physically protect a fringing mangrove forest. 

•	 Deployment of booms is seldom effective because of low viscosity of these 

light products and importance of water-column transport mechanisms, 

but it should be attempted, particularly at stream mouth. 

Crude Oil/Heavy Refined Products 

•	 Oil will coat intertidal zone, with heaviest concentrations either at the 

outer fringe or the high-tide line. 

•	 Penetration into the forest will be limited by the amount of oil, forest 

density, and oil viscosity; weathered, emulsified oils penetrate less. 

•	 Oil can pool onto sediment surfaces and accumulate heavily in detrital 

material such as seagrass wrack. 

•	 Toxicity is due to coating and sediment contamination; there is little 

difference in toxicity among the heavier crude oils and refined products. 

•	 Because of low physical energy in mangrove swamps, oil persistence is 

great and sheens are generated for months. 

•	 Booms should be deployed to attempt to protect the most sheltered areas 

where greatest persistence is likely. 
Cleanup Recommendations 

• Under light accumulations of any type of oil, no cleanup is recommended. 

•	 If sheens are present, use sorbent booms to pick up the oil as it is naturally 

removed, being sure to change booms frequently. 

•	 The only light refined product that might require cleanup is No. 2 fuel 

oil/diesel because of the potential for sediment contamination. 

•	 Heavy accumulations could be skimmed or flushed with low-pressure 

water flooding, as long as there is NO disturbance or mixing of oil into the 

substrate. If substrate mixing is likely or unavoidable, it is better to leave 

the oil to weather naturally. 

•	 Under moderate to heavy accumulations of crude or heavy refined 

products, a detailed, site-specific cleanup plan will be required. This 

cleanup plan should be prepared by experienced personnel and include: 

1.	 General map of entire area impacted and locations of specific areas to 

be cleaned. 

2.	 Detailed maps of each specific area showing the oil locations and type 

of cleanup to be performed at each location. 

3.	 Definition of each type of cleanup. 

4.	 Specific restrictions to prevent further damage. 

•	 Oily debris should be removed, taking care not to disturb the substrate. 

•	 The vegetation should never be cut or otherwise removed. 

•	 Sorbents can be used to wipe heavy oil coating from prop roots in areas of 

firm substrate and with close supervision. 

Coral Reefs 

Coral reefs are mostly subtidal in nature, although the most shallow portions of 

some reefs can be exposed during very low tides. The three major categories of reefs 

are: 

•	 Fringing reefs - long, narrow bands of coral reefs parallel to and near the 

shoreline. When near coastal development, they are susceptible to stress 

from sedimentation and chronic pollution. 
•	 Barrier reefs - similar to fringing reefs except thay are further offshore and 

much broader (e.g., the Great Barrier Reef of Australia). 

•	 Atoll reefs - reefs formed by buildup of coral on the rim of a subsiding 

volcano. They are circular or portions of a circle, forming a sheltered 

lagoon. 

All of the reefs are completely submerged during high tide, and only a few reefs are 

routinely exposed during normal low tides. More commonly, reefs are exposed only 

during extreme low tides a few times a year. 

Review of the literature shows that there have been relatively few studies of reefs 

following exposure to oil spills. There are several very good summaries of the 

literature as of the early 1980s. Loya and Rinkevich (1980) and Ray (1980) compiled 

data on known oil spills near coral reefs and their effects on coral reef communities. 

Tetra Tech (1982) prepared a draft report for the American Petroleum Institute on 

ecological impacts of oil spill cleanup on nine different habitats, including coral 

reefs. They updated the Loya and Rinkevich (1980) list of oil spill case histories, for a 

total of fifteen. These case histories have very little quantitative data, but they 

mostly indicate no or very short-term impacts to coral reefs, except where chronic 

spills occured. It is important to note that these case histories looked for acute 

impacts, whereas it is more likely that any negative effects will be manifested as 

sublethal responses (Fucik et al.,1984). 

There have been very few additional studies of coral reef impacts by oil spills 

reported in the literature since the mid-1980s. There have been laboratory studies, 

comparing oil versus dispersed oil impacts (Dodge et al., 1984; Knap et al., 1985; 

Wyers et al., 1986; Knap, 1987), and studies on the effects of chronic oil pollution 

(Bak, 1987). The only exception is the extensive followup to the 1986 Texaco spill in 

Panama which impacted shallow coral reefs near the Galeta Marine Laboratory of 

the Smithsonian Tropical Research Institute. Guzmán et al. (1991) reported on the 

short-term impacts of the spill after 2.5 years, with delayed and extensive patterns of 

injury observed. This spill had three factors which contributed to the extent and 

degree of damage to coral reefs: 1) large amounts of fresh oil, 2) shallow-water reefs, 

and 3) chronic exposure for months as the oil leached out of adjacent mangroves. 

The potential for impacts from oil spills on reefs can be divided into three main 

categories, as summarized below: 
Low risk 

•	 Reefs located at greater than five meters water depth at low tide; dilution 

should reduce oil concentrations in the water column to below acute 

toxicity levels. 

•	 High energy setting could mix fresh oil into the water column, but 

exposure is more likely to be short (hours to one day). 

•	 Studies have shown healthy reefs rapidly recover from sublethal effects 

[i.e., normal carbon fixation restored within 5-24 hours after exposure 

(Knap, 1987)]. 

•	 Where the reef is exposed to heavy surf, deposition of oil is unlikely. 

Medium risk 

•	 Reefs located in water depths of 1-5 meters below low water, where high 

concentrations of dissolved and particulate oil are possible, especially 

when the oil slick is fresh. 

•	 When the oil is fresh, toxic concentrations may cause acute impacts; more 

likely sublethal impacts may occur (NAS, 1985): 

-Increased algal growth 

-Slower growth rates 

-Lower fecundity (lower number of ovaria per polyp, fewer larvae per 

coral head, and lower settlement rate of planulae) 

-Localized tissue rupture
 

-Premature expulsion of larvae
 

-Excessive mucous production
 

•	 Degree of impact from a spill will be determined by: 

-The oil type 

-How much oil is likely to be mixed into the water column 

-How much weathering of the oil has occurred 
High risk 

•	 Intertidal reefs and reef flats, where direct contact with the oil is likely. 

•	 Sheltered, shallow water settings, where high concentrations of oil are 

likely to persist. 

•	 Where leaching from adjacent area creates a chronic source of oil 

exposure. 

•	 Where coral reef communities are already stressed by pollution, 

sedimentation, thermal quality problems, etc. 
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4	 Biological Resources 

Debra Scholz1, Jacqueline Michel1, Gary Shigenaka2, and Rebecca 

Hoff2 

Page 

Introduction.....................................................................................................4-1
 

Evaluating resources at risk...........................................................4-1
 

Factors affecting oil impacts on biota........................................4-2
 

Overview.............................................................................................................4-3
 

Toxicity...........................................................................................................4-3
 

Bioaccumulation......................................................................................4-7
 

Ecological effects.......................................................................................4-9
 

Summary.....................................................................................................4-9
 

Open Water Communities.......................................................................4-10
 

Marine birds...............................................................................................4-10
 

Marine mammals.....................................................................................4-22
 

Pelagic species............................................................................................4-44
 

Summary.....................................................................................................4-47
 

Nearshore Communities..........................................................................4-48
 

Intertidal.......................................................................................................4-48
 

Summary.....................................................................................................4-51
 

Subtidal..........................................................................................................4-52
 

Summary.....................................................................................................4-55
 

Seafood contamination..............................................................................4-55
 

Case history: Exxon Valdez.............................................................4-60
 

References.........................................................................................................4-66
 

1Research Planning, Inc., P.O. Box 328, Columbia, South Carolina 29202 

2National Oeanic and Atmospheric Administration, 7600 Sand Point Way N.E., Seattle, Washington 

98115 
Chapter 4. 

Biological Resources 

Introduction 

Determining which biological resources may be at risk in an environment 

threatened by an oil spill is an important part of spill response. This 

information will be an integral part of establishing priorities for protection 

efforts, and deciding on an appropriate response strategy. The following 

questions about biological resources are some of the first that will need to be 

answered during a spill event: 

• What are the biological resources (including birds, plants, 

invertebrates, fish, mammals) that inhabit the areas potentially 

impacted? (Consider as well, human uses of resources, such as 

fisheries and recreational activities) 

• What is the likelihood that these resources will be impacted by oil, 

and what kind of impacts can be anticipated? 

• How sensitive are these resources to oil? 

Answers to these questions will provide the information needed to address 

related issues, including establishing priorities for habitat protection, and 

evaluating possible response strategies. 

Evaluating resources at risk 

When drawing up a list of the resources at risk in a given area, seasonal 

migrants as well as resident populations should be included. Detailed 

information on the life stages present at any given season will aid in 

determining the sensitivity of different populations. 

For advance planning, regions may wish to establish databases on biological 

resources and habitat locations in their region. Resource information should 

be updated periodically. Other available sources of information include state 

resource agencies, Federal agencies (such as U. S. Fish and Wildlife Service for 

information on birds and some mammals, NOAA for fisheries and marine 
mammals), experts from local academic or other institutions, Environmental 

Sensitivity Maps (ESI) and personal knowledge. 

Factors affecting oil impacts on biota 

A number of different factors will determine the degree of effects that can be 

expected from an oil spill. These can be grouped into degrees of severity, such 

as, heavy, long-lasting effects, intermediate levels of effects, and 

comparatively little or no effects (NAS 1985). The following factors, many of 

which have been discussed previously, will all be important in determining 

the levels of impact on biota: 

• Geographic location 

• Oil dosage and impact area 

Different habitat types within an area may be impacted quite 

differently. For example, in the intertidal zone, the lower intertidal 

usually contains the most diverse group of species. Frequently, 

however, oil impacts are heaviest in the upper intertidal zone. This 

was the case in many parts of Prince William Sound after the Exxon 

Valdez spill. 

• Oceanographic and meteorological conditions 

The physical exposure and weather conditions at a site will 

determine not only where oil may strand on the shoreline, but will 

also indicate how quickly oil will weather once stranded on that 

shoreline. Habitats in high energy environments will likely 

experience much shorter residence time of oil than habitats in 

sheltered, low-energy environments. 

• Season 

Population concentrations of species that may be present in the 

impacted area will include those that are not year round residents, 

but may be present seasonally in large aggregations. These will 

include migratory birds, and mammals, and fish spawning 

aggregations. Season and temperature will also determine the 

behavior of species present in the area that may affect their 

vulnerability to oil. An example is salt marsh crabs which were 

impacted during winter by a spill in Arthur Kill, New Jersey. Oil in 

sediment drove the crabs out of their burrows during extremely 

cold temperatures, causing increased mortality (Burger et al. 1991). 
•	 Oil type 

The toxic properties of the oil and its longevity (i.e. how quickly it 

will evaporate) will strongly influence the impacts that can be 

expected in a particular habitat. 

Overview 

Toxicity 

Toxicity is defined as, "The inherent potential or capacity of a material to 

cause adverse effects in a living organism" (Rand and Petrocelli 1985). 

Another way of saying this is that no chemical is completely safe, and no 

chemical is completely harmful. Concentration, duration of exposure, and 

sensitivity of the receptor organism will all determine the toxic effect. 

Sensitivity 

Sensitivity to toxic compounds varies greatly by species, by life stage within a 

particular species, and by individual. In general, younger stages are more 

sensitive than adults (for example, eggs and larvae are often more sensitive 

than adult fish), but some exceptions exist (See Figure 4-1; NAS 1985). 

Oil impacts between species groups vary. Though individual exceptions 

undoubtably exist, a broad categorization can be made for the anticipated 

degree of impact as follows (NAS 1985): 

•	 Little to no long-term effects: annelids, gastropods, copepods 

•	 Some effects: macrophytes, barnacles 

• Long-term effects: corals, bivalves, decapod crustacea 

Within one species, individual characteristics will also determine the degree 

of impact, including age, sex and contamination history. A study on kelp 

shrimp found that animals that had been previously exposed to naphthalene 

(a component of oil) had less tolerance to the compound. In contrast, pink 

salmon exhibited the opposite effect; fish that were previously exposed to 

naphthalene had significantly greater tolerance when tested later with 

bioassays (Rice and Thomas 1989). 
Figure 4-1. Toxicity of No. 2 fuel oil to life-cycle stages of selected marine 

shrimp and polychaetes. Life-cycle stages are indicated by size or segment 

number (NAS 1985). 
Acute effects 

Acute toxicity refers to immediate impacts that result in death of the 

organism. One acute effect of oil on shoreline organisms is the physical 

process of smothering (NAS 1985). Intertidal invertebrates and some plants 

may be especially sensitive to smothering. Acute effects can also result from 

the toxic components of the oil. Acute toxicity will be dependent on the toxic 

properties of the oil (a combination of the oil type and weathering), and the 

concentration and dose that the organism receives (See Figure 4-2). 

Studies conducted at the Amoco Cadiz spill in France documented acute 

effects to subtidal amphipods. A reduction in biomass of approximately 40% 

was measured for certain amphipod populations immediately after the spill 

(Dauvin and Gentil 1990). 

A single dose of a toxic substance at a high concentration can have the same 

effect as repeated doses at lower concentrations. The salt marsh plant Juncus 

roemerianus showed the same acute response to one exposure of crude oil at 

a concentration of 1,500 ml/m2, as to 6-10 successive spills of a concentration 

of 600 ml/m2 (de la Cruz et al. 1981). 

Chronic effects 

Some toxic effects may not be evident immediately, or may not cause the 

death of the organism. These are called chronic, or sublethal effects, and they 

can impact an organisms' physiology, behavior, or reproductive capability. 

Chronic effects may ultimately impact the survival rates of species affected. 

Chronic effects are harder to detect than acute effects and may require more 

intensive studies conducted over a longer period of time. 

Many chronic effects result from stress responses in the physiology of an 

organism, such as increased metabolism, increased consumption of oxygen, 

and reduced respiration rate. These can be short term responses, but over 

extended periods of time, may cause other impacts to the organism. A 

common chronic response is reduced growth rates, for example in benthic 

organisms that live in chronically oiled sediments. 
Figure 4-2. Acute toxicity (24- and 96- hour LC50 static tests) of some aromatic 

hydrocarbons for selected marine macroinvertebrates and fish (NAS 1985). 
For plants, primary productivity or photosynthesis may be affected. Low 

concentrations of crude oil (250 ml/m2 and 600 ml/m2) affected primary 

productivity of Juncus salt marsh plants (de la Cruz et al. 1981). 

Effects on reproduction from chronic exposure to oil in sediments has been 

documented for benthic fish species. Effects have been found for those species 

that spend most of their life cycle in intimate contact with contaminated 

sediments, for instance, flatfish such as English sole or Winter flounder 

(Kuhnhold et al. 1978). 

Changes in behavior have also been noted for several species of fish and 

invertebrates when exposed to oil. Littleneck clams (protothaca staminea) 

buried themselves in sediments more slowly and at shallower depths in oiled 

sediments, compared with unoiled sediments. This behavior increased the 

clams vulnerability to predation by Dungeness crabs (Pearson et al. 1981). 

Reduced feeding rates have been measured for lobster larvae, adult copepods, 

and benthic worms (NAS 1985). 

One mechanism of impact of a sublethal effect is the disturbance of an 

organism's chemosensory ability. Dungeness crab were found to have a 

decreased ability to detect littleneck clams (their prey) after exposure to crude 

oil. The blocking or disruption of the crabs chemosensory ability was thought 

to be the cause (Pearson et al. 1981) 

Bioaccumulation 

Bioaccumulation can be defined as the uptake of a contaminant by an 

organism from water directly or through consumption of contaminated food. 

Organisms that live in a contaminated environment, for example, mussels in 

oiled sediments, may appear to be healthy but still contain elevated levels of 

petroleum compounds in their tissue. Some components of oil can be 

bioaccumulated by marine organisms, particularly the group of longer lasting 

compounds known as polycyclic aromatic hydrocarbons (PAH). 

Biomagnification is defined simply as the magnification of concentrations of 

a contaminant over two or more trophic levels. One concern with 
bioaccumulation is that contaminated organisms (such as mussels) may be 

eaten by higher trophic level organisms (such as otters). If biomagnification 

was occurring, the higher level predator (the otter) could concentrate 

contaminants to a level which would cause toxic effects. In the case of 

organisms that are harvested by humans, concerns about bioaccumulation 

may cause restrictions on collecting shellfish or other items consumed by 

humans. 

Bioaccumulation may cause chronic effects to the organism involved and 

may also cause potential food web impacts (Widdows et al. 1987). In a field 

study conducted in Prince William Sound after the Exxon Valdez, 

bioaccumulation of PAH in intertidal mussels, snails, and drills was 

measured. However, no evidence of biomagnification was found (ERCE 

1991). In the case of oil components such as PAHs, the compounds do not 

usually reside in the tissue for long periods of time before they are depurated. 

Thus, biomagnification is not usually a major concern with petroleum 

compounds originating from oil spills. 

Bioavailability and uptake 

Though all animals can take up hydrocarbons from water column directly 

and from food, the processes of uptake vary by species group. 

Macroinvertebrates can take up hydrocarbons, and the majority also 

metabolize them readily, with the exception of the molluscs. Within 

invertebrates, detritus feeding bivalves usually accumulate more 

hydrocarbons than suspension feeders. Depuration rates vary, but can range 

from a few days to much longer. Levels of hydrocarbons in fish are usually 

higher in liver and neural tissue than in muscle tissue. Their efficiency of 

uptake from food may be low (NAS 1985). Fish also have enzyme systems 

capable of processing aromatic hydrocarbons relatively efficiently. 

Contaminated sediments can provide a source of hydrocarbons to benthic fish 

such as flatfish. 

Not all contaminants that are present in the environment will be 

bioavailable to organisms in the habitat. Bioavailability will be determined by 

a set of complex physical and chemical parameters, for instance, the amount 

of particulates and organic matter that may bind to the petroleum 
compounds, or the concentration of dissolved hydrocarbons in the water 

column. 

Ecological effects 

Some ecological effects that alter predator-prey interactions may result from a 

spill and result in changes in species composition or relative numbers of 

species in an area. This may be caused by the elimination of predators due to 

mortality, such as was postulated in the case of the Tsesis spill in Sweden. 

Here, an increase in growth of phytoplankton was measured shortly after the 

spill, and this was postulated to be a result of less than normal predation by 

zooplankton. Since zooplankton had experienced high mortality after the 

spill, this represented a direct predator-prey relationship (Johansson et al. 

1980). 

A similar effect may result from the fact that oil spills sometimes result in 

temporary closures in commercial fisheries. This also removes predatory 

pressure on fish populations, which may result in an increase in the fish 

population. 

Summary 

•	 Resources at risk
 

resident and seasonal populations, life stages
 

•	 Toxicity
 

varies by sensitivity of organism
 

- acute - immediate, of short duration
 

- chronic - sublethal, of long duration
 

•	 Bioaccumulation 

invertebrates accumulate hydrocarbons 

fish accumulate in liver and neural tissue, not in muscle 

biomagnification is not generally found with hydrocarbons 

•	 Ecological effects
 

predator - prey interactions may be affected
 
Open water communities 

Marine birds 

Marine birds can be divided into six broad categories based upon their 

behavior and sensitivities to oil spills. These include: 

•	 Seabirds 

- Surface-feeding pelagic seabirds—albatrosses, petrels, fulmars, 

and shearwaters 

- Diving pelagic seabirds—auks, murres, murrelets, puffins, 

guillemots, and auklets (auks and alcids) 

- Diving coastal seabirds—pelicans, cormorants, frigatebirds, 

tropicbirds, gannets, and boobies 

- Surface-reeding coastal seabirds—kittiwakes, skuas, and jaegers 

•	 Gulls and terns 

•	 Raptors—osprey, bald eagles, and peregrine falcons 

•	 Shorebirds—plovers, turnstones, surfbirds, sandpipers, phalaropes, 

and oystercatchers 

•	 Wadingbirds—herons, egrets, bitterns, rails, ibises, cranes, 

spoonbills, stilts, and avocets 

•	 Waterfowl—swans, geese, diving and dabbling ducks, mergansers, 

coots, gallinules, loons, and grebes 

Effects of oil on birds 

Bird species experience a variety of documented effects when exposed to 

spilled oil. These effects include: 

•	 Fouling of plumage 

•	 Ingestion of oil 

•	 Effects on reproduction 

•	 Physical disturbance 

These effects are outlined below. 

Fouling of Plumage. The primary direct effect from exposure to oil is 

fouling of plumage. Oil causes disruption of the fine structure of the small 

strands that form the feathers, causing loss of their water-repellent 

characteristics. The oiled plumage becomes matted, allowing water to 

penetrate to the body surface, which results in chilling and hypothermia as 

well as a loss of buoyancy. The ultimate cause of death of heavily oiled birds 
is believed to be hypothermia in most cases (Fry and Lowenstine 1985; Wood 

and Heaphy 1991). 

The quantity of oil necessary to result in death of the individual is unknown. 

Tuck (1961) reported that only a small spot of oil on the belly is sufficient to 

kill murres, and Fry and Lowenstine (1985) reported that 3-5 ml on breast 

feathers was able to kill two of three Cassin’s auklets tested. It has been 

theorized that other non-pelagic species may be much less sensitive to small 

quantities of oiling than the more pelagic species such as auks and murres, 

because they do not utilize the cold, offshore waters to the same extent. 

Birkhead et al. (1973) reported observations of visibly oiled gulls, guillemots, 

and razorbills successfully cleaning themselves after several weeks. 

Ingestion of Oil. Oiled birds can readily ingest oil during preening or by 

consuming/scavenging contaminated prey. The effects of ingested oil include 

anemia, pneumonia, intestinal irritation, kidney damage, altered blood 

chemistry, decreased growth, impaired osmoregulation, and decreased 

production and viability of eggs (RPI 1988; Wood and Heaphy 1991). 

Hemolytic anemia is defined as the most severe effect of ingested oil; anemic 

birds cannot dive or forage for food and starve on beaches––even after being 

cleaned. 

The quantity of oil required to elicit the responses outlined above is highly 

variable. The consumption of as little as 0.5 grams of oil has been found to 

inhibit certain physiological responses, while others remain intact (Clark 

1984). As a result, it is not clear to what extent these physiological effects 

contribute to mortality following oiling, given the rapidity of death from 

hypothermia or drowning. It is evident, however, that ingestion of oil can 

contribute to the overall impacts of oil spills. 

Effects on Reproduction. Direct exposure of eggs to oil has the greatest 

potential for damage. Previous studies have shown that small quantities of 

oil (as little as 1 microliter) applied to eggs reduce survival in a number of 

species (Crocker, et al. 1974; Holmes and Cronshaw 1977; Miller et al. 1978; 

Ohlendorf et al. 1978; Stickel and Dieter 1979; Peakall and Gilman 1980; 

Peakall et al. 1981; Clark 1984; Fry and Lowenstine 1985). Exposure during the 
early states of incubation are considered the most toxic. It is easy to 

understand how oiled adult birds can transfer toxic doses of the oil to eggs 

during nesting. Reports of actual impacts to eggs from oiled adults indicate 

there is a significant potential for reduced reproductive success in oiled birds. 

Reproductive success has also been shown to be affected during oil spills. 

Adults that are exposed to sublethal doses of oil and then ingest it may 

produce fewer eggs or cease laying eggs altogether. Although not documented 

for all bird species, there is the potential for oiled birds to experience a decline 

in egg production. The viability of the eggs produced following ingestion 

may also be reduced. 

Furthermore, adult Cassin's auklets and wedge-tailed shearwaters have been 

shown to abandon a nesting colony even when exposed to small quantities of 

oil. Those adults that do attempt to nest often have a delayed or failed egg 

production and low hatching success. Future losses may also be realized as 

breeding failure may result in the birds changing mates in following years 

and further reducing the reproductive success. The effects of oil on other bird 

species are assumed to be similar to those experienced by auklets and 

shearwaters. 

Physical Disturbance. An indirect impact of an oil spill is a result of 

disturbances from the physical intrusion of man during cleanup efforts. The 

influx of personnel and machinery to a spill site can cause a disturbance to 

individual birds, to breeding colonies, and to roosting areas in the vicinity of 

the cleanup site. Disruption of breeding will result in the greatest losses to 

both present and future generations. 

Vulnerability for Species Groups. The overall effects of an oil spill 

differ considerably among bird species, due largely to differences in behavior, 

distribution, and reproduction. These and other characteristics are used to 

identify or rank bird species as to their vulnerability to oil. For ease of 

assimilation, the bird categories have been identified as having either a high 

vulnerability or low vulnerability to oil spills. 

Highly vulnerable bird species are those that are closely associated or are fully 

dependent upon the marine environment. The following list identifies 
characteristics which make some bird species more vulnerable to oil spills 

than others: 

•	 Frequent diving for food 

•	 Prolonged roosting on the water 

•	 Formation of large flocks 

•	 Formation of dense nesting colonies in oil-spill susceptible areas 

•	 Percent of time spent on the open ocean 

•	 Low reproduction rates and cycles 

Using this list of characteristics and observations at spills, the following bird 

groups are considered highly vulnerable to oil spills: 

•	 Seabirds: 

- auks, murres, murrelets, puffins, guillemots, and auklets 

- storm petrels 

- pelicans and cormorants 

•	 Waterfowl: 

- diving sea ducks (eiders, scoters), geese, loons, and grebes 

•	 Raptors:
 

- bald eagles
 

The majority of these birds species spend up to 24 hours associated with the 

water. During a spill, large numbers of these individuals may be affected as 

they are constantly diving for food and form large flocks while roosting on 

the water. During the nesting season, entire breeding colonies may be affected 

or destroyed as they often form dense nesting colonies in areas highly 

susceptible to oil spills. 

Presently, the alcids are considered the most susceptible of all marine birds to 

spilled oil. These species occur in cold offshore waters where they often form 

large flocks and spend much of their time swimming or floating in the water. 

Pelicans as well as the other seabirds listed are considered highly susceptible 

due to their feeding characteristics, small populations, status as an 

endangered species, and low reproduction rates. These birds inhabit 

openwater territories, where the likelihood of encountering spilled oil is 

relatively high. 
During migration, diving sea ducks and geese are highly vulnerable to oil 

spills as they use offshore and coastal marine waters for staging and 

overwintering. These species often occur in very large flocks in relatively 

exposed, open-water areas. Certain species of loons and grebes are also 

considered highly susceptible from oil spills even though they all do not form 

large flocks. The western and Pacific grebes and loon species are highly 

adapted to aquatic existence and rarely leave the water. They occur in openwater marine habitats during much of the year. In addition, the Pacific grebe 

winters in large flocks in coastal marine areas of California, Oregon, and 

Washington. 

Bald eagles are considered to be highly vulnerable to oil spills. Although they 

rarely enter the water and are unlikely to be oiled, they have a small 

population and a very long recovery rate. The major concern regarding bald 

eagles is their predisposition to consuming oiled prey. As mentioned 

previously, ingested oil can have a multitude of effects on bird populations. 

Bird species which are considered as having a low susceptibility to oil spills 

are those that are seldom associated with the open marine environment or 

that are highly adaptable. The following list identifies characteristics which 

make some bird species less vulnerable to oil spills than others: 

•	 Rarely immersed in water 

•	 Large percent of time spent on land or sheltered water bodies 

•	 Prolific breeders 

•	 Able to avoid oiled areas by shifting habitats 

Bird populations which are considered to have a reduced vulnerability to 

spilled oil include: 

•	 Gulls and terns 

•	 Shorebirds 

•	 Waterfowl
 

- dabbling ducks and coots
 

•	 Wading birds
 

- herons, egrets, and rails
 
The majority of these bird species are not as reliant on marine habitats or are 

fairly adjustable in their habitat preferences. Although many of these bird 

species utilize the marine environment, their behavior is such that it is very 

unlikely that they would be impacted by spilled oil. 

Gulls are well known for their ability to exploit a wide range of habitats and 

food sources, in addition to being prolific breeders. It is theorized that gulls 

are readily able to avoid oil spills, since so few oiled gulls have been observed 

during spills. Terns are also considered to have a low risk of being directly 

oiled, although disturbance of nesting colonies may occur during cleanup. 

Shorebirds rarely encounter the water and are unlikely to be directly 

contaminated by spilled oil. It has been shown that shorebirds will avoid 

oiled areas, if there are suitable, unoiled feeding and resting areas available. 

Shorebirds can be indirectly impacted by loss of prey on oiled beaches, 

especially if the oiled area is an important feeding site on a long migration 

route. 

Dabbling ducks are considered to have a low vulnerability to oil because they 

are rarely found in waters where oil spills occur. Their reliance on freshwater 

habitats in particular tends to reduce the likelihood of encountering oil spills. 

Wading birds have low vulnerability to spilled oil because they rarely enter 

the water other than to wade in shallow, sheltered waters. Wading birds feed 

by capturing prey near the surface of the water. Outside of contacting oil on 

their head/face during feeding or on their legs while wading, this category of 

birds are unlikely to be directly impacted by spilled oil. 

Case histories of oil spill impacts on birds. A large proportion of the 

knowledge we have gained regarding birds and oil are from observations at 

previous spills. 

Ixtoc 1. On 3 June 1979, a PEMEX exploratory well, the Ixtoc 1, blew 

out in the Bay of Campeche, Mexico. This spill was not brought under 

control until nine months later, on 27 March 1980. An estimated 140 million 

bbls of oil was released during this time. 
By 6 August 1979, the Ixtoc 1 oil began impacting the Texas coastline. 

“Throughout the late summer and early fall of 1979, the barrier islands along 

the south Texas coastline were periodically impacted by oil. Padre Island and 

the Laguna Madre are known to be one of the most important staging and 

wintering areas for waterfowl, shorebirds, and colonial waterbirds in the 

United States (Getter et al. 1981).” 

Numerous beach bird surveys were conducted. The majority of the birds 

identified during these surveys were shorebirds (e.g., sanderlings and willets). 

The surveys determined that the bird populations responded directly to oil 

concentrations on the beach; as oil moved on shore, birds abandoned the 

affected areas of the intertidal beaches and redistributed themselves into 

relatively clean areas, often further back on the berm tops. By the end of 

August, most of the normal shorebird habitat (the intertidal beach) was oiled. 

As a direct result of the oil presence, the total number of shorebirds declined, 

however, no oiled shorebirds were ever recovered, and it has been theorized 

that the shorebirds shifted habitats to “secondary” areas (Fig. 4-3). 

Birds with oiled plumage never constituted more than ten percent of the total 

population observed during the beach surveys. The percentage of the oiled 

birds increased during late August, with oil coverage ranging from slight 

oiling of the feet to extensive (>75 percent oiling of their bodies). Royal terns 

were initially the species most impacted by the oil spill. By late August, 

“approximately 40 percent of the observed royal terns had oil on their breast 
feathers. However, by mid-September, royal terns avoided the high-tide line 

and congregated on the berm above the tar concentrations” (Getter et al. 1981). 

In addition, many of the wading birds were discovered to have oiled feet from 

feeding in oiled areas. Great blue herons, black-crowned night herons, snowy 

egrets, and cattle egrets were all observed to have heavy coatings of tar/oil on 

their feet. In a few instances, the oiling appeared to impact the bird’s natural 

walking and flying abilities. 

After natural/assisted shoreline cleanup efforts, the shorebirds reinvaded the 

intertidal beaches. At first, the number of birds that returned to the beach 

were less than before the spill, indicating that some reduction of the shorebird 

populations may have occurred. Over time, however, the shorebird 

populations increased due to the influx of migratory birds. 

Only twenty-six oiled birds were recovered and turned over to rehabilitation 

centers during the Ixtoc 1 spill. “Few carcasses or oil-immobilized birds were 

found. Carcasses that were found were mostly pelagic species. Shorebirds 

that succumbed to either direct or indirect effects of oil pollution were likely 

eaten by coyotes...that were often observed patrolling the beaches in the early 

morning” (Getter et al. 1981). The majority (eight) of the birds recovered were 

blue-faced boobies. 

Apex Houston. On 28 January 1986, the Apex Houston left Martinez, 

California, heading for Long Beach, California, under tow by the tugboat Inca. 

The Apex Houston was carrying a cargo of San Joaquin Valley crude oil. On 1 

February 1986, the tow line broke, and upon boarding the Apex Houston, Inca 

personnel discovered that the hatch cover to the number four port tank was 

not in place and that a small but undetermined amount of the crude oil had 

been spilled. 

Large numbers of oiled birds started appearing on beaches from Bodega Head 

to Monterey Bay on 1 February. Over the next few days, thousands of oiled 

birds were recovered. More than 10,500 marine birds were estimated to have 

been affected by this spill (Page and Carter 1986). 
Two species of diving pelagic seabirds, common murres and rhinoceros 

auklets, were severely impacted by this spill, both in terms of the number of 

oiled birds recovered and the percentage of the local population of the species 

affected (Table 4-1). The data of Table 4-1 presents only the observations made 

during the 1-8 February 1988 period, in order to focus on the potential effect of 

the Apex Houston spill. The birds recovered during these eight days 

constitute 87.2 percent of the total of the oiled birds recovered during the 

months of January and February 1986. 

This spill exemplifies how a very small amount of oil can have significant 

impacts to bird populations that are concentrated in a small local area. 

Nestucca. On 22 December 1988, the barge Nestucca spilled 231,000 

gallons of Bunker C just north of the Columbia River (Yaroch 1991). More 

than 3,000 live birds were recovered from Washington shorelines and turned 

in for treatment; 2,000 of these eventually died. Over 6,000 dead birds were 

observed along the shoreline. Common murres made up nearly 80 percent of 

the oiled birds recovered during this spill. Grebes and scoters were also 

significantly impacted (Yaroch 1991). 

In Canada, nearly 3,600 seabirds were collected from the west coast of 

Vancouver Island. As in Washington, common murres were the major 

victims of this spill, making up 42 percent of the recovered birds. Cassin’s 

auklets made up 32 percent of the oiled species (Harding and Englar 1989). 

Exxon Valdez. On 24 March 1989, the oil tanker Exxon Valdez ran 

aground in Prince William Sound, Alaska, spilling approximately 11.3 

million gallons of Alaskan north slope crude oil. Over the next two months, 

the slick encompassed approximately 25,000 km2 of coastal and pelagic waters, 

home to approximately 500,000 marine birds (Piatt et al. 1990). 

Following the initial notification, the International Bird Rescue Research 

Center (IBRRC) established four rehabilitation centers for impacted birds. 

During the course of their six months of operation, 1,630 oiled live birds 

representing 71 different species were captured and brought to the IBRRC 

rehabilitation facilities. An additional 36,500 carcasses were also recovered 

from the impacted area (Holcomb 1991; Wood and Heaphy 1991). The actual 
number of birds recovered only represents a small fraction of the birds 

actually killed, which could range up to 300,000. 

Table 4-1. Estimated number of birds debilitated or killed by oil between 1 and 

8 February 1986 from Salmon Creek, Sonoma County to Point Lobos, 

Monterey County (from Page and Carter 1986). 

Species 

Alive and Sent to 

Rehabilitation 

Centers 

Estimated Total 

Dead on 

Beaches 

Lost 

at Sea Total 

Loons 

Small grebes 

Western/Clark’s grebes 

Unidentified grebes 

Scoters 

Common murres 

Auklets/murrelets 

(Cassin’s suklets)* 

Rhinoceros suklets 

Other species/ 

Unidentified birds 

123 

9 

155 

19 

61 

2,924 

9 

30 

29 

148 

106 

313 

— 

222 

3,595 

168 

(140) 

1,201 

127 

— 

— 

— 

— 

— 

969 

29 

(29) 

335 

— 

276 

115 

468 

19 

283 

7,488 

206 

(169) 

1,566 

156 

TOTAL 3,364 5,880 1,333 10,577 

* The number of Cassin’s auklets within the auklets/murrelets category is in parentheses. 

Individuals from the widespread populations of ducks and alcids that existed 

at the spill site were the most common type of dead birds recovered. Several 

of the more sparsely distributed species, such as bald eagles, puffins, 

cormorants, loons, murrelets, shearwaters, fulmars, and petrels, were also 

impacted in large numbers during this spill (Table 4-2). 

It has been estimated that ten percent of the existing common murre 

population that previously existed in the Gulf of Alaska was affected and that 

more than 50 percent of the population within Prince William Sound was 

killed (Piatt et al. 1990). 

This was the first spill at which large numbers of eagles were oiled. It was 

estimated that 5,000 eagles occurred in the oiled area. In 1989, 153 bald eagle 

carcasses were recovered. Thirty-nine live, oiled bald eagles were sent to 
rehabilitation centers, of which 15 expired. As a result of this problem, a 1990 

Eagle Capture program was initiated as a joint effort between Exxon and the 

U.S. Fish and Wildlife Service. 

During this study, 113 bald eagles were captured and examined for signs of 

oiling and for general health conditions. Of those captured, 74 were 

immediately released because they were not oiled and were generally healthy 

(Figs. 4-4 and 4-5). Thirty-eight of the birds were considered oiled to various 

degrees (light to heavy), however an additional 24 lightly oiled bald eagles 

were released immediately. Consequently, 87 percent (98) of the captured 

birds met release criteria. Fifteen of the captured eagles required further 

medical treatment and were transported to a rehabilitation center (Gibson 

1991). 

Observations by the capture teams indicated that the bald eagles were not 

hunting in oiled areas. During capture efforts, the eagles would ignore 

floating fish snares if they were set too near an oiled area or shoreline. 

Table 4-2. Birds killed by the Exxon Valdez spill which were retrieved from 

Prince William Sound (PWS), Kenai Peninsula (KP), Barren Islands, Alaskan 

Peninsula (AP), and Kodiak between 25 March and 9 June 1989 (Piatt et al. 

1989). 

PWS KP Barren AP Kodiak 

Islands 

Number Retrieved 2,793 4,501 1,912 4,258 6,332 

Percent Retrieved by Bird Type 

Murres 14.9 63.2 88.4 91.1 90.7 

Sea ducks 25.2 8.7 0.5 1.5 0.5 

Murrelets 11.8 4.8 3.7 1.5 2.3 

Grebes 11.7 1.8 0.2 0.3 0.2 

Loons 8.9 2.0 0.3 0.4 <0.1 

Others 27.5 19.5 6.9 5.2 >6.2 
Figure 4-4. The degree of oiling for 113 eagles examined during the 1990 Eagle 

Capture Program as part of the Exxon Valdez monitoring effort (Wood and 

Heaphy 1991). 

Figure 4-5. The health status of 113 eagles examined during the 1990 Eagle 

Capture Program as part of the Exxon Valdez monitoring efforts (Wood and 

Heaphy 1991). 
Marine Mammals 

Marine mammals have a number of behavioral, anatomical, and 

physiological adaptations that enable them to spend most or all of their lives 

in the ocean. As a group, they have evolved to be able to utilize nearly every 

marine environment along the open waters of the world. Along the North 

American continent, the focus of this report, many diverse marine mammal 

species exist in a wide range of ecosystems, from the warm, tropical waters of 

the Atlantic and Pacific Oceans, to the cold, often ice-covered waters of the 

Arctic Ocean. 

In this discussion, pertinent life history data, habitat range, population status, 

and behavior are given for each of the following mammal groups. 

• Cetaceans (whales, dolphins and porpoises) 

• Pinnipeds (seals, sea lions, and walruses) 

• Sea otters 

Primary emphasis is on defining the interaction and effects of oil on marine 

mammals, which occurs primarily in three ways: 

1) direct surface fouling; 

2) direct and indirect ingestion with the affects of bioaccumulation; 

and 

3) inhalation of the toxic vapors released from the petroleum 

hydrocarbons as they evaporate. 

Additionally, any behavioral aspects of the species groups which would 

increase the risk of contamination are identified. A brief synopsis of all 

expected effects of petroleum hydrocarbons on marine mammals is given in 

Table 4-3; primary effects expected for oil exposure by all marine mammals 

are presented first, and unique effects, by marine mammal type, are listed 

next. 
Table 4-3. List of common effects exhibited by marine mammals when exposed to oil. 

Inhalation Surficial Contact Ingestion 

Marine 

Mammals 

(Pertains to 

All Species) 

Whales and 

Dolphins 

Seals, Sea 

Lions, and 

Walruses 

Sea Otters 

- Absorption into the circulatory 

system. 

- Mild irritation to permanent 

damage to respiratory surfaces 

and mucosal membranes. 

May also affect: 

- lungs and other organs. 

- nervous system 

- Irritation to eyes and skin. 

- Increased metabolism. 

- Inhibits thermoregulation. 

Little or no effect is expected. 

- May result in a temporary 

reduction in feeding efficiency for 

baleen whales. 

- Destroys insulative property of 

fur. 

- Young and immature are most at 

risk. 

- Destroys insulative property of 

fur. 

- Young and immature are most at 

risk. 

- Often results in the death of 

oiled individuals. 

Direct Consumption 

May result in irritation/destruction of: 

- intestinal linings. 

- organ damage. 

- neurological disorders. 

- bioaccumulation of toxins. 

Indirect Consumption 

May occur through grooming efforts. 

May result in: 

- transferral of toxins to young via lactation. 

- Direct consumption unlikely to occur. Exceptions 

include killer whales and gray whales due to their 

dietary preferences. 

- Direct consumption unlikely to occur. 

- Indirect consumption may occur from grooming pups. 

- Direct consumption unlikely to occur. 

- Indirect consumption through obsessive grooming 

behavior has been documented causing degenerative 

liver lesions, kidney failure, endocrine imbalances, 

diarrhea, and death. 
Cetaceans 

Cetaceans, an order composed of whales, dolphins, and porpoises, are warmblooded relatives of their terrestrial counterparts. Evolutionary forces have 

altered their four-legged bodies to their present stream-lined, nearly hairless 

forms. Fore and hind limbs have been replaced with flippers/fins, and broad, 

flat tail flukes. Thick layers of subcutaneous fat have replaced furred pelts, 

being a more efficient thermoregulatory aid in their watery environment. 

Two suborders of cetaceans exist today: 

1) Mysticeti or baleen whales. Large whales that travel in loose 

associations and have well established migration routes. With few 

exceptions, these animals have an unlimited, often worldwide, 

habitat range. 

2) Odontoceti or toothed whales, dolphins, and porpoises. This family 

exhibits a broad range in size and contains the majority of the 

animal species within the order Cetacea. These toothed whale and 

dolphin species are very gregarious, often forming large, stable 

groups or pods with strong kinship bonds. 

Table 4-4 lists both the common name and scientific names for the baleen and 

toothed whales, dolphins, and porpoises found in North American waters. 

Additionally, the global range, population estimates, and status of the species 

are listed. As can be seen from Table 4-4, the majority of the baleen whales 

exist worldwide, and are considered endangered by the United States 

Endangered Species Act. Additionally, toothed whales and dolphins have 

worldwide geographical ranges, with a few notable exceptions. However, the 

majority of the toothed whales, dolphins, and porpoises are not on the 

endangered species list. 

Effects of Oil on Cetaceans 

In general, whales, dolphins, and porpoises are considered to have 

the ability to detect and avoid oil and other petroleum hydrocarbons. 

Numerous studies were conducted on dolphins regarding their 

detection abilities (Geraci et al. 1983; Smith et al. 1983; St. Aubin et 

al. 1985). In all instances, the representative test animals were able 
to identify the presence of the pollutant and actively avoided contact 

with surface slicks. Other whales and dolphins 
 

Table 4-4. Geographic range, population estimates, and status of cetaceans common to North America1. 

Geographic Region Population Status* 

ORDER Cetacea 

SUBORDER Mysticeti (Baleen whales) 

FAMLY Balaenida (Right whales) 

Bowhead whale Balaena mysticelus Worldwide 8,500a endangered 

Northern right whale Eubalaena glacialis Worldwide 3,100-3,200 endangered 

FAMILY Balaenopteridae (Rorqual whales) 

Blue whale Balaenoptera musculus Worldwide 11,700 endangered 

Brydes’s whale Balaenoptera edeni Worldwide 30,000-56,000 not listed 

Fin whale Balaenoptera physalus Worldwide 105,000-122,000 endangered 

Humpback whale Megaptera novaengliae Worldwide 9,500-10,000 endangered 

Minke whale Balaenoptera acutorostrata Worldwide 315,800-331,800 not listed 

Sei whale Balaenoptera borealis Worldwide 48,000-63,000 endangered 

FAMILY Eschrichtiidae 

Gray whale Eschrichtius robustus N.E. Pacific 21,000 endangered 

SUBORDER Odontoceti (Toothed whales, dolphins, and porpoises) 

FAMILY Monodontidae 

Beluga Delphinapterus leucas Worldwide 40,000-55,000 not listed 

Narwhal Monodon monoceros Worldwide 29,000a not listed 

FAMILY Delphinidae 

Atlantic white-sided dolphin Lagenorhynchus acutus W.N Atlantic 24,000 not listed 

Bottlenose dolphin Tursiops truncatus Worldwide 24,240-33,840a not listed 

Common dolphin Delphinus delphis Worldwide +1,000,000 not listed 
 

1 

Table 4-4. Continued. 

Geographic Region Population Status* 

FAMILY Delphinidae (continued) 

Hawaiian spinner dolphin Stenella longirostris Worldwide 1.1 million not listed 

Killer whale Orcinus orca Worldwide 1,000a not listed 

Long-finned pilot whale Globicephala melaena Worldwide 13,000-50,000a not listed 

Pacific white-sided dolphin Lagenorhyncus obliquidens Worldwide 50,000b not listed 

Risso’s dolphin Grampus griseus Worldwide 10,000a not listed 

Spotted dolphin Stenella spp. Worldwide 3.3 millionb not listed 

Striped dolphin Stenella coeruleoalba Worldwide 2.3 millionb not listed 

FAMILY Phocoenidae (Porpoises) 

Dall’s porpoise Phocoenoides dalli Worldwide 1.4-2.8 million not listed 

Harbor porpoise Phocoena phocoena Worldwide 18,000a not listed 

Vaquita Phocoena sinus Gulf of California 200-300 endangered 

(entire population) 

Modified from Geraci and St. Aubin (1990). 

* As listed in the United States Endangered Species Act. 

a Estimates for North American populations. 

b Estimates for Eastern North Pacific populations. 
probably would also be able to detect and avoid oil contamination. However, 

in their natural environment, there are many instances where whale and 

dolphin individuals swam directly into an affected area, not seeming to 

notice the oil slicks. The question of lethal and sublethal effects of oil on 

whale, dolphin, and porpoise species has not been successfully answered. The 

historical observations during actual spills on the effects of oil spills on 

whales, by species, are summarized in Table 4-5. 

Direct Surface Fouling. Direct oiling of whales, dolphins, and 

porpoises is not considered a serious risk to the thermoregulatory capabilities 

of these animals. After extensive studies, Geraci (1990) determined that direct 

surface fouling poses little if any problem to these animals. Any irritation 

that were to occur would rapidly recover due to a resistant dermal shield 

found in whale, dolphin, and porpoise skin. This dermal shield has been 

defined as an extraordinarily thick epidermal layer which is highly effective 

as a barrier to the toxic, penetrating substances found in petroleum. 

The baleen whales, which use baleen plates to feed, presents an area of 

concern regarding surface fouling. Could these plates became fouled? and if 

so, Would these individuals survive the oiling? It is possible that oil 

residues would adhere and clog the baleen plates, thereby interfering with the 

affected individual’s feeding. To date, only one baleen whale has ever been 

reported as having its baleen plates fouled by oil (Brownell 1971). In an effort 

to determine the degree of impact, a series of tests were conducted to detect 

the effects of various petroleum hydrocarbons on isolated baleen plates 

(Braithwaite 1983; Geraci and St. Aubin 1982; 1985). The tests show that even 

the heaviest of petroleum compounds may only temporarily reduce a baleen 

whales feeding efficiency. Table 4-3 lists the expected effects of baleen fouling. 

Inhalation. Geraci (1990) has theorized that “a greater threat to whales 

or dolphins is not the thick murky residue [of surface slicks], but the invisible 

gaseous compounds that escaped from it.” Inhalation of the toxic volatile 

fractions from fresh oil spills may produce a variety of problems for these airbreathing mammals. This pathway of exposure would be a threat primarily 

during the first few days after the spill occurs. Table 4-3 identifies the effects 

that may be encountered by whales and dolphins inhaling the volatile 

fractions from an oil spill. 
Table 4-5. Historic interactions and impacts of whales and dolphins with oila. 

Date Location and Source Oil Type and Species Impacts 

Quantity 

Feb. 1969 Santa Barbara, CA; 

Union Oil Well 

Apr. 1970 Alaska Peninsula; 

Source unknown 

1974 Japan; 

Source unknown 

Oct. 1976 Aransas Pass, TX; 

Pipeline leak 

Dec. 1976 Nantucket Shoals; 

Argo Merchant 

Mar. 1978 France; 

Amoco Cadiz 

Sept. 1978 Matagorda Bay, TX; 

Boat grounding 

June 1979 Gulf of Mexico; 

Ixtoc-I 

June 1979 Cape Cod, MA; 

Regal Sword 

Crude oil; 

>30 x 106 gal 

Diesel fuel; 

quantity unknown 

Bunker C; 

11.3 x 106 gal 

Crude oil; 

15,500 gal 

Bunker C; 

7.9 x 106 gal 

Crude oil; 

60 x 106 gal 

Fuel oil; 

3,000 gal 

Crude oil; 

70 x 106 gal 

Bunker C/Fuel oil; 

80,000 gal/6,300 gal 

Gray whales Sixteen stranded whales and dolphins were Pilot whales recovered. No causal relationship was Sperm whales established. 

Common dolphins 

White-sided dolphins 

Killer whales One sick and one dead killer whales were 

observed. No examination was conducted to 

determine causal relationship. 

Porpoise One dead porpoise found. 

Bottlenose dolphins Dolphins swam through the oil without any 

apparent effects. 

Fin whales Forty-three sightings were recorded for 

Pilot whales animals in and around patches of oil. No 

and others obvious reaction was observed. 

White sided dolphins Six stranded animals were recovered. No 

Common dolphins causal relationship was established. 

Pilot whales 

Bottlenose dolphins Twenty dolphins were observed to be 

swimming through the oil without any effect. 

Bottlenose dolphins Animals were sighted in areas with oilSpotted dolphins coated debris. The animals were apparently 

unaffected. 

Humpback whales Animals were observed feeding, surfacing, Fin whales and swimming through heavy concentrations Minke whales of oil. 

Right whales 

White-sided dolphins 

a Table was developed from J.R. Geraci and D.J. St. Aubin (1990) 
Table 4-5. Continued. 

Date Location and Source Oil Type and Species Impacts 

Quantity 

May 1981 Outer Banks, NC; 

Hellenic Carrier 

Mar. 1982 Rodanthe, NC; 

Source unknown 

July 1984 Gulf of Mexico; 

Alvenas 

Mar. 1989 Prince William Sound, AK; 

Exxon Valdez 

June 1990 Gulf of Mexico; 

Mega Borg 

Unknown;
 

3,000 gal
 

Tar;
 

quantity unknown
 

Crude oil;
 

>1 x 106 gal
 

Crude oil;
 

11 x 106 gal
 

Crude oil;
 

4.3 x 106 gal 

Porpoise Unconfirmed report of a dead porpoise. 

Pilot whale One stranded whales was recovered with a 

small patch of dry tar on its skin. 

Bottlenose dolphins One dolphin was swimming in the midst of oil 

patches. Others were observed at the edge of 

the slick. 

Gray whales 

Fin whale 

Minke whales 

Unidentified whales 

Harbor porpoises 

The following quantities of carcasses were 

recovered: 25 gray, 1 fin, 2 minke, and 3 

unidentified whales; 7 harbor porpoises. 

It is possible that these mortalities were of 

natural causes. 

Bottlenose dolphins Dolphins were observed to swim in the midst 

of oil patches while others were observed at 

the edge of the slicks. No observable effect 

was detected. 
Ingestion. There are two forms of ingestion that are considered here: 

1) direct ingestion or the conscious consumption of petroleum 

hydrocarbons; and 

2) indirect ingestion of petroleum hydrocarbons through the 

consumption of contaminated food sources, which includes 

bioaccumulation. 

Direct consumption of petroleum hydrocarbons is considered highly unlikely 

in whales, dolphins, and porpoises, and any quantity consumed is not likely 

to have any direct affect upon the individual. A more likely form of 

petroleum hydrocarbon ingestion is through the incidental consumption of 

contaminated food. Geraci (1990) remarks that most toothed cetaceans (with 

the exception of bottlenose dolphins) are predators that would not scavenge 

oil-killed fish and will also avoid oil-tainted fish. Baleen whales, however, 

are more likely to consume contaminated food sources. For most baleen 

whales, zooplankton comprise the majority of their diets. These small 

crustaceans ingest oil particles and rapidly process them. The consumption of 

a critical dose of petroleum hydrocarbons is a possibility for baleen whales 

feeding in and around an area of a fresh spill. 

Marine mammals have the potential to accumulate petroleum hydrocarbons 

in their tissues. However, this is more likely to occur in cold environments 

where prey organisms, such as zooplankton or benthic invertebrates, 

metabolize hydrocarbons more slowly than in warmer environments (Geraci 

1990; Neff 1990). Because marine carnivores generally do not assimilate 

petroleum compounds from food efficiently, biomagnification does not 

usually occur. Since invertebrates are less able to metabolize hydrocarbons 

than fish, mammals eating low on the food chain (such as walrus or sea otters 

that consume large quantities of bivalve molluscs, or baleen whales that feed 

on zooplankton) are more likely to accumulate hydrocarbons than are top 

carnivores, such as killer whales, that consume large pelagic fish (Neff 1990). 

To date, no sublethal effects on this animal group have ever been attributed 

to bioaccumulation of petroleum hydrocarbons. 
Areas of Special Concern. Table 4-6 identifies the behaviors and habits 

which are presumed to increase the risk of exposure to petroleum 

hydrocarbons by whales, dolphins, and porpoises. 

Table 4-6. Behaviors and habits of whales, dolphins, and porpoises that may 

predispose them to oil exposure. 

1) Habitat Preference—Spills in ice covered waters may increase the risk 

of exposure due to oil entrainment within the ice, and reduced 

weathering of the oil. Habitat fidelity is not strong among cetaceans. If 

an area were affected by oil, it is assumed that the animals will simply 

remove themselves from the area. 

2) Migration Routes—Many species participate in annual migration 

cycles, often through areas of oil exploration. Pelagic species are more 

at risk than in previous history as man’s exploration activities expands 

into deep water areas. Additionally, many species migrate through 

areas of intense petroleum transportation activities, again increasing 

the likelihood of exposure. 

3) Migration Hierarchies—Many species exhibit specific migration 

“pecking orders,” e.g., pregnant females are first to arrive to 

feeding/birthing grounds, then females with calves, then immature 

females, then adult males, and finally immature males. This 

migration pattern may expose an entire section of the migrating 

subpopulation to a spill, adversely affecting the pod. 

4) Dietary Preference—Many species exhibit restricted diets. If a species 

food source were affected, it may be forced to consume contaminated 

food or be forced to adjust its diet. However, as mentioned above, site 

fidelity is not strong among cetaceans and it is assumed that the 

animals would simply move to another, unaffected area to feed. The 

major concern would be for animals feeding prior to beginning a 

migratory journey. The stresses associated with migration preparation 

may adversely affect a cetacean if further stressed by a spill. 

5) Social Structure—Toothed species often travel in pods, acting as a unit. 

As in the case of mass strandings, the herd follows the lead animal. 

During a spill, a whole pod, or a large portion may be adversely 

affected. 

6) Reproduction—The reproductive success may be reduced by exposure 

to a spill. Pregnant females are considered most at risk to effects. 

7) Natural Curiosity—Curiosity in younger animals may increase their 

likelihood of exposure. There are many reports of juveniles “playing” 

with debris on the waters surface. 
Pinnipeds 

Pinnipeds, an order composed of walruses, seals, and sea lions, are probably 

the most common and well known of all marine mammals. Like other 

marine mammals, they are highly adapted to life in the water; they have 

streamlined bodies, paddle-like fore- and hindlimbs, thick layers of 

subcutaneous fat, and other advantageous morphological and physiological 

adaptations. Walruses, seals, and sea lions are highly social and routinely 

leave the water to congregate on sand beaches, rocky shores, and tidal flats for 

resting, breeding, and birthing. 

Three families of pinnipeds exist today: 

1) Phocidae, the true or crawling seals;
 

2) Otariidae, the walking seals; and
 

3) Odobenidae, the walruses.
 

Table 4-7 lists common and scientific names of the 14 species of walruses, 

seals, and sea lions existing in North American waters (walruses have been 

divided into two sub-species). The global range and population estimates of 

the species are also listed. Walruses, seals, and sea lions are not included on 

the U.S. Endangered Species list. 

Effects of Oil on Pinnipeds 

All walrus, seal, and sea lion species are considered to have the ability to 

detect and avoid oil and other petroleum hydrocarbons. To date, no studies 

have been conducted on these animals regarding their detection abilities, but 

anecdotal data indicates that they will avoid a spill. However, in the wild, 

there are also many contradictory incidents where seals, sea lions, and fur 

seals have swam directly into an affected area, not seeming to notice the oil 

slicks. Numerous deaths have been related to direct and indirect exposure of 

seals and sea lions to petroleum hydrocarbons. Table 4-8 summarizes 

observations of pinniped exposure to historic oil spill events. 
 

Table 4-7. Geographic range, population estimates, and status for pinnipeds common to North America1. 

Geographic Region Population 

ORDER Carnivora 

FAMILY Phocidae (Crawling seals) 

Bearded seal 

Gray seal 

Harbor seal 

Harp seal 

Hooded seal 

Northern elephant seal 

Ribbon seal 

Ringed seal 

Spotted seal 

FAMILY Otariidae (Walking seals) 

California sea lion 

Guadeloupe fur seal 

Northern fur seal 

Steller’s sea lion 

FAMILY Odobenidae (Walruses) 

Atlantic walrus 

Pacific walrus 

Erignathus barbatus 

Halichoerus grypus 

Phoca vitulina 

Phoca groenlandica 

Cystophora cristata 

Mirounga angustirostris 

Phoca fasciata 

Phoca hispida 

Phoca largha 

Zalophus californianus 

Arctocephalus galapagoensis 

Callorhinus ursinus 

Eumetopias jubatus 

Odobenus rosmarus rosmarus 

Odobenus rosmarus divergens 

Canadian Arctic and Bering-Chukchi Sea 400,000+ 

E. Canada 70,000 

New England to E. Canadian Arctic 157,000

 California to Aleutians 

E. Canada 2,250,000 

E. Canada; Davis Strait 366,000 

California, Mexico 60,000+ 

Bering-Chukchi Seas 100,000 

E. Canadian Arctic; Bering Sea 2.3 million

 Beaufort and Chukchi Seas 

Bering-Chukchi Seas 225,000 

Mexico to California 145,000+ 

Mexico 1,000+ 

Pribilof Islands, San Miguel 1,300,000+

 Island, Calif. 

California to the Bering Sea 221,000 

Eastern Arctic 25,000? 

Western Arctic and Alaska 160,000 

Modified from J.R. Geraci and D.J. St. Aubin,(1990). 1 
Table 4-8. Historical interactions and impacts of seals, sea lions, and walruses with oila . 

Date Location and Source Oil Type and Species Impacts 

Quantity 

late 1940s Antarctic; 

Ship discharge 

1949 Ramsay Island, Wales; 

Source unknown 

Mar. 1967 English Channel; 

Torrey Canyon 

Jan. 1969 Gulf of St. Lawrence; 

Storage tank 

Feb. 1969 Santa Barbara, CA; 

Union Oil Well 

Nov. 1969 N. Dyfed, Wales; 

Source unknown 

Feb. 1970 Chedabucto Bay and Sable Island, N.S.; 

Arrow 

Feb-Mar 

1970 

Kodiak Island, AK; 

Ship discharge 

Apr. 1970 Alaska Peninsula; 

Source unknown 

Nov. 1970 Farne Islands; 

Source unknown 

Mar. 1972 British Columbia 

Vanlene 

Sept. 1973 Repulse Bay, NWT; 

Ship discharge 

Fuel oil;
 

quantity unknown
 

Fuel oil;
 

quantity unknown
 

Crude oil;
 

30 x 106 gal
 

Bunker C;
 

4,000 gal
 

Crude oil;
 

>30 x 106 gal
 

Unknown;
 

quantity unknown
 

Bunker C;
 

4 x 106 gal
 

Slop oil or oily
 

ballast;
 

quantity unknown
 

Diesel fuel;
 quantity unknown
 

Unknown;
 quantity unknown
 

Bunker B;
 100,000 gal
 

Refuse oil;
 

quantity unknown
 

Unspecified seals Bloodshot eyes. 

Surface fouling with tarry oil. 

Gray seals Pups largely unaffected by thick coating of 

oil. Two fouled pups drowned. 

Gray seals Three oiled seals were recovered, confirmed 

deaths 

Harp seals 10-15,000 seals coasted. 

Unspecified number of dead recovered 

Harbor seals Oiled seals observed. 

Elephant seals Mortalities not linked conclusively to 

Cal. seal lions incident. 

Gray seals 14 oiled. 

Dead pups found. 

No causal relationship established. 

Gray seals 150-160 seals oiled on Sable Island; 500 

Harbor seals seals oiled in Chedabucto Bay. 24 found 

dead, some with oil in mouth or stomach. 

Hair seals Estimated 500 mammals contacted. 

sea lions No mortalities recorded. 

Hair seals 400 seals exhibited unusual behavior. 

No mortalities recorded. 

Gray seal Yearling seal found with oil-stained pelt and 

crusting around mouth. Animal was 

otherwise healthy. 

Seals Seal herds in area were unaffected. 

Ringed seals Hunters killed 5 oil-covered seals. 

a Table was developed from J.R. Geraci and D.J. St. Aubin (1990) 
Table 4-8. Continued. 

Date Location and Source Oil Type and Species Impacts 

Quantity 

1973 Dutch coast; 

Source unknown 

1974-1979 Cape Town, SA; 

Ships and industry 

Aug. 1974 Straits of Magellan; 

Metula 

Aug. 1974 Coast of France; 

Source unknown 

Sept. 1974 Pembrokeshire, Wales; 

Source unknown 

Jan. 1975 Ireland; 

African Zodiac 

Aug. 1977 Greenland; 

USNS Potomac 

Mar. 1978 France; 

Amoco Cadiz 

May 1978 Great Yarmouth; 

UK Eleni V 

Oct. 1978 South Wales; 

Christos Bitas 

Dec 1978 Shetland Is., Scotland; 

Esso Bernicia 

Feb. 1979 Latvia; 

Antonio Gramsci 

Mar. 1979 Cabot Str., N.S.; 

Kurdistan 

Unknown;
 

quantity unknown
 

Chronic discharge
 

Crude oil;
 

14 x 106 gal
 

Fuel oil;
 

quantity unknown
 

Unknown;
 

quantity unknown
 

Bunker C;
 

1.1 x 106 gal 

Bunker C; 

1 x 106 gal 

Crude oil; 

60 x 106 gal 

Heavy fuel; 

1 x 106 gal 

Crude oil; 

840,000 gal 

Bunker C; 

370,000 gal 

Crude oil; 

36,500 gal 

Bunker C; 

2.1 x 106 gal 

Harbor seal Patch of oil inconclusively associated with 

skin lesions. 

Cape fur seals Fur seals lingering in polluted harbor 

without obvious effect. 

S. seal lions Seal lions and fur seals in the area 

S. Am. fur seals apparently unaffected. 

Harbor seals Oil in intestine of one harbor seal. Three 

Gray seals oiled gray seals, one with ingested oil. 

Gray seals Two heavily oil pups drowned when washed 

off beach. 25 pups and 23 adults were fouled. 

Seals Seals in the area were apparently unaffected. 

Ringed seals 16 oiled seals were observed one month after 

other seals the spill. 

Gray seals Two of four dead seals were coated with oil. 

No causal relations was established. 

Seals 20 oiled seals were observed. 

Seals Mortality of 16 of 23 oiled individuals. 

Seals Oiled seals were observed. No mortalities 

were reported. 

Seals One seal killed by oil. 

Gray seals At least 4 gray and 6 harbor seals were 

Harbor seals found dead and coated with oil. No causal 

relationship was established. Oiled seals 

were found on Sable Island 
Table 4-8. Continued. 

Date Location and Source Oil Type and Species Impacts 

Quantity 

Nov. 1979 Pribilof Is., AK; 

F/V Ryuyo Maru 

Fuel oil; 

290,000 gal 

Northern fur seals Some oiled dead pups were found. Causal 

relationship was never demonstrated. 

Feb. 1984 Sable Is., N.S.; 

Well blow out 

Gas condensate; 

quantity unknown 

Gray seals Four oiled seals were observed on Sable 

Island. No mortalities were reported. 

Jan. 1989 Anvers Is., Antarctica; 

Bahia Paraiso 

Diesel fuel; 

233,000 gal 

Crabeater seals 

Elephant seals 

Southern fur seals 

Two crabeater seals were affected. Elephant 

seals and fur seals were oiled, but unharmed. 

Mar. 1989 Prince William Sound, AK; 

Exxon Valdez 

Crude oil; 

11 x 106 gal 

Harbor seals 

Fur seals 

Stellar’s seal lions 

Seals were observed swimming in the oil. 

Thirty-one harbor seals, two fur seals, and 

14 seal lion carcasses were recovered with 

some oil fouling. 
Direct Surface Fouling. Surface fouling effects on walruses, seals, and 

sea lions are summarized in Table 4-3. Furred species, such as the northern 

fur seals, are most likely at risk during an oil spill. However, lesser furred 

seals and sea lions are less threatened by surface oiling. Thick layers of 

blubber retain the animals core temperature. Anecdotal information has 

shown that adult and ringed seal pups are able to survive surficial oiling 

without suffering from hypothermia. This fact has been attributed the thick 

layers of blubber in adults and the utilization of brown fat stores in newly 

born pups (Blix et al. 1979) 

Inhalation. No studies have been conducted on walruses, seals, and 

sea lions regarding the effect or impact of inhaling volatile hydrocarbon 

fractions. It is assumed that these animals would exhibit similar effects 

experienced by other marine mammals. 

Ingestion. There are two forms of ingestion considered here. The 

consumption of petroleum hydrocarbons has been implicated in numerous 

seal and sea lion deaths. Experimental results have revealed a wide variety of 

effects that may result from oil ingestion by specific species. These effects are 

assumed to apply to all walruses, seals, and sea lions, and they vary by the 

amount consumed and the composition of the ingested oil. These studies 

have determined that walruses, seals, and sea lions would be able to tolerate 

the ingestion of small quantities of oil. Symptoms related to oil ingestion by 

walruses, seals and sea lions range from organ diseases to permanent damage 

or death (Table 4-3). 

Animals with a dense fur coat or pelage for insulation have two major 

pathways in which indirect ingestion of petroleum hydrocarbons may 

occur—the consumption of oil-tainted foods and by grooming oil-fouled 

coats. The principal diet of most seals and sea lions consist of cephalopod 

molluscs and fish; these prey items are not likely to accumulate petroleum 

hydrocarbons. However, notable exceptions do exist; walrus and bearded seals 

feed primarily on burrowing bottom animals which do accumulate 

petroleum hydrocarbons. Additionally, some seal and sea lion species in 

North America are also known to consume other seals (primarily pups) and 

birds. When oiled, furred seal and sea lion species begin grooming their coats 
to maintain its insulative properties. It is highly likely that these animals 

will ingest oil through grooming activities. Oiled pups are groomed by their 

mothers, thus increasing the mother’s chance of indirectly ingesting 

petroleum hydrocarbons. Furthermore, there is also the possibility of 

hydrocarbon transferral to pups through ingesting their mother’s lipid-rich 

milk. 

All walrus, seal, and sea lion species are assumed to have the necessary 

enzymes available within their systems to “convert absorbed hydrocarbons 

into polar metabolites which can be excreted into urine. However, some 

proportion of the nonpolar fractions will be deposited in lipid-rich tissues, 

particularly blubber” (St. Aubin 1990a). To date, no evidence of deleterious 

effects related to bioaccumulation of petroleum hydrocarbons have been 

documented. 

Areas of Special Concern. Table 4-9 identifies the behaviors and habits 

which are presumed to increase the risk of exposure to petroleum 

hydrocarbons by walruses, seals, and sea lions. These include habitat 

preferences, reproductive strategies, recognition and avoidance behaviors in 

adult females, and the impact of human activity on this animal group. 

Sea otters 

Sea otters are the smallest marine mammals and are related to weasels, 

badgers, and other members of the Mustelidae. They inhabit marine 

environments in rocky coastal areas from Alaska to California, although 

most live in Alaska. Table 4-10 identifies the current population estimates 

for the sea otter colonies in North America. Like other marine mammals, sea 

otters have streamlined bodies and broadly flattened paws for swimming. 

However, sea otters have no subcutaneous blubber layers and depend entirely 

on fur for insulation. This dense fur pelage is nearly two times as dense as 

found on the Phocid fur seals. Additional adaptations include modified 

dentition which is well suited for consuming their preferential prey, hardshelled mussels, clams, and other macroinvertebrates. 
Table 4-9. Behaviors and habits of walruses, seals, and sea lions that may 

predispose them to oil exposure. 

1) Habitat Preference—Habitats of choice are often within or near areas of 

oil exploration and transportation; the habitats include: sandy and 

rocky shores, fast ice, pack ice, shore leads, polynyas, and oceanic fronts. 

Many of these areas increase an animals risk of exposure due to oil 

characteristics when interacting with particular habitats. For example, 

pack ice, polynyas, and floe areas may entrain the oil and the cold may 

slow weathering. These factors would act to increase the possible 

duration of exposure to individual animals. 

2) Maternal Recognition—Maternal recognition may be hampered if a 

pup becomes oiled. This loss of olfactory recognition may result in the 

pup being abandoned. Oiling of nursery haulouts may result in major 

losses to a breeding subpopulation. Additionally, pups which are 

cleaned at rehabilitation centers may no longer be accepted by the 

mother, again resulting in abandonment. 

3) Reproduction—Contact with oil during the breeding season is thought 

to reduce the reproductive success of the colony. Additionally, theories 

suggest that exposure to oil during the breeding season may result in 

mass, premature delivery of pups (or spontaneous abortions) due to 

stresses during early delivery season in California sea lions. 

Fur seal and sea lion breeding males and elephant seals do not eat 

during the entire breeding season, thus are physiologically stressed and 

weak at the end of the season and more susceptible to any kind of stress 

or contamination. 

4) Interactions with Humans—Cleanup activity during a spill may result 

in abandonment of haulout areas. In certain species, pups may be 

permanently abandoned, while others will eventually return to their 

young. 

Walrus populations often remain in large groups, anywhere from 

several hundred to several thousand in one area. These groups are 

easily startled while on land, resulting in mass stampedes. Any oil 

response operations near walrus haulouts must be conducted with 

extreme care to avoid unnecessary encounters with large groups of 

animals. 

5) Thermoregulation—Furred seals are most at risk from surface oiling. 

Insulative properties of their thick pelage are quickly lost when oiled, 

resulting in a rapid heat loss. In the wild, few animals are expected to 

survive even the lightest oiling. Although pups are considered most 

at risk, experiential knowledge has shown that even extreme oiling of 

Phocid or Otariid pups does not always result in death. 
Table 4-10. Geographic range, population estimates, and status for sea otters 

in North America. 

Geographic Range Population Estimate Source 

Alaska 

Prince William Sound 

100,000 - 200,000 

16,000 

Rotterman and Simon 

Jackson 1988

DeGange et al. 1990 

Washington 260 Benz, personal 

communication 1991 

California 

Pismo Beach to Pt. Año 

Neuevo 

Purisima Point 

San Nicholas Island 

2,000

~2,000 

< 10 

12 

Benz, personal 

communication 1991

Benz, personal 

communication 1991

Benz, personal 

communication 1991 
The sea otters primarily inhabit rocky coastal areas near shore, although they 

often assemble in offshore waters. Sea otters are often found resting among 

the kelp canopy in nearshore waters. These kelp blades are suspected of 

affording protection, as well as reducing drifting during resting periods (Ralls 

and Siniff 1990). Intense site fidelity is often encountered by investigators; 

although the individuals may range from the area, they often return to a 

particular area. In Alaska, migrations occur as individuals travel from 

breeding to wintering areas; this habit is not observed in the California sea 

otters. 

Sea otters are polygamous, with males courting females within their 

territorial ranges. Outside of breeding periods, the animals often associate in 

large groups, with designated male areas and female/female with pup areas. 

These associations often result in large “rafts” of individuals, often exceeding 

100 individuals, all resting together on the water surface. These and other sea 

otter characteristics increase their risk of exposure during oil spills. 

Effects of oil on sea otters 

There are many examples of the devastating effects of oil on sea otter 

individuals and populations. Geraci and Williams (1990) have determined 

that the sea otter is the mammal most likely to be harmed by oil, both 

immediately and in the long-term. A recent report released by the U.S. Fish 

and Wildlife Service (1991) has estimated that 3,500 to 5,500 sea otters were 

killed in Prince William Sound and the Gulf of Alaska as a direct result of the 

Exxon Valdez spill. 

As with other marine mammals, sea otters are considered to have the ability 

to detect and avoid oil and other petroleum hydrocarbons. A study by Siniff 

(1982) analyzed sea otter detection abilities and reaction to the presence of oil. 

The test animals were able to identify the oil and primarily avoided contact 

with surface slicks. However, during this test, the animals investigated the 

slick and became contaminated. In the wild, there are many instances where 

sea otters swam directly into an affected area, not seeming to notice the slicks. 

Numerous deaths have been related to direct and indirect exposure of sea 

otters to petroleum hydrocarbons. 
Direct Surface Fouling. The greatest concern regarding surface fouling of sea 

otters is the effect on the animal’s thermoregulatory system, regardless of age. 

The sea otter has little subcutaneous fat and relies almost exclusively on its 

thick pelage for insulation. Additionally, eyes and mucous membranes are 

expected to be impacted by surface fouling (Table 4-3). 

Inhalation. Sea otters are affected in numerous ways by inhaling the 

toxic vapors of fresh petroleum hydrocarbons. The effects range from mild 

irritation to permanent damage or even death (Table 4-3). 

Ingestion. Sea otters are at risk of direct consumption of petroleum 

hydrocarbons via contaminated prey, particularly molluscs. They also 

constantly groom their pelage, and would ingest oil during grooming. Many 

of the prey items are thought to rapidly process hydrocarbons, but the 

potential for bioaccumulation exists. The effects of oil ingestion are presented 

in Table 4-3. 

Areas of Special Concern. Foremost is the effect of oiling on the 

metabolic and physiologic makeup of the sea otters. Table 4-11 outlines the 

areas of special concern when sea otters are at risk to petroleum hydrocarbon 

exposure. Additional behaviors and habits that often predispose sea otters to 

exposure include: habitat fidelity, grooming behavior, daily habits, and rigid 

metabolic requirements. 
Table 4-11. Behaviors and habits of sea otters that may predispose them to oil 

exposure. 

1)	 Habitat Preference—Sea otters often demonstrate excessive habitat 

fidelity. During the course of their life, sea otters may travel 

periodically, often traveling hundreds of miles, or remain in an area 

without leaving for extended periods. During a spill, sea otters may be 

endangered by remaining in their preferred habitat even with the 

threat of contamination. Even the presence of man may not be enough 

to motivate a sea otter into relocating. Animals which are physically 

relocated during a spill may return before response activities are 

completed. 

Additionally, sea otters often prefer to rest within kelp canopies. It has 

been speculated that this behavior affords the sea otter some form of 

protection from predators and prevents the sea otters from drifting. 

The kelp canopy also entrains oil, therefore increasing the risk of 

exposure. 

2)	 Metabolic Requirements—Sea otters have little subcutaneous fat; they 

rely entirely on their pelage for insulation. As a result, their strict 

metabolic requirement must be continually satisfied These small 

mammals must consume between 22-33 percent of their body weight 

per day (Costa 1978) to maintain their high metabolism. This extensive 

food requirement cannot be interrupted or the animal will suffer 

severe stress, which induces an increased metabolism, which further 

depletes their reserves, and so on. Any factor or force which reduces 

the sea otters ability to forage for food may prove fatal. 

3)	 Grooming Behavior—Due to the extreme necessity of maintaining 

their pelage, sea otters expend a large portion of each day grooming 

their coats. An animal which becomes even slightly oiled will 

obsessively groom trying to reestablish the insulative properties of the 

fur, to the exclusion of all else, even their young. The very act of 

grooming tends to spread the contamination as well as increase 

indirect ingestion of oil. Additionally, female sea otters may spend 20 

percent of their day grooming their pups; if a pup becomes fouled, the 

mother will not only spread the oil on the pup, but will most likely 

become contaminated herself as well as ingesting oil during the 

grooming process. In most instances, surface oiling results in the death 

of the individual. 

4)	 Normal Behavior—Sea otters exhibit a vast array of normal behavioral 

patterns which may predispose them to surface oiling. These 

behaviors include: surface feeding, grooming, resting, and swimming. 

As a result of these behaviors, an entire subpopulation may be 

affected/destroyed if they encounter oil. 
Table 4-11. Continued. 

Feeding behavior—Sea otters forage for food by diving and returning 

to the surface to feed. While lying on their backs, the otter will prepare 

its meal (often consisting of breaking open an invertebrate’s shell with 

rocks). Animals having to expend additional energy foraging for food 

in marginal feeding areas would be more affected by surface oiling as 

their metabolic requirements were already elevated. 

Resting behavior—Sea otters often come together to form living rafts 

while resting on the waters surface. These rafts may contain hundreds 

of individuals. 

Swimming—Sea otters enjoy swimming as part of their daily routine. 

Swimming activities are not limited to areas near their preferred 

habitat; sea otters may travel for several days only to return to their 

home. Both offshore and nearshore waters are utilized. 

5)	 Susceptibility to Oil—Of all marine mammals, sea otters suffer the 

greatest effects when impacted by a spill. Pups are the most susceptible 

to oil as they are totally reliant upon their mothers until weaned. 

Animals that are already experiencing stress (dietary, physical, etc.) may 

succumb to oil impacts more quickly than other individuals. Physical 

contact with oil (through surface fouling, ingestion, or inhalation) is 

almost always fatal. Animals recovered for cleaning during response 

operations have a greater chance for survival due to initiation of new 

clean-up techniques utilized during the Exxon Valdez oil spill. 

Pelagic species 

Effects of oil on pelagic communities are supported by a relatively sparse body 

of information. This is partly because effects on pelagic biota are considered to 

be relatively short lived, and because the dilution factor in the open ocean is 

thought to rapidly reduce any toxic concentrations that may be present under 

an oil spill. Effects on planktonic communities are also difficult to document 

because effects of oil must be separated from the high natural variability and 

seasonality found in these systems. In addition, there are analytical problems 

with detecting low levels of hydrocarbon concentrations in water, and with 

differentiating the source of these hydrocarbons. 

Pelagic ecosystems do support a number of species groups, and concerns about 

impacts to these are raised periodically, especially when response actions such 
as dispersants are considered. Pelagic resources will be discussed in the 

following two categories: 

1.	 Plankton

 bacterioplankton, phytoplankton, and zooplankton
 

2.	 Fish
 

adults, eggs, and larvae
 

Plankton 

Phytoplankton. Phytoplankton are generally less sensitive to the 

effects of oil than zooplankton, but they do experience acute and chronic 

effects from oil at concentrations ranging from 1-10 mg/l (ppm). Unicellular 

algae can take up and metabolize both aliphatic and aromatic hydrocarbons. 

Sensitivity to oil varies by species, as documented by a series of studies 

conducted in mesocosm enclosures by Lee et al. (1987). This series of 

experiments measured the effects of oil on plankton communities over a 

period of 20 days. Certain species of phytoplankton were found to be more 

resistant to the effects of oil (nanoflagellates and small-celled diatoms) than 

other species (centric diatoms). Since the regeneration time is very short for 

algal cells (9-12 hours), any impacts to these populations would probably be 

very short-lived (NAS 1985). 

Oil can affect the rate of photosynthesis in phytoplankton, and thus inhibit 

algal growth. However, at very low concentrations (less than 0.1 mg/l), 

enhancement of growth rates has been recorded (NAS 1985). Measurements 

of plankton taken at the Tsesis oil spill in Sweden (No. 5 fuel oil) found an 

increase in phytoplankton populations after the spill. This apparent anomaly 

could have been caused by high mortalities of zooplankton and thus, 

decreased grazing pressure on the phytoplankton population (Johansson et al. 

1980). 

Bacterioplankton. The bacterial component of the phytoplankton 

increases after an oil spill. This was measured in the Tsesis oil spill in 

Sweden, as was evidence of a rapid biodegradation of hydrocarbons in the 

water column (Johansson et al. 1980). Concentrations of bacterioplankton 

showed large increases after the addition of petroleum or its derivatives in 
the same mesocosm experiments discussed above (Lee et al. 1987). (Nutrients 

were also added to the mesocosms in these experiments). 

Zooplankton. Zooplankton are quite sensitive to the effects of oil, and 

toxic effects can be seen at concentrations ranging from 0.05 to 9.4 mg/l (NAS 

1985). This sensitivity is higher for dispersed and dissolved petroleum 

constituents, and less for floating oils (NAS 1985). Short term effects of oil on 

zooplankton include possible decreases in biomass (usually temporary), as 

well as lower rates of feeding and reproduction. Some species such as 

tintinnids may increase in abundance. This may be due at least in part to an 

increased food supply, since these zooplankton feed on bacteria and small 

phytoplankton (Lee et al. 1987). Long term effects of oil on zooplankton, such 

as changes in community structure, have not been found. 

Zooplankton can take up oil directly from the water, from food, and by direct 

ingestion of oil particles. Zooplankton are thought to play a role in the 

sedimentation of oil in the water column. Oil droplets, as well as oil attached 

to particulates, can be ingested by zooplankton, and later excreted as 

unmodified oil in fecal pellets, which may then sink, and cause a 

redistribution of oil from the pelagic zone to the benthic zone (Conover 1971). 

Fish 

Adult fish. Adult fish do not generally experience acute mortality at oil 

spills, and it is rare to find fish kills after a spill, especially in open water 

environments. (Enclosed habitats such as marshes or lakes may concentrate 

oil enough to cause conditions acutely toxic to fish). Fish can take up 

hydrocarbons through the water column directly and through food, but there 

is no evidence of biomagnification of hydrocarbons in fish. There is a 

commonly held belief that pelagic fish can avoid contamination, but little 

evidence was found to support this generalization in the NAS review (1985). 

There are several studies documenting effects from petroleum hydrocarbons 

to benthic fish species. Many of these studied species such as flatfish that live 

in intimate contact with chronically contaminated sediments. Pelagic fish 

species are less likely to come in contact with dissolved hydrocarbons at toxic 
concentrations from oil spills except for short time periods, and are thus 

unlikely to experience acute or chronic effects. 

Fish eggs and larvae. Fish eggs and larvae experience toxic effects at 

low concentrations of hydrocarbons, ranging from 1-10 ppm (Kuhnhold et al. 

1978). In most cases, eggs and larvae are more sensitive than adults, though 

some exceptions exist. For example, pink salmon eggs were found to be very 

tolerant to benzene and and water-soluble petroleum (Moles et al. 1979). A 

study of eggs and larvae of winter flounder found significant decreases in 

viable hatch of eggs when exposed to 100 ppb No. 2 fuel oil during gonad 

maturation, fertilization, and incubation. Larvae were found to be more 

sensitive than eggs (Kuhnhold et al. 1978). 

Summary 

1. Plankton 

a. Short-lived effects (of duration one month or less) 

b. Zooplankton are more sensitive than phytoplankton 

2. Fish 

a. Limited impacts to adults 

b. Eggs and larvae are more sensitive 

Note: Effects on pelagic communities are difficult to document due to 

high seasonal and natural variability 
Nearshore communities 

Intertidal 

Since the intertidal zone is an area often impacted by oil that strands on 

shorelines, intertidal resources and how they are valued will directly impact 

many decisions about shoreline cleanup. Intertidal biota can be categorized 

into the following groups: 

1.	 plants
 

including algae and wetland plants
 

2.	 infauna
 

animals that live buried in sediments
 

3.	 epifauna 

animals that live on the sediment surface or attached to rocks 

4.	 fish 

Plants 

The main plants in the intertidal zone are the attached macroalgae. Though 

macroalgae may be subject to smothering by oil, they can be quite resilient and 

survive even heavy oiling. A survey of shorelines done after the World 

Prodigy spill in Narragansett Bay in 1989 noted few dead plants, even in 

heavily oiled areas. However, some short term effects on reproduction of two 

species of Fucus were documented. These lasted only for a period of less than 

one month after the spill (Thursby et al. 1990). 

At the Santa Barbara blowout in 1969, shoreline surveys were conducted 

using transects along which intertidal algae were identified. The results of 

this survey were difficult to interpret since there was a strong confounding of 

the impacts from oil impacts with severe storms and increased freshwater 

runoff during the time period immediately after the blowout (Foster et al. 

1971). Observers noted that surf grass (Phyllospadix) growing in the intertidal 

zone was heavily oiled at some sites, and that these plants turned brown and 

died (Foster et al. 1971). 
NOAA studies of intertidal communities impacted by the Exxon Valdez spill 

in Alaska found that attached macroalgae, specifically Fucus survived oiling 

at numerous sites, but were heavily impacted by hot water washing of 

shorelines to remove oil (Houghton et al. 1991). 

Infauna 

Polychaetes and other burrowing invertebrates can play an important role in 

the biodegradation of residual oil in sediments. Lugworms (Arenicola) were 

tested in a lab with contaminated sediments from the Arrow spill of bunker C 

oil that occurred in Nova Scotia in 1970. Sediment reworking by lugworms 

substantially reduced amounts of hydrocarbon in sediments, probably by the 

mechanisms of aerating soil and by providing an environment conducive to 

the growth of bacteria in their tubes. Arenicola could not survive in 

sediments with concentrations of hydrocarbons of 600 ug/g (ppm) or greater 

(Gordon et al. 1978). 

Oligochaetes, especially species such as Capitella capitata, are known as 

opportunistic species that are commonly found in polluted areas. They 

colonize oiled sediments at high densities, as was observed after the Florida 

spill in West Falmouth, Massachussetts in 1969. At this site, Capitella was 

measured at high densities in oiled areas 7 months after the spill (Sanders 

1978). 

Copepods appear to be one group of crustaceans that are less sensitive to oil. 

A field experiment using Prudhoe Bay crude oil added to mudflats in Valdez, 

Alaska did not impact populations of three species of copepods when 

monitored for 30 days (Feder et al. 1990). 

Clams, in contrast, often show long-lasting impacts from oil contamination, 

partly because they usually inhabit fine sediments in low-energy 

environments where oil is likely to be slow to weather and therefore remain 

for long periods of time. Populations of Mya arenaria, a soft shelled clam, 

were studied six years after the Arrow spill in Nova Scotia (Gilfillan and 

Vandermeulen 1978). Clams from areas still contaminated with oil had 

concentrations of hydrocarbons in their tissue of up to 200 ug/g (ppm). 
Clam populations from oiled areas had fewer total numbers, fewer mature 

adults, and a 1-2 year lag in tissue growth, compared with clams from a 

control, unoiled population. 

These soft-shelled clams were thought to be particularly sensitive to the 

adverse effects of oiling since their physiology makes them unable to 

completely close their shells. This means that the clam's mantle and gill 

surfaces are always exposed to sediments and interstitial water, and thus, to 

any contaminants in those media. 

Epifauna 

Epifauna includes attached organisms such as mussels and barnacles, as well 

as motile organisms such as snails and other gastropods and crabs. A study 

from the Arthur Kill in New Jersery following a spill of No. 2 fuel oil in 1990 

found both acute and chronic effects on fiddler crabs (Uca Pugnax). Chronic 

effects resulted in behavior changes that were significantly different from 

control crabs, and which would detrimentally affect the crabs' ability to 

survive and compete (Burger et al. 1991). 

Mussels (Mytilus edulis) have been observed to survive heavy oiling without 

apparent acute effects in Alaska. They are frequently used as indicators of 

bioaccumulation for various contaminants, partly because the species occurs 

widely, and is therefore a convenient test organism. Mussels subjected to 

chronic, repeated exposures of hydrocarbon fractions of diesel oil were found 

to have reduced feeding rates and food absorption efficiency (Widdows et al. 

1987). 

Barnacles, like other crustacea, are acutely sensitive to oil and often 

experience high mortality rates when impacted by oil on shorelines. At the 

Santa Barbara spill, high mortalities were observed for intertidal barnacles 

(Chthamalus fissus) (Foster et al. 1971). 
Fish 

Concerns about impacts from oil contamination to fish in the intertidal 

environment usually involve species that use the intertidal habitat for 

spawning. This includes Pacific herring, fish that spawn on rocky substrates, 

or on fronds of Fucus or other algae growing on rocky substrates. Spawning 

herring populations were a concern in Exxon Valdez in Alaska, and 

important commercial stocks spawn in areas such as San Francisco Bay. 

A study comparing herring eggs from oiled sites with herring eggs from 

unoiled sites in Prince William Sound found no statistically significant 

differences in viability of larvae or survival rates for the two groups of eggs. 

The study did find an overall effect on biology of eggs from oiled sites, 

including a younger age of hatch from oiled sites. Confounding factors in this 

study were the patchy distribution of oil at the impacted sites, and 

temperature and depth differences (TRS 1990). 

Other intertidal spawners that have been of concern at oil spills include surf 

smelt and pink salmon. 

Summary 

1. Plants
 

Macroalgae are quite resistant to effects of oiling
 

Wetland plants are susceptible, but effects vary
 

2.	 Infauna 

a.	 Some invertebrates survive in heavily oiled sediments, 

including copepods, polychaetes, oligochaetes. 

b.	 Polychaetes may facilitate biodegradation processes. 

c.	 Buried bivalves are susceptible to impacts from oiling, and 

often bioaccumulate contaminants. 

3.	 Epifauna 

a.	 Mussels, and other attached bivalves often survive oiling, but 

also bioaccumulate 

b.	 Many crustaceans, including barnacles and crabs, are sensitive to 

acute and chronic effects of oiling 

4.	 Fish
 

Main concerns are for intertidal spawners
 
Subtidal 

Introduction 

Nearshore subtidal habitats can include shallow, soft bottom communities 

such as those found in enclosed bays, as well as eelgrass beds and offshore 

kelp communities. Subtidal habitats are often only lightly affected by oil 

spills, if at all. 

Much of the scientific literature on the effects of oil on soft bottom 

communities comes from studies conducted near offshore oil drilling rigs 

and platforms. While these give some indication of the potential effects of 

petroleum hydrocarbons, they are more indicative of ongoing, chronic 

releases, typical of a continuous source of hydrocarbons rather than a single 

event more typical of an oil spill. However, repeated, long term impacts may 

be important to consider in harbors and areas with heavy vessel traffic. 

Eelgrass beds and kelp beds are of special interest because of their high habitat 

value for marine organisms, including their use as nursery areas for many 

species. These habitats are, in most cases, not impacted by oil spills, but can be 

impacted by cleanup activities. 

Effects on submerged benthic habitats 

Soft bottom, fine sediments. A study conducted by Gray et al. (1990) 

investigated ecological effects on benthic communities near two drilling rigs 

in the North Sea, one in operation for many years, and another recently 

constructed. Changes in the diversity and number of species were noted in 

the area within 500-1000 m of the rigs. Opportunistic species were more 

dominant in these areas. Initial impacts of the newly constructed rig included 

an increased abundance of some species, and changes in the presence and 

absence of rare species. 

An experiment was conducted in subtidal soft bottom habitats in Norway. 

Field plots were treated with low level exposures of oil and compared with 

control plots. One result was a significant decrease in colonization by 

amphipods in the oiled plots. This could have been the result of mortality of 
newly settled larvae or juveniles, or of avoidance by adult amphipods 

(Bonsdorff et al. 1990). 

Studies conducted ten years after the Amoco Cadiz spill examined 

populations of several species of peracarid amphipods in different subtidal 

habitats (Dauvin and Gentil 1990). Immediately after the spill in 1979, heavy 

mortalities of amphipods occurred, with the greatest short term impacts in 

areas with fine sediments. Since these amphipods do not produce pelagic 

larvae, the researchers were interested to find out if the populations had been 

able to recover to levels similar to those measured prior to the spill. Their 

conclusions were that most populations had recovered after ten years, with 

the greatest differences seen in the fine sediment habitats. 

Subtidal stations monitored after the Florida spill in Massachusetts in 1969 

were found to be only lightly impacted by oil and showed little variation in 

species composition or density during a three-year period after the spill 

(Sanders 1978). 

Seagrass beds. Seagrass beds occur both intertidally and subtidally. 

Seagrasses in subtidal beds are rarely impacted by oil spills, since they usually 

do not come in direct contact with the oil, while intertidal plants are at greater 

risk of oiling. In Santa Barbara, after the blowout in 1969, intertidal surf grass 

(Phyllospadix torreyi) turned brown and died after oiling (Foster et al. 1971). 

At the Amoco Cadiz, "almost no" effects were found on a partially oiled 

seagrass bed of Zostera marina. The main impacts to seagrass beds appeared 

to be with the associated fauna (Zieman et al. 1984). 

One reason why seagrasses appear to be less vulnerable to oil impacts is that 

50-80% of their biomass is in their rhizomes, which are buried in sediments, 

thus less likely to be adversely impacted by oil. Thus, even if the fronds are 

affected, the plant may still be alive and able to regrow (Zieman et al. 1984). 

Shallow seagrass beds in tropical habitats, composed of Thalassia sp. were 

impacted by a spill in Puerto Rico in 1973. Strong winds and wave action in 

shallow waters was thought to carry oil into the vegetation, causing the plants 

to die. Subsequently, erosion increased in areas with dead plants. Renewed 
plant growth was observed between one and two years after the spill (Nadeau 

and Bergquist 1977). 

Treatment impacts. Sometimes, the main impacts to seagrass beds 

during a spill are physical impacts associated with response activities. Several 

authors have suggested that hot water washing of intertidal shorelines may 

move oil into subtidal areas, potentially impacting seagrass habitats. This has 

been mentioned in connection with the Exxon Valdez in Alaska (Houghton 

et al. 1991) and at Santa Barbara (Foster et al. 1971). 

At Fidalgo Bay, Washington, a refinery pipeline spill in 1991 impacted a 

shallow bay with extensive eelgrass beds. Though all efforts in spill cleanup 

attempted to protect the eelgrass, it was thought that outboard engines on 

small boats used as part of response activities may have cut some of the grass 

blades. 

Kelp beds. Offshore kelp beds are similar to eelgrass beds in that they 

support extensive benthic and pelagic communities and serve as nursery 

grounds for numerous species. While the benthic community beneath the 

kelp is rarely impacted by oil spills, the kelp fronds often float on the water 

surface and may become oiled or entrain oil. Observers have noted, however, 

that oil rarely sticks to kelp fronds in the water. 

A study conducted after the World Prodigy spill in Narragansett Bay in 1989 

examined two species of subtidal kelp that had been studied prior to the spill. 

For both species, Laminaria saccharina and L. digitata, oiling had no effect on 

growth rates, or on general condition of the plants. 

Observations were made by divers in Macrocystis beds offshore of areas 

impacted by the 1969 spill in Santa Barbara. No evidence of oil impacts to 

benthic habitats in kelp beds was observed. Oil was contained on the surface 

in floating fronds, but did not stick to the plants (Foster et al. 1971). 

Treatment effects. At the Tenyo Maru spill, which occurred off the 

Pacific coast of Washington in 1991, Nereocystis (bull kelp) beds located just 

offshore were observed to be containing floating oil at the surface amongst 
floating fronds. Based on the concern that this oil could pose a threat to sea 

otters, it was proposed that the kelp be cut at the base. This proposal was 

considered and rejected on the basis that kelp removal would adversely 

impact the associated benthic and pelagic communities during their summer 

growing season. 

Summary 

1. Soft-bottom communities 

a.	 Chronic impacts can occur from repeated dosages (such as near 

drilling rigs). 

b.	 Oil spills have limited impacts subtidally, though some sensitive 

species (amphipods) may show long-term effects. 

2.	 Seagrass beds 

Usually not impacted if subtidal, treatments can adversely affect 

these habitats. 

3.	 Kelp beds
 

Usually little-to-no impact on these habitats
 

Seafood contamination 

Background 

An issue of concern which arises in nearly every oil spill incident of any 

significance is that of contamination of seafood resources in the affected area. 

The importance of an explicit consideration of potential impacts cannot be 

overstated, as the implications to diverse interests are substantial. Real and 

potential contamination of seafood resources and the closing of harvesting 

activities affect commercial and recreational fishing interests, peripheral 

activities that support them, and subsistence users, for whom harvested items 

may represent a substantial portion of the diet. The loss of revenue resulting 

from harvest closures and/or the loss of seafood markets carry with them 

widespread implications for economic, social, and possibly cultural 

disruption, as well as litigation for recovery of damages. 

The extent to which an organism may be contaminated results from the 

combination of several factors, including the product to which seafood 
resources are exposed, the route of exposure, the metabolic detoxification 

systems present in organisms of interest, and the tissues eaten by the human 

consumer. 

Nature of the product 

As noted in the oil chemistry sections of this course, the crude oil and 

partially refined petroleum products can be very complex mixtures of 

hydrocarbons that vary from region to region (and within regions, as well). 

Focusing on the aromatic hydrocarbons as a group, it is of some importance to 

note that while they are considered to be hydrophobic, aromatics possess a 

wide range of solubilities. The degree to which a given constituent of interest 

is soluble in water not only determines how and how much an organism 

might be exposed, but also is a major factor in how the compound behaves in 

a biological system. 

The nature of the product also is of importance from another perspective. 

Davis et al. (1984) noted that higher molecular weight constituents of 

petroleum hydrocarbons can be relatively low in acute toxicity, but may have 

a high potential for causing tumors or cancers: 

These high molecular weight (four- and five-ring) compounds need careful 

consideration since potential exists for food web transfer from fisheries to 

consumer, which implies a potential change from resource impact to human 

health risk. 

Route of exposure 

There are three principal ways in which hydrocarbons may interact with an 

organism to become contaminated (Connell and Miller 1981): 

1.	 Ingestion of food contaminated with product. 

2.	 Absorption of dissolved hydrocarbons through respiration, i.e., 

through gill tissues. 

3.	 Absorption of dissolved hydrocarbons from the water through the 

skin. 

The route of exposure can be influenced by a number of related and unrelated 

parameters, including feeding strategy, fat content of the organism, the 
solubility of the product(s), physical characteristics of the water mass, 

reproductive state of the organism, etc. 

A related factor that is also important is the length of exposure. Obviously, 

this will affect not only potential tissue contamination of the organism, but 

also whether the animal experiences any direct acute or chronic toxicity. 

Metabolic detoxification systems 

To varying degrees, all organisms are capable of metabolizing foreign 

compounds in order to render them more easily excretable. The presence or 

absence of enzyme systems capable of processing specific materials in large 

part determines the ease with which hydrocarbons are processed and passed 

from an organism. 

Some invertebrates such as bivalves do not carry the biochemical machinery 

necessary to metabolize petroleum hydrocarbons. As a consequence, aromatic 

hydrocarbons are not readily excreted and instead tend to accumulate in body 

tissues. It is for this reason that bivalves such as mussels, clams, and oysters 

are often used as "sentinel" organisms to assess environmental exposure to 

contaminants. 

The fact that these organisms can concentrate hydrocarbons from the 

environment is of concern from a seafood perspective. Although shellfish 

may not be able to rapidly metabolize aromatic hydrocarbons, human 

consumers are generally able to do so owing to the presence of efficient 

enzyme systems. However, the by-products resulting from metabolism of 

some aromatic compounds can be highly reactive and are known to induce 

cancers or other toxicological effects. 

In contrast to bivalves, fish are considered to be rapid metabolizers of 

aromatic hydrocarbons. This is thought to be attributable to the presence of 

certain enzyme systems (e.g., cytochrome P-450-dependent mixed function 

oxidase, epoxide hydrolase; glutathione-S-transferase) that facilitate the 

removal of the hydrocarbons and metabolites from their bodies. As a result, 

fish will generally not accumulate aromatic hydrocarbons in their flesh. In 
the subsequent discussion of subsistence seafood concerns, other approaches 

to evaluating fish exposure to hydrocarbons are described. 

Tissues eaten by human consumers 

Although it is somewhat obvious that specific portions of a seafood organism 

are favored for human consumption, ethnic and cultural differences in 

consumption patterns must be considered. For example, although 

contamination of muscle tissue of fish would be addressed as a problem in 

most spill situations, the fact that representatives of certain ethnic groups also 

use other parts such as the liver, reproductive organs, or head may necessitate 

a more conservative approach. 

The higher lipid, or fat, content of viscera relative to muscle tissue may 

increase the extent of exposure to lipophilic ("fat-loving") compounds such as 

aromatic hydrocarbons. However, this appears to be less of a concern with 

respect to petroleum-related hydrocarbons than it is for such persistent 

organic compounds as the chlorinated pesticides or polychlorinated biphenyl 

mixtures, primarily because for many animals, aromatics are metabolized and 

removed from tissues more readily than other hydrocarbons. 

Tainting 

Tainting has been variously defined, but generally is considered to be the 

development of flavors or odors in seafood that are not typical of the seafood 

itself. Although causes for tainting are not necessarily limited to exposure to 

hydrocarbons—spoilage, for example, can cause a familiar "off" smell or 

taste—in the context of this discussion, the term will refer to that arising from 

petroleum hydrocarbons. 

It should be noted that by definition, tainting comprises those examples of 

seafood contamination that are identifiable through normal human sensory 

systems such as taste or smell. Tainting, therefore, is determined by 

organoleptic analysis--which is a multisyllabic way of saying the detection of 

oil through taste or smell. The lighter fractions of a petroleum hydrocarbon 

mixture are those that would be most likely to be detected through 

organoleptic sampling; the heavier weight aromatic hydrocarbons, many of 

which have been identified as having carcinogenic implications, would 
remain undetected through smell or taste analyses. An additional 

implication of this is that organoleptic tests would be of greatest use early in a 

spill event, before weathering reduces the more volatile components. 

Because it is a sensory phenomenon, tainting is difficult to quantify. It is 

dependent on both the sensitivity as well as the preference of the individual, 

both of which obviously can be quite variable. Perception, too, enters into the 

determination of tainting. Tidmarsh and Ackman (1986), in an excellent 

review discussion on the subject, note: 

Fear of tainting can be as serious a problem as an actual tainting incident. 

Consumer resistance, closures imposed by regulatory authorities, and embargoes 

on harvesting activities by producers resulting from even the remote possibility 

that seafoods are tainted can cause severe economic losses. 

In an oil spill situation, real or perceived tainting will result in a tremendous 

amount of public and business interest concern, and inevitably, political 

posturing. There are likely to be pressures to improve the measurement of 

the extent of contamination, which will lead to chemical analyses. 

Chemical analysis 

Organoleptic methods of seafood testing are not only limited as to the 

chemical compounds that can be detected (e.g., low vs. high molecular-weight 

aromatic hydrocarbons), but also are limited by a "detection limit," below 

which even a sensitive evaluater cannot smell or taste evidence of tainting. 

An approximate lower limit for organoleptic detection of emulsifiable oil is 

15 ppm, although certain crude oil constituents are detectable at lower levels 

(e.g., kerosene at 0.1 ppm, naphthalene at 1.0 ppm, toluene at 0.25 ppm). 

Other references cited in Connell and Miller (1981) found that tainting is 

caused by levels of refined or crude petroleum products in the range of 4 to 

300 ppm. These levels are generally well above established levels of concern 

for a number of hydrocarbon compounds. 

In order to avoid the detection limitations of organoleptic methods, to 

eliminate the large degree of subjectivity involved, and to elicit relatively 

repeatable quantitative results that can serve as the basis for comparison for 

regional or time-series analyses, chemical methods are used. While chemical 
analyses require laboratory facilities and can be very expensive, they vastly 

improve the range of compounds measurable and the levels to which results 

can be quantified. 

Case history 

There have been many oil spills where commercial fishing concerns have 

arisen, impacts on fishing activities realized, and severe financial burdens 

imposed. During the Amoco Cadiz incident, for example, the oyster industry 

in Brittany was forced to destroy in excess of $2 million worth of seafood 

(Tidmarsh and Ackman 1986), while total costs to the oyster industry were 

estimated at nearly $26 million (Sorenson 1983). Both fish and shellfish were 

reported to have been tainted in the wake of the Torrey Canyon spill (Connell 

and Miller 1981). Closer to home, Blumer et al. (1970) described and studied 

the tainting and chemical contamination of edible shellfish following a spill 

of No. 2 fuel oil in Buzzards Bay, Massachusetts. 

Much less common are spills where subsistence seafood concerns become an 

issue, and in most state waters, these would not be expected to be as 

significant as they were in Alaska, or in the recent Tenyo Maru spill off the 

coast of Washington state. However, subsistence harvesting is not necessarily 

limited to Native American peoples; certain ethnic groups, including recent 

immigrants from Europe or Asia, may rely heavily on subsistence seafoods. 

For the sake of convenience and because the example is a fairly recent one, 

the Exxon Valdez spill is used here as a case history that included both 

commercial fishing concerns, as well as significant subsistence seafood issues. 

Exxon Valdez 

Commercial fishing impacts 

From the beginning of the spill in March 1989, concerns were voiced about 

possible contamination of commercial fishing harvests in the affected area. 

The implications to the seafood industry in Alaska were obvious: Prince 

William Sound and the Gulf of Alaska produce the largest tonnage of halibut 

in the U.S.; Kodiak has consistently ranked as a leading U.S. port in terms of 
catch landing weights as well as values; Prince William Sound alone had 

been expected to produce a salmon harvest worth $70 to 100 million (NOAA 

1990). Other fishing-related activities contributed additional millions of 

dollars of activity to the state economy. 

Although little hard evidence existed that oil was contaminating commercial 

fisheries resources, the Alaska Department of Fish and Game and the 

Department of Environmental Conservation reacted in two ways to allay 

fears about contamination of fish and shellfish: 

1.	 Closure of commercial fisheries in the area most heavily affected by 

oil, where oil was evident on the water surface or on adjacent 

shorelines; 

2.	 Adoption of a "zero tolerance" policy for fish catches, under which 

any visible tainting of commercial catches would result in closure of 

the affected fishery. 

There was evidence that some of the oil sightings which resulted in 

commercial fishing closures were attributable not to the oil spill, but 

ironically, to leakage of refined products from fishing vessels themselves. 

Trajectory models and previous experience of NOAA scientists had suggested 

a low probability that the oil sighted was from the Exxon Valdez, and 

subsequent chemical analysis confirmed that this was true. 

Additional efforts by the U.S. Coast Guard and NOAA provided overflight 

information and trajectory analyses to commercial fisherman in order that 

known or projected areas of contamination could be avoided during fishing 

activities. All of these steps were taken primarily to prevent the market 

perception of contamination and to maintain public confidence in the quality 

of Alaskan seafood. 
Subsistence seafood issues 

(Material for this summary was provided by L. Jay Field, NOAA, and is drawn 

largely from Field and Walker 1990). 

The area affected by the Exxon Valdez spill included 18 mostly rural 

communities with a combined population of over 15,000 residents. Although 

the towns and villages included larger fishing ports such as Kodiak, Seward, 

and Cordova, most of the communities were small, predominantly Alaskan 

Native villages. Residents of the villages relied heavily on subsistence fish, 

shellfish, birds, and mammals to provide protein in their diets. Because of 

this, the oil spill had the potential to affect health and lifestyles in a 

fundamental way, and levels of concern in the villages were understandably 

high. 

One of the first responses to subsistence concerns was the formation of the 

Alaska Oil Spill Health Task Force (OSHTF), an interagency group chaired by 

an Indian Health Service physician with representatives from state and 

federal agencies, native organizations, and Exxon. The task force served as 

the focal point for discussion and for activities to assess the extent of seafood 

contamination. 

Meanwhile, in May and July of 1989, the state of Alaska epidemiologist 

released bulletins discussing health implications of the spill, and advising 

residents to use organoleptic means for determining the safety of harvested 

seafoods: i.e., if the seafood did not appear to be contaminated by visual 

observation, smell, or taste, it was probably safe to eat. 

Concerns of villagers remained high. In early summer of 1989, Exxon began 

planning a study to analyze large numbers of subsistence fish and shellfish for 

aromatic hydrocarbon contamination. At the same time, the U.S. Coast 

Guard and the OSHTF requested that NOAA take an active role in addressing 

subsistence seafood concerns of Native villagers. A result of these events was 

an agreement between Exxon and NOAA to cooperatively study the potential 

contamination of subsistence seafoods collected in areas traditionally fished 

by communities. NOAA and Exxon biologists would make the field 

collections in consultation with representatives from the various villages, 
with chemical analyses performed by the National Marine Fisheries Service 

Environmental Conservation Division laboratory in Seattle. The OSHTF 

reviewed the study objectives and was instrumental in determining means of 

communication of goals and results to affected villages. 

Collections of shellfish, bottomfish, and salmon were made in approximately 

13 subsistence areas, with control samples also collected in unoiled regions. 

Edible tissues from fish and shellfish were analyzed for aromatic hydrocarbon 

contaminants, selected to reflect the constituents found in Prudhoe Bay crude 

oil and to include those that were considered to be persistent in the 

environment with implications for long-term human health impacts. Bile 

from fish was also collected, as fish rapidly metabolize aromatic hydrocarbons 

and the by-products are concentrated in bile prior to excretion. Bile analyses 

were used as a rapid screening test for indications of exposure to 

hydrocarbons. 

In 1989, when levels of exposure to the organisms would have been highest, 

143 samples of shellfish (mussels, clams, chitons) and 210 samples of fish 

(three species of salmon, and halibut) were analyzed. Shellfish from two 

areas showed relatively high levels (>1000 ppb) of total aromatic 

hydrocarbons. One area was Windy Bay, a site on the Kenai Peninsula which 

had been heavily oiled. The other was Near Island, which is adjacent to the 

boat harbor in Kodiak. Two other areas (Chenega and Old Harbor) yielded 

shellfish with levels >100 ppb, while samples from the remainder of the sites 

were generally <10 ppb and comparable to uncontaminated control samples. 

The high concentrations of hydrocarbons in Windy Bay samples were clearly 

associated with the Exxon Valdez spill. Those from Near Island, however, 

were much more questionable in origin, as they were found in an area not 

known to have been directly impacted by the spill. Moreover, the collection 

site was adjacent to a busy boat harbor, where small spills of fuel and other 

petroleum products are common. Examination of the ratios between lowerweight aromatic hydrocarbons and higher-weight aromatic hydrocarbons 

supported the idea that hydrocarbons contaminating the shellfish near 

Kodiak were not of Exxon Valdez origin. Similarly, samples from the 

Chenega site, which showed moderately elevated hydrocarbon levels, were 
collected in an area with many derelict wooden pilings that had been treated 

with creosote, and an area that had also experienced an unrelated fuel oil spill 

in the recent past. 

Generally speaking, tissue hydrocarbon levels in finfish were about an order 

of magnitude less than those found in shellfish. Although bile analysis in 

salmon indicated some exposure to hydrocarbons, of the 210 samples of edible 

fish tissue analyzed in 1989, only 11 samples exceeded 10 ppb total aromatic 

hydrocarbons in edible tissues, and only one exceeded 100 ppb. 

The significance of the hydrocarbon levels found in the subsistence seafoods 

was an extremely difficult issue to address. No advisory levels or other 

guidelines for the safety of foods contaminated with oil were available at the 

time of the spill, and a review of literature showed that little information 

existed on the health effects of oil-contaminated seafood. To interpret the 

study results, NOAA convened two meetings of specialists from several 

disciplines related to human health implications of eating contaminated 

seafood. Representatives included scientists from the U.S. Food and Drug 

Adminstration (FDA), the National Institutes of Environmental Health 

Sciences, the Agency for Toxic Substances and Disease Registry, the University 

of Alaska, NOAA, and Exxon Biomedical Research Sciences. 

The group concluded that finfish from all areas were safe to consume, but 

that shellfish from areas that contained the relatively highest concentrations 

(i.e., Windy Bay and Near Island) should be avoided. These 

recommendations were included in newsletters sent to all villages, and 

OSHTF representatives visited each affected community to present and 

explain the findings, and to answer questions. 

A direct request from the OSHTF to the FDA to perform a risk analysis based 

on the analytical chemistry results and the known patterns of subsistence 

seafood consumption resulted in the issuance of a highly qualified opinion 

that the additional cancer risk imposed by consumption of oil contaminated 

subsistence seafoods—even the most heavily contaminated shellfish from 

Windy Bay and Near Island—was low. 
The success of the risk communication efforts to the villages was mixed. The 

chemistry data and interpretation of results were not successful in allaying 

concerns about subsistence seafood safety. As Field and Walker noted: 

The high degree of alarm experienced by the village communities about 

subsistence food safety made them unreceptive to reassurances based on 

qualitative measures such as organoleptic testing. In addition, their 

apprehensions were reinforced by the long interval between the collection of 

tissue samples for analysis and the communication of interpreted results. A risk 

communication workshop. . .with representatives from six villages revealed 

differences between individuals in the effectiveness of the conclusions about 

food safety. The consensus, however, was that communications efforts need to 

begin immediately following a spill and continue at frequent intervals, and 

that those affected should be directly involved in the process. A variety of 

approaches should be used that include a mix of written and face-to-face 

communication techniques. 

The Exxon Valdez experience illustrates many of the problems that may be 

unavoidable even with well-planned and well-funded efforts to address 

concerns about contaminated seafoods, both from commercial fishing and 

subsistence user perspectives. The suspicion and tendency to disregard 

analytical results from analysis of potentially contaminated seafood that was 

evident with Native communities in Alaska may to some extent reflect 

reactions that could be expected from the public at large in the event of an oil 

spill occurring in an area with important fisheries resources. Noting the 

critical nature of perception in dealing with sensitive markets, the concept of 

highly visible efforts to prevent potentially contaminated seafood from 

reaching the market is worth considering, even if the chances for 

contamination is realistically considered to be low. 

In a summary of the Exxon Valdez experience, Walker and Field (1991) 

observed that initial oil spill response activities have generally assigned a 

lesser priority to human health concerns that might arise from 

contamination of seafood. This was attributed to the low probability that fish 

would be exposed to high levels of hydrocarbons, the ability of fish to 

relatively rapidly metabolize petroleum-related compounds, and the ability of 

human consumers to detect tainted seafood through smell and taste. Because 

the risk to human health has been considered to be low, the National 

Contingency Plan does not provide guidance to planners and responders. As 

a result, fisheries and human health issues are not raised explicitly until 
fishermen, fisheries agencies, or the public do so. Because of the potential for 

substantial impacts attributable to seafood concerns, planners and responders 

would be well-advised to anticipate these considerations and incorporate 

them into regional or local contingency plans. 

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Publishers. 181pp. 
5 Oil Spill Response and Cleanup Techniques 

Jacqueline Michel1, Gary Shigenaka2, and Rebecca Hoff2 

Page 

Introduction.....................................................................................................5-1
 

Open-water response techniques
 

Dispersants..................................................................................................5-1
 

Dispersant types and application methods..........................5-2
 

Review of dispersant tests...............................................................5-11
 

Monitoring of dispersant applications......................................5-13
 

Toxicity of oil spill dispersants.......................................................5-17
 

Mammals.................................................................................................5-27
 

Birds...........................................................................................................5-31
 

Fish..............................................................................................................5-34
 

Crustaceans..........................................................................................5-35
 

Molluscs....................................................................................................5-36
 

Corals.........................................................................................................5-38
 

Microorganisms..................................................................................5-38
 

Plants.........................................................................................................5-40
 

Summary.....................................................................................................5-42
 

Dispersant use guidelines.................................................................5-44
 

Shoreline cleanup methods and application.............................5-50
 

Approved physical treatment methods................................5-50
 

No action..................................................................................................5-51
 

Manual removal.................................................................................5-51
 

Passive collection sorbents........................................................5-52
 

Debris removal...................................................................................5-52
 

Trenching...............................................................................................5-51
 

Sediment removal............................................................................5-53
 

Cold water flooding (deluge).....................................................5-53
 

Cold water low/high pressure.................................................5-54
 

1Research Planning, Inc., P.O. Box 328, Columbia, South Carolina 29202 

2National Oceanic and Atmospheric Administration, 7600 Sand Point Way N.E, Seattle, Washington 

98115 
Page 

Warm water moderate/high pressure.............................5-55
 

Hot water pressure washing....................................................5-56
 

Slurry sand blasting.......................................................................5-57
 

Vacuum...................................................................................................5-57
 

Treatment methods requiring RRT approval.....................5-58
 

Cutting vegetation...........................................................................5-58
 

Chemical..................................................................................................5-59
 

Burning....................................................................................................5-61
 

Nutrient enhancement.................................................................5-62
 

Microbial addition..............................................................................5-63
 

Sediment reworking.......................................................................5-63
 

Shoreline removal, cleansing, and replacement........5-64
 

Other techniques..............................................................................5-65
 

Beach cleaners..............................................................................5-65
 

Elastol...................................................................................................5-65
 

Bioremediation.............................................................................5-68
 

References.........................................................................................................5-99
 
Chapter 5.
 

Oil Spill Response and Cleanup Techniques
 

Introduction 

The majority of oil spills (number of events) occur in coastal waters or in ports. 

Therefore, contamination of the shoreline is likely at most spills, and thus the issues 

of oil recovery and shoreline cleanup must be addressed. Nearly all shoreline 

cleanup methods have some kind of environmental impact, so selection of a 

cleanup method inherently forces us to make some kind of tradeoff of the effects of 

the oil versus the effects of the cleanup. In this chapter, we describe some of the 

commonly used techniques for oil spill response and shoreline cleanup. There has 

been little innovation in the physical removal technologies since the 1970s. The 

only really new techniques developed in the last few years involve chemical and 

biological treatment methods. 

Open Water Response Techniques: Dispersants 

It has been nearly 25 years since the Torrey Canyon oil spill, where large amounts of 

highly toxic degreasers were applied directly to oiled rocky shores, marshes, and sand 

beaches in England. The impacts to intertidal biological communities were 

extensive and well documented (Smith, 1968). This very negative experience led to 

the prohibition of dispersant use in many countries and the perception that all 

dispersants are highly toxic. Since that time, there has been much talk and little 

"action" about dispersants. New formulations have been produced, many of which 

have acute toxicities lower than the constituents and fractions of most crude oil 

products (NRC, 1989). There have been extensive laboratory and field tests on 

effectiveness and toxicity, and workshops and protocols for dispersant-use decision 

making during spills. The number of papers presented at the Oil Spill Conference 

over the last ten years reflects the growing interest in the potential for use of 

dispersants in the first half of the decade and the dropoff in interest in the second 

half as dispersants failed to become an accepted spill response tool: 

1981 - 15 papers in two sessions 

1983 - 10 papers scattered around in various sessions 

1985 - 25 papers 

1987 - 30 papers 

1989 - 15 papers 

1991 - 11 papers 

5-1
 
There are many good reports on dispersants, including the most recent (1989) 

National Research Council publication Using Oil Spill Dispersants on the Sea. In 

this section we only briefly summarize the key issues on dispersant application, test 

results, toxicity, and guidelines for decision making on dispersant use. 

Dispersant Types and Application Methods 

Simply stated, dispersants work because they contain surfactants–chemicals which 

have molecules that have a water-compatible end and an oil-compatible end. At the 

proper concentration and mixing energy, the surfactant molecules can attach to oil 

particles and reduce the interfacial tension between oil and water. This reduction in 

the oil-water interfacial tension allows oil droplets to break off from the slick and 

minimizes the tendency to re-coalesce (Fig. 5-1). 

Figure 5-1. Mechanism of chemical dispersion. A) Surfacant locates at oil-water 

interface. B) Oil slick is dispersed into micelles or surfactant-stabilized droplets. 

(Canevari, 1969.) 

Although the detailed composition of dispersants is proprietary, their general 

characteristics are broadly known. The most commonly used surfactants are 

nonionic formulations, such as sorbitan monooleate, ethoxylated sorbitan 

monooleate, and polyethylene glycol esters of unsaturated fatty acids. Modern 

formulations contain: 

5-2
 
•	 15-75 percent of one or more nonionic surfactants 

•	 5-25 percent anionic surfactant 

•	 Solvent of either:
 

-water
 

-water-miscible hydroxy compounds
 

-hydrocarbons
 

Dispersants are applied either "neat" or diluted. The standard dosage is a 

dispersant:oil ratio of 1:20. Assuming an average slick thickness of 0.1 mm, this 

dosage would require five gallons per acre of dispersant. However, it should be 

noted that nonuniformity of the slick is a very real problem in dispersant 

applications. In the U.S., the effort has been to have a range of aircraft available for 

spraying dispersants on short notice, and there has been considerable research on 

optimization of droplet size and the equipment needed to produce the droplets. 

NRC (1989) lists four criteria for effective dispersal of oil: 

1)	 The dispersant must reach the slick, which can be a major problem if 

strong winds blow the droplets away from the slick, or visibility limits the 

ability to accurately position the aircraft over the slick during application. 

2)	 The dispersant must mix with the oil or move to the oil-water interface. 

This is where droplet size becomes important; too large droplets pass right 

through the slick and too small droplets stay on the oil surface or blow 

away. 

3)	 The dispersant must reach the proper concentration at the interface, so 

that a maximum reduction in the interfacial tension is reached. Note that 

dosage is never uniform or well-known because of nonuniformity in the 

slick thickness. 

4)	 The oil must disperse into droplets. Therefore, some minimum energy is 

needed for dispersants to work. 

These logistical factors are obviously difficult to overcome. An added problem is 

that dispersant efficiency testing shows that many dispersants are not very effective, 

even under controlled laboratory conditions. Fingas et al. (1991a) used the "swirling 

flask" test to measure the effectiveness of four dispersants on a range of crude oils 

(with emphasis on those important to Canada). Table 5-1 lists the test results. It is 

obvious that there are clear differences among dispersants and oils. The average 

effectiveness was as follows: 

Table 5-1. Dispersant effectiveness and oil properties. (Fingas et al., 1991a.) 

5-3
 
• Heavy crude oils 1 percent 

• Medium crude oils 10 percent 

• Light crude oils 30 percent 

• Very light crude oils 90 percent 

• Weathered oils Always lower than fresh 

Weathering is an important factor in the decision to attempt use of dispersants. 

Most researchers have shown that dispersant effectiveness is closely tied to viscosity: 

dispersants are most effective at viscosities below 2000 centistokes (cSt) and not 

effective at all above 10000 cSt (Cormack et al., 1986/87). Figure 5-2 shows the 

increase of viscosity for selected crudes over time, indicating the point after which 

dispersant effectiveness would drop significantly. This information and others has 

led to the rule of thumb that dispersants must be applied within the first 24 hours to 

be effective. 

A recent paper by Fingas et al. (1991b) summarizes laboratory studies on dispersant 

effectiveness correlated to temperature, salinity, dispersant dosage, and the percent 

composition of asphaltenes, aromatics, polar compounds, saturate compounds, and 

waxes. Figures 5-3 through 5-7 shows the results using Alberta Sweet Mixed Blend 

5-4
 
Figure 5-2. Increase of viscosity of several crude oils with weathering. (Cormack et 

al., 1986/87.)

 and Corexit 9527, except where noted. Fingas et al. (1991b) summarized their studies 

as follows: 

•	 Effectiveness increases exponentially with temperature. 

•	 Optimal salinity is 40 parts per thousand, with rapid decreases on either 

side. Dispersants formulated for marine application are not effective at all 

in freshwater. 

•	 Dosage is very important. 

•	 Effectiveness is positively correlated with saturate content. 

•	 Effectiveness is negatively correlated with the asphaltene, aromatic, and 

polar content. 

•	 Effectiveness is not directly related to viscosity, but rather to the asphaltene 

content, which strongly correlates with viscosity. 

5-5
 
Figure 5-3. Variation of dispersant effectiveness with temperature. (Fingas et al., 

1991a.) 

5-6
 
Figure 5-4. Variation of dispersant effectiveness with dispersant quantity. (Fingas et 

al., 1991a.) 

5-7
 
Figure 5-5. Variation of dispersant effectiveness with salinity. (Fingas et al., 1991a.) 

5-8
 
Figure 5-6. Correlation of dispersant effectiveness with A) saturate content, and B) 

aromatic content. (Fingas et al., 1991a.) 

5-9
 
Figure 5-7. Correlation of dispersant effectiveness with A) asphaltene content, and 

B) polar compounds content. (Fingas et al., 1991a.) 

5-10
 
Review of Dispersant Tests 

Field test results have been highly varied. Fingas et al. (1991a) report that there have 

been 107 test spills for determining dispersant effectiveness in the last 12 years. 

Results were reported as an estimate of the effectiveness percentage for only 25 

spills. The average effectiveness was 30 percent, with values ranging from 0 to 100 

percent. Most of the time, effectiveness was determined by measurement of the 

concentrations of oil in the water column below dispersed slicks. Surface slick 

dimensions were used to calculate the amount of dispersed oil. Fingas et al. (1991a) 

argues that this approach is invalid because surface slicks have little positional 

relationship to the underwater dispersed plume. 

Open-ocean field trials are the best indication of dispersant effectiveness and the 

likely concentrations of oil in the water column over time and with depth. Watercolumn concentrations are particularly important in the assessment of impacts to 

organisms. The best-documented field trials in the U.S. were sponsored by API, at 

locations off New Jersey in 1978 and California in 1979, reported in McAuliffe et al. 

(1981). Figure 5-9 shows the California test results for Prudhoe Bay crude oil sprayed 

with Corexit 9527 from aircraft immediately after release. Within 30 minutes, the 

highest concentrations of dispersed oil in the water column averaged 41 ppm at 1 

meter and 10 ppm at 3 m (Fig. 5-7a). Nearly 40 percent of the oil was dispersed into 

the top 2 m. After one hour, downward mixing of the dispersed plume was evident 

(Fig. 5-7b), with 31 percent of the oil in the top 2 m, 24 percent at 2-4 m, and 29 

percent at 4-7.5 m. After three hours, maximum concentrations of 1-2 ppm were 

recorded through 6 m and 0.5 ppm at 9 m. Other field trials in the North Sea, 

Canada, and France have shown similar results (summarized in NRC, 1989, Table 4-

3), with maximum concentrations of 1 to 100 ppm in the top meter. 

These field results are are not very different than the model calculations of Mackay 

and Wells (1983), which predict a maximum concentration of 1 ppm at 10 m depth 

(Fig. 5-8). The general rule that dispersants should not be used in water depths less 

than 10 m is derived from the assumption that 1 ppm is a threshold for acute 

toxicity above which impacts to benthic organisms might occur. 

5-11
 
Figure 5-8. Predicted concentrations of dispersed oil under a slick 0.15 mm thick for 

selected periods after dispersant application. The dots are the actual values from the 

California sea trials in McAuliffe et al. (1981). 

5-12
 
Monitoring of Dispersant Applications 

There have been very few spills in the U.S. where approval was granted for use of 

dispersants in combatting the spill. Typical of emergency conditions was the spill 

associated with the fire and breakup of the Puerto Rican in 1984 off the Farallon 

Islands. Nearly 2,000 gallons of Corexit 9527 were applied to the slicks three days 

after the initial incident. Weather prevented implementation of the water-column 

monitoring program originally required, thus effectiveness was measured by visual 

observation. But, observers were not able to reach consensus on how much oil was 

dispersed, though most estimates ranged from 0 to 30 percent. 

It is obvious that we will never resolve the issue of whether dispersants work and 

what are the impacts to water-column organisms compared to undispersed slicks 

without high-quality field monitoring plans. But, how are we to be prepared for 

such a monitoring program under emergency conditions when quick approval to 

proceed is being sought to optimize effectiveness? The only solution is having a 

detailed, yet flexible plan, trained people, and a lot of luck. NOAA has been 

involved in two "spills of opportunity" where they tested various dispersant 

monitoring strategies: the Pac Baroness off California in 1987 and the Mega Borg off 

Galveston, Texas in 1990. These monitoring results are summarized in Payne et al. 

(1991a; b). Lessons learned from these two spills include: 

•	 There must be good communications among the various aircraft and boats 

involved in direction, observation, and sampling. 

•	 A very detailed plan must be developed, in advance, with the roles and 

responsibilities of each group spelled out. 

•	 Both videotape and 35 mm photography should be used for 

documentation. The video camera should be mounted on the nose of the 

observation helicopter and a remote used to direct it. Whenever possible, 

a surface vessel or other feature should be kept in the field of view for 

reference and scale. 

•	 If water-column sampling is required, continuous flow fluorometers are 

useful but samples are needed for confirmation of dispersed oil 

concentrations. 

•	 For large applications, SLAR and IR/UV remote sensing are good 

techniques for monitoring the slicks. 

5-13 
Figure 5-9. Results of water sampling at the California 1979 dispersed oil 

experiments, where 20 barrels of crude oil were treated (McAuliffe et al., 1981). A) 

Immediately after the application of dispersants, maximum concentrations in the 

top meter averaged 41 ppm. 

5-14
 
Figure 5-9. Continued. B) Concentration of oil (in ppm) in the first hour after 

dispersant application. 

5-15
 
Figure 5-9. Continued. C) Concentration of oil (in ppm) 3-4 hours after dispersant
 

application. Note that the highest concentrations were near the drogue, at about 2
 

ppm.
 

5-16
 
Many groups question whether a monitoring program can, in reality, include a 

water-column sampling component. Only under the best of conditions is it likely 

that a comprehensive and well-conducted water sampling program will be possible. 

In the two recent spill of opportunity dispersant monitoring programs, the spills 

were on-going, with a continual release of fresh oil. In the NOAA studies, the 

monitoring groups had 1-3 days to prepare, and the results were still less than 

optimal. Anyone can imagine what it would be like to get a water sampling 

program off “at first light” after finally getting approval to use dispersants that 

evening! It might be better to concentrate on training and logistics for high-quality 

visual and photographic observations. 

Toxicity of oil spill dispersants 

Introduction 

In 1967, the tanker Torrey Canyon spilled nearly 1 million bbl of crude oil into the 

waters off the coast of England. In the two weeks that followed, approximately 

10,000 bbl of chemical dispersants were sprayed on the impacted waters and 

shoreline in an attempt to remove the spilled oil. The biological results of this 

application bordered on the disastrous, and were highly visible. On rocky 

shorelines, mortality to intertidal organisms was clearly evident; molluscs such as 

limpets, snails, barnacles, and mussels were particularly hard hit. Subsequent 

toxicity evaluations of the most widely used product showed that the concentration 

necessary to kill half of populations of subtidal test organisms in 24 hours (LC50) 

ranged between 0.5 to 5.0 ppm. LC50 values for intertidal organisms ranged between 

5.0 ppm and 100 ppm. The concentrations at which the dispersants were toxic to all 

organisms were much lower than the concentrations required to disperse the 

stranded oil (1:2-4, dispersant:oil), and very much lower than actual application 

amounts (10,000 tons of dispersants to 14,000 tons of stranded oil) (Southward and 

Southward 1978). 

In this instance, ecological impact clearly took a back seat to the mandate to remove 

the spilled product. Priorities were esthetic, not ecological (National Research 

Council 1989). However, the consequences of this treatment philosophy were longterm, and Southward and Southward noted that ten years after the Torrey Canyon 

incident, heavily oiled locations that had received 

5-17
 
repeated applications of the dispersants had apparently not recovered to a state 

comparable to lightly oiled, lightly dispersed areas. 

The National Research Council (1989), in recounting the sequence of events, noted: 

. . .adverse publicity during and after the Torrey Canyon incident gave dispersants a bad 

reputation. Indeed, the experience led to a very cautious attitude toward dispersant use among 

several industrialized nations. 

In the 25 years since the Torrey Canyon, a number of changes have taken place to 

improve the perceptions about dispersants. Nevertheless, dispersant use as a spill 

response technique has been employed relatively sparingly, with mostly 

inconclusive results, in the intervening years. The National Research Council cited 

only only six examples in which dispersants were used operationally in spill 

response between the Torrey Canyon incident and 1989. The Exxon Valdez in 

1989,Mega Borg in 1990, and theVesta Bella barge sinking in the Caribbean in 1991 

involved the use of dispersants, also with mixed results. 

The most significant change affecting the acceptability of dispersant use is associated 

with the dispersants themselves: older dispersant formulations were essentially 

industrial degreasing agents, identical or similar to those used for cleaning engine 

rooms and bilges. These contained a number of toxic hydrocarbon-based 

constituents, such as kerosene, mineral spirits, and naphtha. So-called "second 

generation" oil dispersants have much different formulations, with less toxic 

ingredients such as alcohols, glycols, and glycol ethers (Fingas et al. 1979). One of the 

most common and widely stockpiled of the newer dispersants is Corexit 9527, 

manufactured by Exxon. It is a mixture of non-ionic (48%) and anionic (35%) 

surfactants in a hydrocarbon solvent (17%). The surfactant formulation includes 

ethoxylated sorbitan mono- and trioleates, sorbitan monooleate and sodium dioctyl 

sulfosuccinate. Solvents in Corexit 9527 are ethylene glycol monobutyl ether and 

water (Singer et al. 1990). 

Acute toxicity of newer dispersants appears to be considerably less than the older, 

Torrey Canyon-zera products; Fingas et al. (1979) noted about a 30-fold difference in 

96 hr. tests with rainbow trout. The National Research Council, in its recent review, 

concluded that toxic effects of dispersants are generally less 

5-18
 
than crude oils and refined products. However, exposure to second generation 

dispersants has also been demonstrated to result in adverse effects on marine 

organisms, and it is important to factor toxicological implications of dispersant use 

into the decision matrix for oil spill response. 

General dispersant toxicity considerations 

The explicit consideration of toxicological effects resulting from dispersant use is not 

a straightforward task. It can, in fact, be quite confusing and confounding to the 

decision-making process. The bottom line of toxicity to an ecosystem or a specific 

living resource in question is very much a function of at least five components: the 

dispersant, the oil being dispersed, the nature of exposure (i.e., concentration and 

length), the organism in question, and the life stage of the organism in question. 

The combination of these factors, as well as others that may be relevant in specific 

situations, will determine the ultimate impact on the resources. 

Beyond consideration of the toxicity of dispersants alone, the toxicity of dispersed oil 

that would be expected to result from an application also should be factored into the 

ecological assessment. The National Research Council concluded that acute toxicity 

of dispersed oil was generally attributable to the oil fraction rather than the 

dispersant fraction. Assuming that dispersed and untreated oil invoke the same 

level of toxicity, the shift in the nature of exposure becomes an important 

determinant of effect. That is, are potential toxic impacts being shifted from surface 

waters to the water column? 

The concept of LC50 has been discussed previously in other sections. Briefly, it 

involves the exposure of a population of test organisms to a constant concentration 

of a compound for a specific period of time, usually 24-, 48- or 96-hours. By 

extrapolating the toxicity obtained from a number of different concentrations, the 

exposure level at which half the test organisms die is obtained. Anderson et al. 

(1984) noted that this method, while straightforward in concept, has a number of 

shortcomings, particularly with respect to assessment of petroleum compounds: 

(LC50) tests were usually conducted in closed ("static") systems without feeding test organisms 

or replenishing the toxicants. As more chemical analyses were conducted, investigators began to 

realize that significant amounts of many toxicants sorbed to the walls of vessels, evaporated, 

and were taken up by organisms. In tests with petroleum, there were also problems with 

droplets moving to the surface (forming slicks) and numerous alterations related to different 

specific components. 

5-19
 
Many of the LC50 tests performed and reported in the literature have been based on 

the nominal concentrations of dispersant and/or dispersed oil, and not those 

actually measured in the water to which organisms were exposed (nominal 

concentrations are those based on the volume mixtures of contaminants and not the 

concentrations in the water). This can be a fundamental source of error in 

estimating exposure concentrations, due to the tendencies of hydrocarbons either to 

adhere to test equipment, as well as the difficulties in getting largely hydrophobic 

("water-hating") compounds to dissolve in test waters. 

In order to address some of the inadequacies of classical LC50 toxicity testing and to 

provide a basis for comparing results from many studies using different exposure 

times or concentrations, Anderson et al. (1984) demonstrated the concept of the 

toxicity index. The toxicity index considers exposure duration and toxicant 

concentration to be equal factors in toxicity. The index is expressed as the product of 

the two, with values reported in ppm days or ppm hours. Under the assumptions of 

this approach, a two-day exposure to 10 ppm of a contaminant (yielding a toxicity 

index value of 20 ppm day) should produce the same toxic effect as a five-day 

exposure to 4 ppm, or a ten-day exposure to 2 ppm. 

Singer et al. (1990) reviewed previously reported results as well as new data 

generated in a study of dispersant toxicity to California marine organisms, and 

portrayed calculated toxicity index values in a graphic reproduced below as 

Figure 5-10. 

5-20
 
Figure 5-10.	 Comparison of toxicity index calculations for Corexit 9527. Shaded and solid boxes 

indicate no observed effects concentrations and median effect ranges, respectively, 

obtained by Singer et al. for California species. Arrows indicate toxicity values 

reported with unspecified upper or lower limits. Source: Singer et al. (1990). 

Although this comparison indicated that toxic effects in some organisms might be 

expected at low concentrations that could be encountered in the environment 

following a dispersant application, Singer et al. cautioned that there may be 

problems with the concept underlying the graphic. They questioned the validity of 

toxicity index data based on results they obtained for California species in the course 

of their study. Figure 5-11 shows toxicity index values obtained for two species, one 

a mysid crustacean, and the other a fish. While the results for the mysid appeared to 

support the toxicity index concept, those for topsmelt clearly did not. The index 

values increased with time, suggesting that the fish could mitigate the effects of 

dispersant exposure with time. Singer et al. commented: 

Our data suggest that the toxicity index may overlook the complex physiological and 

biochemical processes which affect toxicity and thus may not provide truly comparable values 

across species. 

5-21
 
Figure 5-11.	 Comparison of daily toxicity index values for two California species, one a mysid and 

the other a fish. Source: Singer et al. (1990). 

The methods employed by Singer and his colleagues in the state of California 

attempted to address many of the inadequacies of other techniques. Nevertheless, 

while no laboratory evaluation will be perfect in its simulation of true 

environmental conditions, useful insights may be obtained from studies employing 

older methods that have since been found to be biased. Results from a number of 

different types of toxicity studies, including those employing "classical" methods of 

assessing acute toxicity, will be presented in this chapter; it is important to remember 

limitations and shortfalls of these approaches. It would appear that more recent 

investigations, particularly in the state of California, may give a more accurate 

picture of dispersant toxicities that might be expected under realistic conditions of 

exposure. Results from the latter investigations will also be discussed later in this 

section. 

A review by Wells (1984) consolidated a large amount of dispersant toxicity 

information available at the time. In his paper, Wells focused on the toxicity of 

Corexit 9527, although information for other formulations is included as well. 

Wells summarized threshold effect concentrations from the review of results for 

organisms ranging from protozoans to birds (Table 5-2). 

5-22
 
Table 5-2. Summary of threshold effects concentrations, from Wells (1984). Expected water column 

concentrations for dispersants, from Wells (1984) and Peakall et al. (1987). 

Concentration 

Effect (mg/l) 

Lethal thresholds <101 - 102, some; 102 - 104, most 

Sublethal thresholds <102 (short exposures), some; >102, most 

Expected initial concentrations in water column 0.1 - 102 

Based on this review by Wells, most of the threshold concentrations reported for 

both the lethal and sublethal effects evaluated were above those anticipated or found 

to occur after field applications of dispersants. However, Wells noted the need for 

more information in several areas related to toxicological evaluations of dispersants. 

Several recommendations were made: 

1.	 Toxicity studies with dispersants should attempt to relate effects and their 

thresholds to specific compositions or major components of dispersants. 

2.	 Studies with dispersants and dispersed oil mixtures should include early life 

stages of commercial and ecologically important species from vulnerable 

habitats and the measurement of key processes known to be sensitive to 

dispersants and hydrocarbons (behavior, respiration, molting, fertilization, 

early embryonic development). 

3.	 Factors influencing toxicity thresholds of dispersants should be identified and 

quantified. 

4.	 Toxic actions of dispersants and their components should be studied in detail 

at realistic exposure concentrations, under simulated and actual field 

conditions. Comparisons should be made between estimated exposure 

concentrations of dispersant components in surface waters and in intertidal 

areas, and between the lowest concentrations required for acute lethal effects 

and those required for sublethal effects. 

5.	 Site-specific hazard assessments should be conducted prior to wide-scale 

usage. Facts and principles of dispersant toxicology must be applied in 

selection of governmental licensing or acceptability tests. 

5-23 
Many of the difficulties inherent in evaluating the toxicological implications of oil 

dispersant use were addressed in a study by Wu (1981). Wu investigated the 

toxicities of a true oil dispersant (BP 1100X) and a surface active agent (Shell Herder) 

on 18 marine species from different taxa, and found that toxicities depended very 

much upon the species tested. The organisms tested included fish, tunicates, 

urchins, starfish, barnacles, shrimp, bivalve molluscs, and gastropods. The oil used 

was diesel oil at 1000 ppm concentration. Some species showed high sensitivities to 

BP 1100X and low with Herder, while for others the opposite was true. Results are 

summarized below in Table 5-3. 

TABLE 5-3.	 Percentages of mortality for different species with treatment of BP 1100X and Shell 

Herder (1000 ppm dispersant/surfactant + 1000 ppm diesel oil). Source: Wu (1981). 

Shell Herder BP1100X Significant/Non 

Organism + diesel + diesel between treatments 

Fish 

Callionymus richardsonii 50.0 ± 14.1 40.0 ± 14.1 NS 

Siganus oramin 82.0 ± 21.9 3.0 ± 2.7 S 

Tunicate 

Styela plicata 4.0 ± 5.5 36.0 ± 11.4 S 

Urchins 

Anthocidaris crassispina 0 0 NS 

Echinodermata mathei 0 0 NS 

Salmacis bicolor 0 0 NS 

Starfish 

Archaster typicus 0 0 NS 

Barnacle 

Balanus amphitrite 0 0 NS 

Mantis shrimp 

Oratosquilla oratoria 40.0 ± 7.1 82.0 ± 8.3 S 

Bivalves 

Anadara broughtonii 2.5 ± 3.5 1.5 ± 3.4 NS 

Anadara granosa 2.0 ± 4.5 0 NS 

Barbatia obliquata 2.0 ± 4.5 4.0 ± 5.5 NS 

Paphia undulata 46.0 ± 13.3 45.0 ± 12.7 NS 

Perna viridis 0 0 NS 

Septifer bilocularis 0 0 NS 

Gastropods 

Babylonia areolata 0 0 NS 

Babylonia formosae 0 0 NS 

Nucella clavigera 0 0 NS 

The table above shows the wide range of results obtained among the different 

organisms. Toxicities were very much dependent on species and the product tested, 

and Wu commented on the implications for evaluating toxicity of products such as 

dispersants: 

5-24
 
The large differences in susceptibility within a single animal group found in the present study. . 

.indicate that neither the absolute nor relative toxicity of an oil dispersant can be ascertained 

by selecting one "representative" species. Due to the time and manpower involved, however, it 

may be impractical to test each product against a large number of species in order to determine 

its toxicity. Even if this is possible, the criteria of passing and failing a dispersant/surface 

active agent would be difficult to establish, since the product might be toxic to some of the 

species but not to the others. 

. . .It seems logical, and more meaningful, from an environmental point of view, that toxicity 

tests should be performed on species which are ecologically important (e.g., "key species" of a 

community or population with a high energy flow value) in identified receiving environments, 

rather than on some animals which are easy to obtain and maintain in the laboratory. 

Specific regional studies on a variety of organisms, as advocated by Wu, have been 

undertaken by California researchers. Investigations of this type will hopefully 

enable more realistic and applicable toxicity data to be factored into dispersant use 

decisions. The California tests are summarized below. 

Toxicity to California marine organisms 

Singer et al. (1990) examined the toxicity of constant low-level exposures of Corexit 

9527 to sensitive life stages of four California marine organisms: giant kelp, 

Macrocystis pyrifera; red abalone, Haliotis rufescens; mysid crustacean, 

Holmesimysis costata; and topsmelt, Atherinops affinis. It was found that the 

organisms had varying degrees of sensitivity to the dispersant. Juvenile red abalone 

and the newly released zoospores of giant kelp were most sensitive, with no 

observed effects concentrations (NOEC) in a range between 0.63 to <2.35 ppm. Larval 

topsmelt were the least sensitive, with NOEC ranging between 12.3 and 14.2 ppm. 

From an applied perspective, it should be remembered that in the above study, the 

test organisms were continuously exposed over periods of time ranging from 24 to 

96 hours. This is common for many studies of toxicity, but not necessarily realistic. 

In an actual dispersant application scenario, exposures to organisms would be 

expected to be transient and continuously declining as the dispersant and oildispersant mixtures are themselves dissipated in three dimensions. Resultant 

toxicities would be dependent upon concentration-time profiles. An article by 

Peakall et al. (1987) included a summary of studies that have examined dispersant 

and oil-dispersant concentrations under treated oil slicks. In these studies, total 

initial hydrocarbon concentrations were found to range between 1-100 ppm. 

However, it was recognized that many constituents of the dispersed oil which 

rapidly dissolve and/or evaporate would decline to parts per billion—or lower— 

levels within minutes or hours. 

5-25
 
Tjeerdema et al. (1990) attempted to address some of the inadequacies of traditional 

toxicity methodologies by conducting a study using the same materials and test 

organisms as Singer et al. above, but exposing the biota to spiked concentrations of 

Corexit 9527. In other words, an initial exposure concentration of dispersant was 

continuously diluted, in order to simulate the situation organisms might be 

expected to realistically encounter during a real application of dispersant. 

Tjeerdema et al. found that the test organisms reacted differently, both qualitatively 

and quantitatively, to spiked exposures than they did to constant concentrations. 

Haliotis (red abalone) were most sensitive to the spiked exposure, as was the case in 

the continuous concentration experiment. NOEC ranged between 5.3 and 8.4 ppm. 

Macrocystis zoospores also reacted similarly in both exposures, with NOEC in the 

spiked experiment between 12.2 and 16.4 ppm. The mysid Holmesimysis had NOEC 

in the range of 8.4 to 20.5 ppm, and the topsmelt Atherinops between 31.0 and 89.8 

ppm; however, in the latter two cases, the shape of the dose-response curve was 

qualitatively different than in the constant exposure. That is, the relationship was 

exponential in character, suggesting that a threshold for effects may exist. Below this 

threshold, the animals may be able to survive and adapt to dispersant exposure, but 

beyond, they are stressed beyond survivability even if the exposure is discontinued. 

Mysids survived the initial spike relatively well, but showed a delayed mortality 72 

to 96 hours after exposure. Topsmelt, on the other hand, showed a greater 

susceptibility to the initial spike but those surviving the spike generally survived 

the entire test period. 

Tjeerdema et al. summarized the implications of their results: 

Data from this study show that inferring toxicity of dispersants in actual use situations from 

laboratory collected, constant exposure data may lead to erroneous conclusions regarding 

environmental impacts. We have seen that traditional constant exposure data on a particular 

species may not give adequate insight into delayed mortality or increased sensitivity under 

realistic exposures of that species. Also, while exposure tests are not perfect models of the "real 

world", our data suggest that even very ephemeral exposure to dispersants at field-measured 

concentrations may be toxic to some marine larvae. Thus, on-scene coordinators must exercise 

increased caution and attention to specific conditions when evaluating dispersant use. 

Investigations into the effects of dispersants and oil-dispersant mixtures are 

summarized below in order to show the range of organisms that have been studied, 

as well as the range of impacts noted. This is not intended to be a comprehensive 

5-26
 
review of toxicological effects studies, but rather, it is to illustrate the diversity of 

effort, approaches and results available (and not available) for groups of organisms. 

More integrative and interpretive research reviews include the previously discussed 

National Research Council (1989), and Wells (1984). The former is a particularly 

nice overview of many aspects related to dispersants and their use, and includes a 

good discussion of toxicity and review of relevant studies. 

Mammals 

Little information is available on the extent of and effects of ingestion of oil by 

pinnipeds and cetaceans. Even fewer studies exist for toxicological and exposure 

reduction implications of dispersant use. Nevertheless, because coastal waters 

where dispesant use would be considered are utilized by a wide range of marine 

mammals, including sea otters, pinnipeds and cetaceans, the potential impacts of 

both oiling and dispersant use should be anticipated. Results presented below 

necessarily focus on oil impacts to mammals, but these are relevant in that a major 

factor in determining the appropriateness of dispersant use in a spill situation. 

Of all the marine mammals, probably the most information related to oil impacts is 

known for sea otters (Enhydra lutris). The most detailed studies to date of oil 

toxicology in sea otters took place during the Exxon Valdez spill in Alaska. 

Unfortunately, information from these studies has been slow to emerge from the 

morass of litigation and natural resource damage assessment. Some observations, 

however, were presented at a 1990 Southern California Academy of Sciences 

conference on wildlife impacts resulting from the Exxon Valdez spill, by Terrie M. 

Williams of International Wildlife Research. These included the following: 

•	 Oil was problematic to sea otters because they spend such a large portion of 

their lives at the surface. 

•	 Very little was known about otters that were brought in from the field either 

for necropsy or for cleaning. 

Lack of knowledge on why otters had died, how the oil had killed them, 

and on routes of exposure 

•	 Three critical medical factors appeared to contribute to cause of death in otters: 

1.	 Unstable temperature, both high and low 

2.	 Hypoglycemia (low blood glucose)
 

Common in first days of the spill
 

Lightly oiled animals had >140 mg/decaliter (dl) glucose
 

5-27
 
Moderately oiled animals had 80 mg/dl 

Heavily oiled animals had 60 mg/dl 

Undetermined whether glucose depression resulted from inability to 

absorb food, impaired ability to hunt, or other reason 

3.	 Emphysema 

Limited to first weeks of spill 

Was devastating to otters 

Sections of lungs blown out, resulted in leaking of gases into body cavity 

Some theories that toluene, benzene-type vapors caused emphysema 

• Most serious impacts were observed early in the spill 

The first and last observations are probably of greatest relevance in relating 

dispersant use to impacts on sea otters. Clearly, experiences from the Exxon Valdez 

and elsewhere have shown that sea otters are particularly at risk from oil exposure. 

In addition to the physiological effects cited above, the impacts on the ability of otters 

to thermoregulate are severe: 20 percent oil cover on a sea otter results in a 

doubling of metabolic rate, and the resultant energy expenditure to maintain body 

heat exceeds that attainable by foraging (Michael Fry, personal comm. 1991). 

Because animals suffered the most severe impacts early into spill events when the 

oil is most toxic, quick response to prevent exposure is of primary importance. The 

use of effective dispersants would be desirable in order to reduce the extent of that 

exposure. However, the effects of dispersant exposure on sea otters has not been 

well researched. It has been speculated (Fry, personal comm. 1991) that impacts from 

oil and the detergents present in modern dispersants may be equally harmful to sea 

otters, in terms of effects on pelt insulation. Further research efforts are needed, 

even for this relatively well-studied marine mammal. 

Information for other mammals, including the pinnipeds and cetaceans, is scant. 

For pinnipeds, it is known that external oiling has little impact on thermoregulation 

due to the presence of blubber layers. In the Exxon Valdez spill, the effects on harbor 

seals were remarkably less severe than for sea otters. There were no observed 

thermoregulatory problems, although some corneal lesions attributable to oil 

exposure were observed. Internal effects of oil ingestion were apparently not 

serious. Although some pups with elevated blood hydrocarbon levels lost weight 

and appeared unhealthy for a time, all recovered. 

5-28
 
Experiences such as these for harbor seals suggest there is less reason to consider the 

use of dispersants when the marine mammal resource at risk is a pinniped species, 

as opposed to sea otters. 

The limited research performed with cetaceans suggests that they are less at risk 

during an oil spill than other living marine resources. Geraci and St. Aubin (1982) 

found that bottlenose dolphins (Tursiops truncatus) could detect as well as avoid oil 

on the surface of the water. 

They also investigated the effects of petroleum hydrocarbons on the physiology of 

cetacean skin, which is structurally and functionally unique among mammals. 

Although bottlenose dolphins were again the principal study species, others such as 

Risso's dolphin (Grampus griseus) and sperm whale (Physeter catodon) were 

included opportunistically. Changes in a number of parameters were examined, 

including skin color, heat of exposed area, cellular damage and healing time, healing 

time of previously damaged skin, damage to functional biochemistry of cells. Some 

minor changes were observed for each parameter following exposure to petroleum, 

but for the most part these were transient in nature. 

Geraci and St. Aubin (1982) also studied the potential for oil fouling of baleen filters 

that mysticete cetaceans use for feeding. It was found that light- to medium-weight 

oils reduced water flow through baleen plates of fin and gray whales, but that flow 

returned to normal within 40 seconds. Fouling with a heavy Bunker C product 

restricted flow for up to 15 minutes, but even though plates were noticeably oiled, 

flow returned to normal. Clearance of the baleen fibers occurred within 15-20 hours, 

even with heavier-fraction oils. Impacts on contamination of food items or physical 

adherence of food to the plates was not examined. 

In summary, Geraci and St. Aubin concluded that impacts on cetaceans from oil 

spills would not be expected to be severe, although it was recognized that many areas 

of oil impacts have not been studied. However, based on the lack of a recognized 

severe risk to cetaceans from oil exposure, rationalizing the use of dispersants based 

on a perceived threat from oil to these marine mammals probably is not warranted. 

5-29
 
It is very clear that the effects of dispersants on marine mammals is poorly described. 

What little guidance that exists for considering potential impacts on marine 

mammals is based on speculation or extrapolation. Neff (1990) summarized the 

situation: 

Virtually nothing is known about the effects of oil dispersants on marine mammals, except as 

they are used to clean oil-fouled sea otters. By removing spilled oil from the sea surface, 

dispersants obviously reduce the risk of contact. The oil remaining, on the one hand, would be 

less sticky, and therefore less likely to adhere to fur, skin, baleen plates, or other body surfaces. 

On the other hand, the surfactants in dispersants may remove natural oils from marine mammal 

fur, thereby decreasing its insulating properties. Cleaning oiled beaches and rocky shores with 

dispersants may be an effective means of preventing oiling of pinnipeds that may wish to haul 

out there. More work needs to be done before we can adequately weigh the advantages or 

disadvantages of using dispersants in such habitats. 

With the exception of sea otters, it would appear that exposure of most marine 

mammals to oil does not result in severe impacts. The ability of marine mammals 

to avoid oiled areas and the lack of demonstrated toxic effects suggest that there may 

be less need to consider dispersant use for protection of mammals than there may be 

for other resources. However, special situations, such as the presence of large 

numbers of sea otters and/or haulout and breeding areas in a spill area, may provide 

substantial impetus to consider dispersant use. 

Birds 

The effects of oil on seabirds are both well known and well described, and are 

discussed elsewhere in this text. Studies examining dispersant impacts, either alone 

or in concert with oil, are much less common. Peakall et al. (1987) summarized the 

available information. 

Reproductive impacts on four species of birds exposed to various combinations of 

oil and dispersant were presented. In the mallard (Anas platyrhynchos), doses of 

Prudhoe Bay crude oil, Corexit 9527, and oil-dispersant mixtures (5:1 and 30:1 

oil:dispersant) applied to the surface of eggs all resulted in marked embryotoxicity, 

with greater effects noted if the application was made early in incubation. The 30:1 

oil:dispersant mixture was found to be significantly less toxic than the oil alone. In a 

related experiment, exposures were made to more closely resemble field conditions 

by exposing mallards to water troughs with oil and dispersant mixtures. In this case, 

the hatchability of eggs exposed to oil alone was reduced, while that from Corexit 

and oil-Corexit was not significantly different from unexposed controls. However, 

5-30
 
the results were variable enough for the investigators to conclude that crude oilCorexit mixtures probably pose the same threat to eggs that oil alone does. 

Studies on weight gain among both mallards and herring gulls exposed to oil and 

oil-dispersant mixtures showed that in mallards, no effect was noted for either oil or 

the mixture. In gulls, a significant decrease in weight gain was found for both oil 

exposure and oil-dispersant exposure, but no difference between the two exposures. 

Only one study that examined oil and oil-dispersant effects in the field was noted by 

Peakall et al. In this investigation, Leach's storm petrels were given either external 

or internal doses of Prudhoe Bay crude or oil-Corexit 9527. No effects were seen in 

the internal dosing, but the highest concentration exposure of external dosing with 

oil-dispersant resulted in significantly higher nest desertions during brooding. No 

significant effects were observed with oil alone. Hatching success for both oil and 

oil-dispersant treated adults was similarly reduced. 

Physiological studies on herring gulls and mallards showed that oil alone and oildispersant mixtures had similar effects on birds. This implied that the assessment of 

exposure hazard was therefore dependent on the nature of exposure. That is, are 

birds more likely to experience a higher degree of exposure through oil remaining 

on the surface, or through oil and oil-dispersant mixtures resulting from a 

dispersant application? 

Because many seabirds are most at risk in an oil spill situation from exposure to oil 

on the surface of the water, it is a reasonable assertion that in theory, the use of 

dispersants should be advantageous because it would decrease the amount of oil 

contacted at the surface. However, unless the dispersants are highly effective, 

Peakall et al. suggest that the differences in oil exposure at the surface are very small, 

and likely to be negligible in terms of the overall oil hazard to the birds. Theoretical 

calculations by Peakall et al. on exposure occurring as a seabird dives through a 

dispersed oil mass indicated that it is likely to be minimal. 

Peakall et al. came to two major conclusions as a result of their review and research. 

First, they found little evidence of a synergistic increase in oil toxicity to birds when 

oil was combined with dispersant. Second, in order to significantly reduce surface 

exposures of seabirds, dispersants need to be highly effective. Recent research has 

5-31
 
suggested that the latter condition is not a reality. For example, Fingas et al. (1991a) 

tested four dispersants with 20 different types of crude oils and refined products, and 

obtained efficiencies of dispersion ranging from 1 percent to 96 percent. The nature 

of the oil product appeared to be a greater determinant of efficiency than did the 

dispersant employed. 

Jenssen and Ekker (1991) found that for eiders (Somateria mollissima) and mallards 

(Anas platyrhynchos) whose plumage was fouled with oil (Stratfjord A crude) or 

crude oil mixed with the dispersants Finasol OSR-5 or OSR-12, oil-dispersant 

mixtures were more potent in reduction of thermoregulatory capability. Both 

exposures resulted in a reduction in the water-repellency of plumage, a resultant 

increase in plumage water absorption, an increase in heat loss, and a compensatory 

increase in heat production. However, much smaller amounts of the oil-dispersant 

mixtures were required to cause the effects. Jenssen and Ekker speculated that the 

reason for this result may be that surfactants in the dispersants more readily adhere 

to the feather structure or bind to waxes that birds preen into their feathers. 

It was also found that the different species were affected to different degrees, with 

eiders more sensitive to the oil-dispersant mixtures than mallards. An explanation 

for the difference may lie in differences in feather structure, and suggests more 

broadly that different species of aquatic birds may respond differently to 

contamination of plumage. 

Jenssen and Ekker ended their article by explicitly addressing the question, "Should 

oil spills at sea be treated with chemical dispersants in order to reduce their impact 

on bird life?" They noted that their results implied that in order to minimize the 

impact of a spill on birds, the concentration of treated oil needs to be very low by the 

time it reaches flock of birds at sea. Results of effectiveness studies were cited in 

which the action of dispersants was indeed very rapid, with resulting concentrations 

in chemically treated slicks very low (Fingas et al. 1991a, however, dispute claims of 

high dispersant efficiencies in field tests). At face value, therefore, dispersant use 

would seem to be advisable for protection of birds, even in light of the study results 

suggesting a higher potency of dispersed oil for adversely impacting 

thermoregulation. 

5-32
 
National Research Council (1989) discussed the implications of dispersant 

inefficiency on bird exposure, and cautioned that while potential biological benefits 

from dispersant use exist for birds (e.g., reduction in surface oil amounts), it is also 

possible that residual sheen from dispersed oil slicks may cover a greater area than 

untreated oil, resulting in potential exposure to more birds rather than fewer. 

5-33
 
Jenssen and Ekker also expressed concerns about potentially increased exposure to 

oil due to dispersant use: 

. . .one should also note that dispersants may have a secondary effect, by increasing the surface 

area of the slick. In a "worst case" scenario, chemical treatment of an oil slick may therefore 

increase the risk of exposure of more birds to less, but more harmful, chemically treated oil 

mixtures. Since the effect of oil-dispersant mixtures on the thermoregulation of seabirds is a 

function of the amount of the contaminant absorbed by the plumage, the effect is dependent on 

both the concentration of the pollutants in the water, and on the volume of contaminated water 

with which the birds come into contact. 

Finally, noting the apparent differences in species effects, they conclude that until 

more data on impacts are available, birds should be prevented from coming into 

contact with chemically treated oil slicks unless the hydrocarbon concentrations are 

known to be very low. 

Fish 

National Research Council (1989) summarized the results of a number of acute 

toxicity tests performed on fish species. Unfortunately, these studies are somewhat 

dated, with most having been published in the 1970s. The summary listed results of 

LC50 tests from 13 separate studies that examined effects on 13 fish species. Eight 

dispersant products were tested, with exposure periods ranging between 48 and 96 

hours. Values for LC50 concentrations ranged between 29 ppm and >10,000 ppm. 

The wide range of results obtained are difficult to interpret, especially given that 

there are many combinations of organism, dispersant, and exposure time. Unless 

the dispersant product/species pair happens to match the exact product/species pair 

of interest or concern, probably the most illuminating aspect of the tabular summary 

is the range of results obtained in the studies, with the implied inability to 

generalize about dispersant toxicity. 

Oyewo (1986) performed acute toxicity tests with the fingerlings of mullet (Mugil sp.) 

and three dispersants (Conco-K, Foremost, and BP 1100X) calculating LC50 

concentrations for three exposure periods (24-, 48-, and 96-hour). There were 

significant differences in LC50 concentrations among products. For example, in the 

96-hour test at about 36 parts per thousand salinity, the LC50 concentration for 

Conco-K was 4.60 ppm, for Foremost was 52.0 ppm, and for BP 1100X was 151 ppm. 

The relative relationships among the three products were consistent across all 

exposures (i.e., toxicity of Conco-K > Foremost > BP 1100X), and in fact, the absolute 

values of the LC50 concentrations were essentially the same for all three products 

5-34
 
across the range of different exposures. Salinity differences did not appear to 

influence the results. The study results suggest the importance of not extrapolating 

a general condition from the results of toxicity testing for a single product. 

Akintonwa and Ebere (1990) tested the toxicity of crude oil (Asabo 16c) and two 

dispersants (Conco-K and Teepol) to two species of freshwater fish (Barbus sp. and 

Clarias sp.) both discretely and in combination. They found that the two dispersants 

were much more toxic to the fish than crude oil alone, and that when the 

dispersants were used in combination with oil, the toxicity of the oil increased. They 

concluded that combining crude oil and dispersant resulted in a higher toxicity than 

that from the dispersant alone. 

Crustaceans 

Ahsanullah et al. (1982) conducted standard LC50-type toxicity tests using a 

hydrocarbon-based dispersant (BP/AB), Kuwaiti crude oil, and an oil-dispersant 

mixture. The key finding in this study was that combining oil with dispersant 

increased the toxicity of the oil to a crab species by a factor of 16. The results 

suggested that the physical effect of the dispersant in emulsifying the oil resulted in 

the increase in toxicity, with the broader implication being that toxicity is in effect a 

measure of the the efficiency of the product: the more efficient the product, the 

more toxic the oil-dispersant mixture. 

However, Ahsanullah et al. included some precautionary comments about 

extrapolating the results to a real-world situation: 

It is difficult to apply these results to an oil spill situation in the marine environment because 

the laboratory conditions do not replicate the hydrographic characteristics of the affected 

areas. This includes wave action, dispersal by currents and the spatial separation of the fauna 

from oil on the surface of the sea or in the case of littoral animals, the physical coating of the 

body surface with oil. 

As an additional component of the fish study cited above, Oyewo (1986) also tested 

three dispersants for acute toxicity to hermit crabs (Clibinarius africanus) and 

obtained results qualitatively similar to those for the fish tested (i.e., the toxicity 

relationship of Conco-K > Foremost > BP 1100X). In 33.5 parts per thousand salinity 

and 24-hour exposure, the LC50 concentrations obtained were, for Conco-K, 9.2 ppm; 

for Foremost 19.4 ppm; and for BP 1100X, >30,000 ppm. The results in different 

exposures and the different salinity were somewhat more variable than was the case 

for the fish, but overall demonstrated the same trend. 

5-35
 
Oyewo also cautioned about the extrapolation of these kinds of results to the real 

world: 

It is necessary to emphasize that results of acute toxicity tests cannot, alone, form the basis of 

any decision on the use of oil dispersants since several other considerations are important in the 

overall decision framework. . .However, relative toxicity data plus a detailed knowledge of 

field effects is a useful combination for ecological predictions and therefore invaluable in 

making decisions on the use of oil dispersants. 

Anderson et al. (1984) examined the seasonal effects of dispersed oil exposure on 

toxicity to coonstripe shrimp (Pandalus danae). Prudhoe Bay crude oil was used in 

the test, with two unspecified dispersant products. Differences in effects were 

observed between the two dispersants, particularly in winter exposures. Although 

significant differences in toxicity were not found between the dispersants in summer 

exposures, the overall levels of toxicity in summer were significantly higher. 

Molluscs 

Hartwick et al. (1981) studied the effects of Alberta crude oil, Corexit 9527, and oilCorexit mixtures on several aspects of littleneck clam (Protothaca staminea) 

behavior and physiology. They found in both laboratory and field experiments that 

Alberta crude oil alone (1000 ppm), or low concentrations (<10 ppm) of Corexit 9527 

were not greatly harmful to the clams. The lack of sensitivity to crude oil contrasted 

to results from other researchers that had suggested a particular susceptibility in 

molluscs. 

It was also determined that the dispersant and oil-dispersant mixtures were more 

toxic to clams than oil alone. Mortality was observed when clams were exposed to 

100 ppm Corexit 9527, and was highest in both the laboratory and in the field when a 

mixture of 100 ppm Corexit 9527 and 1000 ppm crude oil was used. Hartwick et al. 

also found variable results between the laboratory and the field: 

It was. . .apparent that the percentage mortalities resulting from the field experiments were 

much lower than those from the equivalent laboratory tests. Such discrepancies demonstrate 

the difficulty in extrapolating laboratory results to natural spill conditions. 

Some impact on the settlement of clam larvae was noted with oil-dispersant 

mixtures over oil alone. In addition, hydrocarbon analysis of the substrate in 

experimental plots showed that residues penetrated deeper and were measurable for 

longer periods of time in oil-dispersant treated plots. The overall implications of 

5-36
 
the study results were that the impact of oil spill alone on the littleneck clam could 

be expected to be small. However, the use of Corexit 9527 as a dispersant may 

augment adverse impacts by reducing the recruitment of larvae, and by increasing 

the retention time and penetration depth of hydrocarbons into the substrate. 

Ordzie and Garofalo (1981) examined the effects of oil (Kuwait crude), dispersant 

(Corexit 9527), and oil-dispersant mixtures on scallops (Argopecten irradians) and 

two predators, a drill (Urosalpinx cinerea) and starfish (Asterias forbesi). Different 

susceptibilities were found for the three organisms. Scallops were found to be most 

sensitive to dispersant and oil-dispersant mixtures, starfish were sensitive to 

dispersant only, while the drill was insensitive to all test mixtures. 

Similar to results found by Anerson et al. (1984) for shrimp, there appeared to be a 

significant influence of water temperature on the degree of toxicity observed. 

Scallops were found to be most sensitive at water temperatures encountered in the 

summer, and less so at winter temperatures. This seasonal sensitivity was found to 

be dramatic: dispersant concentrations not lethal to scallops at winter temperatures 

caused >50 percent mortality at summer temperatures. The predators were affected 

in an opposite fashion, with treatments having a lesser impact at summer 

temperatures. However, sublethal effects on behavior (ability to recognize prey 

items) increased in predators with increasing temperature. Ordzie and Garofalo 

summarized the implications of their study: 

In order to accurately assess biological effects of a pollutant event, we need to know 

susceptibilities of animals for different seasons. . .Although temperature of ambient water 

could be a significant predictor of scallop susceptibility to dispersant exposure, one should not 

generalise to other organisms. This issue becomes more complex because either the "pollutant 

toxicity" or "animal sensitivity" can be affected by temperature. Accordingly, the temperature 

related susceptibility can be different for each organism, making broad generalisations 

dangerous. 

Corals 

Corals, of course, are a critical habitat only in tropical coastal waters. However, 

review of research into oil and dispersant effects on reef building corals helps to 

define the range of impacts across a diversity of marine organisms. Knap (1987) 

studied the effects of Arabian Light crude oil and oil dispersed with Corexit 9527 (1:20 

mixture, dispersant:oil) and oil dispersed with BP 1100WD (1:10 mixture). 

Laboratory exposures were validated in the field both in winter and summer. Knap 

found that the coral Diploria strigosa appears to be relatively tolerant to brief 

5-37
 
exposures to crude oil chemically dispersed into the water column. Exposure 

concentrations in field experiments ranged from 8 to 25 ppm, and length of 

exposures were 6 hours. However, it was also noted that many of the cryptic 

epifaunal organisms living in the coral reef community (i.e., polychaetes, bivalves, 

crustaceans) displayed a greater sensitivity to the exposures that apparently did not 

harm the coral itself. 

A multi-disciplinary, long-term field assessment of the effects of oil and dispersed 

oil in Panama (Ballou et al. 1989) was interesting in that it illustrated the kinds of 

trade-offs that dispersant use may entail. In this study, sites with three major 

components—mangroves, seagrasses, and coral reefs, were exposed to both oil 

(Prudhoe Bay crude) and dispersed (with non-ionic glycol ether-based product) oil. It 

was found that untreated oil had severe effects on mangroves and associated 

communities and relatively minor impacts on seagrasses and corals. In contrast, 

dispersed oil adversely affected seagrasses and corals. This suggested that the use of 

dispersants shifted toxicity from one compartment (intertidal) to another (subtidal). 

Although the situation of dispersant application to an oil slick far offshore was 

discussed, it was not investigated in this study. However, based on the other results 

obtained, Ballou et al. felt that such an approach might minimize the extent of 

damage to resources in both tidal zones. 

Microorganisms 

Protozoans. Rogerson and Berger (1981) performed toxicological studies using 

Corexit 9527 and ciliate protozoa. The rationale for examining impacts on protozoa 

were twofold: the researchers wished to study a non-traditional experimental 

organism, and they also wanted to examine effects on a trophic level not often 

considered. Rogerson and Berger acknowledged that while ciliates were not found 

in great abundances in pelagic waters, they are abundant in intertidal areas and 

could be of some ecological importance. 

Rogerson and Berger found that the most sensitive ciliate protozoan species tested 

yielded a threshold concentration of 100 ppm Corexit 9527, although other species 

tolerated levels as high as 320 ppm. However, the dispersant in combination with 

crude oil appeared to be much more acutely toxic than the dispersant alone. It was 

found that mixtures with >1.0 ppm Corexit caused the protozoan cells to lyse. 

Because the concentration of crude oil was held constant and the concentration of 

5-38
 
Corexit 9527 varied, Rogerson and Berger reasoned that it was the dispersant 

component of the emulsion that contributed most to toxicity. 

The mechanism of toxicity of the oil-dispersant mixtures was also examined. Two 

hypotheses were that chemical emulsifiers interact with oil to release toxic 

substances, or alternatively, that the mixture is made more available through 

dispersion of fine droplets. It was determined through studies of ingestion rates and 

identification of materials ingested by the ciliates that in this case, toxicity was 

apparently manifested through increased availability of the oil-dispersant mixture. 

The authors speculated that it was probable that the oil acts as a vector through 

which the dispersant is transported into the cell, causing the disruption of cellular 

membranes. 

It may be important to note that this study was performed using both marine and 

freshwater organisms. Corexit 9527 was developed for use in the marine 

environment, and its effectiveness in freshwater is questionable. Although 

evidence was cited that toxicity testing using freshwater organisms should not lead 

to significant errors, the possibility that differences attributable to the test conditions 

cannot be overlooked. 

Microbial degradation. An aspect of dispersant toxicity that is often 

overlooked but should be acknowledged is the impact that dispersant use may have 

on other important processes associated with removal of oil from the environment. 

In particular, Foght and Westlake (1982) found that Corexit 9527 has detrimental 

effects on eucaryotic processes, bacterial activity at sea, and microbial oil-degrading 

processes. In other words, application of dispersant products can potentially 

negatively affect mechanisms of biodegradation. 

The addition of relatively large volumes of carbon-rich dispersants to an oiled environment 

already having a very high carbon to nitrogen. . .ratio (which is not suitable for rapid 

microbial growth) further stresses this environment. The beneficial effects of dispersants in 

providing more oil surface for microbial growth is countered by the additional stress on the 

nitrogen-phosphate level of the environment by the addition of a biodegradable dispersant. . 

.This stress could result in a delay of the oil-degradation process. 

Another study by Bhosle and Mavinkurve (1984), using four unspecified dispersants 

on Saudi Arabian and Bombay High crude oil, elicited mixed results, in which some 

dispersants in combination with Saudi or Bombay crudes either inhibited or 

accelerated biodegradation processes by one of two bacterial species. Reduction in 

5-39
 
biodegradation processes was thought to result from a preferential utilization by 

microbes of carbon sources provided by the dispersant over those in oil. 

Enhancement of biodegradation rates was also observed, possibly due to the increase 

in oil surface area mentioned in the previous study. 

Plants 

Although most of the research on biological impacts of dispersants and dispersed oil 

has examined effects on animals, some plant species have also been studied. The 

overview of toxicity provided in National Research Council (1989) summarizes the 

results of dispersed oil toxicity studies for phytoplankton, diatoms, and vascular 

plants. Of eleven studies, ten found that the toxicity of dispersed oil was greater 

than that for oil alone. However, the results of many of these investigations were 

called into question by the National Research Council because of the use of nominal 

exposure concentrations as opposed to measured concentrations. The studies which 

measured concentrations in the water yielded mixed results, with two studies 

indicating dispersed oil as more toxic than oil alone, one suggesting oil alone as 

more toxic, and one showing them to be equally toxic. 

Much of the research available for evaluating the effects of oil dispersants on plants 

has focused on tropical and subtropical species. For example, Thorhaug and Marcus 

(1987) studied three seagrass species found in the Caribbean and subjected them to 

mixtures of three commonly stockpiled dispersant products (Corexit 9527, Arcochem 

D609, and Conco K(K)) and two crude oils (Louisiana and Murban). They 

determined that at recommended application levels, no significant mortalities 

occurred. Higher concentrations, about an order of magnitude above recommended 

application levels, resulted in the deaths of more sensitive species, especially with 

longer exposures. Widely different results were obtained with different dispersant 

products, with Conco K(K) causing a consistently higher degree of mortality in all 

three seagrass species. The two crude oils yielded similar results. 

A number of studies have examined effects of oil (South Louisiana crude) and 

dispersants on mangroves. Teas et al. (1987) found that crude oil caused a significant 

mortality to treated trees. The use of an unspecified non-ionic water-based 

dispersant sprayed onto previously oiled mangroves increased this mortality. 

Application of oil predispersed with a glycol ether-based product had no effect in 

reversing the mortality attributable to oil, although mortality was not increased by 

5-40
 
dispersant use. These results suggested that because oil exposure results in 

significant impacts on mangroves, all efforts should be made to prevent contact. 

Use of a dispersant, particularly a glycol ether-based product, may be justified as part 

of the response, since its effects appear to be no worse than the oil itself. 

A longer term approach to assessment of the effects of dispersant use among 

mangrove trees was undertaken by Wardrop et al. (1987). They evaluated the 

toxicities of Arabian Light crude oil, Tirrawarra crude oil, the dispersant BP-AB, and 

oil-dispersant mixtures on mangroves in a fringing Australian marsh. Sublethal 

effects such as defoliation, leaf damage, pneumatophore damage, flowering and 

fruiting were monitored for three years. The results were interesting in that initial 

toxicity of the oil was apparently increased through the use of a dispersant, but after 

three months those mangroves treated with dispersed Arabian Light showed a 

higher degree of productivity over both Arabian Light crude alone and the unoiled 

controls. This apparent growth stimulation had been reported elsewhere for 

mangroves exposed to various hydrocarbon products. The Tirrawarra crude 

mixtures did not show a similar increase in growth, and in fact, produced somewhat 

fewer leaves. 

Summary 

Unfortunately, it is not possible to present a rote formula for determining ecological 

consequences of the use of dispersants during a spill situation. As should be 

apparent from the examples cited above, the effects are highly dependent on a 

number of factors, some of which are relatively undefined in terms of their 

importance. 

As a spill responder, it will not be possible for you to anticipate all of the 

implications of dispersant use. However, keeping in mind some of the insights that 

have been learned may help in the decision-making process. 

•	 The number of combinations of oil, dispersant, organism, life stage, nature of 

exposure, time of year, etc. that are possible in an area make a prediction of 

the ecological impacts of dispersant use very difficult. Several studies suggest 

that effects can vary significantly with different combinations of parameters, 

usually making generalizations inappropriate. 

5-41 
•	 The common wisdom in the case of the newer generation dispersants is that 

they are no more toxic than crude or refined oils to which they might be 

applied, and that toxicity resulting from an oil-dispersant mixture is largely 

attributable to the oil component. Some recent studies suggest otherwise, but 

more carefully designed and administered investigations clearly would be 

useful. 

•	 Conceptually, the use of dispersants moves an oil product from one physical 

environment (the air-water interface) to another, or others (the water column 

or the benthic environment). However, no dispersant is 100 percent effective; 

application will result in variable amounts in each physical compartment, 

with resultant impacts proportional to the partitioning. 

•	 Laboratory studies suggest that the toxicity of dispersants is correlated with 

efficiency: the more efficient a product is in moving oil into the water 

column, the greater the toxicity to organisms in the water column or in the 

benthos. 

•	 It is difficult to extrapolate results from the laboratory to anticipated results in 

field exposures. Comparison of such results within the same study show a 

wide variation, with field mortalities attributable to exposure lower than 

those in the laboratory. However, some methods employed in these 

assessments may introduce biases that inaccurately portray toxicities. 

•	 Certain life stages of organisms, particularly early reproductive stages, appear 

to be most at risk from exposure to dispersants. 

•	 Mature life stages of animals are more tolerant to exposures to oil-dispersant 

mixtures. However, consideration of life cycle timing is critical, since 

physiological stresses imposed by reproductive or other activities may 

increase the susceptibility to both oil and dispersants. 

•	 Dispersants can either enhance or inhibit biodegradation of oil, apparently 

depending on the dispersant product, the oil, and the specific bacteria 

involved. 

5-42
 
There are distinct advantages in planning for dispersant use. The need to apply a 

dispersant on spilled oil very early into the event in order to maximize the 

efficiency of dispersion is the major motivating factor for anticipating conditions in 

specific regions. An integral part of this process should be the explicit consideration 

of ecological impacts, which may involve fairly detailed resource surveys and 

toxicological studies of effects on organisms of concern. Ideally, this would include: 

•	 Identification of sensitive life stages and commercially important marine 

species for discrete areas of the coast. 

•	 Critical periods of time for those species that may affect sensitivities to 

both oil and dispersants. 

•	 Laboratory and/or field evaluations of the effects of oil, dispersant, and 

oil/dispersant mixtures, using products that could be transported or used 

in the event of a spill. 

Although the collection and interpretation of this information can be both timeconsuming and costly, it is a prerequisite to assessing ecological trade-offs 

realistically for the use of dispersants to treat an oil spill. An observation by 

Anderson et al. (1984) seems to be valid for the current situation in evaluating 

dispersant toxicity: 

. . .both field measurements of dispersed oil and estimates of dilution rates within a specific 

body of water can play an important role in estimating the impact on local species. Such 

assessments can be made after a spill, but it is our hope that our state of understanding will 

advance to a level that will allow us to accurately predict the comparative hazards of no 

action versus dispersant application. Only after more data are gathered. . .on a variety of 

organisms and ecosystems will we be in a position to make this type of accurate assessment. 

Dispersant use guidelines 

There are a number of methods for oil spill response and cleanup, both on the water 

and on shorelines. These range from doing nothing, to strictly mechanical means, 

such as booming or skimming, to chemical methods exemplified by the use of oil 

dispersants or elasticizers, to biological treatments like fertilizers or microbial mixes 

to enhance biodegradation. When a spill occurs, some sort of evaluative framework 

must be used to determine what approaches are to be used. Decision-making 

methods that have been formulated (usually decision trees) to provide a structure 

for crafting approaches generally incorporate evaluation of the use of dispersants. 

The decision of whether to apply dispersants involves considering the logistical and 

5-43
 
physical constraints on their use, as well as biological restrictions. Fraser (1989) 

provides a good overview both of oil spill decision-making methods in general, and 

dispersant-use guidelines in particular. He noted that the mandate to consider the 

anticipated outcome of dispersant use lacks specific direction: 

Most of the published decision diagrams show dispersant use as an alternative to mechanical 

containment and recovery, assuming the mechanical means are not effective. In almost all cases, 

the question is posed, "Will environmental impacts associated with chemical dispersion be less 

than those occurring without chemical dispersion?" But (with few exceptions), no guidance is 

offered to the on-scene coordinator to answer this question. 

Alaska and California have a fairly typical decision tree for dispersant use (Fraser 

1989; Alaska Regional Response Team 1991; Figure 5-12). 

Figure 5-12. Dispersant decision matrix for Alaska and California. Source: Alaska Regional 

Response Team Dispersant Working Group (1991). 

5-44
 
As this diagram shows, dispersant use will be considered as a response option only 

when mechanical containment and recovery actions are not considered to be 

feasible. It is also apparent that implementation of this decision tree requires a 

significant amount of information to be gathered prior to the actual time of decision, 

including an explicit evaluation of comparative impacts between untreated and 

dispersed oil. As Fraser has noted, however, no guidance is offered as to how to 

make this determination. 

The state of Alaska has taken steps to anticipate resource impacts that may result 

from dispersant applications through the designation of use zones. This constitutes 

the major difference between the Alaska and California 

decision-making processes: the dispersant use criteria developed for use in Alaska 

classify coastal waters into three dispersant use zones. In all cases, the use of 

dispersants will be based on the determination that the impact of dispersants or 

dispersed oil will be less harmful than non-dispersed oil. The zones are defined by 

physical parameters such as bathymetry and currents, biological considerations such 

as sensitive habitats or fish and wildlife concentration areas, nearshore human uses, 

and time required to respond. The three zones are defined as follows: 

Zone 1: Use of dispersants is acceptable. The On-Scene Coordinator (OSC) is not 

required to seek approval by the EPA or the state prior to dispersant use, but is 

required to notify both of the decision as soon as possible. 

Zone 2: Dispersant use is conditional, in order to protect sensitive wildlife and 

other resources. The OSC is required to consult with the RRT and to obtain 

approval from the EPA and the state prior to use of dispersants. 

Zone 3: Dispersant use is not recommended. However, dispersant use may be 

permitted if, on a case-by-case basis, it is determined that disturbance of the 

organisms and direct exposure to dispersants or dispersed oil would be less 

harmful than the impact of spilled oil. Consultation is required with the RRT, 

and approval of the EPA and state are necessary. 

In Alaska, sensitive wildlife and other resources that are to be considered for 

dispersant use decisions have been identified as including: 

•	 endangered or threatened species protected by Federal and state 

governments; 

5-45
 
•	 nesting, spawning, breeding, and nursery areas for mammals, birds, fish, 

and shellfish; 

•	 fish and wildlife concentration area where these animals feed, rest, or 

migrate; 

•	 sensitive marine habitats, including
 

- seagrass beds
 

- kelp beds
 

- shellfish beds
 

- tidal flats
 

- marshes
 

- shallow subtidal areas
 

- low energy bays and harbors
 

- rocky intertidal areas
 

•	 aquaculture and commercial areas which are shallow enough to allow 

impacts from oil spills; and 

•	 recreational and industrial areas 

Evaluation of potential impacts to these resources has been factored into the use 

designations that have been established for specific areas, with the result being zonal 

configurations that may change during the course of the year to account for varying 

resource sensitivities. For example, the area around the Valdez tanker loading 

facility is designated as a Zone 1 region from October 16 to February 28, when 

fisheries resources such as juvenile salmon and herring spawning and rearing areas 

as well as fishing activities are least abundant. From March 1 to October 15, when 

fisheries resources and harvest activities are at a peak, the area is considered as a 

Zone 2 dispersant category. 

Implicit in these designations are certain assumptions about the effects of 

dispersants on organisms and resources of interest or concern. The increased 

restrictions on dispersant use that are imposed on areas with aggregations of 

mammals, birds, fish, and shellfish imply that dispersants and dispersed oil are 

considered to be at least as harmful as untreated oil. The toxicity studies cited in the 

preceding discussion show that impacts vary widely among organisms, dispersants, 

oils, life stages, water temperatures, and the like, and suggest that studies directed at 

specific combinations that are relevant for specific areas would be useful in planning 

exercises. The investigations on sensitive life stages of California marine organisms 

(i.e., those by Tjeerdema et al. and Singer et al. discussed in the preceding section) 

provide a good basis for evaluation of dispersant use impacts and subsequent 

designation of dispersant use zones. 

5-46
 
Research Planning, Inc. (RPI), has had considerable experience in evaluating both 

the effectiveness of dispersants as well as resource impacts resulting from dispersant 

use. RPI has been participating in the development of simplified dispersant-use 

guidelines (RPI 1991) that could be incorporated into a computer-based expert system 

for use in spill response decisionmaking. Some of the salient features of the RPI 

work have a broader application in formulating dispersant use guidelines include 

the following considerations: 

1. First, determine the quick and easy answers that eliminate the use of 

dispersants. 

1.	 Is the oil dispersible? NO for light petroleum products (No. 2 fuel, jet fuel, 

gasoline). NO for very heavy products (heavy No. 6 fuel, Bunker C, asphalts, 

residuals). Possible YES for all other oil types. 

2.	 If the oil has formed an emulsion, then it is no longer dispersible. 

3.	 Is the wave height between 1 and 10 feet? If lower, then dispersants are not 

very effective, because of insufficient mixing forces. If higher, then 

dispersants are not recommended because of sufficient natural mixing, as well 

as logistical problems. 

4.	 Is sufficient dispersant available in time for use? This issue is the window of 

opportunity during which the oil is dispersible. The time frame depends on 

the meteorological conditions, and oil type. The transition is gradual. 

5.	 Is this in a RRT preapproval area? This is a question response personnel need 

to know the answer to in advance. If the answer is no then it must be 

determined if approval can be obtained within the time frame indicated 

above. 

6.	 Is the water depth in the spill area greater than 30 feet? If NO then dispersants 

are not to be used. Field studies and mathematical models show that oil 

concentrations under a dispersed a dispersed slick will have concentrations of 

1 ppm or greater down to 30 feet. With 1 ppm set as the maximum safe 

concentration, dispersants could not be used in less than 30 feet, with the 

entire water column concentration being above the 1 ppm level. 

5-47
 
2. Answer other predetermined questions that have been specified to 

eliminate the use of dispersants. For example: 

1.	 Are there any water intakes in the area? If YES then dispersants are not to be 

used. 

2.	 Are there critical subtidal resources? This includes nursery grounds, 

spawning aggregation areas, or other areas of particular sensitivity. If these 

exist in the area being considered, then dispersants are not to be used. 

3. Compare subtidal and intertidal impacts of oil and dispersed oil. 

1.	 Intertidal effects of exposure to oil - Considers shoreline sensitivity for 

beaches, marshes, and tidal flats. Incorporates assessment of animal 

sensitivity and ranking through a system examining possibility of oiling, 

sensitivity to oil, environmental/commercial/recreational status (i.e., 

endangered, commercial fishery, federally managed). 

2.	 Intertidal/subtidal effects of dispersed oil - Shoreline impact would be 

expected to be reduced with increased effectiveness of the dispersant; subtidal 

impact may increase. Subtidal animal toxicity is calculated, and impact values 

assigned to the animals. Calculations include determining the ppm-hour 

concentrations over a 24 hour period, and comparing that to the toxicity data 

of the animal to determine the percent mortality at the given ppm-hours. 

3.	 Compare the weighted values for the effects of dispersed oil and the effects of 

oil. The parameter with the lower number has the least adverse effect. 

In summary, general guidelines (i.e., decision trees) for the use of dispersants exist 

for many regions. Considering impacts to biological resources is a component of 

these guidelines, but guidance for how to do this is generally vague. By defining, in 

advance, those resources considered to be sensitive or otherwise of importance, and 

estimating or determining the effects of oil and dispersed oil on those resources, 

decision-makers may then define dispersant use zones that will greatly simplify 

dispersant use decisions during spill incidents. 

5-48
 
Shoreline Cleanup Methods and Application 

Approved Physical Methods 

A wide range shoreline cleanup methods are used during oil spills. Listed below are 

the more commonly used methods, including the objective, description, applicable 

shoreline types, guidelines on when to use the method, general biological 

constraints, and potential environmental effects. These descriptions were initially 

written as part of the Shoreline Treatment Manual developed in 1989 during the 

first year of the Exxon Valdez spill cleanup program. They were revised in 1991 as 

part of an effort by Region III for preplanning for oil spill cleanup requirements and 

approvals. 

1. No Action 

OBJECTIVE: 

No attempt to remove any stranded oil, to minimize impacts to the 

environment or because there is no proven effective method for cleanup. 

DESCRIPTION:
 

No action is taken.
 

APPLICABLE SHORELINE TYPES:
 

Can be used on all shoreline types.
 

WHEN TO USE: 

If the shoreline is extremely remote or inaccessible, when natural removal 

rates are very fast, or cleanup actions will do more harm than leaving the oil 

to be removed naturally. 

BIOLOGICAL CONSTRAINTS: 

This method may be inappropriate for areas where high numbers of mobile 

animals (birds, marine mammals, crabs, etc.) use the intertidal zone or 

adjacent nearshore waters. 

ENVIRONMENTAL EFFECTS:
 

Intertidal — The same as the oil.
 

Subtidal — The same as the oil.
 

2. Manual Removal 

OBJECTIVE:
 

Removal of stranded surface oil with hand tools and manual labor.
 

DESCRIPTION: 

Removal of surface oil and oily debris by manual means (hands, rakes, 

shovels, etc.) and placing in containers for removal from the shoreline. No 

mechanized equipment is used. 

APPLICABLE SHORELINE TYPES:
 

Can be used on all shoreline types.
 

5-49
 
WHEN TO USE: 

Generally used on shorelines where the oil can be easily removed by this nonmechanical means. Most appropriate for light to moderate oiling conditions. 

BIOLOGICAL CONSTRAINTS: 

Foot traffic over sensitive areas (shellfish beds, algal mats, bird nesting areas, 

dunes, etc.) is to be restricted. May be periods when shoreline access is 

restricted (e.g., bird nesting, mammal pupping). 

ENVIRONMENTAL EFFECTS: 

Intertidal — Minimal if surface disturbance by cleanup activities and work 

force movement is limited. 

Subtidal — None. 

3. Passive Collection Sorbents 

OBJECTIVE: 

Removal of oil by sorption onto oleophilic material placed in the intertidal 

zone. 

DESCRIPTION: 

Sorbent material is placed on the surface of the shoreline substrate allowing it 

to absorb oil as it is released by tidal or wave action. Oil removal is dependent 

on the capacity of the particular sorbent, energy available for lifting oil off the 

shoreline, and degree of weathering. 

APPLICABLE SHORELINE TYPES:
 

Can be used on any shoreline type.
 

WHEN TO USE: 

When the shoreline oil is mobile and transport of oil is expected on or off the 

site. The oil must be of a viscosity and thickness to be released by the substrate 

and absorbed by the sorbent. Often used as a secondary treatment method 

after gross oil removal, and along sensitive shorelines where access is 

restricted. 

BIOLOGICAL CONSTRAINTS:
 

None, although this method can be slow thus allowing oil to remain in
 

critical habitats during sensitive periods of time.
 

ENVIRONMENTAL EFFECTS: 

Intertidal — None, except for the amount of oil remaining on the shoreline 

after the sorbents are no longer effective. 

Subtidal — None. 

4. Debris Removal 

OBJECTIVE:
 

Removal of contaminated debris and logs.
 

DESCRIPTION: 

Manual or mechanical removal of debris from the upper beachface and the 

zone above high tide beyond the normal wash of waves. Can include cutting 

and removal of oiled logs. 

5-50 
APPLICABLE SHORELINE TYPES:
 

Can be used on any shoreline type, where safe access is allowed.
 

WHEN TO USE: 

When driftwood and debris is heavily contaminated and, either a potential 

source of chronic oil release, an aesthetic problem, or a source of 

contamination of other organisms on the shoreline. 

BIOLOGICAL CONSTRAINTS: 

Disturbance to adjacent upland areas should be minimized. Foot traffic over 

sensitive intertidal areas (shellfish beds, algal mats, bird nesting areas, dunes, 

etc.) is to be restricted. May be periods when shoreline access is restricted (e.g., 

bird nesting, mammal pupping). 

ENVIRONMENTAL EFFECTS:
 

Intertidal — None.
 

Subtidal — None.
 

5. Trenching 

OBJECTIVE:
 

Remove subsurface oil from permeable substrates.
 

DESCRIPTION: 

Dig trenches to the depth of the oil and remove oil floating on the water table 

by vacuum pump or super sucker. Water flooding or high-pressure spraying 

at ambient temperatures can be used to flush oil to the trench. 

APPLICABLE SHORELINE TYPES:
 

Can be used on beaches ranging in grain size from fine sand to gravel.
 

WHEN TO USE: 

When large quantities of oil penetrate deeply into permeable sediments and 

cannot be removed by surface flooding. The oil must be liquid enough to 

flow at ambient temperatures. 

BIOLOGICAL CONSTRAINTS: 

Trenches should not be dug in the lower intertidal when attached algae and 

organisms are abundant. 

ENVIRONMENTAL EFFECTS: 

Intertidal — On gravel beaches, there may be a period of beach unstability as 

the sediments are redistributed after the trenches are filled in. 

Subtidal — None. 

6. Sediment Removal 

OBJECTIVE:
 

Removal of surface oiled sediments.
 

DESCRIPTION:
 

Oiled sediments are removed by either manually using hand tools or
 

mechanically using various kinds of motorized equipment. The oiled
 

material must be transported and disposed of off-site.
 

5-51 
APPLICABLE SHORELINE TYPES: 

Can be used on any shoreline with surface sediments. On rocky coasts, only 

manual removal is feasible. Equipment is to be used only on beaches, with 

special supervision to minimize sediment removal. 

WHEN TO USE: 

When only very limited amounts of oiled sediments have to be removed. 

Should not be considered where beach erosion may result. Care should be 

taken to remove the sediments only to the depth of oil penetration, which 

can be difficult with heavy equipment. 

BIOLOGICAL CONSTRAINTS: 

Mechanized equipment may be restricted when sensitive habitats are adjacent 

(e.g., stream mouths, tidal flats, marshes, or dunes). 

ENVIRONMENTAL EFFECTS: 

Intertidal — The equipment is heavy, and required support personnel is 

extensive. May be detrimental if excessive sediments are removed without 

replacement. All organisms resident in the beach will be affected, though 

the need for removal of the oil may be determined to be the best overall 

alternative. 

Subtidal — Release of oil and fine-grained oily sediments to the water during 

sediment removal activities and tidal flushing of the excavated beach surface. 

7. Cold Water Flooding (Deluge) 

OBJECTIVE: 

To wash surface oil and oil from crevices and rock interstices to water's edge 

for collection. 

DESCRIPTION: 

A large diameter header pipe is placed parallel to the shoreline above the 

oiled area. A flexible perforated header hose is used during deluge of 

intertidal shorelines to better conform to their profiles. Ambient seawater is 

pumped through holes in the header pipes and flows down the beach face to 

the water. On porous beaches, water flows through the substrate pushing 

loose oil ahead of it (or floats oil to the water's surface) then transports the oil 

down slope for pickup. Flow is maintained as long as necessary to remove 

the majority of free oil. Oil is trapped by booms and picked up with a 

skimmer or other suitable equipment. 

APPLICABLE SHORELINE TYPES: 

Beaches with sediments coarser than sand, and gently sloping rocky 

shorelines. Generally not applicable to mud, sand, vegetated, or steep rocky 

shorelines. 

WHEN TO USE: 

On heavily oiled shorelines when the oil is still fluid and loosely adhering to 

the substrate; and where oil has penetrated into cobble or boulder beaches. 

5-52
 
This method is frequently used in combination with other washing 

techniques (low or high pressure, cold or warm water). 

BIOLOGICAL CONSTRAINTS: 

Not appropriate at creek mouths. Where the lower intertidal contains rich 

biological communities, flooding should be restricted to tidal stages when the 

rich zones are under water, to prevent secondary oiling. 

ENVIRONMENTAL EFFECTS: 

Intertidal — Habitat may be physically disturbed and smothered as sand and 

gravel components are washed down slope. Organisms may be flushed into 

lower tidal zones. 

Subtidal — Oiled sediment may be transported to shallow subtidal areas, 

contaminating them and burying benthic organisms. 

8 a. Cold Water/Low Pressure Washing 

OBJECTIVE: 

Remove liquid oil that has adhered to the substrate or man-made structures, 

pooled on the surface, or become trapped in vegetation. 

DESCRIPTION: 

Low pressure washing with ambient seawater sprayed with hoses is used to 

flush oil to the water’s edge for pickup. Oil is trapped by booms and picked up 

with skimmers or sorbents. Can be used with a deluge system on beaches to 

prevent released oil from re-adhering to the substrate. 

APPLICABLE SHORELINE TYPES: 

On heavily oiled gravel beaches, rocky coasts, riprap and seawalls where the 

oil is still fresh and liquid. Also, in marshes and mangroves where free oil is 

trapped. 

WHEN TO USE:
 

Where adhered oil is still fresh and must be removed due to continued
 

release of oil.
 

BIOLOGICAL CONSTRAINTS: 

May need to restrict use of flushing to certain tidal elevations so that the 

oil/water effluent does not drain across sensitive low tide habitats. In 

marshes, use only at high tide and either from boats or the high-tide line to 

prevent foot traffic in vegetation. 

ENVIRONMENTAL EFFECTS: 

Intertidal — If containment methods are not sufficient, contamination may 

be flushed into lower intertidal zone. 

Subtidal — Oiled sediment may be transported to shallow subtidal areas, 

contaminating them and burying benthic organisms. 

8 b. Cold Water/High Pressure Washing 

OBJECTIVE: 

Remove oil that has adhered to hard substrates or man-made structures. 

5-53 
DESCRIPTION: 

Similar to low pressure washing except that water pressure is up to 100 psi. 

High pressure spray will better remove oil that has adhered to rocks. Because 

water volumes are typically low, may require placement of sorbents directly 

below treatment areas. 

APPLICABLE SHORELINE TYPES: 

Rocky shores, riprap, and seawalls. Can be used to flush floating oil or loose 

oil out of tide pools and between crevices on rocky shores. 

WHEN TO USE: 

When low pressure washing is not effective at removal of adhered oil, which 

must be removed due to continued release of oil. When directed water jet 

can remove oil from hard to reach sites. To remove oil from man-made 

structures for aesthetic reasons. 

BIOLOGICAL CONSTRAINTS: 

May need to restrict use of flushing to certain tidal elevations so that the 

oil/water effluent does not drain across sensitive low tide habitats. 

ENVIRONMENTAL EFFECTS: 

Intertidal — Removes many organisms on the surface. May drive oil deeper 

into the substrate if water jet is improperly applied. If containment methods 

are not sufficient, contamination may be flushed into lower intertidal zone. 

Subtidal — Oiled sediment may be transported to shallow subtidal areas, 

contaminating them and burying benthic organisms. 

9. Warm Water/Moderate-to-High Pressure Washing 

OBJECTIVE: 

Mobilize thick and weathered oil adhered to rock surfaces prior to flushing it 

to the water’s edge for collection. 

DESCRIPTION: 

Sseawater heated up to 100° is applied at moderate to high pressure to 

mobilize weathered oil that has adhered to rocks. The warm water may be 

sufficient to flush the oil down the beach. If not, "deluge" flooding and 

additional low or high pressure washing can be used to float the oil to the 

water’s edge for pickup. Oil is trapped by booms and picked up with 

skimmers or sorbents. 

APPLICABLE SHORELINE TYPES: 

Rocky shores, gravel beaches, riprap, and seawalls that are heavily oiled. 

WHEN TO USE: 

When the oil has weathered to the point that low pressure washing with cold 

water is not effective at removal of adhered oil, which must be removed due 

to continued release of oil. To remove oil from man-made structures for 

aesthetic reasons. 

BIOLOGICAL CONSTRAINTS: 

Must restrict use to certain tidal elevations so that the oil/water effluent does 

not drain across sensitive low tide habitats (damage can result from exposure 

5-54
 
to oil, oiled sediments, and warm water). Should be restricted adjacent to 

stream mouths, tide pool communities, and similar rich intertidal 

communities. 

ENVIRONMENTAL EFFECTS: 

Intertidal — Can kill or remove most organisms. If containment methods are 

not sufficient, contamination may be flushed into lower intertidal zones 

that would otherwise not be oiled. 

Subtidal — Oiled sediment may be transported to shallow subtidal areas, 

contaminating them and burying benthic organisms. 

10. Hot Water/High Pressure Washing 

OBJECTIVE: 

Dislodge trapped and weathered oil from inaccessible locations and surfaces 

not amenable to mechanical removal. 

DESCRIPTION: 

Water heaters mounted offshore on barges or small land-based units heat 

water up to 170°F, which is usually sprayed by hand with high pressure 

wands. Used without water flooding, this procedure requires immediate use 

of vacuum (vacuum trucks or super suckers) to remove the oil/water runoff. 

With a deluge system, the oil is flushed to the water surface for collection 

with skimmers or sorbents. 

APPLICABLE SHORELINE TYPES: 

Rocky shores, gravel beaches, riprap, and seawalls that are heavily oiled. 

WHEN TO USE: 

When the oil has weathered to the point that even warm water at high 

pressure is not effective at removal of adhered oil, which must be removed 

due to continued release of oil. To remove oil from man-made structures for 

aesthetic reasons. 

BIOLOGICAL CONSTRAINTS: 

Restrict use to certain tidal elevations so that the oil/water effluent does not 

drain across sensitive low tide habitats (damage can result from exposure to 

oil, oiled sediments, and hot water). Should be restricted near stream 

mouths, tide pool communities, etc. Released oil must be recovered to 

prevent further oiling of adjacent environments. 

ENVIRONMENTAL EFFECTS: 

Intertidal — All attached organisms in the direct spray zone will be removed 

or killed, and significant mortality of the lower intertidal communities will 

result even when used properly. Where the intertidal community is rich, 

the tradeoff between damage to the intertidal community from the hot 

water washing versus potential damage from leaving the oil has to be 

weighed. 

Subtidal — Oiled sediment may be transported to shallow subtidal areas, 

contaminating them and burying benthic organisms. 

11. Slurry Sand Blasting 

5-55
 
OBJECTIVE:
 

Remove heavy residual oil from solid substrates.
 

DESCRIPTION: 

Use of sandblasting equipment to remove oil from the substrate. May include 

recovery of used (oiled) sand in some cases. 

APPLICABLE SHORELINE TYPES:
 

Seawalls and riprap. Equipment can be operated from boat or land.
 

WHEN TO USE: 

When heavy oil residue is remaining on the shoreline, which needs to be 

cleaned for aesthetic reasons, and even hot water wash is not effective. 

BIOLOGICAL CONSTRAINTS: 

Not to be used in areas of oyster/clam beds, or areas with high biological 

abundance on the shoreline directly below or adjacent to the structures. 

ENVIRONMENTAL EFFECTS: 

Intertidal — Complete destruction of all organisms in the intertidal zone. 

Subtidal — Possible smothering of subtidal organisms with sand. When the 

used sand is not recovered, introduces oiled sediments into the subtidal 

habitat. 

12. Vacuum 

OBJECTIVE:
 

Remove free oil pooled on the substrate or from the water surface in
 

sheltered areas.
 

DESCRIPTION: 

Use of a vacuum unit with a suction head to recover free oil. The equipment 

can range from small portable units which fill individual 55-gallon drums to 

large supersuckers that are truck-mounted and can lift large rocks. Can be 

used with water spray systems to flush the oil towards the suction head. 

APPLICABLE SHORELINE TYPES: 

Can be used on any shoreline type if accessible. May be mounted offshore on 

barges, onshore on trucks, or as individual units on boats or ashore at low 

tide. 

WHEN TO USE: 

When free, liquid oil is stranded on the shoreline (usually along the high-tide 

line) or trapped in vegetation which is readily accessible. 

BIOLOGICAL CONSTRAINTS: 

Special restrictions should be identified for areas where foot traffic and 

equipment operation should be limited, such as rich intertidal communities. 

Operations in wetlands are to be very closely monitored, with a site-specific 

list of restrictions. 

ENVIRONMENTAL EFFECTS: 

Intertidal — Minimal impacts if used properly and minimal substrate is 

removed. 

5-56
 
 

Subtidal — None. 

Treatment Methods Requiring RRT Approval 

Research and development is ongoing for both new and improved oil spill 

treatment methods. Various chemical and biological degradation techniques are 

currently being tested for effectiveness and toxicity, and they may be approved for 

use in certain situations. Methods considered to be of potential use in this area are 

described below. 

13. Cutting Vegetation 

OBJECTIVE:
 

Removal of oiled vegetation to prevent oiling of wildlife.
 

DESCRIPTION: 

Manual cutting of oiled vegetation using weed eater, and removal of cut 

vegetation with rakes. The cut vegetation is bagged immediately for disposal. 

APPLICABLE SHORELINE TYPES:
 

Marshes composed of emergent, herbaceous vegetation.
 

WHEN TO USE: 

Use when the risk of oiled vegetation contaminating wildlife is greater than 

the value of the vegetation that is to be cut, and there is no less destructive 

method to remove or reduce the risk to acceptable levels. 

BIOLOGICAL CONSTRAINTS: 

Strict monitoring of the operations must be conducted to minimize the 

degree of root destruction and mixing of oil deeper into the sediments. Access 

to bird nesting areas should be restricted during nesting season. 

ENVIRONMENTAL EFFECTS: 

Intertidal — Removal of the vegetation will result in loss of habitat for many 

animals. Cut areas will have reduced plant growth for up to two years. 

Along exposed section of shoreline, the vegetation may not regrow, 

resulting in erosion and permanent loss of the habitat. Trampled areas 

(which is inevitable) will recover much slower. 

Subtidal — Long term impacts would be increased sediment load in the 

subtidal area as a result of increased erosion in the intertidal area. 

14 a. Chemical Oil Stabilization with Elastomizers 

OBJECTIVE:
 

Solidify or gelatinize oil on the water surface or a beach to keep it from
 

spreading or escaping.
 

DESCRIPTION: 

Chemical agent enhancing polymerization of the hydrocarbon molecules 

applied by semi-liquid spray or as a dry chemical onto the oil in the proper 

5-57
 
dosage. Depending on the nature and concentration of the polymerizing 

agent, the oil can be rendered viscoelastic, but still fluid, gelatinous, or 

semisolid. The primary purpose is to stabilize the oil keeping it from 

spreading or escaping, causing oiling elsewhere. May reduce the solubility of 

the light (and more toxic) fractions, by locking them into the polymer. This 

reduces both air and water exposure. Depending on the beach type and 

equipment used, recovery may be enhanced. Elastol is an example of an oil 

stabilizing agent. 

APPLICABLE SHORELINE TYPES: 

Suitable on shorelines of low permeability where heavy oil has pooled on the 

surface, except vegetated shorelines. 

WHEN TO USE: 

When heavy concentrations of liquid oil are on the substrate and adjacent 

water body, and physical removal can not be completed prior to the next tide 

so that the oil is likely to move to a more sensitive shoreline type. Should be 

used in conjunction with booming or other physical containment. 

BIOLOGICAL CONSTRAINTS: 

Not suitable for vegetated or riprap shore types. Should be avoided when 

birds or other wildlife that may be more adversely impacted by the congealed 

oil can not be kept away from the treated shoreline. The congealed oil may 

stick to vegetation and wildlife, increasing physical damage to both. On riprap 

the congealed oil may remain in crevices where it may hamper recovery and 

prolong the release of sheens. 

ENVIRONMENTAL EFFECTS: 

May enhance the smothering effect of oil on intertidal organisms. Thus, the 

treatment should be considered only for heavily oiled beaches where 

smothering effects are already maximal. The congealed oil may stick to 

vegetation and wildlife increasing physical damage, such as impaired flight in 

birds or impaired thermoregulation in mammals and birds whose feathers or 

fur become oiled. 

14 b. Chemical Protection of Beaches 

OBJECTIVE:
 

Pretreat shoreline to prevent oil from adhering to the substrate.
 

DESCRIPTION:
 

Certain types of water-based chemicals, some of which are similar in
 

composition to dispersants, are applied to beaches in advance of the oil.
 

APPLICABLE SHORELINE TYPES: 

Coarse- and fine-grained sand beaches, seawalls and piers (particularly piers or 

waterfront facilities that are of historical significance), eroding bluffs, wavecut platforms, and riprap. 

5-58
 
WHEN TO USE: 

When oil is projected to impact an applicable shoreline, particularly those 

which have high recreational or aesthetic value. 

BIOLOGICAL CONSTRAINTS: 

May not be suitable for nutrient-rich environments, particularly in confined 

waters. The toxicity of shoreline treatment products is reportedly much less 

than that of oil, but the toxicity of each product should be evaluated prior to 

consideration for use. 

ENVIRONMENTAL EFFECTS: 

The long-term environmental effects of these procedures are unknown. A 

toxic effect of the chemical can be anticipated. Additionally, the nutrient load 

to nearshore and interstitial waters may lead to eutrophication. Whether the 

predicted reduced residence time of the oil on the beach will increase the 

survival rate for sessile and interstitial organisms is unknown. 

14 c. Chemical Cleaning of Beaches 

OBJECTIVE:
 

To increase the efficiency of oil removal from contaminated areas.
 

DESCRIPTION: 

Special formulations which can be characterized as weak dispersants are 

applied to the substrate, as a presoak and/or flushing solution, to soften 

weathered or heavy oils to aid in the efficiency of flushing treatment 

methods. The intent is to be able to lower the temperature and pressure 

required to mobilize the oil from the substrate. 

APPLICABLE SHORELINE TYPES: 

On any shoreline where deluge and water flushing procedures are applicable 

WHEN TO USE: 

When the oil has weathered to the point where it will not flow using warm 

to hot water. This approach may be most applicable where flushing decreases 

in effectiveness as the oil weathers. 

BIOLOGICAL CONSTRAINTS: 

Will required extensive biological testing for toxicity and water quality 

sampling prior to receiving approval for use. The concern is that the treated 

oil will be dispersed in the water column, and thus impact water column and 

subtidal organisms. Field tests will be required to show that use of a beach 

cleaner does not reduce overall recoverability of the oil. Use may be restricted 

where suspended sediment concentrations are high, adjacent to wetlands and 

tidal flats, and near sensitive subtidal resources. 

ENVIRONMENTAL EFFECTS: 

If more oil is dispersed into the water column, there could be more oil sorbed 

onto suspended sediments and transfered to subtidal habitats, particularly 

along sheltered shorelines. Intertidal habitats might survive better, if cooler 

water temperatures are possible. 

5-59
 
15. In Situ Burning 

OBJECTIVE:
 

Removal of oil from the shoreline by burning.
 

DESCRIPTION: 

Oil on the shoreline is burned, usually when it is on a combustible substrate 

such as vegetation, logs, and other debris. Oil can be burned off of 

nonflammable substrates with the aid of a burn promoter. 

APPLICABLE SHORELINE TYPES:
 

On any shoreline type except tidal flats.
 

WHEN TO USE:
 

Early in the spill event, after ensuring that the product is ignitable.
 

5-60
 
BIOLOGICAL CONSTRAINTS: 

Should only be considered for use in the upper intertidal or supratidal zones 

since destruction of plants and animals from heat and burn promoters will be 

extensive. This technique is subject to restrictions and permit requirements 

established by federal, state and local laws. It should not be used to burn 

PCB's, wastes containing more than 1,000 ppm of halogenated solvents, or 

other substances regulated by EPA. 

ENVIRONMENTAL EFFECTS: 

Little is known about the relative effects of burning oiled wetlands compared 

to other techniques or natural recovery. Burning may cause significant air 

pollution, which must be considered when weighing the potential benefits 

and risks of the technique. The combustion products may travel great 

distances before deposition. 

16. Nutrient Enhancement 

OBJECTIVE: 

To speed the rates of natural microbial degradation of oil by addition of 

nutrients (specifically nitrogen and phosphorus). Microbial biodegradation is 

the conversion by microorganisms of dissolved and dispersed hydrocarbons 

into oxidized products via various enzymatic reactions. Some hydrocarbons 

are converted to carbon dioxide and cell material, while others are partially 

oxidized and/or left untouched as a residue. 

DESCRIPTION: 

Nutrients are applied to the shoreline in one of several methods: soluble 

inorganic formulations which are dissolved in water and applied as a spray at 

low tide, requiring frequent applications; slow-release formulations which are 

applied as a solid to the intertidal zone and designed to slowly dissolve; and 

oleophilic formulations which adhere to the oil itself, thus they are sprayed 

directly on the oiled areas. 

APPLICABLE SHORELINE TYPES:
 

Could be used on any shoreline type where safe access is allowed.
 

WHEN TO USE: 

On moderately to heavily oiled shorelines, after other techniques have been 

used to remove as much oil as possible; on lightly oiled shorelines where 

other techniques are not effective; and where nutrients are a limiting factor in 

natural degradation. 

BIOLOGICAL CONSTRAINTS: 

Not applicable in shallow water, restricted embayments where nutrient 

overloading may lead to eutrophication, or where toxicity of nutrients, 

particularly ammonia, is of concern. There must be no risk of oxygen 

depletion. Use is to be restricted adjacent to stream mouths, tide pools, etc. 

Contact toxicity of oleophilic formulations may restrict areas of direct 

application. Bioassay test results should be carefully evaluated, as other 

chemicals in the formulations could be toxic to aquatic organisms. 

5-61 
ENVIRONMENTAL EFFECTS: 

Tests in Alaska showed that interstitial oxygen concentrations did not 

decrease to such an extent that it limited the supply of oxygen available to the 

bacteria. The fertilizer applications that increased nutrient concentrations and 

microbial activity did not harm the nearshore environment. About 99 

percent of butoxyethanol, a toxic component of the Inipol formulation, (the 

fertilizer commonly used in Alaska) degraded to nontoxic compounds within 

24 hours after Inipol treatments of cobble shorelines. Researchers also found 

no evidence that the nutrients released from the treated shorelines 

stimulated algal blooms. 

17. Microbial Addition 

OBJECTIVE: 

To speed the rates of natural microbial degradation of oil by addition of 

nutrients and microbial products. Microbial biodegradation is the conversion 

by microorganisms of dissolved and dispersed hydrocarbons into oxidized 

products via various enzymatic reactions. Some hydrocarbons are converted 

to carbon dioxide and cell material, while others are partially oxidized and/or 

left untouched as a residue. 

DESCRIPTION: 

Formulations containing hydrocarbon-degrading microbes and fertilizers are 

added to the oiled area. The argument is made that indigenous organisms 

will be killed by the oil, so new microbial species need to be added to being the 

process of biodegradation. 

APPLICABLE SHORELINE TYPES:
 

Could be used on any shoreline type where safe access is allowed.
 

BIOLOGICAL CONSTRAINTS: 

Not applicable in shallow water, restricted embayments where nutrient 

overloading may lead to eutrophication, or where toxicity of nutrients, 

particularly ammonia, is of concern. There must be no risk of oxygen 

depletion. Use is to be restricted adjacent to stream mouths, tide pool 

communities, etc. Bioassay test results should be carefully evaluated, as other 

chemicals in the formulation could be toxic to aquatic organisms. 

ENVIRONMENTAL EFFECTS:
 

Yet to be evaluated for full-scale field applications.
 

5-62
 
18. Sediment Reworking 

OBJECTIVE: 

Rework oiled sediments to break up the oil deposits, increase its surface area, 

and mix deep subsurface oil layers, which will expose the oil to natural 

removal processes and enhance the rate of oil degradation. 

DESCRIPTION: 

Beach sediments are rototilled or otherwise mechanically mixed, with the use 

of heavy equipment on gravel beaches. The oiled sediments in the upper 

beach area may also be relocated lower on the beach to enhance natural 

cleanup during reworking by wave activity (berm relocation). 

APPLICABLE SHORELINE TYPES: 

Should be used only on beaches exposed to significant wave activity. Tillingtype activities work best on beaches with a significant sand fraction; large 

equipment can be used to relocate sediments up to boulder size. 

WHEN TO USE: 

On beaches with significant amounts of subsurface oil, where sediment 

removal is unfeasible (due to erosion concerns or disposal problems); also 

where surface oil deposits have started to form pavements or crusts. 

BIOLOGICAL CONSTRAINTS: 

Could not be used on beaches near shellfish-harvest or fish-spawning areas, 

or near bird nesting or concentrations areas because of the potential for 

constant release of oil and oiled sediments. Sediment reworking should be 

restricted to the upper part of the beach, to prevent disturbance of the 

biological communities in the lower intertidal area. 

ENVIRONMENTAL EFFECTS: 

Intertidal — Due to the mixing of oil into sediments, this process could 

further expose organisms which live below the original layer of oil. 

Repeated mixing over time could delay the reestablishment of organisms. 

Relocated sediments would bury and kill organisms. There may be a period 

of beach unstability as the relocated sediments are redistributed. 

Subtidal — There is a potential for release of contaminated sediments to the 

nearshore subtidal habitats. 

19. Shoreline Excavation, Cleansing and Replacement 

OBJECTIVE:
 

To remove and clean oiled sediments, then place them on the beach.
 

DESCRIPTION: 

Oiled sediments are excavated using heavy equipment on the beach at low 

tide. The sediments are loaded into a container for washing. Cleansing 

methods include hot water wash or physical agitation with a cleansing 

solution. After the cleansing process, the rinsed materials are returned to the 

original area. Cleaning equipment must be placed close to beaches in order to 

reduce transportation problems. 

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APPLICABLE SHORELINE TYPES: 

Sand- to boulder-sized beaches, depending on the limitations of the cleanup 

equipment. The beaches must be exposed to wave activity, so that the 

replaced sediments can be reworked into a natural distribution. 

WHEN TO USE: 

Applicable on beaches with large amounts of subsurface oil, where permanent 

removal of sediment is undesired and other cleanup techniques are likely to 

be ineffective. 

BIOLOGICAL CONSTRAINTS: 

Excavating equipment must not intrude upon sensitive habitats. Only the 

upper and supratidal areas should be considered. Generally restricted in 

spawning areas. There may be site-specific constraints limiting placement of 

temporary sediment storage piles,. Replaced material must be free of oil and 

toxic substances. The washing must not change the grain size of the replaced 

material, either by removal of fines or excessive breakage of friable sediments. 

ENVIRONMENTAL EFFECTS: 

Intertidal — All resident organisms will be affected, though the need for 

removal of the oil may be determined to be the best overall solution. 

Equipment can be heavy, large, and noisy, disrupting wildlife. 

Transportation to site may entail aircraft, land vehicles, or barges, which 

contribute to environmental disruption. There may be a period of beach 

unstability as the replaced sediments are redistributed. 

Subtidal — May release oil and fine-grained oily sediments into the water 

during excavation. This is a concern due to tidal flushing of beach 

sediments and exposed excavations. 

Other Techniques 

Beach Cleaners 

During the Exxon Valdez oil spill, Exxon spent considerable time and money 

developing an effective and low-toxicity chemical cleaner which would speed the 

removal of weathered oil from the beaches of Prince William Sound. Their 

approach was to use the chemical as a presoak to be applied prior to water washing, 

to soften the oil and increase removal efficiences at lower temperatures. Exxon 

conducted a detailed screening program of commercially available products to find 

the product which would remove the most oil but also had low dispersive 

properties. It was not acceptable to have the oil removed by dispersion to the 

nearshore water column. 

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Exxon eventually developed their own product, Corexit 9580, and conducted 

extensive bioassays and field effectiveness tests in Alaska (Fiocco et al., 1991). This 

product was shown to have very low toxicity, in both laboratory bioassays and in situ 

testing of run-off water from full-scale field testing sites. The main concern about 

the product was recoverability of the released oil; during tests, it appeared that the 

released oil was dispersed more into the nearshore water than at control sites. Beach 

cleaners might be appropriate for cleaning man-made structures, such as seawalls 

and riprap, assuming that the oil can be recovered. Since recovery was still an issue 

in the most extensive testing yet conducted on beach cleaners, their use without 

further testing is unlikely. 

Elastol 

Elastol is a commercial product composed of polyisobutylene in a white powder 

form. Polyisobutylene is a non-toxic constituent found in foodstuffs. Issues on 

application of Elastol for oil spill response include: 

•	 Elastol increases the resistance of spilled oil to being pulled apart or broken 

up (viscoelasticity) by temporarily altering hydrocarbon molecular shape. 

•	 The treated oil must be pulled; pushing it makes it lose its elastic 

properties. 

•	 The effects of Elastol are reversible. 

•	 Application: 

-Traditionally applied as a powder from conventional dusters 

-Recently applied as a slurry mixture with a 15 percent calcium stearate 

coating with water. Has consistency of "cream of wheat." 

• Application rates vary with oil type, with lower rates for heavier oils: 

-Light oil spills: 1000-2000 ppm 

-Bunker C spills: 100-200 ppm 

• Lower application rates are recommended because they allow the oil to 

revert back to its original condition more readily and at lower costs. 

•	 Starts working in 15-60 minutes, with faster times for lighter oils. 

•	 Elastol particles float, due to the coating. Dissolution occurs after mixing 

with hydrocarbon liquids. 

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__________________________________________________________ 

__ 

__________________________________________________________ 

__ 

__________________________________________________________ 

__ 

• Toxicity: 

-Very low toxicity (see below) 

-Lowers toxicity of oil by "binding" soluble toxic fractions into the 

"Elastoil" mixture. 

Artemia salina Fundulus heteroclitus 

Toxicant	 48 hour LD50 (ppm) 96 hour LD50 (ppm) 

Elastol >18,000 >18,000
 

No. 2 fuel oil 600 3,200
 

1:10 mixture
 

(Elastol:No. 2 fuel oil) >3,200 >18,000
 

Seagrasses showed no toxic effects 

CONCERNS: 

•	 Non-uniform application results in "clumping" of oil/Elastol mixture 

into highly viscous, sticky masses. Can be countered with sawdust. But 

behavior of this sticky mass when the mixture strands on the shoreline is 

of concern. 

•	 Potential problems for birds, fur-bearing mammals, marshes, mangroves, 

etc. Do not know difference in impacts to oiled versus "Elastoiled" 

animals. 

•	 Recovery is best with a specially designed drum skimmer, which must be 

transported to the site, causing delays. 

PHYSICAL EFFECTS (based on laboratory, tank, and field tests) 

•	 There was no simple correlation between oil type and effectiveness. 

•	 Elastol increased these physical properties of oil: 

-Viscoelasticity 

-Slick thickness (only at application rates greater than 1 percent). 

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•	 Elastol decreased the extent of oil slick spreading. 

•	 Elastol did not affect these oil properties: 

-Evaporation rate 

-Flash point 

-Weathering rates 

•	 Emulsion formation tendency tests have produced mixed results; 

formation of emulsion decreases the effectiveness of Elastol. 

•	 Elastol reduced the effectiveness of chemical dispersants applied after 

Elastol use by up to a factor of 10. 

•	 Elastol reduced natural dispersion by up to three orders of magnitude (so it 

could be used to reduce oil levels in the water column in shallow water 

conditions). 

Observations from a test of Elastol on a heavy black oil spill in New York harbor on 

26 December 1988, as recorded by Ed Levine, the NOAA SSC, are: 

“Approximately 25 minutes after application of Elastol B to the oil a 

thickening of product was observable. At this time the vacuum hose was 

used to begin removing the product from the creek. Due to the amount of 

floating debris included in the oil, a problem was encountered with clogging 

of the nozzle by this debris, however, at this time it was not significantly 

greater than non-treated oil. 

...“After approximately one hour from the original application of Elastol, we 

changed the removal sites to the lee of the floating dock. The product 

encountered here was quite thick and exhibited stretch lines as the vacuum 

nozzle was applied to it. The oil could be observed migrating towards the 

vacuum source. The nozzel was then moved to an area of untreated oil. A 

marked difference in the thickness and behavior of the oil could be noted. 

This oil was approximately the consistency of water, while the treated oil was 

like thick molasses. Also noted was the increased recovery of water with the 

untreated oil, as opposed to the treated oil, which removed mostly oil.” 

Although Elastol has had very little field testing, it appears to work as advertised. 

Recovery is still a problem, as is the case for any type of spilled hydrocarbon. 

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Bioremediation 

Bioremediation should be considered in the context of the entire suite of spill 

treatment technologies, including the option of no treatment. Only when there is a 

clear reason for using bioremediation should its potential use be pursued. 

Bioremediation is considered promising because it enhances natural biodegradation, 

which occurs in most areas where oil is spilled. In fact, in areas that are lightly oiled, 

natural, unassisted biodegradation may be the best "treatment." The key question to 

ask in these circumstances is, Can bioremediation offer an improvement over 

natural levels of biodegradation? It will probably be necessary to conduct a smallscale test of the proposed bioremediation technique to answer this question. 

Bioremediation is most promising as a long-term treatment, so there should be no 

hurry to attempt to rush through an evaluation procedure during the first few 

hours after a spill occurs. Alternate techniques exist for immediate spill response 

that have been tried and tested more extensively. If a need for longer-term 

shoreline treatments is identified, then bioremediation can still be considered 

effectively days or weeks after the spill event. 

Before becoming involved in the details of protocols and planning considerations, it 

may be useful to step back for a moment and evaluate the three main types of 

bioremediation currently being considered for oil spill response: fertilizer 

application, microbial additions, and open-water applications. 

Fertilizer 

Use of fertilizer for accelerating biodegradation on oiled shorelines is the most welldocumented and well-researched type of bioremediation. Many aspects of the 

technology are promising, particularly its potential use in areas that would be 

affected detrimentally by more intrusive physical treatments. However, the variable 

results from field tests confirm that this is not yet an off-the-shelf technique that can 

be applied to oiled shorelines with the expectation of success in all cases. Perhaps 

the most enlightening aspect of many of the studies of fertilizer use is that 

unassisted biodegradation does occur at high rates in many locations, and that the 

no-treatment option perhaps should be considered more frequently. 

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Bioremediation with fertilizer is complicated, because natural biodegradation rates 

vary considerably (from days to months) depending on the environment and the oil 

in question. Temperature is an important consideration, as is the amount of organic 

matter and nutrients, salinity, and oxygen. This means that caution must be 

exercised when applying results from one area to an application in another 

environment. Like most other treatment technologies, decisions will probably need 

to be made on a case-by-case basis. What works in one situation may not be effective 

or may be inappropriate for another situation. Monitoring should be conducted to 

verify the effectiveness of the application, and to document any adverse impacts. 

Fertilizer may be most appropriately considered in the following situations, if it is 

determined that nutrients may be limiting: 

Sheltered shorelines that are heavily oiled, when techniques for physical 

removal of the oil are impractical or infeasible, or have already been attempted; 

Shorelines with substantial subsurface oil that may degrade very slowly. (In this 

case, increased oxygen may need to be supplied to the subsurface); 

Sensitive environments, especially marshes and wetlands that will be impacted 

adversely by other cleanup methods. 

Fertilizer will be inappropriate in circumstances such as the following: 

Environments that are already nutrient-rich (nutrients are not limiting in these 

cases—see Prall's Island discussion). This can be tested by measuring background 

nutrient levels before beginning a bioremediation experiment. 

For short term, immediate response actions. Usually, physical techniques will 

first be used to remove as much oil as is feasible, and then fertilizer may be 

considered for longer-term, follow-up treatment. 

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Microbial products 

Use of microbial products for treatment of open environments is still an 

experimental technology. Few microbial products can show increased degradation 

over use of fertilizer alone when tested under standardized laboratory conditions. 

No data that currently exist show that microbes increase biodegradation in open 

environments when they are compared with use of fertilizer alone. The same 

environmental constraints that affect fertilizer treatments also apply to microbial 

products, with the added uncertainty of whether the supplemental microbes will 

survive and become active in a foreign environment. Microbial products would 

theoretically be useful in environments that are lacking indigenous microbes, but 

this has not been the case at most environments studied in the context of marine oil 

spills. 

At this time, the use of microbial products in open environments for treatment of 

oiled shorelines should be considered for experimental testing purposes only. 

Further, until the National Environmental Technology Applications Corporation 

(NETAC) protocols are in place, a considerable burden of evaluating unknown 

products rests with the spill responder. The decision on whether to use microbial 

products should be made only after careful evaluation of the products available, and 

after evaluating data on their toxicity and effectiveness. Without reliable data on 

the effectiveness and potential toxicity of a microbial product, it will be impossible to 

make an informed decision on its application in the marine environment. 

Open-water. Open-water bioremediation is presently the least promising 

bioremediation technology. Since bioremediation is a long-term process which does 

not begin to significantly degrade oil until a period of several days to several weeks 

after exposure to oil, it is questionable whether it could work on an oil slick. Much 

of the initial loss of oil in slicks is through evaporation, and it is doubtful that 

biodegradation is actively occurring during this time period (since the volatile 

fractions of the oil are toxic to bacteria). Thus, a bioremediation product, whether 

fertilizer or microbial, would have to become active during a window of time after 

the volatile fractions of the oil have evaporated and before the oil has formed 

weathered compounds that are more resistant to biodegradation. The 

bioremediation product must also stick to the oil and remain at the surface-water 

interface for an extended period of time. 

5-70 
The unknown questions about open-water bioremediation will be difficult to 

answer due to the logistical problems of conducting research on oil slicks. The long 

history of attempting to document the effectiveness of dispersants also applies to 

open-water bioremediation techniques. Controlled field studies under real oil spill 

conditions are extremely difficult to conduct, and research on intentionally spilled 

oil even more so. Since open-water use of bioremediation is highly experimental, 

and many substantial questions still need to be answered, this technology should 

presently not be considered in any situation other than a research context. 

Monitoring recommendations 

There is no single measure that will accurately measure effectiveness or toxicity of a 

bioremediation application. Most of the larger bioremediation monitoring 

programs that have been undertaken have used a combination of the techniques 

discussed, depending on their specific concerns and objectives (DuPont 1991; Prince 

et al. 1990; Pritchard et al. 1991). For example, the Alaska studies measured several 

different parameters for toxicity, water quality and effectiveness (See Table 5-4). As a 

minimum, a monitoring plan at a bioremediation field test or application should 

include at least the following endpoints: 

1) To measure effectiveness, track changes in indicator hydrocarbon compounds by 

gas chromatography/mass spectroscopy (GC/MS). Samples should be collected at 

least at the beginning and end of the sampling period at control and treated sites. 

2) Conduct toxicity testing using bioassays to determine acute and/or chronic 

toxicity to aquatic organisms (see NETAC protocols for examples.) Bioassays 

should include sediment bioassays if the bioremediation chemicals are likely to 

lodge in sediments. Testing should include test sites and control sites. 

3) Monitor environmental impacts to aquatic habitats through chemical analysis of 

sediments or water for potentially toxic compounds (such as heavy metals) that 

may be part of a bioremediation product. Samples should be collected at the 

beginning and end of the sampling period at control and treated sites. 

Biodegradation versus bioremediation 

Biodegradation is the natural process whereby bacteria or other microorganisms 

alter and break down organic molecules into other substances, such as fatty acids and 

carbon dioxide. Bioremediation is the act of adding fertilizers or other materials to 

contaminated environments, such as oil spill sites, to accelerate the natural 

biodegradation process (U.S. Congress 1991). Bioremediation is also used in 

5-71
 
terrestrial and other applications, including sewage treatment, terrestrial oil spills, 

and experimentally for hazardous wastes. 

Three main types of bioremediation technologies are currently being developed or 

applied for treatment of oil spills: addition of fertilizer to oiled shorelines, addition 

of microbial products to oiled shorelines, and addition of fertilizer and/or microbial 

products to open water oil slicks. Since all of these technologies attempt to accelerate 

biodegradation, this report presents a short summary of the processes of 

biodegradation of oil, a discussion of some of the potential uses of this technology, 

including specific instances where bioremediation has been applied at oil spills, and 

presents guidelines for evaluation and monitoring of bioremediation applications. 

How does biodegradation work? 

Biodegradation is one of the main ways in which spilled oil is weathered. It occurs 

in most environments, but at varying rates, depending on localized environmental 

conditions and on the composition of the oil (for example, heavier oils are more 

resistant to biodegradation than lighter oils) 

(Atlas 1975). Among the many environmental factors that will affect biodegradation 

rates, oxygen, nutrients, and temperature are probably the most important (Atlas 

1981; DeFlaun and Mayer 1983). 

Simply adding oil to an environment will stimulate growth of indigenous microbes, 

since the oil provides increased amounts of carbon, the microbes' food source (Lee 

and Levy 1991). Several researchers have documented a lag period before 

indigenous microbial communities begin to degrade oil (Fusey and Oudot 1984; 

NOAA 1980). This may be due to the fact that oil is initially toxic to microbial 

organisms, and the most toxic fractions must be weathered before microbes can 

grow, a time period of several days to several weeks (Lee and Levy 1989b). 

The primary processes of microbial degradation are aerobic (requiring oxygen), 

though anaerobic degradation may occur at very low rates. Low-energy, sheltered 

environments probably have the lowest rates of biodegradation, especially in 

subsurface sediments. Oil in anaerobic sediments in marshes or other 

environments may degrade very little, with oil persisting in some cases for several 

years (Delaune et al. 1980; Atlas 1981; Lee and Levy 1991). High-energy 

environments usually show rapid biodegradation, in part because of physical 

5-72
 
weathering, but also because wave action supplies oxygen and nutrients to the 

microbial communities, facilitating biodegradation (Lee and Levy 1989a). See the 

OTA report for a thorough discussion of the chemical processes of biodegradation 

(U.S. Congress 1991). 

Microbial populations that undergo rapid growth in the presence of spilled oil may 

become limited by inadequate amounts of nutrients, such as nitrogen and/or 

phosphorus. Field tests on biodegradation of a waxy crude oil (Terra Nova crude) in 

sandy beaches found that fertilizer addition was effective in accelerating 

biodegradation in areas that were heavily oiled, but less so in areas that were lightly 

oiled (little acceleration was measured in these areas). This was due to the fact that 

unassisted biodegradation occurred very rapidly in the lightly oiled areas (Lee and 

Levy 1991). Nutrients are less likely to be limiting to microbial population growth 

in the water column for degradation of suspended oil particles, than for oil on 

shorelines or concentrated in oil slicks (Atlas 1981). 

At extremely high salinities, biodegradation is inhibited (Ward and Brock 1978), but 

this is not likely to be a problem in the normal range of salinities usually 

encountered in marine and coastal environments (Lee and Levy 1989a). 

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Types of bioremediation 

Nutrient addition (fertilizer) 

The theory behind bioremediation by nutrient addition is simple: microbes already 

living on an impacted shoreline have a sudden new source of food—carbon 

compounds in the spilled oil. After the initial toxicity of the oil wears off (usually by 

evaporation of the volatile compounds) and after indigenous species of 

hydrocarbon-degrading microbes become acclimated, they begin to "eat" the oil, and 

their population grows. At this point, the sudden increase in numbers of microbes 

may deplete existing supplies of nutrients (specifically nitrogen and/or phosphorus) 

and this may limit further growth of the microbial population. With added 

nutrients, the microbial population can continue to increase, and degrade oil at a 

faster overall rate, than without the supplemental nutrients. 

Numerous laboratory studies on fertilizer enhancement of oil biodegradation by 

naturally occurring microbes have concluded that fertilizer enhancement has 

potential as a treatment technique for oiled shorelines (NOAA 1978; Atlas 1981; Lee 

and Levy 1987; Lee and Levy 1989a). Field experiments have also been conducted, 

but these have not always corroborated the laboratory results (Fusey and Oudot 1984; 

Lee and Levy 1991). Results from field tests are less clear, in part because it is 

difficult to actually measure biodegradation outside of the laboratory. It is also 

difficult to determine statistical differences in biodegradation rates between control 

areas and fertilized areas in the field due to environmental variability and high 

spatial variability in the distribution of oil in sediments of impacted areas. It also 

appears that biodegradation rates can vary substantially between environments, 

probably due to environmental factors such as temperature or other very localized 

conditions (Prince et al. 1990; DuPont 1991; Pritchard et al. 1991). 

The potential advantages of any bioremediation technique must be balanced against 

possible detrimental environmental effects, including introduction of 

contaminants, toxicity to aquatic organisms, and physical impacts. Some fertilizer 

products, whose primary use is in a terrestrial setting, may contain trace metals as 

micro-nutrients (e.g., copper or mercury) that would be introduced into an aquatic 

environment with potentially much more significant toxicological effects (Mearns 

1991). Others may produce by-products such as ammonia and/or nitrates that are 

toxic to aquatic organisms at certain concentrations (U.S. EPA 1989). Intertidal 

organisms that are directly exposed during application of the undiluted fertilizer 

5-74
 
 

solution may be adversely impacted. In addition, physical disturbance from the 

application process and from monitoring will have some impacts on the shoreline, 

especially in sensitive environments such as marshes. 

Fertilizer use is still experimental in marine environments; therefore, any 

application should include a monitoring program to determine whether the desired 

objectives have been met, and whether any adverse impacts have been minimized 

to acceptable levels of risk. Following are summaries of different types of fertilizers 

and application techniques that have been used in bioremediation experiments or 

applications. 

Types of fertilizers 

Fertilizer addition can involve a variety of application techniques and numerous 

commercial fertilizer products, some that have been developed specifically for use 

on oil spills, and others that have been adapted from agricultural or domestic use. 

These products can be grouped into three basic categories: soluble inorganic 

fertilizers, oleophilic fertilizers, and slow release fertilizers. Each is discussed in 

more detail below. 

Soluble inorganic fertilizers. Inorganic fertilizers include a wide variety of 

water-soluble lawn or agricultural fertilizers that can be mixed with seawater and 

sprayed on shorelines. These fertilizers can be formulated with different ratios of 

nitrogen and phosphorus and usually include small quantities of trace elements. 

Some advantages of inorganic fertilizers are that they are readily available, 

inexpensive, and usually consist of compounds with well known properties. 

However, since these fertilizers are water-soluble, they may be washed off the 

shoreline by tidal action, requiring frequent, repeated applications. There may also 

be some direct toxicity (i. e. burning) to plants or animals in the intertidal zone that 

are directly impacted during the application process. 

Oleophilic fertilizers. Oleophilic fertilizers were developed to solve the 

problem of fertilizers washing off rocks or beaches. Oleophilic (literally, "oilloving") fertilizers are chemically "sticky" and adhere to oil on rocks or other 

substrates. In theory, these fertilizers are designed to remain at the oil-water 

interface and are therefore readily accessible to oil-degrading microbes. In Prince 

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William Sound, Alaska, the oleophilic fertilizer Inipol EAP 22 was applied 

extensively to oiled shorelines and was investigated in several monitoring studies. 

Inipol contains oleic acid (a source of carbon), urea (a source of nitrogen), 

tri(laureth-4)-phosphate (a surfactant), and 2-butoxy-ethanol (another surfactant) 

(Pritchard et al. 1991). Since addition of oil alone will stimulate bacterial growth, the 

presence of oleic acid in the fertilizer complicates evaluation of the effectiveness of 

oleophilic fertilizers such as Inipol. Do these products appear to work better because 

the microbes are eating the carbon in the fertilizer instead of the spilled oil? Lee and 

Levy (1989b) concluded that addition of an oleophilic fertilizer to a low-energy beach 

contaminated with crude oil was ineffective as a bioremediation agent because the 

microbes were preferentially eating the organic components of the fertilizer instead 

of the oil. 

Several scientists have argued that Inipol appears to be effective because it is acting 

primarily as a chemical surfactant rather than as a bioremediation agent. 

Surfactants, such as the ones in Inipol, are found in cleaning agents and dispersants. 

Inipol contains approximately 10% 2-butoxy ethanol, a common ingredient in 

household cleaning agents, and also one of the ingredients in the dispersant Corexit 

9527 (Exxon 1989a; Keyser 1991; Exxon 1989b). Critics have argued that some of the 

dramatic visual effects noted during field observations using oleophilic fertilizers 

are a result of the surfactant properties of the fertilizer, rather than from stimulated 

biodegradation. 

Several components of Inipol are toxic to humans and other organisms at certain 

concentrations. These include 2-butoxy-ethanol, and urea, which produces 

ammonia when it comes in contact with water. 2-butoxy-ethanol is toxic to 

mammals, especially in the first 48 hours after application. Effects on humans 

include eye and skin irritation, and damaged blood cells with repeated exposure. 

This requires that special safety precautions be taken for workers who handle Inipol, 

such as wearing clothing (rubber boots and aprons) or respirators if exposure to 

fumes or dust is likely (Exxon 1989b). 

Slow-release fertilizers . Slow-release fertilizers are designed to release 

quantities of fertilizer over a longer period of time, and to remain in the area where 

they are applied. They include various brands of fertilizer mixes, packaged in 

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dissolvable capsules or briquettes. These formulations, in theory, release small 

quantities of nutrients slowly over a period of time. While briquettes may move 

about on the beaches with tidal action, granules will usually lodge among pebbles 

and cobbles and remain in the intertidal zone. In this way, the dosage of fertilizer is 

controlled at low levels and release of fertilizer to the subsurface may be facilitated as 

granules work their way down into sediments. 

Several brands of slow-release fertilizers were tested in Prince William Sound in 

1989 by EPA, and one granule product, CustomblenTM, was subsequently applied 

extensively on shorelines (Pritchard et al. 1991). Customblen contains nutrients 

(ammonium nitrate, calcium phosphate, and ammonium phosphates) encased in a 

polymerized vegetable oil (Prince et al. 1990). Assuming that the pellets remain in 

the intertidal zone, Customblen does not need to be applied as frequently as liquid 

fertilizers. Some possible disadvantages include the possibility that pellets may 

wash away or lodge at the high tide zone on high-energy beaches. Concentrations of 

pellets higher than the recommended application could collect in one location (such 

as a tidal pool) and create concentrations of ammonia that could be toxic to aquatic 

organisms. 

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Fertilizer applications 

Exxon Valdez 

March 1989 - 1991 

In March 1989, approximately 350 miles of shoreline in Prince William Sound were 

oiled with North Slope crude oil from the Exxon Valdez spill (Pritchard and Costa 

1991). In the early summer, following preliminary results from a bioremediation 

test program conducted by the EPA's Alaska Oil Spill Bioremediation Project, the 

Alaska RRT approved the use of fertilizer as bioremediation to treat oiled 

shorelines. A number of constraints were placed on the use of fertilizer, including a 

restriction to areas that were well-flushed, and a prohibition from applying fertilizer 

in sensitive areas such as near anadromous fish streams. The decision on whether 

to apply bioremediation to specific shorelines was made on a segment-by-segment 

basis. In 1990, continued use of bioremediation as a shoreline treatment was 

approved with the requirement that a monitoring program be conducted to evaluate 

the effectiveness and safety of the bioremediation applications (U.S. Congress 1991; 

Prince et al. 1990; Pritchard et al. 1991). 

The studies conducted in 1989 and 1990 in Prince William Sound were 

comprehensive and investigated the effectiveness of different types of fertilizers at 

several sites, including several test and control plots. Monitoring also included 

sampling and analysis of various water quality parameters and toxicity testing (Table 

5-4; Prince et al. 1990; Pritchard et al. 1991). 

Effectiveness: Though several articles published about the bioremediation studies 

in Prince William Sound have claimed dramatic and successful results (Pritchard 

and Costa 1991), a careful evaluation of the data leads to a more cautious conclusion 

(Kellogg 1991). Though studies conducted in both years were carefully designed and 

included control plots, all of the data had high levels of variability, making it 

difficult to determine overall differences between fertilized plots and control plots. 

1989 Studies: In 1989, one of two treated test plots in Passage Cove (treated with 

water-soluble fertilizer applied with sprinklers) showed statistically significant 

differences in oil residue weight when compared with the control site. The second 

test site (treated with Inipol and Customblen) did not show a significant difference 

in oil residue weight compared with the control site. (Measures of oil residue 

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weight varied at all sites by up to two orders of magnitude.) Microbial counts 

showed no significant differences in numbers of microbes between treated and 

control plots. However, significant differences were found between numbers of 

bacteria at oiled sites versus unoiled sites, demonstrating that the presence of oil by 

itself will stimulate microbial growth (Pritchard et al. 1991). 

At a second study conducted in 1989 at Snug Harbor, measurements of oil residue 

weight over time were highly variable among all plots, including control plots. 

(Values ranged over an order of magnitude.) Decreasing trends in oil residue 

weight were found at all plots, including the control plot. No data showing 

statistical comparisons were presented, but there did not appear to be strong 

differences between control and treated plots in oil residue weight loss over time. 

Gas chromatograph analyses showed degradation rates that appeared to be higher at 

treated sites (Pritchard et al. 1990; Pritchard et al. 1991). 

1990 Studies: The studies conducted in 1990 encountered the same problem as those 

in 1989 with highly variable distributions of oil in sediments. This resulted in such 

high levels of variability in measures of oil residue weight, that detecting differences 

by quantitative analysis was deemed impossible without greatly increased numbers 

of samples (approximately an order of magnitude greater; Prince et al. 1990). 

Analyses using gas chromatography that tracked specific compounds showed 

qualitatively that biodegradation was occurring, but differences between control and 

treated sites were difficult to detect. Overall results of effectiveness were 

inconclusive. 

There are several reasons why the results from both years were somewhat 

inconclusive: background rates of biodegradation were found to be "surprisingly 

high" at control plots; second, there could be strong differences in local 

environmental conditions that either favor or inhibit biodegradation at each 

individual site. Further, a process of declining returns would be expected in 1990, 

since most of the remaining oil was weathered, and thus more 

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resistant to biodegradation. These studies can be interpreted as showing that some 

fertilized sites showed trends with increased rates of biodegradation, with stronger 

evidence of effectiveness in the first year. 

Toxicity: Bioassays conducted using oyster and mussel larvae showed some acute 

toxicity, while bioassays using mysids showed no acute effects. These were 

conducted with water samples from beaches after treatment with both Inipol and 

Customblen (Sanders and Gray 1989; Prince et al. 1990; Pritchard et al. 1991). No 

chronic toxicity tests were conducted, nor were analyses made for sediment toxicity 

or direct toxicity of Inipol to intertidal organisms. 

Prall's Island, New Jersey 

June 1990 - December 1990 

In January 1990, a pipeline at the Exxon Bayway refinery in Linden, New Jersey 

broke. Fuel oil was spilled into the Arthur Kill waterway, contaminating a beach on 

the Prall's Island bird sanctuary. Most of the oil was removed by physical means, but 

these efforts were halted in March 1990, partly to avoid impacts to migrating birds 

using the area. Exxon Research and Engineering received permission to conduct a 

bioremediation experiment on part of the beach with remaining oil (DuPont 1991). 

The experiment used a slow-release fertilizer (Customblen) placed in two shallow 

trenches dug in the intertidal zone. In an attempt to get around the usual high 

variability in distribution of oil on the beach, bags of beach substrate containing 

known concentrations of oil were buried in each test plot. Samples from each of 

these bags were measured for total petroleum hydrocarbons (TPH) at the end of the 

experiment to compare rates of biodegradation (DuPont 1991). Microbial counts 

made on beach samples taken before fertilization showed high background levels of 

microbes in the test area. Background levels of nitrogen and phosphorus were also 

high when measured prior to the beginning of the experiment (DuPont 1991). 

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Effectiveness: The overall results showed no clear trends of increased rates of 

biodegradation from fertilized plots. This was, in part, due to the high variability in 

the levels of TPH measured in soils and sampling bags from all plots, including the 

control plot. Some problems were experienced with possible cross-contamination of 

the control plot (nutrients leaching from the treated plots into the control plot), and 

this may have obscured any differences between them. The fact that high numbers 

of microbes were measured in the substrate before the fertilizer treatment began may 

be an indication that background levels of biodegradation were naturally high. This 

is not surprising since Prall's Island has been chronically impacted by oil spills in the 

past, and indigenous microbial populations may be well adapted to the presence of 

hydrocarbons. Also, the previously existing high levels of nitrogen and phosphorus 

would suggest that nutrients may not be a limiting factor in this system. 

Toxicity: Though no bioassays were conducted as part of this experiment, levels of 

ammonia in offshore and interstitial waters were generally below levels that would 

be toxic to aquatic organisms (EPA 1989). Levels of dissolved oxygen in offshore 

waters and in the interstitial waters of the test plots were monitored throughout the 

experiment. Ammonia levels were highest in the lower intertidal areas of the 

treated plots, ranging from 4-10 ppm, while levels at the control plot ranged from 0-

2 ppm. 

Microbial products 

Adding microbes to contaminated areas, also known as "seeding," is conducted to 

enhance biodegradation of an oil-impacted area with selected strains of microbes 

that are known to be capable of degrading hydrocarbons. However, the effectiveness 

of adding microbes to the environment to enhance biodegradation is not well 

supported in the scientific literature (Atlas 1981). In fact, studies indicate that 

addition of microbes to an open environment probably does not increase 

biodegradation because "foreign" strains of bacteria, out-competed by indigenous 

species, disappear quickly from the microbial community (Lee and Levy 1989b). 

No strain of bacteria, whether indigenous or from a product application, is likely to 

degrade oil actively until after the most toxic components of the oil have evaporated 

(Lee and Levy 1987). Therefore, claims of "instant success" from microbial products 

should be regarded with skepticism. The argument is made that indigenous 

organisms will be killed by the oil, so new microbial species need to be added to 

begin the process of biodegradation. In fact, studies have found that most areas of 

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the world contain some microbes that are capable of degrading oil, and that these 

usually grow rapidly when they have acclimated to an oil spill (Lee and Levy 1989a). 

Currently, no genetically engineered microorganisms are being considered for use in 

bioremediation (U.S. Congress 1991). 

To date, few objective scientific studies have been conducted that have tested 

microbial products currently on the market. The most comprehensive was 

conducted by Venosa et al. (1991a, 1991b) of the EPA Office of Research and 

Development in Cincinnati. In brief, the lab study compared the biodegradation of 

weathered Prudhoe Bay crude oil using individual applications of 11 microbial 

products and fertilizer alone at 15 ̊C. Two products showed a statistically significant 

increase in biodegradation over fertilizer. However, these products performed as 

well with sterilized (dead microbes) as with live microbes. Both of the two highest 

performers were then tested in a controlled, replicated field test in Alaska. In the 

field, no significant difference in oil residue weight or total resolvable alkanes could 

be detected among the control plots, the fertilized plots, or the plots treated with 

microbial products. (See also the discussion below on the results from Seal Beach.) 

Most microbial products either contain or recommend use of some type of fertilizer, 

so the concerns about potential toxicity discussed in the section on fertilizer should 

be considered here as well. In addition, concerns have been raised about microbial 

products that contain strains of bacteria that are potential human or animal 

pathogens. Other chemicals that are possibly part of microbial products (such as 

binders or surfactants), could also be toxic to aquatic organisms. Therefore, bioassays 

or other toxicity testing should be conducted as part of monitoring. 

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Microbial applications 

Apex Barges, Texas 

August 1990 

A collision between three Apex barges and the tanker Shnoussa occurred on July 28, 

1990, spilling approximately 700,000 gallons of a partially refined oil into Galveston 

Bay. Shorelines and marshes along the northern shore of the Bay were 

contaminated by the oil approximately one week after the initial spill. The Texas 

Water Commission received approval from the Region 6 RRT to conduct a trial 

application of a microbial bioremediation product (Alpha BioSea) to a contaminated 

marsh (Mearns 1991). RRT approval was given under certain guidelines, including 

that the application be done only in areas where mechanical recovery of oil was not 

feasible, and that a scientifically sound monitoring program be conducted. The 

Texas Water Commission carried out the monitoring program with consultation 

from NOAA and EPA representatives who also acted as on-site observers. 

On August 5 the pre-mixed solution containing the microbial product and a 

nutrient mix was applied to the marsh by a high-pressure hose from a small boat. 

Samples of water and sediment were collected both before treatment and at 

approximately 24, 48, and 96 hours after the treatment. Additional samples were 

collected at 9,10, and 11 days after the intitial application. All samples were sent to 

an EPA laboratory for analysis. 

Effectiveness: No noticeable differences between treated and untreated plots could 

be discerned in samples collected 48 hours after treatment. Results from EPAanalyzed samples are not yet available, but samples analyzed by NOAA using gas 

chromatography/mass spectroscopy showed no apparent changes in the relative 

abundances of specific compounds in the oil before and after treatment. Many 

problems experienced in the monitoring program prevented the collection of useful 

information and made the results of the experiment unclear. These problems 

included poor control over application of the product, disturbance of the test areas by 

livestock and numerous human activities, and a too-short period of sample 

collection after the application (Table 5-4; Mearns 1991). 

These results are not surprising for several reasons. First, since Galveston Bay is 

chronically impacted by oil spills, one could expect that indigenous populations of 

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bacteria would be well adapted for hydrocarbon degradation. Therefore, it is 

questionable whether additional microbes were needed in this environment. 

Second, the short period of the monitoring could probably not have measured any 

acceleration in biodegradation rates if it had in fact occurred, since biodegradation 

usually does not begin until several days or weeks after a spill. Third, there is no 

way to separate any effects due to the microbial product from effects due to the 

fertilizer. Fourth, the feed stock oil was already in a degraded form (Mearns 1991). 

The Alpha BioSea product should have been tested first in the laboratory to 

determine if it could accelerate biodegradation when compared with fertilizer alone. 

Toxicity: Water samples collected after the application were tested and found to be 

acutely toxic to mysids. Additional concerns about potential toxic effects of trace 

metals in the nutrient mix were raised by Mearns (1991). 

Seal Beach, California 

November 1990 

A well blowout offshore of Seal Beach, California occurred on October 31, 1990, 

releasing approximately 400 gallons of crude oil into the atmosphere, resulting in 

the oiling of approximately two to three acres of marsh grasses in the Seal Beach 

National Wildlife Refuge (U.S. Department of the Interior 1990; U.S. EPA 1991b). 

Bioremediation treatment with a microbial product plus fertilizer was undertaken 

one week after the blowout, followed by an application of fertilizer alone two weeks 

later. Treatment consisted of hand spraying of grass blades with a combination of a 

microbial product used in sewage treatment plants (INOC 8162) and a commercial 

fertilizer (Miracle Gro 30-6-6). Samples of unoiled, oiled, and treated, and oiled grass 

were collected and analyzed by the EPA Environmental Research Laboratory in Gulf 

Breeze, Florida (U.S. EPA 1991b). 

Effectiveness: The results of a number of laboratory tests performed on samples 

taken from the marsh showed no differences between oiled and treated grasses and 

oiled grasses with no treatment. Measures of degradation included most probable 

number counts of bacteria and 14C mineralization, a relative measure of 

biodegradation rate. In addition, a laboratory study was performed by EPA to 

compare the ability of the INOC product to degrade Prudhoe Bay crude oil with 

uninoculated (nutrient only) controls. After 7 and 16 days of incubation, little or no 

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difference was found in the amount of four indicator compounds in the flask 

containing the product compared with the control flask. Thus, the microbial 

product was not effective in accelerating biodegradation of oil under controlled 

laboratory conditions (U.S. EPA 1991b). 

Toxicity: The U.S. Fish and Wildlife Service has collected samples of plants and 

invertebrates and intends to analyze these tissues for presence of hydrocarbon 

compounds (Goodbred 1991). These analyses have not yet been performed, and no 

other toxicity testing has been reported to date. 

Open-water bioremediation 

Studies from the early 1970s in laboratory and simulated large tank situations have 

investigated the use of addition of fertilizer on open water oil slicks (Atlas and 

Bartha 1973). However, to date, no studies have evaluated use of bioremediation 

(microbial or fertilizer) in an open ocean situation. From a research viewpoint, it is 

still unknown whether bioremediation would be effective on a recently spilled, 

open-water oil slick. 

Biodegradation in the water is thought to occur at the water surface (Lee and Levy 

1989a). Therefore, any product or nutrient added would need to stay at this interface 

and follow the oil slick as it moves. For bioremediation to be successful on open 

water, the nutrients or products would have to remain with the oil slick for the time 

it takes microbes to become acclimated to the oil and to begin biodegrading. 

As in shoreline applications, the question has been raised, Do bioremediation 

products applied on open water actually act as dispersants or surfactants, 

redistributing oil into the water column? If this is the case, should these products 

then be considered dispersants and not bioremediation agents? (If these products are 

considered dispersants, they are covered by separate regulations.) 

The same concerns for potential toxicity that have been discussed for use of 

fertilizers and microbes on shorelines also apply to open-water applications. The 

dilution factor is likely to be much greater on open water, however, and this is likely 

to lessen the risk from direct toxic effects. As with dispersants, monitoring will 

present very real difficulties, including formidable logistics for applications, 

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measurements or observations, and the difficulty of collecting samples that will 

provide meaningful data. 

Open-water applications 

Mega Borg, Texas 

June 1990 

The Mega Borg spill in 1990 is the only known application of a microbial product to 

an open-water oil slick in the United States. The Mega Borg supertanker was 

transferring its cargo of Angolan crude oil at a location approximately 60 nautical 

miles off the coast from Galveston, Texas, when an explosion caused a fire and 

subsequent release of oil. Oil was released continuously for nine days. The Region 6 

RRT gave approval to the Texas Water Commission to conduct an experimental, 

open-water application of a microbial product to the slick. The microbial product 

was applied from a Coast Guard vessel twice, 6 and 9 days after the initial explosion. 

Sampling was conducted from a Texas A&M University research vessel and 

included samples of surface water and subsurface samples from 1 and 9 m depths. 

Three of these samples were sent to the EPA Gulf Breeze Lab for toxicity testing 

(Parrish and Albrecht 1990; Research Planning 1991). 

Several problems were encountered during the experiment, including interference 

by skimmers working in the same area where the first application was made, and 

logistical problems with the sampling vessel, resulting in no sample collection 

during the first application. A dispersant test was also conducted during this spill 

(Payne et al. 1991), causing further competition for logistics platforms. 

Effectiveness: Results from the percentage of oil found in samples of mousse from 

surface water were inconclusive since no differences could be detected between 

samples collected before and after the bioremediation application. As stated by the 

Texas General Land Office report: "The high variability in these samples... 

demonstrates the difficulty of obtaining comparative and consistently representative 

samples in the open ocean, and the unequal mixing of the oil on the water surface." 

(Texas General Land Office 1990 p.10). 

The Texas General Land Office relied heavily on visual observations made several 

hours after the application to evaluate the experiment (Texas General Land Office 

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1990). Since it is unlikely that microbial activity could have begun this quickly after 

application (see background discussion), it is likely that the observed visual changes 

in the appearance of the slick were caused by physical processes such as dispersion. 

This experiment demonstrates both the difficulties inherent in attempts to conduct 

open-water experiments and the inconclusive results that can be expected from 

open-water bioremediation. 

Toxicity: Results of the EPA Gulf Breeze Lab's acute (96 hour) bioassays performed 

on silversides and mysids showed no acute effects, but the researchers questioned 

whether the samples were actually collected in an area impacted by the oil slick, 

since no trace of oil was found in the samples (Parrish and Albrecht 1990). The 

bioremediation product was not directly tested for toxicity. 

Evaluation of bioremediation technologies 

The EPA Interim Guidelines provide guidance for establishing protocols for the use 

of bioremediation in spill response, and include several sections relating to 

evaluation of bioremediation techniques and products. The Guidelines offer a 

comprehensive discussion of feasibility assessment, screening of bioremediation 

agents, logistics, and monitoring. A useful guide for screening of bioremediation 

proposals or plans are the seven points of concern listed in section 1-2 of the 

guidelines (EPA 1991a.) 

For screening specific bioremediation products, a four-tiered protocol is being 

developed by the National Environmental Technology Applications Corporation 

(NETAC) for standardized testing and evaluation of bioremediation products. 

(These protocols are in appendix B of the Interim Guidelines). The NETAC 

protocols include preliminary screening, laboratory testing (including toxicity 

testing), microcosm testing, and field testing. When in place, bioremediation 

products will be required to pass through these tiers in order to be approved for 

consideration at oil spills. These protocols are still in the development stage and are 

expected to be finalized in approximately one year. 

Since bioremediation is not yet a fully developed, off-the-shelf technology, a 

preliminary evaluation should be undertaken prior to the development of spill 

response plans, such as those suggested in the Interim Guidelines. This evaluation 

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should determine whether certain bioremediation techniques have reached a stage
 

where they are ready to be considered for use in spill response, or for experimental
 

testing, or not at all.
 

Following the NETAC approach using sequential evaluation tiers, a similar process
 

can be applied to the bioremediation techniques discussed in this report, considering
 

them as technologies in various stages of development. These can be looked at
 

through four "evaluation tiers" as follows:
 

1) Is the technique supported in theoretical research?
 

2) Has the technique been tested in the laboratory?
 

3) Has the technique undergone small-scale field testing?
 

4) Has the technique been applied in an open environment on a large
 

scale with monitoring? 

Rationale 

The rationale for these tiers is as follows: a technique should first be shown to be 

effective in the lab, where conditions can be controlled. This should represent an 

ideal case for proving, through scientific methods, that a technique works as 

intended. However, a technique which is proven to be effective in the lab may not 

be equally effective under field conditions, which are much more variable and 

unpredictable. Certainly, if the performance of a product is poor in the lab, then 

more research and refinement of the product needs to be done before it should be 

considered for field application. Only when a technique has been shown to work in 

lab and field tests should it be considered for a larger-scale application. If a technique 

cannot be shown to work in controlled lab and field tests, it is more appropriately 

considered in a research context than in a response context. 

Evaluation tiers 

1) The first tier is the theoretical research and development of the idea and theory 

behind the technology. At the present time, all of the three proposed 

applications for bioremediation at marine oil spills have some basis in research 

theory, though this is more strongly supported for some applications (fertilizer) 

than for others (microbial seeding and open-water bioremediation). 

2) The second tier is testing the technology and proving that it works effectively 

under controlled laboratory conditions. Fertilizer has been repeatedly shown to 

be effective in laboratory flask tests, while only a few microbial products have 

been shown to be effective in lab tests (conducted by laboratories other than those 

of the manufacturing company). Open-water applications have not been 

successfully tested under controlled conditions. 

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3) The third tier is a small-scale field test in an open environment. Both fertilizer 

and microbial bioremediation have undergone field testing, with mixed results. 

Results from two field tests with microbial products did not show increased 

degradation over fertilizer (U.S. EPA 1991b; Venosa et al. 1991b). Field tests using 

fertilizer alone have been shown to increase biodegradation in some plots, but 

not with overall statistical significance (Prince et al. 1990; DuPont 1991; Pritchard 

et al. 1991). Results from the open-water bioremediation application at the Mega 

Borg yielded no conclusive results about effectiveness of open-water applications 

(Texas General Land Office 1990). 

4) The fourth tier is equivalent to a response action, i.e., large-scale field application 

with monitoring. In normal circumstances, a technique would have successfully 

passed through the first three tiers before any considerations were made for large 

scale applications. However, due to the unplanned nature of oil spill response in 

the past, many techniques were tried before previous evaluation tiers had been 

completed. For example, fertilizer was applied on a large scale as part of 

treatment of shorelines in Prince William Sound in conjunction with smallerscale field tests. Neither microbial applications to shorelines nor open-water 

bioremediation have been made in other than in small, experimental 

circumstances. 

In several cases, decision makers and oil spill responders have been asked to 

consider large-scale bioremediation applications in open environments without 

having any information about prior scientific research or laboratory testing of the 

particular technique. Such attempts to rush into use of a potentially untested or 

invalid bioremediation technique are unfortunate in that they usually result in 

confusion about effectiveness, and risk an unsuccessful application of 

bioremediation. Worse, such attempts could divert resources away from other 

potentially more effective cleanup treatments, and could potentially add negative 

impacts to environments already affected by an oil spill. 

Monitoring 

Since all forms of bioremediation are still experimental in open environments, and 

because local environmental conditions will affect how a particular technique 

works, a monitoring program should be set up with any bioremediation application 

to determine whether the technique is working as intended. The monitoring 

process may be more costly than the application itself, and this should be weighed 

with other factors when considering whether to use bioremediation as part of a spill 

response. 

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To be effective, monitoring should be well planned and include carefully selected 

control sites. Replicate sampling of all test and control plots should be included 

when possible. Important factors to consider when setting up a monitoring program 

include the questions to be asked, the endpoints to be measured for answering these 

questions, the type of samples to be collected, where the samples will be collected, 

and the time frame for sampling. (See EPA Interim Guidelines for further 

discussions on monitoring). 

Questions to be addressed by monitoring 

One of the most basic parts of a monitoring program is to define clearly which 

questions or concerns the program is being designed to answer. Nearly always these 

will include, Is this technique effective? Or, Did the technique accelerate the rate of 

biodegradation of oil in the area of concern relative to an untreated control? In this 

case, a measure of the biodegradation rate is necessary, so that the rates in the treated 

area can be compared with rates in a similar, untreated area. Another major 

concern is, Are there detrimental effects from the treatment? Usually the potential 

for toxicity to aquatic organisms will be a concern for resource agencies and, in some 

cases, other potential environmental effects such as eutrophication or physical 

impacts from sampling. Additional questions may be posed, depending on the 

situation. All such questions must be formulated in advance so that the monitoring 

program can be designed to gather the data necessary for addressing the issues of 

concern. After the basic questions are identified, endpoints can be chosen and a 

sampling plan developed. 

Sampling endpoints 

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Endpoints are a specific definition of what is meant by a general term like effective. 

What, exactly, will be used to determine whether a technique is effective? The 

endpoints to be measured should be selected in advance to avoid confusion when 

interpreting monitoring results. In general, it is better to avoid reliance on 

qualitative measures such as "visual differences," which are very difficult to 

interpret, and may vary depending on the observer. 

Some specific endpoints are discussed below for measuring... 

1) biodegradation 

2) toxicity 

3) other environmental effects 

1) Biodegradation 

Measuring biodegradation is not a simple task, and it has become a central part of 

monitoring for effectiveness of bioremediation techniques. Most of the 

measures that have been used in bioremediation experiments involve laboratory 

tests performed on samples collected in the field. These are relative measures, 

but they are the best that are available at the present time. 

a.	 Visual observations: Visual observations can indicate a number of processes, 

such as dispersion, movement of oil from the surface, oil attaching to substrate 

in a product (such as cornstarch, an additive in some microbial products), photooxidation (a physical process), or other weathering processes. There is no way to 

determine what a visual change represents without corroboration from more 

specific measurements. Visual observations are also very difficult to standardize 

between observers. (See discussion of Apex Barges, Mega Borg and Alaska 

incidents). 

b.	 Total petroleum hydrocarbons: A commonly used method for measuring the 

overall reduction of oil at a bioremediation test site is to take sediment samples 

before bioremediation and again some time after application and measure these 

for total petroleum hydrocarbons (TPH). (This is also referred to as oil residue 

weight). 

Consistently, studies measuring TPH have been unable to detect differences 

between sites because of high spatial variability in the distribution of oil in 

sediments (Prince et al. 1990). Therefore, TPH has in most cases, not proved 

useful for determining effectiveness of bioremediation. 

The difference between starting and ending concentrations of TPH measures not 

only loss of hydrocarbons from biodegradation, but also losses from physical 

weathering. Further, TPH does not provide information on the toxicity of the 

remaining components of the oil. Despite these drawbacks, TPH is still proposed 

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as a measure of effectiveness in bioremediation experiments because it provides 

a gross indicator of the amount of remaining oil, and it is less costly than other, 

more detailed chemical analyses such as gas chromatography. 

c.	 Gas chromatography: Many experts in the field recommend the use of gas 

chromatography and mass spectroscopy to characterize the biodegradation 

process, since the use of measures of total residue (such as TPH) are many times 

not adequately informative (Walker et al. 1976; Prince et al. 1990). Gas 

chromatography can trace patterns of specific compounds that are only broken 

down by microbial processes, thus tracking biodegradation separately from 

physical weathering. Examples of indicator compounds that are used in this way 

are hopane compounds and the ratio of C18 to phytane. Gas chromatography 

will also indicate what percentage of the oil is made up of the more toxic 

components. Gas chromatography is, however, more expensive than other, 

more gross chemical measures, and this will limit the number of samples that 

can be analyzed. 

d.	 Microbial counts: Methods such as most probable number counts (MPN) 

estimate the number of microbial cells in a sediment sample. These types of 

counts are accurate only within an order of magnitude, and are not a measure of 

microbial activity, but only of the number of microbial bodies. (Some percentage 

of microbes are usually in a dormant state.) Microbial counts can be used as a 

rough indication of the microbial population in an area, and to determine 

whether the microbial population has grown in response to a bioremediation 

application. 

e.	 Mineralization: A widely used measure of microbial activity is 14C 

mineralization. This is a relative index of bacterial activity with specific 

substrates, not an absolute measure total oil degradation (Lee and Levy 1989a). 

Sediment samples are collected from test plots and brought to the laboratory 

where the biodegradation rates of the microbes in the sample are measured. 

Studies using mineralization include the two Alaska experiments (Prince et al. 

1990; Pritchard et al. 1991) and Seal Beach (U.S. EPA 1991b). In these cases, 

mineralization rates were quite variable between samples and between sites, but 

some trends could be discerned, showing higher rates at some treated sites 

compared with rates at control sites. 

2)	 Toxicity 

Toxicity can be monitored by collecting water samples and analyzing for specific 

compounds or by conducting bioassays. Many bioremediation monitoring 

programs have measured water samples for concentrations of ammonia or other 

chemicals of concern (Alaska studies, Prall's Island). Acute bioassays will give a 

good indication of immediate toxic effects to aquatic organisms. (Acute tests were 

performed in Alaska and at the Apex Barges incident). Chronic bioassays are 

important for assessing long-term, non-lethal effects, and may be indicated in 

long-term treatments or treatments involving repeated applications. 

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3)	 Other environmental effects: 

Other possible environmental effects that may be of concern include 

eutrophication in offshore waters or other detrimental effects on water quality. 

Eutrophication is not likely to be a problem in well-flushed systems, or over a 

short time period in sheltered environments. Studies in Prince William Sound 

and at Prall's Island found no elevated levels of nutrients offshore of treated 

beaches (DuPont 1991; Pritchard et al. 1991). Eutrophication can be monitored by 

measuring levels of nutrients and dissolved oxygen in offshore waters before and 

after treatment applications. 

Sampling design 

An appropriate sampling design helps ensure that the data collected provide 

answers to the initial questions posed in the monitoring plan. Sampling may be 

simple or very complex, but it should correspond to the objectives of the 

monitoring. Sample design includes consideration of control sites, number of 

samples, locations of sample collection, timing of sampling, and sample handling 

and analysis. It is more useful to take a few carefully thought-out samples than to 

take numerous samples without proper planning and follow-through. 

Controls 

Sampling controls are an essential part of any scientific experiment. Since 

bioremediation is an acceleration of biodegradation over the background rate, it is 

necessary to know the background rate for comparison. Without a comparison 

value, there is no way to tell whether bioremediation was successful, or whether it 

was a superfluous exercise. Since the state of the art of bioremediation is still 

evolving, any open-environment application should be considered experimental, 

and should require a control. Data collected without controls will be of limited 

utility for assessing effectiveness. 

In some cases, recognized standards or criteria exist that can be used as comparison 

values for measuring toxicity or other adverse environmental impacts. Values such 

as EPA ambient water quality criteria, or sediment toxicity standards can serve this 

function. 

Usually a control will consist of a sample plot that is as similar to the test plot as 

possible, but far enough away so that it will not be influenced by the treatment. At 

the Prall's Island experiment, the control site was located adjacent to treated sites on 

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both sides, and it is likely that nutrients from the treated sites leached into the 

control site, thereby contaminating it. 

Ideally, the control plot should be treated identically to the treated plot, except for the 

actual treatment. For instance, if the treatment involves sprinkling the area with 

fertilizer mixed with seawater, the control should be sprinkled with seawater 

without fertilizer. A different type of control was exemplified by the use of bags of 

sediment with known quantities of oil planted in test sites at Prall's Island. This was 

a promising idea that attempted to address the problem of high spatial variability of 

oil distribution in sediments. Unfortunately, in this case it did not yield the desired 

result (less variability in the data). But the concept could be experimented with and 

refined further. 

How many samples? The number of samples to be collected depends on the 

question being asked, on the kind of data analysis to be done, and on the resources 

available. A larger number of samples often allows greater power for statistical 

analysis, but will be more costly. One strategy is to collect a large number of samples 

in the field and then to analyze only a subset of the samples collected, depending on 

the initial results. A small number of samples will provide an indication of the 

processes occurring, but may not be representative of the entire study area. 

Where to sample? Where samples should be collected is tied closely to the number 

of samples and to the sample analysis. Often, the sample area is divided into 

sections based on conditions such as oiling (e.g., heavily oiled, lightly oiled, 

unoiled), or substrate type (e.g. cobble, gravel). A representative sample is then 

collected from each section. The Alaska studies in 1989 conducted tests at two sites, 

one heavily oiled and one moderately oiled, then sub-divided one site into plots of 

cobble and gravel substrate (Pritchard et al. 1991). 

When possible, avoid taking samples in areas with outside influences that may 

confound the results, such as areas near outfalls or freshwater streams. Samples 

taken in the middle of the plot will usually be more representative than samples 

taken along the edge. Another method is to lay a grid pattern over a map of the test 

area and choose samples randomly in each designated area. 

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Timing of sample collection: The appropriate time frame for collecting samples will 

depend on the questions being addressed. For example, for monitoring the 

effectiveness of bioremediation on a beach, samples could be collected before 

application, soon after application, and at several subsequent intervals of several 

weeks' duration. In contrast, if monitoring for toxicity, the time scale will likely be 

much shorter, probably immediately after application and at several subsequent 

times hours after application (4 hours, 8 hours, etc.). The Galveston Bay monitoring 

program was an example of a time frame that was probably too short for monitoring 

biodegradation, though it was appropriate for monitoring toxicity. (See Table 5-4 for 

comparison of monitoring time frames). 

Analysis and protocol for handling samples: The laboratory designated to conduct 

the analysis should be consulted prior to sampling to ensure that samples are 

handled appropriately. 

Monitoring recommendations 

There is no single measure that will accurately measure effectiveness or toxicity of a 

bioremediation application. Most of the larger bioremediation monitoring 

programs that have been undertaken have used a combination of the techniques 

discussed, depending on their specific concerns and objectives (DuPont 1991; Prince 

et al. 1990; Pritchard et al. 1991). For example, the Alaska studies measured several 

different parameters for toxicity, water quality and effectiveness (See Table 5-4). As a 

minimum, a monitoring plan at a bioremediation field test or application should 

include at least the following endpoints: 

1) To measure effectiveness, track changes in indicator hydrocarbon 

compounds by gas chromatography/mass spectroscopy (GC/MS). Samples 

should be collected at least at the beginning and end of the sampling 

period at control and treated sites. 

2) Conduct toxicity testing using bioassays to determine acute and/or chronic 

toxicity to aquatic organisms (see NETAC protocols for examples.) 

Bioassays should include sediment bioassays if the bioremediation 

chemicals are likely to lodge in sediments. Testing should include test sites 

and control sites. 

3) Monitor environmental impacts to aquatic habitats through chemical 

analysis of sediments or water for potentially toxic compounds (such as 

heavy metals) that may be part of a bioremediation product. Samples 

5-96
 
should be collected at the beginning and end of the sampling period at 

control and treated sites. 

5-97
 
References 

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Adverse Ecological Impacts. American Petroluem Institute Publication No. 4398. 

Washington, DC. 98 pp. 

Atlas, R. M. 1981. Microbial degradation of petroleum hydrocarbons: an 

environmental perspective. Microbiol. Reviews (45): 180-209. 

Atlas, R. M. 1975. Effects of temperature and crude oil composition on petroleum 

biodegradation. Appl. Microbiol. (30): 396-403. 

Atlas, R.M. and R. Bartha. 1973. Stimulated biodegradation of oil slicks using 

oleophilic fertilizers. Environ. Sci. and Technology (7): 538-541. 

Bobra, M., P. Kawamura, M. Fingas, and D. Velicogna. 1987. Mesoscale application 

and testing of an oil spill demulsifying agent and Elastol. Ottawa, Ontario, Canada: 

Environment Canada. 41 pp. 

Breuel. 1981. Oil Spill Cleanup and Protection Techniques for Shorelines and 

Marshlands. Park Ridge, New Jersey: Noyes Data Corp. 404 pp. 

Cairns, J., Jr. and A.L. Buikema, Jr., (eds.). 1984. Restoration of Habitats Impacted by 

Oil Spills. Butterworth Publishers, Boston, Mass. ???pp. 

Canevari, G.P. 1969. The role of chemical dispersants in oil cleanup: in D.P. Hoult, 

(Ed), Oil on the Sea. New York: Plenum Press. pp. 29-51. 

CONCAWE. 1987. A Field Guide To Coastal Oil Spill Control And Clean-up 

Techniques. The Hague, The Netherlands. 112 pp. 

Cormack, D., W.J. Lynch, and B.D. Dowsett. 1986/87. Evaluation of dipsersant 

effectiveness. Oil and Chem. Poll. (3): 87-103. 

DeFlaun, M. R. and L. M. Mayer. 1983. Relationships between bacteria and grain 

surfaces in intertidal sediments. Limnol. Oceanogr. (28):873-881. 

Delaune, R.D., G.A. Hambrick III, and W.H. Patrick, Jr. 1980. Degradation of 

hydrocarbons in oxidized and reduced sediments. Marine Poll. Bull. (11): 103-106. 

DuPont Environmental Remediation Services. 1991. Final Report Prall's Island 

Bioremediation Project. Florham Park, New Jersey: Exxon Research and 

Engineering. 

ERCE and PENTEC. 1991. Evaluation of the condition of intertidal and shallow 

subtidal biota in Prince William Sound following the Exxon Valdez oil spill and 

5-98
 
subsequent shoreline treatment. Seattle: Hazardous Materials Response and 

Assessment Division, National Oceanic and Atmospheric Administration. Two 

Volumes. 

Exxon Corporation. 1989a. Material Safety Data Sheet, Inipol EAP 22. Houston: 

Exxon Company, U.S.A. July 28, 1989. 

Exxon Corporation. 1989b. Material Safety Data Sheet, Corexit 9527. Houston: Exxon 

Chemical Company. October 25, 1989. 

Fingas, M., I. Bier, M. Bobra, and S. Callaghan. 1991b. Studies on the physical and 

chemical behavior of oil and dispersant mixtures. Proceedings of the 1991 Oil Spill 

Conference, March 4-7, 1991, San Diego, California, pp. 419-426. 

Fingas, M.F., R. Stoodley, N. Stone, R. Hollins, and I. Bier. 1991a. Testing the 

effectiveness of spill-treating agents: laboratory test development and initial results. 

Proceedings of the 1991 Oil Spill Conference, March 4-7, 1991, San Diego, California, 

pp. 411-414. 

Fiocco, R.J. and seven others. 1991. Development of Corexit 9580–A chemical beach 

cleaner. Proceedings of the 1991 Oil Spill Conference, March 4-7, 1991, San Diego, 

California, pp. 395-400. 

Fusey, P. and J. Oudot. 1984. Relative influence of physical removal and 

biodegradation in the depuration of petroleum-contaminated seashore sediments. 

Marine Pollution Bulletin (15): 136-141. 

Geraci, J.R. and D.J. St. Aubin. 1982. Study of the effects of oil on cetaceans. Report 

BLM/YL/SR-82/01. Washington, D.C.: Bureau of Land Management, U.S. 

Department of the Interior. 274pp. 

Goodbred, S., Environmental Contaminants Specialist, U.S. Fish and Wildlife 

Service, Laguna Niguel, California, personal communication, July 31, 1991. 

Hayes, M.O., E.R. Gundlach, and C.D. Getter. 1980. Sensitivity ranking of energy port 

shorelines. Proceedings of the Specialty Conference on Ports ‘80, May 19-20, 1980, 

Norfolk, Virginia, pp. 697-708. 

Hayes, M.O., J. Michel, and B. Fichaut. 1991. Oiled gravel beaches: A special problem. 

Proceedings of the Specialty Conference on Oil Spills, Management and Legislative 

Implications, published by American Society of Civil Engineers. pp.444-457. 

Interagency Shoreline Cleanup Committee. 1989. Field Shoreline Treatment 

Manual. Valdez, Alaska: Prepared by National Oceanic and Atmospheric Admin., 

Alaska Department of Environmental Conservation, Alaska Department of Fish 

5-99
 
and Game, U.S. Fish and Wildlife Service, U.S. Environmental Protection Agency, 

and Exxon. 

Kellogg, S.T. 1991. Review of 1990 Bioremediation Monitoring Program Final 

Report. Memo to State of Alaska Department of Environmental Conservation, 

February 11, 1991. Moscow, Idaho: University of Idaho. 23 pp. 

Keyser, G.E. 1991. Bioremediation in Prince William Sound. DRAFT. Valdez, 

Alaska: Regional Citizens' Advisory Council. May 14, 1991. 

Lee, K. and E.M. Levy. 1991. Bioremediation: waxy crude oils stranded on lowenergy shorelines. Proceedings of the 1991 Oil Spill Conference, March 4-7, 1991, San 

Diego, California, pp. 541-547. 

Lee, K. and E. M. Levy. 1989a. Biodegradation of petroleum in the marine 

environment and its enhancement. In: Aquatic Toxicology and Water Quality 

Management, J. O. Nrigau and J. S. S. Lakshminarayana (eds.). New York: John 

Wiley & Sons. pp. 218-243 

Lee, K. and E. M. Levy. 1989b. Enhancement of the natural biodegradation of 

condensate and crude oil on beaches of Atlantic Canada. Proceedings of the 1989 Oil 

Spill Conference, February 13-16, 1989, San Antonio, Texas, pp. 479-486. 

Lee, K. and E.M. Levy. 1987. Enhanced biodegradation of a light crude oil in sandy 

beaches. Proceedings of the 1987 Oil Spill Conference, April 6-9 1987, Baltimore, 

Maryland, pp. 411-416. 

Mackay, D. and P.G. Wells. 1983. Effectiveness, behavior, and toxicity of dispersants. 

Proceedings of the 1983 Oil Spill Conference, February 28-March 3, 1983, San 

Antonio, Texas, pp. 65-71. 

McAuliffe, C.D., B.L. Steelman, W.R. Leek, D.E. Fitxgeral, J.P. Ray, and C.D. Barker. 

1981. The 1979 Southern California dispersant treated research spills, Proceedings of 

the 1981 Oil Spill Conference, March 2-5, 1981, Atlanta, Georgia, pp. 269-282. 

Mearns, A. 1991. Observations of an oil spill bioremediation activity in Galveston 

Bay, Texas. NOAA Technical Memorandum NOS OMA 57. Seattle: Hazardous 

Materials Response Branch, National Oceanic and Atmospheric Administration. 

38 pp. 

Meyers & Associates, and RPI, Inc. 1989. Oil Spill Response Guide. Park Ridge, New 

Jersey: Noyes Data Corp. 314 pp. 

National Research Council. 1989. Using Oil Spill Dispersants on the Sea. 

Washington, D.C.: National Academy Press. 335 pp. 

5-100 
NOAA MESA Puget Sound Project. 1978. Microbial degradation of petroleum 

hydrocarbons. EPA- 600/7-78-148. Seattle: U.S. Environmental Protection Agency. 

NOAA MESA Puget Sound Project. 1980. Petroleum biodegradation potential of 

northern Puget Sound and Strait of Juan de Fuca environments. EPA-600/7-80-133. 

Seattle: U.S. Environmental Protection Agency. 

National Research Council. 1989. Using Oil Spill Dispersants on the Sea. 

Washington, D.C.: National Academy Press. 335 pp. 

Owens, E.H. and A.R. Teal. 1990. Shoreline cleanup following the Exxon Valdex oil 

spill–field data collection within the SCAT program: Proceedings of the 13th Arctic 

and Marine Oil Spill Program Technical Seminar, June 6-8, 1990, Edmonton, 

Canada, pp. 411-421. 

Parrish, R. and B. Albrecht. 1990. Acute toxicity of three Gulf of Mexico water 

samples to mysids (Mysidopsis bahia) and silversides (Menidia beryllina). Gulf 

Breeze, Florida: U.S. EPA Environmental Research Laboratory, 5 pp. 

Payne, J.R., and nine others. 1991a. Dispersant trials using the Pac Baroness, a spill 

for opportunity, Proceedings of the 1991 Oil Spill Conference, March 4-7, 1991, San 

Diego, California, pp. 427-433. 

Payne, J.R., and seven others. 1991b. Mega Borg oil spill dispersant efficiency testing. 

Seattle: Hazardous Materials Response Branch, National Oceanic and Atmospheric 

Administration. 39 pp. plus appendices. 

Prince, R.C., J.R. Clark, and J.E. Lindstrom. 1990. Bioremediation monitoring 

program. Anchorage: Exxon, EPA, Alaska Department of Environmental 

Conservation. 85 pp. plus appendices. 

Pritchard, P. H. and C. F. Costa. 1991. EPA's Alaska oil spill bioremediation project. 

Environ. Sci. Technol. (25): 372-379. 

Pritchard, P. H., R. Araujo, J.R. Clark, L.D. Claxton, R. B. Coffin, C.F. Costa, J.A. 

Glaser, J. R. Haines, D.T. Heggem, F.V. Kermer, S.C. McCutcheon, J.E. Rogers, A.D. 

Venosa. 1991. Interim report, oil spill bioremediation project, summer 1989. Gulf 

Breeze, Florida: U.S. EPA, Office of Research and Development. 264 pp. plus 

appendices. 

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Glaser, J. R. Haines, D.T. Heggem, F.V. Kermer, S.C. McCutcheon, J.E. Rogers, A.D. 

Venosa. 1990. Interim report, oil spill bioremediation project, summer 1989. Gulf 

Breeze, Florida: U.S. EPA, Office of Research and Development. 224 pp. 

5-101 
Research Planning, Inc. 1991. The Mega Borg oil spill, summary of spill response 

activities. Rockville, Maryland: NOAA Damage Assessment and Restoration 

Center. Draft. 55 pp. 

Sanders, N. and Gray E. 1989. Alaska oil spill bioremediation project workshop 

summary, November 7-9 1989. Washington, D.C.: EPA Office of Research and 

Development. 8 pp. 

Sanders, N. and E. Gray. Alaska Oil Spill Bioremediation Project Workshop 

Summary. Rockville, Maryland: Technical Resources, Inc. 8 pp. 

Smith, J.E. 1968. Torrey Canyon Pollution and Marine Life. New York: Columbia 

University Press. 

Tetra Tech. 1982. Ecological Impacts of Oil Spill Cleanup: Review and 

Recommendations. Draft report submitted to American Petroleum Institute, Wash., 

D.C. 

Texas General Land Office. 1990. Mega Borg oil spill off the Texas coast, an open 

water bioremediation test. Austin, Texas. 30 pp. 

Tjeerdema, R.S., M.M. Singer, G.M. Scelfo, D.L. Smalheer, L.M. Swall, G.E. Croston, 

D.M. Fry, and M. Martin. 1990. The toxicology of oil spill cleanup agents. Report 

UCSC/IMS-90/1. Sacramento: California Department of Fish and Game. 175pp. 

U. S. Congress, Office of Technology Assessment. 1991. Bioremediation for marine 

oil spills - background paper. OTA-BP-0-70. Washington, D.C: U. S. Government 

Printing Office. 31 pp. 

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Niguel, California: U.S. Fish and Wildlife Service, November 15, 1990. 3 pp. 

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Division. 

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plans. Washington, D. C: Subcommittee on National Bioremediation Spill 

Response, Bioremediation Action Committee. April 6, 1991. 27 pp. 

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U.S. EPA Environmental Research Laboratory, Draft, March, 1991. 22 pp. 

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Siddique. 1991a. Protocol for testing bioremediation products against weathered 

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Diego, California, pp. 563-570. 

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microbial products in enhancing oil degradation in Prince William Sound field 

plots. Proceedings of the 17th Annual Hazardous Waste Conference, April 9-11, 

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environments. Applied and Environmental Microbiology (35): 353-359. 

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the Ontario Great Lakes. Burlington, Ontario: Environmental Emergency Division 

of Environment Canada. 111 pp. plus 9 appendices. 

5-103
 
6 Field Methods for Oil-Spill Response 

Miles O. Hayes and Jacqueline Michel1 

Page 

Introduction.....................................................................................................6-1
 

Reconnaissance Studies of Large Areas.......................................6-1
 

Photography..............................................................................................6-5
 

Guidelines for Detailed Shoreline Contamination Surveys 6-7
 

References.........................................................................................................6-10
 

1Research Planning, Inc., P.O. Box 328, Columbia, South Carolina 29202 
Chapter 6.
 

Field Methods for Oil-Spill Response
 

Introduction 

Oil spills, by their very nature, create a sense of urgency and chaos with respect to 

the collection of meaningful field data. To do so requires discipline and a systematic 

approach. In this chapter, we present a number of methods that have proved useful 

to us in gathering data at dozens of oil spills. It is important that the methods used 

are relatively simple and that the same methodology is followed throughout the 

spill response. In this discussion, emphasis is placed on gathering data relevant to 

making clean-up decisions and recommendations for protection of resources at risk. 

Reconnaissance Studies of Large Areas 

Hayes et al. (1973) developed a systematic sampling program for rapidly classifying 

large sections of coastline in Alaska. This method, called the Zonal Method, has 

been modified somewhat for application in the assessment of the initial extent and 

persistence of oiling at major oil spills. 

This modified zonal method is described in detail below: 

1)	 Collection and study of available literature, aerial photographs, maps, and 

charts occurs as soon as possible. Maps on the scale of 1:24,000 are available 

from the U.S. Geological Survey (USGS) for most sections of the United 

States. These are most useful for delineating oil distribution, as well as for 

determining coastal geomorphology. Charts of all U.S. coastal areas may be 

obtained from NOAA and are usually readily accessible from marinas in the 

impacted area. Aerial photographs are more difficult to obtain rapidly and 

have to be ordered through either the federal or state government. 

2)	 An aerial overflight of the entire area is conducted during low tide to observe 

maximum exposure of the intertidal area. An aerial survey allows an 

extremely rapid assessment of the entire spill site and is especially useful in 

determining the relationship between regional geomorphology and oil 

distribution. Inflight observations are recorded both verbally on tape and 

photographically with a hand-held 35-mm camera (for details, see discussion 

on photography which follows), or a videocamera (preferably both). The 

flight is conducted at 500-1,500 ft. altitudes, although higher or lower altitudes 

6-1
 
can be taken if desired and local flight regulations permit it. Either a 

helicopter or fixed-wing (high-wing) aircraft may be used. 

3)	 Specific areas are selected for detailed study, based on the aerial survey, local 

maps, and oil distribution. The sampling interval depends on the variety of 

coastal types, as well as logistical and financial considerations. Areas selected 

are representative of the local geomorphology, habitat type, and oil 

distribution. 

4)	 Two types of stations are set up: (a) visual inspections stations and (b) zonal 

stations. 

Visual inspection stations. - These sites are surveyed rapidly to determine 

coastal type, aerial extent of oil coverage, and the thickness and depth of 

buried oil layers as observed in small trenches dug across the beachface. The 

value of these studies, usually initiated to establish habitat protection and 

clean-up priorities, is greatly enhanced if the field team includes an 

experienced field ecologist. Ideally, the team should include: (a) a coastal 

geomorphologist; (b) a coastal ecologist; and (c) a field technician well-versed 

in chemical sampling techniques. Photographs are taken to document oil 

distribution, biological impact, and coastal morphology. Notes taken are 

recorded in a field notebook and verbally on tape. 

Zonal stations. - The oil distribution, sediment type, biota, and 

geomorphology at these stations are studied in much greater detail than at the 

visual inspection stations. The following tasks are performed at each station: 

a) A topographic profile is run from the back beach to seaward of the low 

water line, using a horizon-leveling technique which will be 

demonstrated in the field. Two permanent stakes are established, a back 

stake (BS) located well back of the normal storm wave erosion zone, and a 

front stake (FS) just behind the spring high-tide swash line. The profile is 

run within two hours of low tide in microtidal (TR = 0-2 m) or mesotidal 

(TR = 2-4 m) areas. In macrotidal areas (TR = >4 m), the upper intertidal 

zone is exposed for a greater amount of time, and profiles can be run 

within three hours of low tide. Examples of both blank and completed 

profile data sheets used for these surveys are given at the end of this 

chapter. At each horizontal-distance reading on oiled beaches (usually a 

maximum of 3 m), it is necessary to record the change in elevation, the 

6-2
 
percent oil coverage (estimated along that section of beach) and the oil 

thickness (as read off the profile rod). Comments noted on the profile 

sheet should include sediment type, geomorphic variations (berm crest, 

cusp horn, etc.), oil appearance, and biological information (species and 

abundance). The high-tide swash line and water level should be indicated. 

Stake heights are recorded in case erosion or deposition occurs that far up 

the beach between repetitive profiles. 

b) Sediment samples are taken at three equidistant sites along the profile. 

Sampling sites are usually marked before running the profile, so they can 

be appropriately located on the profile sheet. If possible, an unoiled 

sample is taken for textural analysis; otherwise, the oil will have to be 

removed by a tedious chemical process. In some cases, surface oil should 

be scraped away. The sediment sample should consist of 100-200 g of 

sediment taken to a depth of 10-15 cm. If the sediment is coarse gravel, a 

photograph (with scale) is taken of the site and the grain size is estimated 

using the comparator chart given in Figure 3-14. Sediment size may also 

be measured from the projected image after the photograph is developed. 

If time and costs demand, one sediment sample taken at the mid beachface 

will suffice. The remaining sampling sites should be described in detail as 

to sediment size and sorting. 

Oiled sediment samples of both surface and subsurface oil contamination 

are usually collected. In gravel areas, surface samples may be individual 

clasts placed into the sample jars for analysis, usually for detailed 

characterization and analysis of weathering trends. In non-gravel areas, 

the surface samples come from the top 2 cm of sediment. Subsurface 

samples are collected from discreet intervals, frequently from the bottom 

of the oiled sediments in trenches dug in the beach. Other intervals are 

collected as appropriate. No samples are composited; the samples are 

usually “grab” samples. All samples are numbered sequentially, with 

surface samples denoted ‘A’; subsurface samples denoted ‘B’; and so on. 

Samples are collected with clean scoops and placed in pre-cleaned glass jars 

with teflon-lined caps. 

c) Visible effects of the oil on biological communities are observed and 

recorded. The location and distribution of oiled (and clean) sessile 

organisms are photographed and described in order to determine temporal 

6-3
 
changes in the population. In each case, a 15-cm or 30-cm scale is placed in 

the picture in order to determine the area of the surface photographed 

(e.g., 0.8 m2) for mortality counts. In most cases, more detailed biological 

surveys augment and expand upon the findings of the reconnaissance 

surveys. 

d) Trenches are dug along the profile line to discern the distribution of 

buried oil. The thickness, depth of burial, and general consistency of the 

oil are described. Photographs are taken of all the trenches. On some sand 

beaches, it is useful to dig a trench across the entire beachface. Data 

concerning the extent of buried oil are necessary to accurately determine 

the quantity of oil incorporated within the intertidal zone. Samples are 

usually taken of the oiled layers within the trench to determine quantity 

and composition of the oil. 

e) A hand-drawn sketch is made of the zone surrounding the profile line to 

force the geomorphologist to carefully observe all aspects of the site. Both 

a blank and filled-in examples of field sketch forms are given in the 

materials at the end of this chapter. On the sketch, the following should 

be noted: 

1) Beach morphology 7) Critical epifauna and flora 

2) Profile line 8) Cleanup operations if in progress 

3) Sample locations (or effects if completed) 

4) Oil distribution 9) All samples taken 

5) Trench locations 10) All photographs taken 

6) Depth of buried oil 

5)	 Sand samples are analyzed for size characteristics by standard sieving 

techniques (Folk, 1968) or by a rapid sediment analyzer. If these instruments 

are not readily available or time is critical, grain size can be estimated using a 

grain-size comparator which illustrates premeasured size classes for direct 

comparison to the sample (using a hand lens). 

6)	 The coast is categorized into its geomorphological components and oil 

distribution is superimposed onto base maps. Oil distribution may be 

categorized as follows*: 

6-4
 
 

Very light - <5 percent coverage (of the intertidal zone) 

Light coverage - 25 percent coverage 

Moderate coverage - 25-65 percent coverage 

Heavy coverage - >65 percent coverage 

*	 These boundaries and terms (i.e., very light, light, moderate, heavy) are 

frequently in dispute at a spill. The measures need to be standardized. 

7)	 Follow-up surveys and overflights are necessary to determine longer-term oil 

retention, cleanup effectiveness, and geomorphic changes. 

The following equipment is required to carry out this type of reconnaissance survey: 

Cameras (including video cameras) 

Two profile rods (1.5 m long marked at 2 cm intervals) 

Day pack, which contains: a) plastic sediment sample bags, b) photo scales, c) 

hand level, d) compass, e) sand grain-size comparator, f) hand lens, g) 

measuring tape (30 m, marked in cm), h) film, i) Write-in-the-Rain field 

notebook, j) orange surveyor’s marking tape and orange spray paint, and 

(k) a tool for scraping sides of trenches (e.g., plasterer’s trowel). 

Plastic, box-type clip board, which contains: a) profile sheets, b) sketch sheets, 

c) gravel grain-size comparator, d) percentage estimate chart, e) roundness 

chart, f) plastic one-foot rule (marked in cm), g) extra lead pencils (plus 

erasers), h) magic markers, and i) sample-labeling tape. 

Four-foot stakes to mark survey sites, two per site—2 x 2 wood stake for front 

stake and metal fence post for back stake. 

Shovels and sledge hammers. 

Photography 

Professional quality photographs are absolutely essential during spill response. 

Photographs convey ideas and information much more effectively than written 

words alone. In transmitting data, a photograph should assist—not confuse and 

irritate—the audience. Video-taping equipment is a necessity for documenting spill 

occurrence and distribution. Following are some helpful hints to avoid some of the 

common pitfalls made by scientists photographing an oil spill site. 

6-5
 
1) Film is cheap!! Don’t be afraid to take pictures. The expenses associated with 

a scientific oil spill response often run into hundreds of thousands of dollars. 

2) Cameras. The field camera must be durable, preferably lightweight, and have 

a through-the-lens light meter. Many of the new 35-mm, single-lens, reflex 

compact cameras by Nikon, Minolta, Olympus (etc.) fulfill these 

requirements. 

3) Lens. A 50-mm or 55-mm lens gives the viewer the most realistic picture of 

the object. A low F-stop (1.4-1.8) is necessary to be able to take pictures under 

varying light conditions. A UV filter should be used to protect the lens. The 

use of a polarizing filter during good light conditions eliminates much of the 

glare coming off the water (used primarily during overflights, unless the sun 

is extremely bright). 

4) Beach Shots. At least three photographs should be taken of the beach: (1) up 

and (2) down the coast and (3) directly perpendicular to the beach. At zonal 

stations, additional photographs should include those of the profile line, 

trenches, and all aspects of oil distribution and biological effects. A person in 

the photograph is useful for discerning scale and depth of field. 

5) A Straight Horizon. One of the most common problems for the beginner 

coastal photographer in taking pictures is a crooked horizon—make sure it is 

straight! In order to present a balanced photograph, it should be composed of 

approximately one-third sky (sometimes less) and two-thirds land. 

6) Shutter Speed. The slower the shutter speed, the greater the depth of field. 

We most often use 1/125 of a second or 1/60 of a second during darker 

conditions. 

7) Film Type. We have found that Kodachrome-64 gives us good pictures both 

on the beach and during overflights. It is a wide-latitude film capable of 

absorbing exposure errors, gives natural colors, and does not appear grainy. 

Good quality black-and-white prints can also be made. In addition to K-64, we 

also take some high-speed Ektachrome (ASA 400) in the field in case of poor 

light conditions. Film is constantly being upgraded. We recommend that 

you experiment with other types of film. But, don’t use it at a critical spill 

until you have tried it on a beach somewhere. 

6-6
 
8) Bracketing. Take the shots you feel are most important as your light meter 

reads, and then two others at ±1/2 F-stop. This will be a better guarantee of 

getting the correct exposure. Always check your light meter against other 

cameras. Change the battery regularly. 

9) Shooting into the Sun. On a bright day (looking toward the sun), your 

camera will read at a closed aperture. This will result in an underexposure or 

a dark photograph of the beach. In order to get the correct exposure, take the 

light reading out of the sun’s glare or open up the aperture 1/2 to 1 F-stop. 

10) Close-Up Photographs. For determining the biological and geological impact 

of an oil spill, the close-up photograph is most useful. In all cases, an object of 

well-known size must be placed in the photograph for scale. Preferably, the 

scale should be marked in centimeters and placed in the lower right-hand 

corner of the photograph. The 15-cm scale that you will receive at the course 

works very well. NEVER place the scale in the center of the photograph. The 

camera should be held parallel to the surface to be photographed to prevent 

out-of-focus edges. 

11) Aerial Photographs. Aerial photographs are usually down-stopped 1/2-1 Fstop. The exact setting varies greatly from camera to camera and should be 

tested beforehand. If you are not sure about your camera, shoot straight on. 

Shutter speed should be set at 1/250 or faster, if possible. Don’t steady the 

camera by leaning against the plane (vibrations!). Photographs should be 

taken through an open window or door, if possible; if not, at least make sure 

the window is clean. Again, be careful to avoid crooked horizons. Also, 

beware of reflections—wear dark shirts to minimize reflection. 

Guidelines for Detailed Shoreline Contamination Surveys 

At any spill of a significant size, a repetitive, detailed systematic survey of the extent 

and degree of shoreline contamination is needed for: 

1) Assessment of the need for shoreline cleanup. 

2) Documentation of spatial oil distribution over time. 

3) Internally consistent historical record of stranded oil patterns for use by 

other scientific surveys on intertidal and nearshore subtidal impacts. 

6-7 
Survey teams must use uniform terminology for describing shoreline oil. If all 

survey teams are using the same terms and definitions, then there is a greater 

likelihood of consistency in oil reports. Therefore, the attached shoreline survey 

forms were developed for recording field observations on the extent and degree of 

shoreline contamination. These forms are similar to those used at the Exxon 

Valdez spill, the development of which was spearheaded by Ed Owens and other 

Woodward Clyde, Inc. scientists under contract with Exxon. The forms given in this 

manual were customized by J. Michel of RPI to the spill conditions and coastal 

geomorphology of the Arabian Gulf. Each geographic area impacted by a spill will 

require that minor modifications be made to these forms in order for them to 

conform to the local geomorphological, ecological, and oiling conditions. 

During a shoreline survey, the entire shoreline should be systematically 

inventoried. If this is not possible, then selected sites representative of a larger area 

should be surveyed in more detail. Individual sites should be on the order of 

several hundred meters long. These representative sites can be monitored over 

time for tracking the changes in oil distribution. The temporal changes in the 

stranded oil will provide important information on the need and priorities for 

shoreline cleanup. 

There are four different pages to the survey forms. The Shoreline Oil 

Terminology/Codes sheet lists all the terms to be used to describe the oil, sediments, 

and other features, on the forms and sketches. Training of the survey teams should 

include review of photographs and videos of each type of oil and extensive 

discussion of the range of types likely to be encountered in the field. The sheet 

should be taped to a clipboard for ready referral in the field. 

The Shoreline Survey Form is used to record the observations at each site in a 

systematic manner. For each type of oil on the shoreline, the team would enter in 

check marks for the distribution and location by tidal zone. For example, the 

dimensions of individual asphalt pavements and tar mats would be recorded; each 

tar mat or pavement would be numbered and shown on the attached site sketch. 

Any trenches dug to observe subsurface oil would also be numbered and located on 

the attached sketch. For each trench, the form allows ready recording of the depth of 

the trench, its location in the intertidal zone, a description of the subsurface oil, the 

depth interval of the subsurface oil, the depth of the water table, and the nature of 

6-8
 
the subsurface sediments. With this type of information, repeat surveys can be 

made to measure the change in both surface and subsurface oil over time. 

Two types of sketches are recommended. The site sketch should cover the entire 

shoreline section being surveyed, in plan view. The coastal geomorphology and oil 

distribution should be shown. The location and number of tar mats, asphalt 

pavements, trenches, etc. are delineated. The sketch is very important; it allows 

others to get a sense of the site and interpret the other data on the forms. Because of 

the scale of most sites, no photograph can capture the site, except for low-altitude 

aerial photography. The sketch also forces the team to make systematic and more 

complete observations. Attached is an example site sketch. Any symbology used on 

the sketch should be added to the legend. For example, different patterns can be 

used to show substrate types. The codes should be used as abbreviations on the 

sketch. 

A second type of sketch form is for recording trench descriptions. These descriptions 

are very important in recording the nature of buried oil, which may pose longerterm problems with oil persistence and beach erosion. The Trench Description 

Form allows for quick recording of the sediments and oiling with depth. This 

information will be critical in assessment of the potential volumes of sediment 

removal, if needed. Trench descriptions from the 1991 Exxon Valdez surveys are 

included as examples. The presence and extent of buried oil has both operational 

and scientific applications. 

6-9
 
References 

Folk, R.L. 1968. Petrology of sedimentary rocks. Austin: Hemphill’s Publ. 186 pp. 

Hayes, M.O., E.H. Owens, D.K. Hubbard, and R.W. Abele. 1973. Investigation of form 

and processes in the coastal zone: in D.R. Coates (Ed.), Proc. 3rd Annual 

Geomorphology Symp. Series, Binghamton, N.Y., pp. 11-41. 

6-10
 











7 Monitoring/Sampling 

Rebecca Hoff1 

Page 

Collecting and analyzing data...............................................................7-1
 

Introduction...............................................................................................7-1
 

Establishing objectives and endpoints.....................................7-2
 

Sampling design.............................................................................................7-5
 

Controls..........................................................................................................7-6
 

Locations of samples..............................................................................7-7
 

Timing of sample collection...............................................................7-8
 

Qualitative and quantitative data.....................................................7-8
 

Some considerations for analyzing data................................7-11
 

Some simple ways to gather data...............................................7-11
 

Summary...........................................................................................................7-12
 

References.........................................................................................................7-12
 

1National Oceanic and Atmospheric Administration, 7600 Sand Point Way N.E., Seattle, Washington 

98115 
Chapter 7. 

Monitoring/Sampling 

Collecting and analyzing data 

Introduction 

There are numerous ways that sampling and monitoring enter into oil spill 

response activities. Frequently, some sampling will be done immediately 

after the spill to help determine the immediate response. Taking samples of 

the oil to determine a "fingerprint" (identify the source of the oil) is one 

example. Some response activities will be approved contingent on a 

monitoring program being conducted, such as using dispersants, or 

bioremediation. In these cases, oil spill response personnel will find 

themselves involved in decisions regarding monitoring programs that are 

conducted in conjunction with these response techniques. 

Response personnel may also, on occasion, wish to initiate monitoring 

projects themselves. These could be simple projects designed to answer 

questions about the effectiveness of a particular response, or to provide follow 

up monitoring after a spill. Knowing what environmental impacts were 

associated with the spill as well as the response activities can be very useful 

information that may be applicable when responding to future spill events. 

Though not all spill response personnel will be directly involved in the 

collection of samples and the design of experiments, they will be in positions 

where they need to interpret data and make decisions based on these 

interpretations. Some possible examples include determining the validity of 

studies of new response techniques, evaluating bioassays to determine if 

adverse environmental effects can be expected, or evaluating studies on the 

effectiveness of particular treatments. 

Even a basic knowledge of statistics and a minimum comfort level with 

analyzing data will help to defuse the "mystique" often inspired by the use of 

data and numbers. Being able to form one's own opinions about studies and 

7-1
 
results will provide a real advantage over having to rely on someone else's 

interpretations, especially in a field that is as politically charged as oil spill 

response. 

Establishing objectives and endpoints 

Objectives 

Stating a clear objective often seems so obvious that it is not explicitly 

mentioned by people considering sampling projects. However, it is 

frequently the case that objectives are not well thought out, and consequently, 

data is collected that does not answer the question originally intended. When 

objectives are clearly defined and explicitly stated, then hypotheses and 

sample designs follow easily from them. Figures 7-1 and 7-2 present several 

examples of objectives that might be used in studies associated with oil spill 

response. 

Hypotheses 

Though not all sampling plans and experiments will involve the use of 

formal hypotheses, many questions lend themselves to a simple hypothesis 

test, which can then be subjected to a statistical test. An hypothesis is merely a 

restatement of the objective in statistical language that can later be subjected 

to a statistical test, where the hypothesis will be accepted or rejected, 

depending on the data results. Experiments that have several components 

may have several different hypotheses. Formulating an explicit hypothesis 

will also necessitate selecting the endpoint to be used for determining 

whether the hypothesis is accepted or rejected. 

Endpoints 

Endpoints are specific measures of the objectives of the experiment, and 

determine how parameters such as “effectiveness” or “toxicity” or 

“similarity” will be measured. Endpoints should ideally be a measurable 

quantity, such as “the concentration of PAH in tissue, measured as dry 

weight,” or “the relative abundance of selected species counted in intertidal 

quadrats.” Endpoints may include qualitative data, as in the fingerprinting 

example in Figures 7-1 and 7-2, but the type of data and the way it will be used 

should be specified as closely as possible. To establish endpoints, any 

7-2
 
Bioremediaton 

Effectiveness: Will proposed bioremediation with 'BIO-Wonder' work here? 

Objective: 

Will the bioremediation treatment degrade oil faster or in greater
 

quantities than background rates?
 

Hypothesis:
 

The mean TPH from plot A (oiled, treated) will be the same as the
 

mean from plot B (oiled, untreated)
 

Null hypothesis:
 

Ho: Xa (treated) = Xb (untreated)
 

Endpoint: 

Chemical measurement of total petroleum hydrocarbon (TPH) in 

sediment samples collected from each plot. 

Toxicity: Will 'Bio-Wonder' harm the environment? 

Objective: 

Will 'Bio-Wonder' cause toxic effects to marine organisms?
 

Hypothesis: 

Bioassays using oyster larvae will show the same acute mortality rates
 

with 'Bio-Wonder' as with plain seawater
 

Null hypothesis
 

Ho: Mp (product) = Ms (seawater)
 

Endpoint:
 

Mortality of bivalve larvae after 48 hours
 

Figure 7-1. Examples of objectives, hypotheses and endpoints for a 

bioremediation example 

7-3
 
 

Oil Fingerprinting 

Is all the oil found on the beach from the spill? 

Objective 

Is the oil sampled from the beach the same as that carried by the 

stricken tanker? 

Hypothesis 

Oil collected from site A (on beach) is the same as oil collected from the 

slick emanating from the tanker 

Null hypothesis
 

(Not applicable)
 

Endpoint 

Gas chromatographs, will be compared between the two samples with a 

focus on specific tracer compounds. 

Figure 7-2. Examples of objectives, hypotheses and endpoints for an oil 

fingerprinting example. 

7-4
 
laboratories that will be used for analysis should be consulted prior to 

sampling to ensure that samples are handled appropriately. Though most 

people understand the need for objectives and even hypotheses, in many 

cases, even elaborate and costly experiments do not select in advance the 

endpoint that will be used to answer to the original question. This is 

especially pertinent for environmental parameters that may be difficult to 

define, as well as measure (for example, “biodegradation” or “environmental 

recovery”). 

Two major problems can result from the failure to select an endpoint for an 

experiment: 

1). The data collected may not have been handled appropriately for the 

analyses that are needed; 

2). The type of data or the way it was collected may not be appropriate 

to answer the original objective. 

Specific selection of endpoints is also very important when several parties are 

involved in an experiment, as is frequently the case with oil spill monitoring. 

At the conclusion of the project, it may be found that the data collected do not 

answer the question posed. Or, when several different kinds of data are 

collected, disagreement may ensue between the different parties involved 

over what constitutes the "real" endpoint, and thus, the "real" result. 

Sampling design 

An appropriate sampling design helps ensure that the data collected provide 

answers to the initial questions posed. Sampling designs may be simple or 

very complex, but they should follow after the objectives and endpoints that 

have been selected. Sample design includes consideration of control sites, the 

number of samples, the locations where samples will be collected, the timing 

of sampling, and sample handling and analysis. For monitoring or sampling 

projects other than very simple ones, the best procedure will be to consult 

with a statistician while still in the planning stage. 

7-5
 
Controls 

A crucial part of most experiments is the reference or control site. Most 

objectives will involve detecting differences, or making comparisons, and 

thus require a baseline, or reference from which to measure change. In the 

absence of some sort of reference, interpreting the data will be difficult and 

possibly meaningless. In theory, controls should be replicates of the tested 

plot or experimental unit, the same in every way, except for the treatment 

applied. Some examples of possible controls are listed below: 

• For a laboratory flask test: seawater containing no product

 (e.g. dispersant or bioremediation) at the same salinity and

 temperature as in the treated flask 

• For a field study: a marsh plot containing the same plant species,

 with similar densities and oiling effects as the treated plots 

In practice, control sites in field studies will never be completely identical to
 

the test sites. Usually, one must settle for a "representative control" that is as
 

similar or as representative as is feasible. Other options include the use of
 

experimental units placed in the environment, such as sediment boxes. This
 

technique was used by Berge (1990) to study colonization of biota to sediments
 

impacted by oil, compared with control sediments.
 

One way to establish controls at spills of opportunity is by the use of "setasides" (areas that are impacted by oil that are set aside, and left untreated for
 

experimental purposes). NOAA arranged for such "set asides" immediately
 

after the Exxon Valdez spill. Having these sites made it possible to conduct
 

the long term study of treatment effects in Prince William Sound that is still
 

ongoing.
 

Numbers of samples
 

The number of samples to be collected will depend on:
 

• the question being asked, 

• the kind of data analysis to be done (including the statistical 

certainty desired) 

7-6
 
•	 practical considerations (area available, time and access, personnel, 

cost) 

A larger number of samples often allows greater power for statistical analysis, 

but will be more costly. If the parameter being measured is highly variable, 

such as the distribution of oil in sediments, a large number of samples will be 

needed to have the power necessary to conduct statistical testing. A small 

number of samples will provide an indication of the processes occurring, but 

may not be representative of the entire study area. One strategy is to collect a 

large number of samples in the field and then to analyze only a subset of the 

samples collected, based on the initial results. 

In many field sampling situations, the number of samples that can be 

collected will be limited by logistics and practical considerations. These may 

include the area available, time and access constraints, personnel, cost, etc. In 

any event, it will almost always be more useful to take a few carefully 

thought-out samples than to take numerous samples without proper 

planning and subsequent follow-through. 

Locations of samples 

The locations chosen for sampling will depend on the number and types of 

habitats or shoreline types to be investigated, as well as on the sample analysis 

that will be conducted. A common approach is to select one or more plots to 

be sampled, with each plot representing a particular environment or 

treatment. Then, random sampling can be conducted within each plot. In a 

marsh monitoring, for example, transects could be placed in a control marsh, 

a trampled section of marsh, and in a washed section of marsh. Then 

replicate quadrats would be located randomly along each quadrat. 

When possible, it is best to avoid taking samples in areas with outside 

influences that may confound the results, such as areas near outfalls or 

freshwater streams. Samples taken in the middle of a plot will usually be 

more representative than samples taken along the edge. One method for 

locating samples within a plot is to lay a grid pattern over a map of the test 

7-7
 
area and choose samples randomly in each designated area. (See Figure 7-3 

for examples of different sample designs using plots). 

Timing of sample collection 

Timing refers to both the duration of the experiment, and the frequency with 

which samples will be collected. This could vary from a one-time sample 

collection, up to a multi-year monitoring program where sampling is 

conducted seasonally. As for other aspects of sample design, the appropriate 

time frame for collecting samples will depend on the questions being 

addressed. For this, one must refer back to the original objectives. 

Some preliminary information will be helpful when determining both 

duration and frequency. For instance, 

•	 Does the parameter of interest vary seasonally? 

•	 Is there a minimum length of time necessary for acquiring useful 

information from the sampling program? 

Dispersant monitoring, for example, will be conducted on a very short time 

frame, on the order of a several hours to days. Bioremediation, in contrast, 

must be sampled over a period of at least a week, and preferably over several 

weeks to be able to detect biodegradation. Ecological processes are ideally 

monitored seasonally over a long time frame, of several years duration, if 

possible. 

Qualitative and quantitative data 

Data can be categorized into two rough types, qualitative and quantitative. 

Qualitative data is best described as descriptive; information that helps 

describe something, and gives the experimenter general background 

information. Qualitative data does not enable one to attribute a degree of 

certainty to the conclusions, since it does not include measures of variance. 

Because of this, qualitative data cannot be extrapolated to a larger 

environment or population. 

7-8
 
Figure 7-3. Some two-dimensional probability sampling designs for sampling 

over space (NAS 1985). 

Qualitative data is useful for data exploration purposes, for identifying 

possible trends, and for "getting a feel for what is going on." Certain kinds of 

investigations are, by nature, descriptive, such as those that would address the 

following questions: 

What kind of oil is this?
 

What type of habitat is this?
 

7-9
 
What species of plants or animals live here? 

Initial, or pilot investigations will often be qualitative, and serve as a first 

source of information to use in developing future sampling plans. Field 

observations, made in the form of simple field notes, are very important 

types of qualitative data. Observations from people on the scene, that record 

things such as weather patterns, unusual occurrences, where oil was 

observed, etc. may be very helpful in clarifying what actually happened at a 

later date. 

Qualitative data is limited, in that it cannot be used in the following ways: 

•	 Extrapolating to broader universes 

(the sample collected may not be representative of other areas) 

•	 Statistical testing 

(all statistical tests assume certain things about the data, for instance, 

that the samples were collected in a randomized manner) 

Quantitative data means data that has been collected from random sampling, 

with some measure of variability (replication), and is representative of a 

larger population or universe. Quantitative data will usually result from a 

carefully planned experimental design. The advantages of this type of data 

area that there are many options for analysis, including performing statistical 

tests, and attributing statistical significance to the results. 

As discussed earlier, it is by no means always necessary to obtain quantitative 

data. If the objective can be met by a simple collection of qualitative data, 

then there may be no reason to conduct more elaborate sampling. 

Some considerations for analyzing data 

When looking at your own or data collected from other sources, it is 

important to be on the lookout for measures of uncertainty that might make 

the results questionable. Two sources of uncertainty in sampling are bias and 

systematic sampling errors. Bias could result if something in the sampling 

plan or the sample collection makes the samples not representative of the 

7-10
 
population being studied. Systematic errors stem from errors that occur 

while sampling such as malfunctioning equipment. 

When laboratory analyses are performed, look for the existence of a quality 

assurance, quality control program that cross-checks laboratory work. Also 

examine the detection limits of the work, to know the degree of accuracy of 

the data. 

Some simple ways to gather data 

Useful information can be gathered by people who will be on scene at 

incidents in several ways that do not involve excessive cost or effort. Some 

examples of these are as follows: 

•	 Establish intertidal transects on shorelines 

- survey species found along the transects 

- survey the species found inside quadrats 

- photograph the transect and/or the quadrats to determine 

percent cover of vegetation or invertebrates 

•	 Establish test plots corresponding to different treatment techniques 

•	 Observe impacted areas over time 

- re-visit the site at definite intervals (seasonal, monthly) 

- take photographs from marked areas or known vantage points 

7-11
 
 

Summary 

•	 Objectives, hypotheses and endpoints should be clearly specified

 before a sampling project is designed 

• Sample design will include the following: 

- Proper controls, 

- An appropriate number of samples 

(this will depend on the analysis to be conducted), 

- Locations representing the habitats being studied, 

- Duration and frequency of sampling appropriate to the 

objectives. 

•	 Qualitative data is descriptive in nature and cannot be extrapolated 

to broader populations 

•	 Quantitative data can be used for statistical testing, but must be from 

random samples 

•	 Uncertainty in data can result from 

- biases in sampling, or systematic errors 

- errors in analysis 

(check for quality control and detection limits) 

•	 Some simple ways to monitor 

- establish transects 

- use photography 

- establish plots by treatment 

- re-visit impacted sites 

7-12
 
References 

Berge, J. A. 1990. Macrofauna recolonization of subtidal sediments. 

Experimental studies on defaunated sediment contaminated with crude oil in 

two Norwegian fjords with unequal eutrophication status. I. Community 

responses. Mar. Ecol. Prog. Ser. Vol. 66: 103-115. 

Baker, J. M and W. J. Wolff (eds). 1987. Biological Surveys of Estuaries and 

Coasts. Cambridge, England: Cambridge University Press. 

Eberhardt, L. L., and J. M. Thomas. 1991. Designing environmental field 

studies. Ecol. Mono. 61:53-73. 

Gilbert, R. O. 1987. Statistical Methods for Environmental Pollution 

Monitoring. New York: Van Nostrand Reinhold Company. 320 pp. 

Hurlbert, S. H. Pseudoreplication and the design of ecological field 

experiments. 1984. Ecological Monographs 54:187-211. 

Lewis, J. R. 1982. The composition and functioning of benthic ecosystems in 

relation to the assessment of long-term effects of oil pollution. Phil. Trans. R. 

Soc. Lond. B 297:257-267. 

Scheaffer, R. L., Mendenhall, W. and L. Ott. 1986. Elementary Survey 

Sampling, Third Edition. Boston: PWS Publishers. 324 pp. 

Zar, J. H. 1984. Biostatistical analysis. Englewood Cliffs, New Jersey: 

Prentice-Hall Inc. 718 pp. 

7-13
 
8	 The Archetypical 

Environmental Sensitivity Index 

Jacqueline Michel1 

Page 

Introduction.....................................................................................................8-1
 

Elements of an Environmental Sensitivity Mapping System 8-3
 

General Coverage and Types of Information......................8-3
 

Habitats..........................................................................................................8-4
 

Biological Resources..............................................................................8-12
 

Human-Use Areas.................................................................................8-21
 

How Sensitivity Maps Are Used.........................................................8-23
 

Contingency Planning.........................................................................8-23
 

Spill Response............................................................................................8-24
 

1Research Planning, Inc., P.O. Box 328, Columbia, South Carolina 29202 
Chapter 8. 

The Archetypical Environmental Sensitivity 

Index 

Introduction 

Environmental Sensitivity Index (ESI) maps have been an integral component of oil 

spill contingency planning and response since 1979, when the first ESI maps were 

prepared days in advance of the arrival of the oil slicks from the Ixtoc 1 well blowout 

in the Gulf of Mexico. Since that time, ESI atlases have been prepared for most of 

the U.S. shoreline, including Alaska and the Great Lakes. Figure 8-1 shows the areal 

coverage of existing ESI atlases and Table 8-1 lists the publication date, number of 

maps, and scale for each atlas. With the exception of northern and central 

California, central Texas, and Mississippi, all of the atlases have been prepared with 

funding by the National Oceanic and Atmospheric Administration (NOAA). 

Furthermore, all the ESI atlases, except for those listed above and the Chukchi Sea in 

Alaska, were prepared using standardized methods and products (Hayes et al., 1980; 

Getter et al., 1981). Sensitivity mapping projects have also been conducted for 

coastal areas of France, Germany, Italy, Nigeria, Kuwait, Saudi Arabia, Oman, 

United Arab Emirates, Malaysia, and New Zealand, among others. 

Traditional sensitivity maps have been produced in color-coded paper maps, of 

limited distribution (because of the cost of reproduction), and without a means for 

ready updating. With the advent of Geographic Information System (GIS) software 

for microcomputers, automation of ESI information has been a major new focus. 

Digital, georeferenced databases are being developed for natural resources 

management at federal, state, and local levels. These digital databases can provide a 

ready source for development of automated sensitivity maps for oil spills. With the 

power of GIS, sensitivity mapping moves from a static product of limited 

distribution to a valuable tool for planning and response to oil spills. The first use 

of GIS technology for production of ESI maps was in Louisiana, where satellite 

imagery was used to update air photograph interpretations to produce the base maps 

and intertidal habitat rankings. The technique is being further refined for NOAA by 

RPI into an all-digital ESI product for southeastern Alaska. 

Table 8-1. Listing of all environmental sensitivity index (ESI) atlases published for 

the United States. 

Name Year Published No. of Maps Map Scale 

Alabama 1981 20 1:24,000; 1:62,500 

Alaska 1982-1986 371 1:63,360 

California 1980-1986 75 1:24,000; 1:40,000 

Connecticut 1984 17 1:24,000 

Delaware/New Jersey/ 1985 59 1:24,000 

Pennsylvania 

Florida 1981-1984 217 1:24,000 

Georgia 1985 29 1:24,000 

Hawaii 1986 86 1:20,000; 1:24,000 

1:32,500; 1:40,000 

1:62,500; 1:80,000 

1:100,000 

Louisiana 1989 98 1:50,000; 1:95,000 

1:100,000; 1:105,000 

Maine 1985 77 1:24,000; 1:40,000 

Maine/New Hampshire 1983 25 1:24,000; 1:40,000 

Maryland 1983 119 1:24,000 

Massachusetts 1980 49 1:24,000 

Michigan 1985-1986 38 1:24,000; 1:50,000 

1:62,500; 1:163,360 

New York 1985 77 1:24,000; 1:50,000 

North Carolina 1983 113 1:24,000; 1:62,500 

Lake Erie 1985 66 1:24,000; 1:62,500 

Oregon/Washington 1986-1989 81 1:24,000; 1:62,500 

Puerto Rico 1984 35 1:20,000 

Rhode Island/Massachusetts 1983 18 1:24,000; 1:25,000 

South Carolina 1982 50 1:24,000 

Texas 1979-1980 34 1:24,000; 1:40,000 

U.S. Virgin Islands 1986 8 1:24,000 

Virginia 1983 113 1:24,000 

Washington 1984-1985 80 1:24,000; 1:62,500 

Total 1,954 
As the oil spill response community moves towards development of automated 

sensitivity maps, it is important to define what comprises the archetypical ESI 

mapping system. This guideline can help define the collection of data for the 

system, allowing for regional differences in resource distribution, data availability 

and currency, and extent of supporting information. The primary objective of this 

analysis is to outline the basic elements of a sensitivity mapping system. The second 

objective is to describe how sensitivity maps are used for contingency planning and 

during spills. These uses will drive the development of automated systems, the 

user interface, pre-set queries, standardized output formats, and map symbology. 

Elements of an Environmental Sensitivity Mapping 

System 

General Coverage and Types of Information 

The areal coverage of existing marine sensitivity maps is along the coastal zone and 

extending up rivers to the “head of tide,” or the furthest inland extent of tidal 

influence. Along coastal, navigable rivers, the ESI maps extend to the boundary of 

the U.S. Coast Guard response zone, except along the Mississippi River, where the 

ESI maps extend to Baton Rouge. Existing maps extend to Troy on the Hudson 

River, to Trenton on the Delaware River, and to the John Day Dam (river mile 215) 

on the Columbia River. As part of a special Florida project, the Appalachicola River 

was mapped to the upper reaches of Lake Seminole. 

In the Great Lakes, all of Lake Erie, eastern Lake Michigan, St. Mary's River, and 

both sides of the St. Lawrence River from Lake Ontario to the New York/Canada 

border have been mapped. Work is currently underway to produce ESI atlases in 

digital format for the U.S. shoreline of Lake Ontario and the Wisconsin shoreline of 

Lake Michigan. 

Nearly all of the maps of the lower 48 states have been prepared at a scale of 1:24,000, 

using U.S. Geological Survey (USGS) 7.5 minute quadrangles as the base map. 

There are a few exceptions where USGS maps were not available or at the 

appropriate scale. For all of Alaska, 15-minute USGS topographic quadrangles at a 

scale of 1:63,360 have been used as base maps. Southeast Alaska-Part I is being done 

as a totally digital product. Columbia River and Louisiana have been produced with 

the intertidal shoreline types in digital format. 
ESI maps are comprised of three general types of information: 

1)	 Habitats–which are further divided into: 

A)	 Intertidal shoreline habitats, which are ranked according to a scale 

relating to sensitivity, natural persistence of oil, and ease of cleanup. 

B)	 Subtidal habitats, which are utilized by oil-sensitive species or are 

themselves sensitive to oil spills, including eelgrass beds, kelp, and 

coral reefs. 

2) Biological Resources–including oil-sensitive animals and plants. 

3)	 Human-Use Resources–specific areas that have added sensitivity and 

value because of their use by humans, such as high-use amenity beaches, 

parks and marine sanctuaries, water intakes, and archaeological sites. 

Each of these elements are briefly discussed in the following section. 

Habitats 

Intertidal Shoreline Types.–Intertidal habitats are at risk during spills because of the 

high likelihood of being directly oiled when floating slicks impact the shoreline. Oil 

fate and effects vary significantly by shoreline type, and many cleanup methods are 

shoreline-specific. The concept of mapping coastal environments and ranking them 

on a scale of relative sensitivity was originally developed in 1976 for lower Cook 

Inlet (Michel et al., 1978). Since that time, the ranking system has been refined and 

expanded to cover shoreline types for all of North America, including the Great 

Lakes and riverine environments. Table 8-2 lists the various existing ESI 

classifications for intertidal shoreline types. There are significant regional differences, to account for the different coastal types. For most areas, the 1-10 scale was 

used, with subdivision of the numerical ranking for different shoreline types with 

similar relative sensitivity. 
Table 8-2. Summary of the various ESI ranking scales used throughout the United 

States. 

ESI ALASKA 

NO. 

1 Exposed rocky 

shores 

2 Wave-cut 

platforms 

3 Fine sand beaches 

4 Coarse sand 

beaches 

5A Exposed tidal flats 

(low biomass) 

5B 

6A Sand and gravel 

beaches 

6B 

7A Gravel beaches 

7B Exposed tidal flats 

(high biomass) 

8A Sheltered rocky 

shores 

8B 

9 Sheltered tidal 

flats 

10A Marshes 

10B 

11 

WEST COAST
 

Exposed rocky 

shores/seawalls 

Wave-cut 

platforms 

Fine sand beaches 

Coarse sand 

beaches 

Sand and gravel 

beaches 

Gravel beaches 

/exposed riprap 

Exposed tidal flats 

Sheltered rocky 

shores and coastal 

structures 

Sheltered tidal 

flats 

Marshes 

COLUMBIA 

RIVER 

Unvegetated 

steep banks and 

cliffs 

Sand/gravel 

beaches 

Riprap 

Flats 

Vegetated banks 

Marsh/swamp 

TEXAS
 

Exposed scarps 

Exposed finegrained sand 

beaches 

Sheltered finegrained sand 

beaches 

Exposed tidal flats 

(low biomass) 

Mixed sand and 

shell beach 

Exposed tidal flats 

(moderate 

biomass) 

Sheltered tidal 

flats 

Salt marshes 
Table 8-2. Continued. 

ESI 

NO. 

LOUISIANA FLORIDA/PUERTO 

RICO/USVI 

SOUTHEAST 

(AL/GA/SC) 

MID-ATLANTIC 

(MD,VA,NC) 

1 Developed/ 

unforested 

upland 

Exposed rocky 

shores/seawalls 

Exposed seawalls Consolidated 

shores/seawalls 

2 Sand beach/spoil 

bank 

Exposed rocky 

platforms 

Not present Exposed fine 

sand beaches 

3 Tidal mudflat Fine sand beaches Fine sand 

beaches 

Sheltered fine 

sand beaches 

4 Freshwater flat Coarse sand beaches Coarse sand 

beaches 

Coarse sand 

beaches 

5A 

5B 

Salt marsh 

Fresh marsh 

Sand/gravel beaches Sand and shell 

beaches 

Exposed tidal 

flats 

6A 

6B 

Swamp Gravel beaches/ 

Riprap 

Riprap Riprap 

7A 

7B 

Mangroves Exposed tidal flats Exposed tidal 

flats 

Supratidal 

marshes 

8A 

8B 

Sheltered rocky 

shores/seawalls 

Sheltered 

seawalls 

Freshwater 

marsh/swamps 

9 Sheltered tidal flats Sheltered tidal 

flats 

Sheltered tidal 

flats 

10A 

10B 

11 

Exposed marshes/ 

mangroves 

Sheltered marshes/ 

mangroves 

Marshes 

Sheltered 

marshes 

Fringing 

intertidal 

marshes 

Extensive 

intertidal 

marshes 
Table 8-2. Continued. 

ESI
 

NO.
 

1 

2 

3 

4 

5A 

5B 

6A 

6B 

7A 

7B 

8A 

8B 

9 

10A
 

10B
 

DEL/NJ/PA
 

(Not present) Exposed rocky 

shores 

Eroding bluffs Wave-cut 

platforms 

Fine sand beaches Fine sand beaches 

Coarse sand Coarse sand 

beaches beaches 

Sand and gravel Sand and gravel 

beaches beaches 

Exposed tidal flats 

(MA) 

Gravel beaches Gravel beaches 

Riprap Riprap 

Exposed tidal flats Exposed tidal flats 

Vegetated Sheltered rocky 

riverine banks shores 

Sheltered tidal Sheltered tidal 

flats flats 

Marshes Marshes 

NORTHEAST 

(NY to ME) 

GREAT LAKES
 

Exposed bedrock Vertical rocky 

bluffs/seawalls shores/seawalls 

Exposed Exposed bluffs 

unconsolidated 

sediment bluffs 

Shelving bedrock Fine sand beaches 

shores 

Sand beaches Coarse sand 

beaches 

Sand and gravel Mixed sediment 

beaches beaches 

Gravel beaches Gravel beaches, 

riprap, and cross 

levees 

Riprap structures Exposed tidal flats 

Vegetated bluffs 

Sheltered bluffs Vegetated low 

(bedrock) banks 

Sheltered 

impermeable 

structures 

Low banks Cypress/hardwood swamps 

Fringing Freshwater 

wetlands marshes 

Extensive Saltwater 

wetlands marshes 

APALACHICOLA 

RIVER 

11 

The intertidal ranking scheme is based on an understanding of the coastal 

environment, not just the substrate type and grain size. The sensitivity ranking is 

an integration of the: 

1) Shoreline type (substrate, grain size, tidal elevation, origin), 

2) Exposure to wave and tidal energy, 

3) Analysis of the natural persistence of the oil on the shoreline, 

4) Biological productivity and sensitivity, and 

5) Ease of cleanup without causing more harm. 

All of these factors are used to determine the relative ESI ranking for a shoreline 

segment. Key to the rankings is an understanding of the relationships between 

physical processes and substrate which produce specific geomorphic shoreline types 

and predictable patterns in oil behavior and sediment transport patterns. 

Historically, the rankings were defined from field surveys and literature analysis, 

then mapped directly as the shoreline type during aerial surveys. The most 

common shoreline rankings used in the U.S., with a short summary of the oil 

behavior, biological sensitivity, and ease of cleanup, are listed below. 

1) Exposed, vertical rocky shores and seawalls. 

These shoreline types are exposed to high wave energy or tidal currents, 

which tend to keep oil offshore by reflecting waves. The substrate is 

impermeable so oil remains on the surface where natural processes will 

quickly remove any oil that does strand. Also, any stranded oil tends to form 

a band along the high-tide line or splash zone, above the elevation of the 

greatest biological value. No cleanup is required or recommended. Along 

developed shorelines, exposed concrete seawalls and steel bulkhead are manmade equivalents. 

2) Wave-cut rocky platforms, scarps in clay, and exposed sedimentary bluffs. 

These shorelines are also low in rank because they are exposed to high wave 

energy. However, they have a flatter intertidal zone, sometimes with small 

accumulations of sediment at the high-tide line, where oil could persist for 

up to several weeks to months. Biological impacts can be severe, particularly 

if there are tidal pool communities on the rocky platforms. Cleanup is not 

necessary except for removal of oiled debris and tarballs at the high-tide line 

in areas of high recreational use or to protect a nearshore resource. 
3) Fine-grained sand beaches. 

Compact, fine-grained sand beaches inhibit oil penetration, and, as they 

generally accrete very slowly between storms, the depth of oil burial is 

minimal. Cleanup is simplified by the hard substrate. Biological utilization 

is low and populations can recover after a few months. 

4) Coarse-grained sand beaches. 

Coarse-grained sand beaches are ranked higher because of the potential for 

higher oil penetration and burial, which can be as great as one meter. 

Cleanup is more difficult, as equipment tends to grind oil into the beach 

because of the loose packing of the sediment. 

5) Mixed sand and gravel beaches. 

Because of higher permeabilities, oil tends to penetrate deeply into sand and 

gravel beaches, making cleanup by removal of contaminated sediment 

difficult without causing erosion and sediment disposal problems. These 

beaches undergo seasonal variations in wave energy and sediment 

reworking, so natural removal of deeply penetrated oil may only occur 

during storms with a frequency as low as 1-2 per year. Biological utilization is 

low, because of the sediment mobility and rapid drying during low tide. 

6) Gravel beaches and riprap. 

Gravel beaches are ranked the highest of all beaches primarily because of the 

potential for very deep oil penetration and slow natural removal rates of 

subsurface oil. The slow replenishment rate of gravel makes removal of 

oiled sediment highly undesirable, and so cleanup of heavily oiled gravel 

beaches is particularly difficult. For many gravel beaches, significant wave 

action (meaning large enough waves to rework the sediments to the depth of 

oil penetration) occurs only every few years, leading to long-term persistence 

of subsurface oil. Riprap is a man-made equivalent, with added problems 

because it is usually placed at the high-tide line where the highest oil 

concentrations are found and the clasts are not reworked by storm waves. 

Often, the only way to clean riprap is by removal and replacement. 

7) Exposed tidal flats. 

Oil does not readily adhere to or penetrate the compact, water-saturated 

sediments of exposed sand flats. Instead, the oil is pushed across the surface 

and accumulates at the high-tide line. Because of the high biological 

utilization, however, impacts to benthic invertebrates by exposure to the 

water-accomodated fraction or by smothering can be significant. Sometimes, 

highly mobile sand flats, such as those at the mouths of large inlets, are 

ranked lower when infaunal densities are low. 
8) Sheltered rocky shores and seawalls. 

Spilled oil tends to coat rough rock surfaces in sheltered settings, and oil 

persistence is long-term because of the low wave energy. Mapping should 

differentiate between solid rock surfaces which are impermeable to oil and 

rocky rubble slopes which tend to trap oil beneath a veneer of coarse boulders. 

Both types can have large amounts of attached organisms, supporting a rich 

and diverse community. Cleanup of these shorelines is always labor 

intensive and can affect biological communities. 

9) Sheltered tidal flats. 

The high biological utilization, soft substrate and low energy setting makes 

these habitats highly sensitive to oil spill impacts and almost impossible to 

clean. Usually any cleanup efforts result in mixing oil deeper into the 

sediments and prolonging recovery. 

10) Vegetated wetlands. 

Marshes, mangroves, and other vegetated wetlands are the most sensitive 

habitats because of their high biological utilization and value, difficulty of 

cleanup, and potential for long-term impacts to many organisms. Where 

there are multiple wetland types present, different rankings can be assigned 

based on likelihood of being oiled, relative wave energy, species composition, 

and geomorphology (see Virginia rankings in Table 8-2). 

With GIS capabilities, it may be possible to build the shoreline sensitivity 

classification from other basic parameters, such as substrate, sediment size or type, 

elevation, width, slope, general geomorphology, general biological sensitivity, etc., 

then use algorithms to calculate exposure to wave and tidal energy for each 

shoreline segment and assign a sensitivity rank. However, this type of sensitivity 

ranking must be done in a highly supervised classification mode. Although existing 

intertidal habitat maps are a good source for mapping discrete classes, i.e., gravel, 

sand, or mud, they are not good sources when these classes are mixed (sand and 

gravel), and they do not contain the information needed to identify coastal 

geomorphological types. The existing ESI maps are usually the best source of 

information on intertidal habitats for ranking of shoreline sensitivity. The scale of 

mapping is usually at +100 feet for maps made on U.S. Geological Survey 7.5 minute 

quadrangles. 

Development of a standardized sensitivity mapping protocol brings up some special 

questions on shoreline mapping issues. 

• Should all intertidal habitats be ranked on a scale of 1 to 10? 
•	 If so, should subdivisions into 5A, 5B, etc. be used for different 

shoreline types of similar sensitivity? 

•	 Should an "ESI number" always refer to a specific shoreline type? 

That is, should ESI = 9 always be sheltered tidal flats? 

From one perspective, the 1 to 10 ranking scheme is not as important as the 

shoreline classifications. The relative rank can be assigned or calculated based on 

the various factors listed above and attribute data. However, the ESI rankings have 

significant precedent and acceptance. If a 1 to 10 ranking was always used, then one 

would always know that the most sensitive shoreline type was ESI = 10, without 

having to consider that there might be an ESI = 11 type. Thus, the ESI numbers 

would not always refer to a specific shoreline type, but the relative sensitivity to the 

impacts of spilled oil. In fact, seldom has a responder asked about a shoreline type 

by its ESI number; instead, responders either ask, "Where are the marshes?" or 

"What is most sensitive?" 

Nearly all of the existing ESI maps follow this basic 1 to 10 convention, with little 

variation in the assignment of ESI number by shoreline type (Table 8-2). The only 

exceptions are: Virginia, Maryland, and North Carolina, which have marshes 

ranked ESI = 7, 8, 10, and 11; Louisiana which has ESI = 1 to 7; and the Columbia 

River which has ESI = 1 to 6. In an automated system, the ESI rank would be part of 

the attribute information, along with the specific shoreline geomorphology, so that 

thematic maps could be made using any combination of data attributes. 

Because the sensitivity mapping system will eventually be applied to most of the 

U.S., including coastal, lacustrine, and riverine systems, uniformity in classification, 

color-coding, and symbology will be of great benefit. Research on optimization of 

mapping colors and symbology for ESI maps is currently underway, and the results 

will be published in a separate report. 

Subtidal Habitats.–In a subtidal setting, oil vulnerability of habitats is much lower 

because they are not likely to be directly contaminated by floating slicks. Exceptions 

include some sites or tidal stages when these habitats become intertidal. The 

sensitivity of a subtidal habitat usually derives from the species which use the 

habitat. Thus, kelp beds, which have not been shown to be 
directly affected by oil, are nonetheless very sensitive because they provide habitat 

and shelter for animals which are sensitive, such as sea otters. These habitats 

represent whole communities which have complex interrelationships and 

functions. The subtidal habitats have not traditionally been ranked; rather, they 

have been treated more as living resources which vary in sensitivity with season 

and location. The approach has been to map only the subtidal habitats that have 

been determined to be most sensitive. In the past, mapping has covered: 

• Eelgrass beds 

• Submerged aquatic vegetation 

• Worm reefs 

• Large beds of kelp 

• Coral reefs 

Other subtidal bottom types have not been included. If there are other subtidal areas 

that are important to a specific species, those areas are designated according to the 

species, life stage present, and season of use, not the habitat. 

Biological Resources 

There are numerous animal and plant species that are potentially at risk from oil 

spills. Table 8-3 lists the major groups (elements) and sub-groups of species which 

are included on sensitivity maps. There are seven major biological elements and 

each element is further divided into groups of species with similar ecological 

behavior relative to oil spills. Each of these sub-element groups is composed of 

individual species that have similar oil-spill sensitivities. For example, there are 

eight sub-elements for birds, with raptors including those species of accipiters, 

falcons, and osprey which nest close to major waterbodies and feed on fish or 

seabirds. On the maps, the distribution of oil-sensitive fish and wildlife is mostly 

shown by patterns and symbols representing these ecological groupings, with 

annotations for each species present. 
Table 8-3. Components of biological and human-use resources included on 

sensitivity maps 

Data Element Sub-Element Comments 

Habitats Shoreline Types ESI or other geomorphological class 

Eelgrass Beds/SAV Includes all types of subtidal grass 

beds 

Kelp 

Coral Reefs 

Worm Beds 

Marine Mammals Whales Seasonal use areas; Migration routes 

Dolphins Population concentration areas 

Sea Lions Haulouts 

Seals Haulouts 

Sea Otters Population concentration areas 

Manatees Population concentrations areas 

Walruses Haulouts 

Polar Bears 

Terrestrial Mustelids Concentration areas 

Mammals 

Rodents Concentration areas 

Deer Intertidal-feeding species 

Bear Intertidal feeding areas 

Birds Diving Coastal Birds Rookeries; Forage/wintering areas 

Waterfowl Wintering areas; Migration 

stopover areas 

Alcids Rookeries; Wintering concentration 

areas 

Petrels/Fulmars Rookeries 

Shorebirds Nesting beaches; Migration stopover 

areas 

Wading Birds Rookeries; Critical forage areas 

Gulls/Terns Nesting sites 

Raptors Nest sites; Critical forage areas 

Fish Anadromous Fish Spawning streams 

Beach Spawners Spawning beaches 

Kelp Spawners 

Nursery Areas For estuarine, demersal, pelagic fish 

Reef Fish Includes fish using hardbottom 

habitats 

Special concentrations Estuarine and demersal fish 
Table 8-3. Continued 

Data Element Sub-Element Comments 

Mollusc Oysters 

Mussels 

Clams 

Scallops 

Abalone 

Conch/whelk 

Squid/octopus 

Seed beds; Leased beds; Abundant 

beds 

Leased beds; Abundant beds 

Harvest areas; Abundant beds 

Harvest areas; Abundant beds 

Harvest areas; High concentrations 

Harvest areas; High concentrations 

Harvest areas; High concentrations 

Crustaceans Shrimp 

Crabs 

Lobster 

Nursery areas 

Nursery areas; High concentration 

sites 

Nursery areas; High concentration 

sites 

Reptiles Sea Turtles 

Alligators 

Nesting beaches 

Concentration areas 

Recreation Beaches 

Marinas 

Boat Ramps 

Diving Areas 

Boating/Fishing 

State Parks 

High-use recreational beaches 

High-use recreational areas 

Management 

Areas 

Marine 

Sanctuaries/National 

Parks 

Refuges 

Preserves/Reserves Areas of special biological 

concern/WMA 

Resource 

Extraction 

Subsistence 

Commercial Fisheries 

Water Intakes 

Mining 

Aquaculture sites 

Log storage areas 

Officially designated harvest sites 

Industrial; Drinking water; Power 

plants 

Intertidal/subtidal mining leases 

Fish/shrimp/bivalves/plants 

Cultural Archaeological Sites 

Native American Res. 

Note that under “Comments” on Table 8-3 is listed the types of areas which should 

be included. Many marine and coastal species are wide-ranging; they can be present 

over a very large area at any time. Maps or data indicating the entire area of 

occurrence of fish species, for example, can cover very large areas and thus not help 

responders in assessing resources at risk and protection priorities. However, natural 

resources are most at risk from oil spills when: 

•	 Large numbers of individuals are concentrated in a relatively small area, 

such as bays where rafts of waterfowl concentrate during migration and 

overwintering. 

•	 They come ashore for birthing, resting, or molting, such as seal haulouts. 

•	 Early life stages are present in somewhat restricted areas, such as nursery 

areas for anadromous fish, turtle nesting beaches, and bird rookeries. 

•	 Areas important to specific life stages or migration patterns, such as 

foraging or overwintering sites, are impacted by oil. 

•	 Specific areas are known to be vital sources for seed or propagation. 

•	 The species are threatened or endangered. 

•	 A significant percentage of the population is likely to be exposed to oil. 

Therefore, sensitivity maps show where these most sensitive species, life stages, and 

areas are located, not the entire area over which the species are known to occur. 

Several types of distributions are shown. Point locations (in the form of latitude 

and longitude) are used for sites of very small areal extent, such as bird rookeries 

and mammal haulouts. Range bars or lines are used to show sites along a shoreline 

which is used for a specific activity, such as the length of a stream used for spawning 

by anadromous fish or the extent of a beach where turtles nest. Biological 

distributions which are spread over an area are shown by polygons with patterns, 

such as oyster seed beds, important nursery areas for estuarine fish, or high 

concentration waterfowl overwintering areas. 

Table 8-4 lists the associated data for each element which should be included, at the 

species level. These data allow identification of the most sensitive periods 


for each species and determination of protection priorities on a seasonal basis. For 

each species or species group, detailed information is provided on the life stage 

present by month of year. 

For mammals and birds, life stages include adult, adult breeder, and juvenile, or just 

present if the life stage is unknown. Not present is indicated to differentiate from 

no data available. The earliest start and latest end dates for breeding activity of 

marine mammals and birds are used to determine the presence of eggs or young. 

Calving dates apply only to whales, dolphins, and manatees, whereas pupping dates 

apply to sea lions, seals, and sea otters. The number of individuals or breeding pairs 

is listed (if known); otherwise descriptive qualifiers of the number or relative size of 

the population likely to use the area are indicated. For example, heavily used seal 

haulouts can be ranked as high, whereas sites which are infrequently used can be 

ranked as low. Previously, information on sensitivity maps showed only presence 

of these animals by season; the user had to obtain numbers of animals present and 

life stage and breeding status from other sources or general life-history profiles. The 

availability of life-stage and concentration information helps planners and 

responders make better decisions on protection and cleanup priorities. 

For terrestrial mammals, breeding information is usually not included since these 

data are seldom known. Rather, the life stage presence by month is used to indicate 

when young are likely to be present. 

For fish, emphasis is placed on important spawning and rearing areas in shallowwater environments, where sensitive life stages are concentrated and at risk of 

exposure to high levels of oil in the water column. Therefore, shallow water and 

intertidal spawning areas are shown for anadromous fish, beach spawners such as 

grunion, and kelp spawners such as herring. The entire length of stream used for 

spawning by anadromous fish is shown. Nursery areas for larval and juvenile fish 

in estuarine settings, particularly for species of commercial or recreational 

importance, are highlighted. Reef and shallow hardbottom habitats are included as 

areas of fish concentration at risk from floating slicks. Life-stage information 

includes larvae and eggs, and breeding activity includes start and end dates for 

spawning and outmigration of fry. 

Molluscs and crustaceans are always indicated as areas, designated as important seed 

beds, harvest areas, abundant beds, or otherwise high concentration areas. Life 
stages present for each month include adults, juveniles, larvae, and eggs, and 

breeding activity start and end dates include mating and spawning. The 

concentration descriptors can be used to designate relative importance of the site or 

area. For example, seed oyster beds would be designated as high, whereas viable but 

closed oyster beds would be designated as low. The objective is to provide 

responders with the information needed to determine protection priorities. 

The only information usually shown for turtle nesting beaches is the start and end 

date for laying of eggs and hatching of the young. For all other life stages, turtles 

range widely and have no habitat preferences which increase their likelihood of 

encountering oil. Information for alligators is shown as areas of occurrence, with 

designation of life stages present, if known. 

Threatened and endangered species are shown with a special flag to indicate their 

management status. Species on both state and federal lists are shown. It may be 

very important to include the expert contact for a specific resource, someone who 

could be contacted to provide current species status or special protection 

requirements. General, resource-wide contacts, such as the State Historic 

Preservation Office for archaeological sites, should be listed elsewhere. However, 

this section of the database lists the key person or agency knowledgeable about a 

specific resource, if there is one. 

In the past, standardized symbols for each of these resources have been used, with 

general color patterns for major ecological groups. Symbols are used to represent 

important species groupings within a major group. For example, a different symbol 

is used for each of the eight sub-grouping under birds in Table 8-3. These symbols 

allow the user to readily identify the general group of organism and its general risk 

without having to know the specific species composition. As mentioned above for 

habitats, there is an on-going research effort to identify symbology and patterns for 

use in generation of hardcopy maps and screen views from GIS databases. 

On the ESI maps, biological resource information is noted by colored circles (Fig. 8-

2). The color of the circle identifies the type of organism present: yellow = 
marine mammal; green = bird; orange = shellfish; blue = fish; red = reptile. 

Biological groups are identified by symbols within the circles (Table 8-5). Numbers 

in the circles refer to species or species groups listed in each atlas. Dots in the circle 

indicate seasonality. This information allows the prediction of species’ presence or 

absence during a specific time of the year. A red border indicates that the species is 

rare, threatened, or endangered. The location and range of species are indicated by 

the bars and arrows that extend from the circle. Special symbols identify the 

approximate perimeter of kelp beds and the extent of seagrass beds. 

Figure 8-2. Key to information provided on colored biological markers on the ESI 

maps. 

Areas of socioeconomic importance (major state and local parks and marinas) may 

support high-intensity recreational use, knowledge of which would be important to 

the on-scene coordinator. These areas are marked by a black decal on a white 

background. In addition to parks and beaches, other shoreline areas have been 

specially designated for scenic, wildlife, or other values. These areas include 

reserves, preserves, refuges, and ecological areas. They are marked by a brown circle 

and a star with a number keyed to the area’s name and the agency with controlling 

authority. For the California ESI maps, approximate boundaries are given for Areas 

of Special Biological Significance as designated by the State Water Resources Control 

Board. 

Human-Use Areas 

Previously designated as socio-economic resources on ESI maps, human use areas 

can be divided into four major components (Table 8-3): 

• High-use recreational use and shoreline access areas 

• Officially designated natural resource management areas 

• Marine and coastal resource extraction sites 

• Close-to-shore archaeological and cultural sites 

Each of these components are discussed below. 

As for biological resources, recreational areas shown on sensitivity maps should 

include high-use recreational beaches and sport-fishing, boating, and diving areas. 

Shoreline parks indicate high amenity value. Boat ramps and marinas are shown, 

both as recreational sites and for shoreline access. Marina size (number of slips) can 

help set protection priorities. Name/phone contacts for marinas and parks can 

facilitate notification and collection of information on site suitability for shoreline 

access and construction details needed for operations support. 

Officially designated natural resource management areas include national parks and 

marine sanctuaries, national wildlife refuges, wildlife management areas, preserves 

and reserves set aside by various agencies and organizations, and other ecological 

sites that have special resource management plans or status. In the event of a spill, 

the contact and phone number for the management area are needed for notification 

and inquiry as to current conditions (e.g., number/species of waterfowl actually 

present or expected in the near future). Likewise, contact information for water 

intakes and aquaculture sites (including exact location, depth of intake, use, volume, 

presence of alternative sources) is critical. 

Where appropriate, log storage sites and intertidal/subtidal mining leases are 

included so that appropriate protection and cleanup strategies can be developed. 

Each has a unique problem or issue which can significantly complicate oil removal 

strategies. Log storage sites can contain large numbers of valuable wood products, 

which, when oiled, must be cleaned at great expense prior to sale. Owners of 

intertidal mining leases must be contacted before removal of oiled 
sediment can begin. For each site, the boundary, owner/user contact, and type of 

activity should be provided. 

High-value commercial fishing areas are a very critical component, particularly 

leased shellfish beds and near-shore, shallow-water fisheries such as crabbing, 

shrimp harvest, lobster harvest, and estuarine fisheries. Many times the concern is 

to minimize impacts to the catch and fishing equipment as gear is pulled from the 

water through surface slicks. For each area, the boundary, species being utilized, 

time of use, and data on catch for that area should be provided. Non-commercial 

seafood harvest areas, including subsistence use areas, identify sites where 

monitoring of seafood quality may be needed to protect local populations in the 

event of a spill. 

The most sensitive type of archaeological sites are those that are actually located in 

the intertidal zone, such as parts of Alaska where subsidence exposes important sites 

to coastal erosion. Also, sites located very close to the shoreline where they may be 

crossed by response or cleanup crews should be shown. The type and status (e.g., on 

National Register) of each site should be included. If there are multiple sites in a 

general area, then the area and number of sites should be indicated. Site-specific 

information for some highly sensitive or important archaeological resources may 

need to be restricted in distribution to prevent unnecessary site visits by the curious, 

as well as destruction by vandals. In such a case, then the general area of the sites 

should be designated and a contact for access to specific location information and 

methods of protection provided. 

How Sensitivity Maps are Used 

Contingency Planning 

Integral to the prespill planning process is the designation of protection priorities for 

selected spill scenarios so that site-specific protection equipment requirements can 

be identified. These priorities, as determined by local, area, and/or regional 

planning committees, are derived from analysis of the resources at risk. 

Preplanning also includes development of shoreline cleanup strategies, based on the 

shoreline type and use. 
Sensitivity maps play an extremely important role in training and the development 

of credible spill scenarios. In particular, seasonal differences in resource presence 

and sensitivity can be significant, altering the resources at risk, protection priorities, 

and appropriate response and cleanup activities. For example, the presence of early 

life stages of commercially important fish and shellfish species in the water column 

usually precludes the use of dispersants in the vicinity. However, in the winter, 

when large numbers of waterfowl are concentrated in nearshore waters, dispersant 

use might be a viable means to reduce bird impacts. Cleanup priorities are often 

driven by the seasonal arrival of a species or sensitive life stages, such as 

concentrating efforts to remove oil from turtle nesting beaches prior to the arrival of 

nesting turtles. Just the physical disturbances of cleanup activities have been shown 

to disrupt nesting success of birds, so setting exclusion dates for cleanup activities by 

species can significantly affect cleanup planning and scheduling. 

Preplanning is made more powerful with access to an automated system; just being 

able to generate maps at various scales increases the power of planning. Very 

detailed maps are needed for site-specific protection strategies and equipment prestaging. In contrast, maps of sensitive resources are oftentimes better presented in 

overview for analysis of risks and priorities. For example, the need, type, and 

location of bird rescue operations in Puget Sound is best determined by analysis 

using maps of nesting colonies and waterfowl concentration areas for the entire 

Sound, with symbols and patterns representing relative size and species sensitivity. 

Ad hoc querying by the user for any combination of resource information is needed 

for automated systems. Thus, unique, non-interfering symbology is critical, and this 

is very difficult to achieve for all the ranges of possible combinations. 

Spill Response 

When the initial notification of an actual or potential spill is received, ESI maps are 

consulted to determine what resources are likely to be present and their relative 

risks to impacts from exposure to oil. Having all the resource information on one 

set of maps, addressing oil spills, greatly facilitates this resources-at-risk assessment. 

The maps are multi-disciplinary, allowing quick evaluation of the potential 

magnitude of the spill's impact, based on the initial information on the spill and the 

general trajectory of the slick. Only if such data 
have been compiled onto one set of maps can they be quickly used to support timecritical decisions, such as the use of chemical agents to disperse the slick or where 

are the most important sites for exclusion booming. 

Once the area of impact is more defined, the resource information is used to create 

spill-specific sensitivity maps (based on impact area and season). These spill-specific 

maps are distributed to response personnel in the field and command posts for 

incorporation into response strategies and determination of protection priorities. 

These maps are be used to identify potential bird and mammal impacts so that 

appropriate rescue and cleanup actions can be planned. Resource managers for the 

impacted areas are contacted to verify the species and numbers of animals actually 

present and to determine specific response strategies. 

As the response moves from establishing priorities to developing cleanup criteria, 

sensitivity maps are used to determine the need and limitations of shoreline 

cleanup techniques. Used in conjunction with degree-of-oiling maps, summary 

maps and statistics can be generated to show the areas proposed for various 

treatment methods, or the percent of a shoreline type proposed for treatment. 

Exclusion zones can be plotted for certain types of cleanup activities; for example, 

exclusion zones for aircraft above bird rookeries and marine mammal haulouts 

during nesting and pupping season can be plotted on maps for distribution to pilots. 

The location of exclusion booms can be shown on maps for distribution to boaters, 

to show areas which they should avoid. 

In the future, determination of resources at risk and protection strategies during oil 

spills will be assisted by the development of GIS applications with automated 

mapping functions. State and federal agencies are using GIS technology for 

management of natural resource information, and applications for oil spill 

planning and response are planned in many states. Automation brings many 

powerful tools to the spill response community and managers of natural resources. 

However, a word of caution. The role and benefit of automated sensitivity mapping 

in spill response may be overvalued–too much may be expected too soon, and there 

are many complex issues that need to be resolved. Furthermore, it will take years to 

digitize the data. However, GIS technology will facilitate the generation of thematic 

maps for specialized planning requirements and preparation of maps at various 

scales. It should be noted that the primary 
analytical products of an oil spill GIS are still maps, which are distributed to many 

types of users. GIS technology provides the ability to analyze complex spatial data 

trends and display the results in a powerful geographical format. However, the 

tough decisions still must be made in an environment where conditions rapidly 

change and systems may not be able to keep up with the pace. 
Chapter 9.
 

Glossary of Oil Spill Terms
 

acute 

Having a sudden onset, lasting a short time. Can be used to define either the 

exposure or the response to an exposure (effect). The duration of an acute 

aquatic toxicity test is generally 4 days or less and mortality is the response 

measured (Rand and Petrocelli 1985). 

arcuate 

A bowed or curved delta with the convex margin facing the body of water; 

also known as fan-shaped delta. 

aromatic hydrocarbon 

Carbon-hydrogen compounds characterized by the presence of at least one sixcarbon ring structure. 

bbl 

Barrel, a unit of liquid volume for petroleum products. Equivalent to 42 

gallons. 

bioaccumulation 

A general term describing a process by which chemicals are taken up by 

aquatic organisms from water directly or through consumption of food 

containing the chemicals (Rand and Petrocelli 1985). 

bioassay 

A test used to evaluate the relative potency of a chemical by comparing its 

effect on a living organism with the effect of a standard preparation of the 

same type of organism (Rand and Petrocelli 1985). 

biodegradation 

The breakdown of organic compounds by microorganisms. 

biomagnification 

The result of the process of bioaccumulation by which tissue concentrations 

of bioaccumulated chemicals increase as the chemical passes up through two 

or more trophic levels (Rand and Petrocelli 1985). 

cetacean 

The group of wholly aquatic mammals that includes whales and dolphins. 

9-1
 
chronic 

Involving a stimulus that is lingering or continues for a long time; often 

signifies periods from several weeks to years, depending on the reproductive 

life cycle of the aquatic species. Can be used to define either the exposure or 

the response to an exposure (effect). The chronic aquatic toxicity test is used to 

study the effects of continuous, long-term exposure of a chemical or other 

potentially toxic material on aquatic organisms (Rand and Petrocelli 1985). 

cuspate 

A crescent-shaped bar joining with the shore at both ends. 

depuration 

A process that results in the elimination of a material from an aquatic 

organism. 

emphysema 

A pulmonary disorder characterized by overdistension and destruction of the 

air spaces in the lungs. 

eucaryotic 

Organisms possessing nucleated cells, essentially all organisms except bacteria 

or viruses. 

gneiss 

A variety of rocks with a banded or coarsely foliated structure formed by 

regional metamorphism. 

hydrophobic 

Lacking an affinity for, repelling, or failing to adsorb or absorb water. 

hypoglycemia 

Abnormally low levels of glucose in the blood. 

LC50 

Concentration of any toxic chemical that kills 50 percent of the organisms in a 

test population per unit time. 

lipophilic 

Having an affinity for, attracting, or the ability to adsorb or absorb lipids (fats). 

metabolite 

Any substance involved in or a product of metabolism. 

mysid 

9-2
 
Planktonic shrimp-like crustaceans that carry their young in a pouch; hence, 

the common name "opposum shrimp." 

mysticete 

The baleen whales. 

NOAA 

National Oceanic and Atmospheric Administration 

NOEC 

No observed effect concentration, the highest dosage of a compound 

administered in a toxicity test that does not produce toxic effects. Also called 

no observed effects level, or NOEL. 

nominal concentration 

In chemical or toxicological studies with oil, the concentration of a compound 

expressed as total oil mixed per unit volume water (as opposed to oil 

concentration in the water phase). 

OSC 

Federal On-Scene Coordinator 

OSHTF 

Oil Spill Health Task Force, an interagency group formed to address issues of 

seafood contamination and human health implications during the Exxon 

Valdez oil spill. 

ordered population 

A population is ordered if the elements within the population are ordered in 

magnitude according to some scheme (Scheaffer et al. 1986). 

orogeny 

The process of mountain formation, especially the intense deformation of 

rocks by folding and faulting which, in many mountainous regions, has been 

accompaniedb y invasion of molten rock and volcanic eruption. 

osmoregulatory mechanism 

Any physiological mechanism for the maintenance of an optimal and onstant 

level of osmotic activity of the fluid in and around the cells. 

PAH 

Polycyclic aromatic hydrocarbons 

population or universe 

Refers to the entire collection of measurements about which one wishes to 

draw conclusions (Zar 1984). 

9-3
 
random population 

A population is random if the elements of the population are in random 

order (Scheaffer et al. 1986). 

SSC 

NOAA Scientific Support Coordinator, one of the OSC’s Special Forces 

designated in the National Contingency Plan. 

surfactant 

Surface active agent, a soluble compound that reduces the surface tension of 

liquids, or reduces interfacial tension between two liquids of a solid. 

toxicity 

“The inherent potential or capacity of a material to cause adverse effects in a 

living organism” (Rand and Petrocelli 1985). 

trophic level 

Any of the feeding levels through which the passage of energy through an 

ecosytem proceeds; examples are photosynthetic plants herbivorous animals, 

and microorganisms of decay. 

organoleptic 

The detection of contamination of food items through smell or taste. 

ppm 

Parts per million, a measurement of concentration. Can also be expressed in 

units of weight, for example, as milligrams/kilogram (mg/kg) or 

micrograms/gram (μg/g) 

pinniped 

the group of marine mammals that includes seals, walruses, and sealions. 

tainting 

The development of flavors or odors in foods that are not typical of the food 

itself. 

toxicity index 

The concept of toxicity evaluation in which toxicant concentration and 

toxicant exposure time are considered to be equal factors in resultant toxicity. 

Expressed as a product of the day, as in ppm days or ppm hours. 

zoospore 

Motile, flagellated asexual reproductive cell in protozoans, algae, and fungi. 

9-4
 
10 Appendices
 

Page
 

Case Studies......................................................................................................10-1
 

Santa Barbara Channel......................................................................10-3
 

Arrow..............................................................................................................10-2
 

Exxon Valdez..............................................................................................10-3
 

Texaco Refinery........................................................................................10-5
 
Case Histories
 

Santa Barbara Channel Oil Spill: Spill Summary 

On 28 January 1969, a Union Oil drilling platform offshore of Montecito had a 

blow-out. Oil was released from the well at various rates for several weeks. On 

February 16, Union Oil placed the first steel hood to accumulate the oil. Over 3.3 

million gallons have been estimated to have been released. Nearly 1.3 million 

gallons had come ashore by 8 February, contaminating over 160 km of shoreline. 

There was a period of very heavy rainfall during the spill, with reports by divers 

of oily debris sinking at the fresh water/suspended sediment plume contact with 

salt water. Dispersants were used for over a year, with 25,080 gallons used in 

March 1969. Heavy oil slicks covered large areas of kelp. Straw was widely used 

as a sorbent. 

Lessons learned 

•	 Although large amounts of oil were held in the kelp beds for weeks, the 

oil did not adhere to healthy vegetation. No oil was observed in diving 

surveys beneath the kelp or on the bottom. 

•	 Most of the oil was removed from the beach within months by winter 

storms. 

•	 Some oil was buried on depositional sand beaches, but was removed by 

the following November. 

•	 Oiled straw was much more persistent than oiled sediments. 

•	 It was hypothesized that some oil sank when it came in contact with high 

loads of suspended sediments. 

•	 Impacts to marine mammals were very small; no impacts to whales or 

elephant seals, but some mortality of sea lions which was not proven to be 

related to the spill. 

•	 Large numbers of seabirds were affected, with little success at
 

rehabilitation.
 

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•	 Most surprisingly, very little damage was observed to intertidal organisms 

and no direct impacts to fish (although the commercial fishery was 

impacted). 

References 

Straughan, D. 1971. Biology and bacteriology, Volume 1: Biological and oceanographical survey of the Santa Barbara Channel oil spill 1969-1970. Sea Grant Pub. 

No. 2. Los Angeles: Allan Hancock Foundation, Univ. S. Calif. 426 pp. 

Kolpack, R.L. 1971. Physical, chemical,and geological studies, Volume II: 

Biological and oceanographical survey of the Santa Barbara Channel oil spill 

1969-1970. Sea Grant Pub. No. 2. Los Angeles: Allan Hancock Foundation, Univ. 

S. Calif. 477 pp. 

Arrow Spill, Chedabucto Bay, Nova Scotia: Spill Summary 

The tanker Arrow ran aground on 4 February 1970, spilling about 3 million 

gallons of Bunker C fuel oil. Over 300 km of shoreline were contaminated. 

Storm waves drove the oil into the water column, both during the spill and as 

the oil was eroded off the beaches. This particulate oil persisted for over three 

months, and it was incorporated by copepods into fecal pellets. As much as 10 

percent of the oil in the water column was associated with the copepods, and 7 

percent was found in the fecal pellets. Extensive mechanical cleanup of gravel 

beaches was conducted, including removal of oiled sediments. Impacts to 

intertidal communities were locally severe. In sheltered areas, oiled sediments 

were highly persistent, and, five years later, high levels of oil were found in 

clams but not mussels or algae. Oiled pavements remain in sheltered areas as of 

1991. 

Lessons learned 

•	 Heavy oils can be transferred to bottom sediments via uptake by copepods 

which then pass the oil with fecal material to the bottom. 

•	 Natural removal of oil from high-energy shorelines occurred quickly, 

with only small amounts of tar remaining in sheltered 

microenvironments. 

10-2
 
•	 In sheltered shorelines, asphalt pavements, buried oil layers, and
 

contaminated interstitial water can persist for over twenty years.
 

•	 Removal of oiled gravel can result in increased beach and cliff erosion. 

•	 Long-term impacts to intertidal communities are associated with 

persistent oiled sediments, with lower bivalve recruitment rates, lower 

species diversities, lower shell growth rates for clams, and dieback of 

brown algae still detectable six years after the spill. 

References 

Thomas, M.L.H. 1978. Comparison of oiled and unoiled intertidal communities 

in Chedabucto Bay, Nova Scotia. J. Fish Res. Board Canada, Vol. 30, No. 1, pp. 83-

90. 

Conover, R.J. 1970. Some relations between zooplankton and Bunker C oil in 

Chedabucto Bay following the wreck of the tanker Arrow. J. Fish. Res. Board 

Canada, Vol. 28, pp. 1327-1330. 

Exxon Valdez, Prince William Sound, Alaska 

Summary 

On March 24, 1989, the tanker Exxon Valdez, en route from Valdez, Alaska, to 

Los Angeles, California, grounded on Bligh Reef in Prince William Sound, 

Alaska. Eleven tanks were torn open in the grounding, spilling an estimated 11 

million gallons of Prudhoe Bay crude oil. 

Cleanup operations began almost immediately, and continued at varying levels 

of effort over the next two and a half years (and may not be entirely completed). 

In 1989, the treatments embraced a range of methods that included skimming, 

booming, manual pickup, wiping, and tilling, high-pressure hot-water washing, 

bioremediation, and tests of a number of other mechanical and chemical 

methods. In 1990, manual pickup, berm relocation tilling, and bioremediation 

were the principal methods employed. In 1991, pickup, berm relocation tilling, 

and bioremediation continued at a much reduced group of sites that showed 

evidence of significant oiling. 

In July of 1990, a cooperative interagency research project was begun to evaluate 

the effects of oiling and treatment on the biological communities of the intertidal 

10-3
 
zone, and to study the course of recovery from both. Designed as a long-term 

monitoring effort, the program has continued into 1991 and beyond. Original 

funding sponsors of the project included NOAA, the U.S. EPA, the U.S. Coast 

Guard, and the American Petroleum Institute/Minerals Management Service. 

Exxon USA provided vessel and aircraft logistics in 1990. In 1991, the Marine 

Spill Response Corporation also became a sponsor, while Exxon withdrew 

completely. The intent was to create a long-term monitoring program to track 

recovery and differences in rates of recovery among sites that had received 

different degrees of oiling and treatment, with the ultimate goal of providing 

guidance as to the ecological effects of treatment methods. 

Results of observations 

•	 Significant differences were noted among sites that were a) oiled and hot 

water washed, b) oiled and not hot water washed, and c) unoiled. At sites 

where hot water washing was employed, important representatives of the 

intertidal community were missing or seriously depleted. 

•	 While evidence of bioaccumulation was noted in some intertidal organisms, 

particularly mussels, there was no evidence of biomagnification through the 

food web. 

•	 Although eelgrass studies showed adverse impacts related to oiling in 1990, by 

1991 such differences were not observable. 

•	 By 1991, most areas showed signs of recovery being well underway. However, 

the sites that had experienced the most severe treatments in 1989 were still 

obviously retarded in the extent of recovery noted. In addition, some 

intrusively treated sites that appeared normal from the perspective of algal 

cover showed a severely altered animal community structure relative to less 

harshly treated sites. 

Lessons learned 

•	 High pressure hot water washing can be effective in mobilizing stranded oil 

so that at least some can be recovered from the shoreline. However, the 

temperatures and pressures typically used in such operations result in a wide 

range of adverse biological impacts, from sterilization of the treated intertidal 

zone to movement of oil residues from one zone to another. 

10-4
 
•	 Although negative biological impacts were observed to have resulted from 

both oiling and intrusive shoreline treatment, those attributable to treatment 

predominated. At the most severely treated locations, only minimal signs of 

recovery were evident in fall of 1991. 

•	 However, at most oiled sites, the process of recovery appeared to be well 

underway in 1991. 

•	 Limited evidence suggests that it may be possible to mediate the adverse 

impacts of washing by reducing both temperature and pressure of the water. 

Areas where such judgement was used show lesser degree of impact than 

those where 140° high pressure washing was used. 

•	 It is very important to monitor and document as accurately as possible the 

extent of oiling on shorelines, and the treatments that take place. Lack of 

detailed information on both of these seriously hinder subsequent evaluation 

of recovery. 

•	 If a monitoring program is to be established, it is very important to designate 

areas where no treatment is to take place. However, it may be very difficult to 

obtain consensus on this, particularly in highly visible, heavily utilized, or 

heavily populated areas. 

Texaco Refinery Spill, Fidalgo Bay, Washington 

Summary 

During a tanker offloading operation on February 22, 1991, a shoreside booster 

pump failed at the Texaco March Point refinery. A large piece of the pump 

casing broke and was thrown 90 feet, and North Slope crude oil began pouring 

from the pump. The oil flowed across a field and into a drainage ditch, and 

ultimately oil entered Fidalgo Bay through two culverts. 210,000 gallons of oil 

were estimated to have spilled, with approximately 20-30,000 gallons entering 

Fidalgo Bay. 

Fidalgo Bay is a relatively small and shallow embayment in northern Puget 

Sound near the city of Anacortes, Washington. It is characterized by a broad mud 

flat intertidal area, and large subtidal eelgrass beds. The shoreline surrounding 

Fidalgo Bay, although it includes fringing marsh vegetation, is not exactly a 

10-5
 
pristine environment: much of the area was diked and filled for agricultural 

purposes in the late 1800s and early part of this century, and presently, a state 

highway borders two sides of the bay. 

In an effort to keep the oil from contaminating the extensive eelgrass beds and 

the herring spawn that was associated with it at the time of the spill, the oil that 

was present along the shore was effectively boomed in, preventing it from 

moving into the offshore eelgrass beds but holding it against portions of the 

shoreline and variably contaminating part of the fringing marsh. The spill took 

place during an unusually high tide series and oil reached portions of the 

shoreline only occasionally flooded. 

Skimming operations took place on the water, while on the shoreline, a number 

of different cleanup methods were employed. Some rubble substrate that had 

been oiled was removed and replace with clean substrate, to minimize oil 

exposure to smelt that use the area for spawning. Other areas were hand wiped 

to remove visible oil. Heavily oiled portions of the marsh/shoreline were 

vacuumed using vacuum trucks. Where possible, low pressure ambient 

temperature seawater was used to lift oil in conjuction with vacuuming. Lightly 

oiled areas were raked with pom pom material. Pom pom-type booms were 

strung along the shoreline to capture oil that seeped or was flushed into the 

water. 

In April, in order to evaluate the progress of recovery in the marsh, NOAA 

began a simple program of monitoring the chemistry and biology of the marsh 

area, and sampling visits have continued on a regular basis since then. The 

sampling program has consisted primarily of monthly photographs of a series of 

0.25 m2 quadrats established in oiled and unoiled areas, and chemistry collections 

of marsh sediments. Samples for analysis of below-ground biomass were 

collected during the initial visit and will likely be collected on an annual basis. 

Results of observations 

•	 Chemical analyses of the most heavily impacted portions of the shoreline 

indicated that the weathering of the North Slope crude oil began at a slow rate 

relative to that observed in the initial weeks of the Exxon Valdez spill. 

However, the rate in Fidalgo Bay accelerated significantly during the warm 

months of July and August. 

10-6 
•	 Marsh plants were relatively dormant until June, when noticeable growth 

occurred at both oiled and unoiled sites. Growth continued through 

September. 

•	 Areas with heaviest amounts of oil remaining on the surface showed little or 

no growth of marsh plants. However, areas with moderate amounts of oil 

had steady growth through the growing season. 

•	 Areas that were subjected to the most foot traffic have been among the 

slowest to recover. 

Lessons learned 

•	 Even simple qualitative projects can yield useful insights into how areas 

recover from environmental insults and how treatment can affect the process 

of recovery. 

•	 Removal of spilled oil in marshes resulting in relatively low biological 

impacts is possible under certain circumstances that are related to the physical 

and biological characteristics of the marsh, the intrusiveness of the remedial 

technique, the season of the year, and other considerations. 

•	 Removal of the oil has apparently speeded the recovery of those portions of 

the marsh where it occurred. 

•	 Techniques to minimize the impacts of foot traffic and equipment access 

resulted in significantly lesser adverse effects on the recovery of the marsh. 

•	 However, minimization of impacts required near constant vigilance and 

threat of financial discomfort. 

10-7