Oil Spills in

Coral Reefs

PLANNING & RESPONSE CONSIDERATIONS

U.S. DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration • National Ocean Service • Office of Response and Restoration

NAT OI NAL OCEANIC AND ATMOSPHERIC ADMINISTRAT OI N

U.S. DEPARTMENT OF COMMERCE

July 2010
Cover photo: NOAA. Florida Keys National Marine Sanctuary .

Oil Spills in Coral Reefs: Planning and Response Considerations

Second edition edited by: Ruth A. Yender,1 and Jacqueline Michel2

First edition edited by: Rebecca Z. Hoff1

Contributing Authors: Gary Shigenaka,1 Ruth A. Yender,1 Alan Mearns,1 and Cynthia L. Hunter3

1 NOAA Office of Response and Restoration, 2 Research Planning, Inc., 3 University of Hawaii

U.S. Department of Commerce

National Oceanic and Atmospheric Administration

National Ocean Service

Office of Response and Restoration

July 2010
Oil Spills in Coral Reefs: 

Planning and Response Considerations

Table of Contents

Chapter 1. Coral Reef Ecology 7

Chapter 2. Global And Local Impacts To Coral Reefs 19

Chapter 3. Oil Toxicity To Corals 25

Chapter 4. Response Methods For Coral Reef Areas 37

Chapter 5. Coral Reef Restoration 51

Chapter 6. Coral Case Studies 59

Appendices

Glossary 79

Coral Websites 81

Figures

Figure 1.1. Coral reef types 8

Figure 1.2. Example of a fore reef community and reef zones 9

Figure 4.1. Overview of possible impacts at a vessel accident 38

Tables

Table 1.1. Spawning mode and occurrence in some common corals 12

Table 3.1. Stress responses shown by corals exposed to oil and oil fractions 30

Table 4.1. Laboratory studies of toxicity of chemically dispersed oil to coral 45

Table 4.2. Studies examining impacts of chemically dispersed oil to corals. 46

Table 6.1. Summary of Case Studies and Oil Impacts 77

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Oil Spills in Coral Reefs: Planning and Response Considerations
–5–

Introduction

This guide is intended to serve several functions and several audiences. We hope that 

resource agency personnel and responders of all types working in or planning for response in 

coral reef regions will find useful information here. It is not intended to be a specific guide for 

choosing cleanup methods, as many good versions of these exist already. Rather, we summarize 

current research on coral reefs from the perspective of those who may need to make decisions 

about response in these regions and present the information in an accessible format for people 

with some science or response background. Experienced responders unfamiliar with coral reefs 

may want background on coral ecology and terminology; biologists may want an overview of 

toxicity issues related to coral and response and cleanup applied to coral reefs in particular. We 

have organized the topics by chapters, each of which can be read independently, with additional 

references provided at the end of each chapter.

Chapter 1, on coral reef ecology, introduces pertinent aspects of this unique ecosystem. A 

glossary defines specialized terms. Environmental impacts on coral from anthropogenic and 

natural causes are increasing at rapid rates, so we have summarized these in Chapter 2, to help 

readers understand the background conditions of coral reefs today. Chapter 3, on oil toxicity, is a 

current review of the research available on oil toxicity to coral. We also address how to evaluate 

scientific studies that attempt to measure oil toxicity in laboratories or field settings. In Chapter 4, 

we discuss general guidance for responding to spills in coral reefs and provide specific considerations for open-water cleanup measures. Chapter 5 discusses the emerging science of restoration 

of damaged reefs and presents data on recovery patterns and rates from a variety of impacts in 

coral habitats. Lastly, we have compiled several case studies that illustrate a range of issues—some 

spills seem to have had very little impact on coral while others inflicted severe and long-lasting 

damage on nearshore resources. Some remote spills had long-term impacts to the entire ecosystem. On a more positive note, several cases illustrate new technologies being used to restore coral 

reefs. Each chapter provides additional references and, at the end of the report, we present a list 

of web sites that link to useful data on reefs. This publication is part of NOAA’s Coral Reef Conservation Program designed to protect and restore the nation’s coral reefs and assist conservation of 

reef ecosystems internationally. This program includes efforts to monitor and assess coral health, 

map coral reef ecosystems, conduct research to better understand biological, social and economic 

factors which effect coral reefs, partnerships to reduce the adverse affects of fishing, coastal development and pollution, and identify coral reef areas for special protection.

Introduction
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Oil Spills in Coral Reefs: Planning and Response Considerations

Coral habitat in the Hawaiian Islands (NOAA).
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Chapter 1. Coral Reef Ecology

Chapter 1. Coral Reef Ecology

Key points

•	 There are four major reef types (patch, fringing, barrier, atolls).

•	 Reef-building corals generally require high light, high oxygen, low turbidity, low nutrients,

warm seawater temperature (18–30°C), and open ocean salinity (33–36 parts per thousand;

ppt).

•	 Coral reefs depend on currents for dispersal and accumulation of planktonic spores, larvae and

juveniles.

•	 Thousands of animal and plant species are associated with coral reefs. Coral reefs provide food

and shelter for a wide variety of fish and invertebrates.

•	 Most corals reproduce annually during spawning events that are synchronized by seasonal

seawater temperature changes, lunar cycle, and time of day.

•	 Stony corals have many growth forms, including massive, branching, plate-like, finger-like, and

encrusting; different growth forms may respond to environmental impacts differently.

•	 Growth rates in corals vary among species, with branching corals growing faster than massive

corals.

•	 Predation, competition, diseases, and storms are the primary reason for coral reef death by

natural causes.

•	 Anthropogenic sources of reef mortality include sedimentation, overfishing, and pollution.

•	 Coral reefs are tremendously important economic and natural resources.They protect shorelines and support fisheries, recreation, and tourism.

Types of reefs, geographic distribution, and environmental influences

There are four major reef types (Figure 1.1):

patch reefs – small, isolated formations

fringing (or apron) reefs – reefs directly bordering shorelines

barrier reefs – former fringing reefs separated from the shoreline by a lagoon

atolls – former fringing reefs encircling submerged volcanic islands

Reef communities are reefs in the earliest developmental stages where structural accretion 

has either not yet occurred or is being continually interrupted by environmental disturbance.

Coral communities also occur in areas where conditions are not conducive to reef development, 
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Oil Spills in Coral Reefs: Planning and Response Considerations

but where reef coral species can survive.Zones in each reef type (Figure 1.2) are defined by their

depth and wave exposure. Coralline algae and occasional encrusting or low-profile corals dominate the reef crest at 0–2 meters (m) deep, the area of highest wave energy.

Seaward of and below

the reef crest, the fore reef consists of buttresses and channels (spurs and grooves) that dissipate

wave forces and allow for offshore transport of reef material.The fore reef zone (~2–10 m deep)

generally supports the highest coral diversity and coverage. The outermost and deepest zone 

is the reef slope, descending from the fore reef to the lower depth limits of coral development 

Figure 1.1. Coral reef types, including atoll, fringing, barrier and patch reefs

Fringing Reefs

Barrier Reefs

Atolls

Reef crest

L a g o o n

Patch reef

Reef slope

Reef flat
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Chapter 1. Coral Reef Ecology

(~100 m).Protected from heavy wave action, reef flat and back reef zones are calmer environments that support growth of coral, algae, and seagrass communities. The greatest reef development occurs on the leeward, protected sides of islands or atolls, where there is less erosion from 

wave action.

Reefs may begin on pre-existing subsea platforms, such as volcanoes or shoal banks, but 

become coral reefs by continuous buildup of the remains of bottom-dwelling marine animals and 

plants that grow in shallow tropical and sub-tropical environments. Calcium carbonate from skeletons and sediments accumulate at up to a few centimeters each year, over thousands of years, 

Figure 1.2. Example of a fore reef community and reef zones, including fore reef, reef flat and back reef
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Oil Spills in Coral Reefs: Planning and Response Considerations

to form reefs. These reefs provide habitat for some of the most biologically diverse ecosystems on 

Earth.

Reef-building corals require high light, high oxygen, low turbidity, low nutrients, warm seawater (18–30°C), and open ocean salinity (33–36 ppt).

Exceptions generally represent sub-optimal

conditions. For example, reef-building corals in Hawai’i have been reported living under very low 

light conditions more than 150 m deep. Corals may survive short periods of stress during extreme 

low tides, periodic flooding with fresh water, and suspended sediments by retracting polyps and 

increasing mucus production. Corals may even recover from stress-induced bleaching by gradually replenishing zooxanthellae in their tissues. The metabolic costs of survival under stressful 

conditions decrease growth and reproductive potential.

The rotation of the earth and the Coriolis effect generate major ocean currents.These currents

move clockwise in the Northern Hemisphere and counter-clockwise in the Southern Hemisphere.

Equatorial currents and counter-currents, and dominant northerly and southerly flows mix and 

disperse larvae across geographic areas within ocean basins. Wind and tide-driven currents exert 

more local effects on water movement and dispersal.

Coral reefs depend on currents to bring food and nutrients, and to disperse and accumulate 

planktonic spores, larvae, and juveniles that recruit to and replenish populations and species.Periodic changes in prevailing currents (e.g., during El Niño-Southern Oscillation events) may interrupt

normal processes, but may also bring recruits from populations that are normally downstream of a 

particular reef area.

Reef biodiversity

Thousands of animal and plant species are associated with coral reefs. Scleractinian corals are 

the dominant structural reef-builders on most reefs. However, many species of algae and other 

organisms, like snails, oysters, clams, worms, and sponges, produce calcium carbonate skeletons.

When these skeletons accumulate in the interstices of the reef, they cement the structure together 

over time. Relatives of scleractinian corals are the gorgonians—octocorals such as sea fans, sea 

plumes, sea whips, and leather corals. Referred to collectively as “soft corals,” octocorals either lack 

a skeleton or produce a reduced, flexible skeleton. Sea anemones are other coral relatives, commonly found on reefs in a variety of sizes and habitats. Yet another coral relative are the zoanthids, 

commonly found atop reef flats or in the intertidal zone.

Coral reefs provide food and shelter to a wide range of fish and invertebrates, including crustaceans (crabs, lobsters, shrimp), echinoderms (sea urchins, sea cucumbers, brittle stars, crinoids),

boring, encrusting, and upright sponges, molluscs (bivalves, snails, octopus, nudibranches), and

worms belonging to dozens of phyla. Fish range from the smallest gobies to 2 m-long groupers or 
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Chapter 1. Coral Reef Ecology

sharks. Sea turtles shelter in reef overhangs and forage for sponges and other food items; manatees feed in reef-associated seagrass beds.

Associated habitats: seagrasses and mangroves

Seagrass beds are often found in sandy patches in back reef and reef flat environments. Their 

root systems stabilize sediments and their high primary productivity supports detritus-based food 

webs important to omnivorous reef organisms. Closer to shore, mangroves protect nursery areas 

for juvenile reef fish, crustaceans, and molluscs.They also serve as filtration systems for coastal

runoff and protect shorelines from erosion. In Hawai’i, however, mangroves were introduced in the 

early 1900s and have spread rapidly among the main islands. Many people feel that in Hawai’i they 

are a weedy pest species because they have altered and now dominate many coastal areas.

Coral physiology 

An individual coral, or polyp, is a sac-shaped organism with a central mouth surrounded by 

a ring of tentacles.Like their cnidarian relatives—sea anemones, jellyfish, and hydroids—corals

have a simple body plan consisting of only two tissue layers: ectoderm and gastroderm. In corals, 

the ectoderm secretes a calcium carbonate cup (corallite) into which the polyp may retract.Polyp

sizes vary from <1 mm to many centimeters in diameter. Although some coral species consist only 

of single polyps, most corals form colonies consisting of thousands of interconnected polyps. All 

polyps in a colony are genetically identical (clones) because they all budded from the original

founding individual.

Corals may be carnivorous, capturing small prey that become trapped on their mucus-covered surfaces or entangled by specialized stinging cells on the tentacles. They absorb dissolved 

organic materials from surrounding waters and also produce their own food. Tiny, single-celled 

algae called zooxanthellae live within the coral cells and generate energy-rich compounds 

through photosynthesis.This“food”is translocated to the coral host, providing the majority of its

energy and carbon requirements. The key to the ecological success of reef-building corals, this 

symbiotic relationship requires adequate, but not excessive, sunlight for the algae to be productive through photosynthesis.

Corals are sedentary marine animals with no specialized organs or sensory systems. Instead, 

corals use passive diffusion through their thin living tissues to obtain oxygen and expel waste 

products. They produce mucus for protection and to clear fine debris from tissue surfaces. A diffuse nerve network connects polyps within a colony and allows response to physical and chemical 

stimuli.
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Oil Spills in Coral Reefs: Planning and Response Considerations

Coral reproduction

Corals reproduce sexually and asexually using a wide repertoire of strategies. For example, 

gametes (eggs and sperm) are produced within the mesenteries that partition the coral polyp.A

coral may be either male or female (gonochoric), or hermaphroditic, with a mixture of male and

female polyps within a colony or with male and female gonads within a single polyp. In further 

evidence of their reproductive flexibility, some polyps or entire colonies may change sex from year 

to year.

Gametes may be released (broadcast) into the surrounding seawater to fertilize or, in some

instances, eggs are retained and fertilized in the polyp where they are brooded until they have 

developed into larvae called planulae. Coral eggs may contain maternally inherited zooxanthellae 

at the time of their release, or they may acquire them from the environment before or soon after 

settlement.Planulae swim weakly using cilia (hair-like motor appendages).Ocean currents transport planulae for several days, weeks, or even months before settlement. This planktonic dispersal 

of larvae may seed reefs far from the parent colonies.

Most corals reproduce annually during spawning events that are synchronized by seawater 

temperature changes, lunar cycle, and time of day. Mass spawning events in which most corals 

release gametes over a few nights occur in many reefs (e.g., Flower Garden Banks, Tortugas, the

Great Barrier Reef), while in other regions, different coral species spawn at different seasons, moon

phases, or times.Because eggs are generally lipid-rich and positively buoyant, whole slicks of

gametes are often seen at the surface during and after spawning events.

Table 1.1. Spawning mode and occurrence in some common corals are shown below (G=gonochoric, H=hermaphroditic, S=broadcast spawner, B=brooder)

Hawaii Sex Mode Month Lunar Phase Time

Porites compressa G S Jun–Sep full 2300

Porites lobata G S Jun–Aug full varies

Fungia scutaria G S Jun–Nov full 1700

Pocillopora meandrina H S Apr–Jun full 0730

Pocillopora damicornis H B all all varies

Montipora dilitata H S Jun–Aug varies 2200

Montipora capitata H S May–Sep new 2100

Florida Sex Mode Month Lunar Phase Time

Porites porites G/H B Nov–Feb — —

Montastrea annularis H S Aug–Sep — 2200

Montastrea cavernosa H S Aug–Sep — 2100

Montastrea faveolata H S Aug–Sep — 2000

Acropora palmata H S Aug — 2300
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Chapter 1. Coral Reef Ecology

Corals commonly reproduce both asexually and sexually. Fragments of colonies broken by 

wave action or buds produced by individual polyps may re-cement and survive independently on 

the reef.Thus, numerous colonies on a reef may represent clones of single individuals.Branching

growth forms are more prone to fragmentation than are encrusting or massive species. There are 

often significant geographical differences in how well a species can reproduce from fragments, 

and these may be exacerbated by other environmental factors like water quality.

Growth and longevity

Corals grow at different rates depending on the morphology of the colony and the environmental conditions.

Branching species with linear extension rates of up to 20 cm/year grow faster

than massive colonies (~1 cm/year);species with dense skeletons grow slower than more fragile

species. Colonies living in areas where high wave energy abrades and breaks coral show more 

compact or encrusting growth forms than their relatives living in calmer locations.

Some species of corals (e.g., Pocillopora meandrina, many Acropora spp.) grow to a specific size

(~50 cm, 10–15 years for P. meandrina) and die.Other corals (e.g., massive Porites and Montastrea)

appear to be able to survive and grow indefinitely. Colonies of Porites evermanni near Kealakekua 

on the island of Hawai’i are over 20 m in diameter and were large when Captain Cook sailed 

into the Hawaiian Islands more than 200 years ago. Thus, colonies of some coral species may be 

extremely long lived. However, the longevity of individual polyps in massive Porites is on the order 

of 5–7 years as determined by growth tracks in skeletal sections.

Species diversity

The degree of coral biodiversity varies geographically, ecologically, historically, and geologically. The number of coral species on Florida and Hawaiian reefs is similar at 45 and 52 species, 

respectively. However, there are more than 70 reef-building coral species in the Caribbean; counting deepwater and non-reef-builders brings this number to well over 100. In the main Hawaiian 

Islands, there are an additional 29 non-reef building deepwater species, and at least 10 other species are found in the Northwest Hawaiian Islands that do not occur on main island reefs.

Soft corals, sea whips, and sea fans (octocorals), and massive colonies of star coral (Montastrea 

spp.) and brain coral (Colpophyllia natans) dominate reefs in Florida and the Caribbean.Before

bleaching and disease outbreaks of the 1980s–1990s, thickets of elkhorn (Acropora palmata) and

staghorn (A. cervicornis) corals were common shallow-reef species but have now been largely

replaced in some areas by lettuce coral, Agaricia spp. Massive Porites (P. lobata and P. evermanni),
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Oil Spills in Coral Reefs: Planning and Response Considerations

branching Porites (P. compressa), encrusting (Montipora spp.), and cauliflower and lace coral (Pocillopora meandrina and P. damicornis) dominate Hawaiian reefs.

Geographic variability 

Very different assemblages of dominant organisms characterize Atlantic/Caribbean and

Pacific reefs. Associated habitats are quite different as well: while seagrass beds and mangroves 

are common and important components of Atlantic/Caribbean coastal ecosystems, they are generally much less abundant on Pacific island.

For example, Hawai’i has just two species of seagrass

that, while important as sediment stabilizers and as food items for sea turtles, are very small plants 

with blades less than 2 cm long. In contrast, seagrasses in Florida and elsewhere have large morphology and diverse community structure with three primary species.

Another important distinction between Florida and Pacific island reefs is in their continental 

vs. oceanic derivation. While seagrass beds and reef communities extend in relatively shallow 

water for many kilometers from Florida shorelines, Pacific island reef slopes drop steeply from 

nearshore to hundreds of meters down in fairly short linear distances. One result of this is a much 

higher level of species uniqueness seen on Pacific Island reefs. Hawai’i has among the highest 

endemism rates for coral reef organisms in the world with roughly 25% of all the animals seen on 

Hawaiian reefs being unique to Hawai’i.

Mortality, disease, and physical impacts

Corals can die from any number of causes. Predators include both fish and invertebrate feeders. On Atlantic and Caribbean reefs, parrotfish, damselfish, coral-eating snails, and fireworms are 

primary coral predators. In the Pacific, parrotfish, blennies, damselfish, butterflyfish, and puffers 

are major fish predators on corals;the Crown-of-Thorns seastar (Acanthaster planci) occasionally

undergoes sudden population expansions that can inflict significant damage to corals. Competition for space with algae, sponges, and other sedentary, benthic organisms may result in partial or 

complete coral mortality. Regional losses of significant herbivorous grazers like the urchin Diadema are thought to significantly impact competition for coral settlement and recruitment.

Diseases that affect corals include relatively recent and devastating outbreaks of White (WBD)

and Black Band Disease (BBD) and others (aspergillosis,“white pox,”“white plague,”“yellow band”),

particularly in Florida and the Caribbean.WBD affects only acroporid corals, while BBD has been

reported from six scleractinian species; “white plague Type II” has been reported from 17 coral species in the Florida Keys.

WBD and BBD are generally infrequent and sporadic on reefs at one point
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Chapter 1. Coral Reef Ecology

in time, with some corals affected while adjacent colonies are not, but cumulative tissue loss of up

to several millimeters per day may kill many relatively slow-growing coral species.

Though the source of most coral diseases is largely unknown, some progress has been made.

The major component of BBD is Phormidium corallyticum, a photosynthetic cyanobacterium. Here, 

coral tissue is killed by lack of oxygen and exposure to hydrogen sulfide produced by the bacterium and associated microorganisms.

BBD is more common on reefs subject to sedimentation,

high nutrients, and elevated seawater temperatures. Aspergillosis, a disease that causes tissue 

death and disintegration of the axial skeleton of sea fans, is caused by an organism similar to the 

terrestrial fungus, Aspergillus sydowi, which some researchers believe may arise from spores and 

iron enrichment borne by dust transported via the jet stream from Saharan Africa.

Storms and high wave energy abrade, break, and bury shallow-water colonies as well as those 

downslope. Storm-associated sediment runoff and freshwater flooding may also smother or kill 

corals, particularly those in shallow and nearshore waters. Most corals live within a few degrees 

of their upper temperature tolerance range. Recent instances of elevated seawater temperatures 

have killed large number of corals, sometimes more than 100 m deep. Such mortality is preceded 

by a rapid loss of the pigmented symbiotic zooxanthellae from the corals, a stress response known 

as coral bleaching.

Human uses

Coral reefs are tremendously important economic resources, protecting shorelines and supporting numerous recreational activities, tourism, and fisheries. In Hawai’i, reef-related tourism 

activities bring an estimated $800 million annually and employ over 7,000 people. Tourism-related 

services contribute $1.2 billion to the Florida Keys economy every year. Legal decisions aimed at 

recovering costs for damage to reef areas have valued reef areas at as much as $2,833 per square 

meter, based solely on costs of restoration and lost tourism revenues.

Recreational and commercial fishing annually bring many more millions of dollars to Hawai’i, 

Florida, and other islands or regions with viable reef resources. Subsistence and commercial food 

harvest from reefs include fish, octopus, lobster, and crab. The U.S. Coral Reef Task Force estimates that the annual value of reef-dependent commercial and recreational U.S. fisheries is over 

$200 million. A large, growing aquarium trade also depends on reef species; based on collection 

reports, over 420,000 aquarium fish were exported from Hawai’i alone in 1995, and this number is 

believed to be substantially underestimated.
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Oil Spills in Coral Reefs: Planning and Response Considerations

For further reading

Antonius, A. 1985. Coral diseases in the Indo-Pacific: a first record. Marine Ecology 6:197–218.

Babcock, R.and A.Heyward.1986.Larval development of certain gamete-spawning scleractinian

corals. Coral Reefs 5:111–116.

Barnes, R.and E.Ruppert.1994.Invertebrate Zoology. New York: Saunders College Publishing.

1089 pp.

Birkeland, C.1997.Life and Death of Coral Reefs. Norwell, Massachusetts: Kluwer Academic Publishers. 536 pp.

Clark, A. and D. Gulko. 1999. Hawai’i’s State of the Reefs, 1998. Honolulu: State of Hawaii Department of Land and Natural Resources.

Darke, W.and D.Barnes.1993.Growth trajectories of corallites and ages of polyps in massive

colonies of reef-building corals of the genus Porites. Marine Biology 117:321–6.

Davies, P. S. 1984. The role of zooxanthellae in the nutritive energy requirements of Pocillopora 

eydouxi. Coral Reefs 2:

181–186.

Dubinsky, Z. 1990. Ecosystems of the World: Coral Reefs. New York: Elsevier. 525 pp.

Edmunds, P. 1991. Extent and effect of black band disease on a Caribbean reef. Coral Reefs 10:

161–165.

Glynn, P. 1991. Coral reef bleaching in the 1980’s and possible connections with global warming.

Trends in Ecological Evolution 6:175–179.

Grigg, R. 1988. Paleoceanography of coral reefs in the Hawaiian-Emperor chain. Science 240:

1737–1743.

Gulko, D. 1998. Hawaiian Coral Reef Ecology. Honolulu: Mutual Publishing. 245 pp.

Hayes, R. and N. Goreau. 1998. The significance of emerging diseases in the tropical coral reef ecosystem. Revista de Biología Tropical 46:

173–185.

Humann, P. 1993. Reef Coral Identification: Florida-Caribbean-Bahamas. Jacksonville: New World 

Publications. 239 pp.

Jokiel, P. 1980. Solar ultraviolet radiation and coral reef epifauna. Science 207:1069–1071.

Jokiel, P., C. Hunter, S. Taguchi, and L. Watarai. 1993. Ecological impact of a freshwater reef “kill” in 

Kaneohe Bay, Oahu, Hawaii.Coral Reefs 12:177–185.

Kolinski, S. and E. Cox. 2003. An update on modes and timing of gamete and planula release in 

Hawaiian scleractinian corals with implications for conservation and management. Pacific Science 

57:17–27.
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Chapter 1. Coral Reef Ecology

Kuta, K. and L. Richardson. 1996. Abundance and distribution of black band disease in the northern Florida keys. Coral Reefs 15:

219–223.

Maragos, J. 1977. Order Scleractinia. Reef and Shore Fauna of Hawaii: Section I. ProtozoaCtenophora.

In:Devaney, D.and L.G.Eldredge (eds.), Reef and Shore Fauna of Hawaii, B.P.Bishop

Museum Press, Honolulu.pp.158–241.

McDermid, K., M. Gregoritza, and D. Freshwater. 2002. A new record of a second seagrass species 

from the Hawaiian archipelago: Halophila decipiens Ostenfeld. Aquatic Botany 74:257–262.

Peters, E. 1993. Diseases of other invertebrate phyla: Porifera, Cnidaria, Ctenophora, Annelida, 

Echinodermata.Pathology of Marine and Estuarine Organisms.Couch and Fournie (eds.), Diseases 

of other invertebrate phyla: Porifera, Cnidaria, Ctenophora, Annelida, Echinodermata. Pathology of 

Marine and Estuarine Organisms, CRC Press, Boca Raton, Florida.

Richardson, L., W. Goldberg, R. Carlton, and J. Halas. 1998. Coral disease outbreak in the Florida 

Keys: Plague Type II. Revista de Biología Tropical 46:187–198.

Richmond, R. and C. Hunter. 1990. Reproduction and recruitment of corals: comparisons among 

the Caribbean, the Tropical Pacific and the Red Sea. Marine Ecology Progress Series 60:185–203.

Santavy, D. and E. Peters. 1997. Microbial pests: coral diseases in the Western Atlantic. Proceedings 

8th International Coral Reef Symposium 1:

607–612.

Tissot, B.N.and L.E.Hallacher.2003.Effects of aquarium collectors on coral reef fishes in Kona,

Hawaii. Conservation Biology 17:1759–1768.

Mangrove forest in the Florida Keys National Marine Sanctuary (NOAA OR&R)
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Oil Spills in Coral Reefs: Planning and Response Considerations

Close-up of bleached fire coral after oiling during the Bahía las Minas spill 

in Panama (Arcadio Rodaniche)
–19–

Chapter 2. Global And Local Impacts To Coral Reefs

Chapter 2. Global And Local Impacts To Coral Reefs

Key points

•	 Coral reefs worldwide are under stress from a variety of global and local impacts.

•	 High sea surface temperatures bleach coral.

•	 Bleaching may cause little to nearly 100% mortality, depending on its severity.

•	 Overfishing is pervasive on many coral reefs and may contribute to ecosystem shifts.

•	 Increased sedimentation may slow coral growth and affect reproduction.

•	 Coral reefs recover from damage caused by tropical storms in varying time frames.

The effects of spill response operations in coral reef environments must be viewed as one of 

many anthropogenic and natural impacts that affect corals worldwide. These include both global 

impacts, such as sea surface warming and increasing levels of carbon dioxide, and local impacts 

such as land-based pollutants, sedimentation, overfishing, and physical disturbances.

Alarming trends in reef degradation have been noted since the late 1970s: live coral cover 

has significantly decreased and there have been major changes in coral species composition.

Researchers have identified specific causes for many of these phenomena, such as the link 

between rising sea surface temperatures and coral bleaching. Since multiple impacts have a 

compounding effect on coral reef habitats, we need to understand the background health of reefs 

when assessing another impact, like an oil spill and its associated response activities.

Global warming impacts and bleaching 

Global warming detrimentally impacts coral in several ways. Levels of atmospheric carbon 

dioxide are increasing, causing rises in sea surface temperature (SST), and this, in turn, increases

the frequency and severity of coral bleaching. Levels of carbon dioxide are also increasing in seawater, resulting in weaker coral skeletons, reduced coral extension (growth) rates, and an increased

susceptibility to erosion on reefs. Global warming is also linked to greater frequencies of severe 

storms, which are a major cause of physical damage to reefs.

Coral bleaching is defined as the loss of the zooxanthellae that live symbiotically in the coral 

polyps.Bleaching occurs naturally and is related to various stressors, including increased or

decreased light, reduced salinity, and temperature changes. Recent widespread “mass bleaching” 

events are thought to be a relatively new phenomenon.There have been eight major bleaching

events worldwide since 1979; the most severe to date destroyed an estimated 16% of the world’s 
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Oil Spills in Coral Reefs: Planning and Response Considerations

coral reefs in 1998. Hardest hit were reefs in the Indian Ocean, Southeast Asia, and the far western 

Pacific.

Elevated SST is the major cause of mass bleaching in coral.In 1998, NOAA’s“HotSpot”program accurately predicted bleaching based on recorded SST for most geographic regions. The 

NOAA NESDIS website provides current readings of SST worldwide (Appendix 2).

Bleaching can kill or otherwise damage coral, depending on the severity and duration of the

temperature increase and the sensitivity of the individual coral species. Corals can survive mild 

bleaching, as zooxanthellae have some ability to recover, but severe bleaching may kill nearly all 

the corals affected. Corals that withstand bleaching still suffer reproductive impairment, slowed 

growth, and decreased ability to calcify and repair themselves. These impacts persist even when 

coral recover their zooxanthellae after bleaching.

Overfishing and other ecosystem disturbances

Heavy fishing has both decreased biodiversity and shifted the ecosystem structure of fish and 

reef communities. Overfishing has been implicated in ecosystem-wide disturbances on coral reefs, 

often with other effects such as disease or pollution. In Jamaica, a combination of overfishing 

and disease removed fish and urchin herbivores from the reef habitat, resulting in proliferation of 

fleshy algae and up to 90% decreases in coral cover. Destructive fishing practices, such as the use 

of dynamite and poisons, common in some areas of the Pacific, directly damage and kill coral.

Overfishing is widespread on coral reefs, even in areas previously considered undisturbed, 

according to 1997 worldwide reef surveys. This study found a widespread lack of top predators 

(often the target species for fishing) in most areas surveyed.Few reefs were without anthropogenic impacts, even though most reefs surveyed were far from population centers or known pollution sources.

Outbreaks of the coral-eating Crown of Thorns starfish have damaged many reefs in the IndoPacific region, including the Australian Great Barrier Reef.

We don’t know why these outbreaks

occur, but theories include possible connections to nutrient runoff and to the removal of starfish 

predators.

Sedimentation and nutrient enrichment

Increased sedimentation is stressful to corals because it reduces the ambient light available 

for photosynthesis, clogs coral polyps and, in large quantities, can smother or bury entire coral 

colonies. Sedimentation can result from poor land use practices, such as logging, coastal develop-
–21–

Chapter 2. Global And Local Impacts To Coral Reefs

ment, dredging, and from tropical storms. Ship groundings, which destroy reef structures, also 

create coral rubble and subsequent increases in sedimentary material.

Chronic input of nutrients to coral reef ecosystems can increase plankton and algal growth, 

especially in enclosed lagoons.Kaneohe Bay, Hawai’i was one of the first documented cases of

domestic sewage pollution contributing to an overgrowth of corals by algae. Increased plankton growth increases turbidity and lowers light levels, impeding coral growth and reproduction.

Chronic inputs of sewage and agricultural runoff can also reduce biodiversity on impacted reefs, 

and may favor the growth of fleshy algae.When combined with reduced grazing (which may be

caused by fishing or disease), fleshy algal growth takes over areas previously covered by coral.

Corals vary widely in their tolerances to nutrients, salinity, and sedimentation. Nearshore reefs 

on shallow continental shelves are more likely to experience fluctuations in these parameters, and 

corals habituated to these environments tend to tolerate such fluctuations better than do oceanic 

species. However, when salinity or sedimentation changes faster or more frequently than usual 

(from increased frequency of storms or freshwater runoff, for example), even tolerant species may

not be able to adapt.

Invasive species

In isolated coral reef environments, the introduction of an alien species (fish, invertebrate,

or algae) can devastate the reef ecosystem.Introductions can occur through marine debris, ship

groundings, ballast water, scientific research, and poor management strategies. On the island of 

O’ahu, some 19 species of algae have been introduced since 1950. At least four of these species 

successfully over-grow living coral. Alien sponges have also been observed overgrowing coral.

Moreover, introduced fish may completely shift feeding guild assemblages on reefs. Areas with 

endemic species populations, such as Hawai’i and the Galapagos Islands, are at high risk from alien 

species introductions.

Physical disturbances

Tropical storms periodically hammer coral reefs. Whether hurricanes, cyclones, or typhoons, 

these storms can cause varying degrees of physical damage to reef structures and associated 

organisms, especially those in shallow waters.Storms exacerbate other injuries, such as bleaching, impacts from coastal construction, anchoring, or grounding. With no compounding impacts 

(bleaching, disease outbreaks), reef environments rely on natural recruitment mechanisms to

recover, though this may take decades.
–22–

Oil Spills in Coral Reefs: Planning and Response Considerations

Physical disturbances to nearshore reefs from coastal construction (shading from piers, filling,

etc.) also cause permanent reef destruction.Structural damages from anchors and ship groundings will be discussed in Chapter 5.

Cumulative impacts

Coral reefs, like most ecosystems, are inherently resilient to naturally occurring impacts and 

can recover over varying time frames. For example, some coral fragments broken off during hurricanes regrow vegetatively and recolonize adjacent areas.

However, repeated impacts in rapid

sequence or too many major impacts over a short period of time can reduce an ecosystem’s ability to recover. Severe impacts may set in motion species shifts that cause long-term ecosystem 

changes.A recent case study in Belize showed that the combined impacts from severe bleaching followed by physical damage from Hurricane Mitch reduced coral recruitment substantially 

compared with areas that sustained only hurricane damage. Reefs recovering from bleaching may 

be more susceptible to disease, or more sensitive to toxic impacts from oil or other pollutants.

Current evidence shows that nearly all coral reefs are under stress. An additional stress, like an oil 

spill and associated response operations, would thus tend to have a greater impact than if it had 

occurred in a healthy, more pristine system.

In May of 2006, the National Marine Fisheries Service (NMFS), published a final rule to list elkhorn coral (Acropora palmata) and staghorn coral (A. cervicornis) as threatened species under the

Endangered Species Act (ESA) of 1973. This listing was based on a determination that both corals

were in danger of extinction from a combination of factors throughout all or a significant portion 

of their U.S. range, in the foreseeable future.

When NOAA Fisheries Service lists a species as threatened under the ESA, it must propose and 

publish a special rule to issue protective regulations and exceptions to provide for the conservation of threatened species. These may include measures to enact certain protections, including the 

prohibition for anyone under the jurisdiction of the United States to“take”the coral species (with

certain exceptions for scientific research, enhancement, or restoration activities).

The International Union for Conservation of Nature and Natural Resources (IUCN) Red List of

Threatened Species is a comprehensive, global approach for evaluating the conservation status of 

plant and animal species. The list serves as a reference to guide conservation activities of governments, non-governmental organizations and scientific institutions. Prior to 2007, only a single 

coral species was "red-listed" by IUCN as threatened (i.e., classified as vulnerable, endangered, or

critically endangered). In 2007, the number of species increased to 4; but in 2008, the total number

of designated threatened species jumped to 235 (IUCN, 2010).
–23–

Chapter 2. Global And Local Impacts To Coral Reefs

There are at least two important implications for oil spill response from designations of this 

type: In the U.S., listing under the ESA confers a higher resources at risk status to the potentially 

affected species, and requires special consultation by response personnel with trustee representatives; and more broadly, determination of threatened status suggests that the potentially affected 

species are already subjected to stresses that likely affect sensitivity to oil exposure and/or cleanup

impacts.

For further reading

Gulko, D., J.E.Maragos, A.M.Friedlander, C.L.Hunter, and R.E.Brainard.2000.The status of

coral reefs in the Hawaiian archipelago. In: Status of Coral Reefs of the World: 2000. C. Wilkinson, Ed.

Australian Institute of Marine Science, Dampier, Western Australia, pp.219–238.

Hodgson, G. 1999. A global assessment of human effects on coral reefs. Marine Pollution Bulletin 

38:345–355.

Hoegh-Guldberg, O. 1999. Climate change, coral bleaching and the future of the world’s coral 

reefs. Marine Freshwater Research 50:839–866.

Hughes, T. P. 1994. Catastrophes, phase shifts, and large-scale degradation of a Caribbean coral 

reef. Science 265:1547–1551.

Kleypas, J.A., R.W.Buddemeier, D.Archer, J.Gattuso, C.Langdon, and B.N.Opdyke.1999.

Geochemical consequences of increased atmospheric carbon dioxide on coral reefs. Science 284:

118–120.

IUCN. 2010. www.iucnredlist.org/documents/.../2010_1RL_Stats_Table_1.pdf

Mumby, P.J.1999.Bleaching and hurricane disturbances to populations of coral recruits in Belize.

Marine Ecological Progress Series 190:27–35.

NOAA, National Marine Fisheries Service. 2006. Endangered and Threatened Species: Final Listing 

Determinations for Elkhorn Coral and Staghorn Coral. Federal Register / Vol. 71, No. 89 / Tuesday,

May 9, 2006, 26852-26861.

NOAA, National Marine Fisheries Service. 2007. Threatened elkhorn & staghorn corals and the 

Endangered Species Act (ESA): Frequently asked questions. 2 pp.

NOAA’s website for coral bleaching hotspots:http://psbsgi1.nesdis.noaa.gov:8080/PSB/EPS/SST/

climohot.html.

Paine, R. T., M. J. Tegner, and E. A. Johnson. 1998. Compounded perturbations yield ecological 

surprises. Ecosystems 1:535–545.

Roberts, C. M. 1995. Effects of fishing on the ecosystem structure of coral reefs. Conservation Biology 9:

988–995.
–24–

Oil Spills in Coral Reefs: Planning and Response Considerations

Russ, G. R. and L. J. McCook. 1999. Potential effects of a cyclone on benthic algal production and 

yield to grazers on coral reefs across the central Great Barrier Reef.Journal of Experimental Marine 

Biology and Ecology 235:

237–254.

Tomascik, T. and F. Sander. 1987. Effects of eutrophication on reef-building corals III. Reproduction of the reef-building coral Porites porites. Marine Biology 94:

77–94.

White, A. T. and H. P. Vogt. 2000. Philippine coral reefs under threat: lessons learned after 25 years 

of community-based reef conservation. Marine Pollution Bulletin 40:537–550.

Wilkinson, C. R. 1999. Global and local threats to coral reef functioning and existence: review and 

predictions. Marine Freshwater Research 50:867–78.

Wilkinson, C.2000.Status of Coral Reefs of the World:2000 (Online).Available:Global Coral Reef

monitoring network, http://www.icirforum.org (11/28/00).

Diver studying coral growth as part of TROPICS study (Research Planning Inc.)
–25–

Chapter 3. Oil Toxicity To Corals 

Chapter 3. Oil Toxicity To Corals 

Key points

•	 Spill impacts vary in severity with the specific conditions at a given spill, including oil type and

quantity, species composition, and the nature of oil exposure.

•	 Oil can kill corals, depending on species and exposure.

•	 Longer exposure to lower levels of oil may kill corals as well as shorter exposure to higher concentrations.

•	 Chronic oil toxicity impedes coral reproduction, growth, behavior, and development.

•	 The time of year when a spill happens is critical, since coral reproduction and early life stages

are particularly sensitive to oil.

•	 Branching corals are more sensitive to oil impacts than are massive or plate-like corals.

•	 Laboratory toxicity studies should mimic actual spill conditions to the extent possible.

Introduction

Evaluation of oil toxicity is not an easy task, since each spill presents a unique set of physical, 

chemical, and biological conditions. The term “oil” includes substances that are chemically very different, ranging from highly toxic and volatile refined products, to less acutely toxic but persistent, 

heavier fuel oils. Different species and life stages within a species have varying sensitivities and 

thus may respond very differently to oil exposure.

Exposure pathways

How corals are exposed to oil bears directly on how serious the impact will be. There are three 

primary modes of exposure for coral reefs in oil spills.In some areas (especially the Indo-Pacific),

direct contact is possible when surface oil is deposited on intertidal corals. Presuming that some 

portion of spilled oil will enter the water column either as a dissolved fraction or suspended in 

small droplets, this potential exposure pathway must be considered in most cases. Subsurface oil 

is a possibility in some spills, particularly if the spilled product is heavy, with a density approaching 

or exceeding that of seawater, and if conditions permit oil to mix with sediment material to further 

increase density.
–26–

Oil Spills in Coral Reefs: Planning and Response Considerations

Evaluation of risk based on exposure pathway is a complex calculus that is highly spill-dependent. Relevant questions that feed into the determination are linked to the considerations above 

and include:

•	 Are corals in the affected area intertidal?

•	 At what depths do the subtidal corals occur?

•	 Does this spilled oil have a component of lighter, more water-soluble compounds?

•	 Will sea conditions mix oil on the surface into the water column?

•	 Is there a heavier component to the oil that raises the possibility of a density increase through

weathering and association with sediment that could sink the oil to the bottom?

•	 Will residual oil on adjacent shorelines (e.g., mangrove forests) provide a source of chronic oil

exposure?

Areas with intertidal corals could be considered at greatest risk in a spill because of the 

increased potential for direct contact with a relatively fresh oil slick. Regardless of differences in 

susceptibility by species or physical form, direct oil contact is most likely to result in acute impact 

because in this kind of exposure scenario the oil is fresher, with a greater proportion of more toxic 

lighter aromatic hydrocarbons.

Water column exposure

Coral exposure via the water column can be a serious route under some circumstances.

Because much of the constituent material in oil has a relatively low solubility in water, in general

coral may be protected from exposure by overlying waters. However, if rough seas and a lighter, 

more soluble product are involved, subtidal corals may experience harmful exposure when oil 

mixes into the water column. The absolute levels of exposure would be expected to be much 

lower than those encountered by direct contact with intertidal slicks, since only a small fraction of 

the total oil can mix into the water column either in solution or physically suspended. However, 

the components of the oil mix most likely to enter the water column are those generally considered to be most acutely toxic. Corals may therefore be exposed to “clouds” of naturally dispersed 

oil driven into the water column under turbulent conditions, with impacts dependent on exposure 

concentrations and length of exposure.

Where significant amounts of oil remain on adjacent shorelines after termination of cleanup

efforts, such as in mangrove forests, where inaccessible oil is left for natural removal, coral reefs 

may be affected by chronic oil exposure. There could also be episodic releases of higher amounts 
–27–

Chapter 3. Oil Toxicity To Corals 

of oil during high-energy events. This process was one factor in the long-term effects of the 1986 

Bahía Las Minas crude oil spill in Panama.

Heavy fuel oil exposure

Heavier fuel oils contain fewer of the light fractions identified with acute toxicity than do 

refined and crude oils (although these bunker type oils are sometimes“cut”with lighter materials

to facilitate loading and transfer).If they remain on the water surface, spills of heavier fuel oils are

less of a concern from a reef perspective, but more of a concern for protection of other habitats 

like mangrove forests where they can strand and persist for long periods of time, indirectly affecting coral reefs by chronic exposures as the oil is removed by natural processes. However, the heavy 

oils can also weather or mix with sediment material and increase in density to the point where 

they may actually sink—which provides a direct route of exposure to subtidal corals. Although 

acute toxicity characteristics of heavy fuel oils may be lower, the potential for significant physical 

effects from smothering is greatly increased.

Laboratory studies

Concentrations and exposure

Although many laboratory studies of oil toxicity to coral can be found in the literature, interpreting results from a spill response perspective is complicated by the experimental methods 

used. Many laboratory studies on the effects of oil on corals have limited applicability to real-life 

oil spill scenarios because of the way corals were exposed during the experiments, or how oil 

exposure was quantified. Many early studies on oil toxicity to coral relied on severe, direct exposure methods that were difficult to extrapolate to actual spill conditions. In addition, few studies actually quantified the exposure concentrations to corals, relying instead on a calculated, or 

nominal, value derived simply from the amount of oil mixed with a volume of water.Because only

a fraction of the oil mixes directly into the water, the true toxicity levels can be assumed to be 

much lower than reported. This makes it difficult to compare studies or extrapolate data to real-life 

conditions.

During actual oil spills, oil concentrations do not remain constant, but vary over time. Oil is 

most concentrated at the very beginning of a spill when the product is consolidated in one location and relatively unweathered. As the spill spreads laterally and weathering processes begin, oil 

concentrations rapidly decline. These changing exposure levels can be simulated in experiments 

by reducing oil levels after a specified amount of time. Studies focusing on dispersed oil impacts 

use pulse exposures with flow-through systems, in which concentrations dissipate with time.
–28–

Oil Spills in Coral Reefs: Planning and Response Considerations

When trying to estimate real-life exposures, it is important to carefully evaluate the methods used 

when applying data from laboratory studies.

Field studies

Field studies offer the best opportunity to understand the effects of oil spills under realistic 

conditions, but are uncommon in a coral reef habitat.One of the best examples is the 1986 Bahía

Las Minas crude oil spill in Panama. This extensive series of studies documented both short-term 

mortality to corals and long-term, sublethal impacts to reproduction and growth lasting five 

years or longer. Guzmán et al. compared cover of common coral species at six reefs before 1985 

and three months after the oil spill at Bahía Las Minas.At one heavily oiled reef, total coral cover

decreased by 76 percent in the 0.5–3 m depth range and by 56 percent in the >3–6 m range.Cover

decreased less at moderately oiled reefs and either increased or did not change at the unoiled reference reefs. The branching species Acropora palmata nearly disappeared at the heavily oiled site, 

but increased by 38 percent at the unoiled reefs. Coral colony size and diversity also decreased 

significantly with increased oiling.(See case studies for more detail.)

The 1984 TROPICS effort, sponsored by the American Petroleum Institute, was the most carefully designed and monitored attempt to perform a large-scale field experiment with corals and 

oil. Intended to provide a degree of realism within a more controlled setting than an actual spill, 

TROPICS examined short- and long-term effects of oil and dispersed oil to mangroves, seagrass, 

and coral reefs. Of these habitat types, coral reefs were least affected by exposure to oil alone, 

showing minimal short-term (0–20 months) and no long-term (10 years) effect to corals in an

intentionally oiled zone. Mangroves were the most severely impacted, even 10 years after oiling.

Acute effects

A review of laboratory and field studies on acute effects of oil to corals can be confusing, since 

different studies appear to show contradictory results. Widespread coral mortalities following 

actual spills have been reported only infrequently, even when associated reef-dwelling organisms 

have perished. It may be that acute toxicity is not the best indicator of oil impact, and that adverse 

effects to the coral would be manifested over the longer term.

Oil exposure can kill coral, however, on varying time frames. Early studies of acute oil toxicity to coral used severe exposure conditions, such as directly coating coral with oil or submerging coral in marine diesel for 30 minutes. It is surprising that any of the test corals survived at all.

Sometimes, a colony was not killed outright after a “dunking” in pure product, but later showed a 

steady decline in condition over a long period (>100 days) before dying.
–29–

Chapter 3. Oil Toxicity To Corals 

A 1990 study by Harrison, using methods more comparable to spill conditions, found that 

low-level exposures almost completely disintegrated coral tissues after 48 hours. While they had 

selected a coral species known for its sensitivity to stress (A. formosa), these results suggest that

longer exposure (4–48 hrs) to low concentrations of oil may be more toxic than shorter exposures

at higher concentrations.

Recent studies have found enhanced phototoxicity from short-term and very low exposures 

to fluoranthene (a polynuclear aromatic hydrocarbon in oil) under outdoor light conditions (thus

including ultraviolet radiation during the day) with the coral Porites. Interestingly, the upper sides 

of the coral fragments exposed to outdoor light exhibited bleaching and mortality within 3 to 6 

days, whereas the under sides of each sample was normal. The calculated lethal concentration 50 

(LC50) for the upper sides was an order of magnitude lower (14 times more toxic) than the lower

sides of the corals. Also, replicate exposures under laboratory light conditions resulted in significantly less severe effects.

Because corals grow in shallow, clear water with good light penetration,

photoenhanced toxicity is likely to a significant mechanism, making corals much more sensitive to 

oil impacts than previously understood based on laboratory studies.

Differences in tolerance by coral species may be an important consideration but physical form 

may be more significant.Branching corals appear to be among the most susceptible whereas massive corals are more tolerant of oil exposure in laboratory studies.

Bahía Las Minas field investigations noted that nearly all branching corals were killed in oiled reef areas. Thus, researchers could 

conduct longer-term studies only on massive species of coral.

The old notion that coral reefs do not suffer acute toxicity effects from oil floating over them is 

probably incorrect. Certainly, direct coating increases the severity of impact, but high oil concentrations in the water columns during a spill may also kill some species.

Chronic effects

Chronic effects of oil exposure have been consistently noted in corals and, ultimately, can kill 

the entire colony. Chronic impacts include histological, biochemical, behavioral, reproductive, and 

developmental effects (see Table 3.1).Field studies of chronically polluted areas and manipulative studies in which corals are artificially exposed to oil show that some coral species tolerate 

oil better than other species. In contrast to acute toxicity studies, nearly all researchers studying 

chronic effects have documented sublethal changes in exposed corals. Advances in technology 

now allow the detection of effects at cellular and genetic levels.

Sublethal oil exposure affects many normal biological functions, including reproduction and 

recruitment, which may have the greatest potential to adversely impact coral survival. A host 
–30–

Oil Spills in Coral Reefs: Planning and Response Considerations

of studies show that oil reduces coral fertility, decreases reproductive success, and inhibits early 

life stage development.A spill occurring at just the wrong time in a given area, at the peak of

reproductive activity, could cause immediate and long-lasting harm to the communities of corals 

themselves. For example, several species of the coral Montastrea in Florida spawn during August 

and September. This would be a time when these communities would be at greater risk for reproductive impacts (see Table 1.1).

Table 3.1. Stress responses shown by corals exposed to oil and oil fractions (updated from Fucik et al. 1984).

Response References

Tissue death Johannes et al. (1972); Reimer (1975); Neff and Anderson (1981); Wyers 

et al. (1986)

Impaired feeding response Reimer (1975); Lewis (1971); Wyers et al. (1986)

Impaired polyp retraction Elgershuizen and de Kruijf (1976); Neff and Anderson (1981); Knap et al. 

(1983); Wyers et al. (1986)

Impaired sediment clearance ability Bak and Elgershuizen (1976)

Increased mucus production Peters et al. (1981); Wyers et al. (1986); Harrison et al. (1990)

Change in calcification rate Birkeland et al. (1976); Neff and Anderson (1981); Dodge et al. (1984); 

Guzmán et al. (1991, 1994)

Gonad damage Rinkevich and Loya (1979b); Peters et al. (1981)

Premature extrusion of planulae Loya and Rinkevich (1979); Cohen et al. (1977)

Larval death Rinkevich and Loya (1977)

Impaired larval settlement Rinkevich and Loya (1977); Te (1991); Kushmaro et al. (1996); Epstein et 

al. (2000)

Expulsion of zooxanthellae Birkeland et al. (1976); Neff and Anderson (1981); Peters et al. (1981)

Change in zooxanthellae primary production Neff and Anderson (1981); Cook and Knap (1983); Rinkevich and Loya 

(1983)

Muscle atrophy Peters et al. (1981)

Oil also impairs two fundamental bioenergetic components for the entire coral reef community: primary production by the zooxanthellae symbionts in coral, and energy transfer via coral 

mucus. While some studies indicate that these effects are transient and that corals can recover 

from them in the absence of oil, circumstances of individual spills, including stress from other 

sources such as increased water temperature, will dictate whether these would be of concern to 

responders and resource managers.
–31–

Chapter 3. Oil Toxicity To Corals 

Bioaccumulation

Oil quickly and readily bioaccumulates in coral tissues and is slow to depurate. This may 

be linked to the high lipid content of the tissues. Uptake into the symbiotic zooxanthellae also 

occurs. Researchers have found that petroleum hydrocarbons are deposited into the calcareous 

exoskeleton of corals, which introduces the possibility of using coral skeletons as historical records 

of hydrocarbon contamination in an area.Bahía Las Minas field studies indicated that corals took

up hydrocarbons from the water column, as opposed to sediments. Studies of cores up to 42 cm 

in length collected from the Arabian Gulf in 2003 detected petroleum biomarkers in several coral 

annual bands related to major pollution events in the region;however, the oil remaining in these

cores had been altered over time such that the biomarker ratios in the oil residues differed from 

Gulf crude oils.

Associated reef organisms

In addition to corals themselves, oil may also adversely affect the associated fish, invertebrates, and plants in the coral reef community. Turtles and marine mammals may be seasonal 

inhabitants of the reef, and may be susceptible to direct oil exposure since they must surface regularly to breathe.

Broad generalizations on oil toxicity are not very helpful for such a diverse group

of species, life histories, and life stages. Though the scientific literature on oil toxicity to coral reef 

fish is limited, one can assume that they would show similar ranges in sensitivity to oil as would 

fish from temperate areas. Likewise, toxicity information on invertebrate groups could be generally inferred from data collected on related organisms from other habitats. Fish in open waters 

are thought to be able to avoid oil, although fish kills have been documented at several spills in 

shallow coral reef habitats (see the Morris J. Berman and Wake Island case studies).Since many

coral reef fish have small home ranges and are residents of the reef, it follows that they would be at 

higher risk from oil exposure than non-resident, more widely ranging fish.

Some groups of invertebrates are known to be very sensitive to oil, including many crustaceans. As with coral reef fish, there are a number of documented incidents where invertebrates 

were killed after an oil spill. Some invertebrates, such as bivalves and snails, may not be acutely 

impacted by oil, but may accumulate oil components such as polynuclear aromatic hydrocarbons 

(PAH) in their tissues.Species sensitivity varies greatly.Generally, early life stages are more sensitive than adult organisms, though there are exceptions. Consulting local experts and the broader 

toxicity literature is in order to assess oil toxicity to specific organisms in the reef community.

Also of concern are concentrations of fish and invertebrate larvae, which often are found 

within the upper water column where they may come in contact with oil products. Marine larval 
–32–

Oil Spills in Coral Reefs: Planning and Response Considerations

organisms may be more susceptible to oil toxicity given their surface-to-volume ratio and limited 

ability to steer clear of a spill.Larvae and other plankton serve as major food sources for a variety

of coral reef organisms (including corals themselves).Larvae thus may serve as a mechanism for

ingestion of oil products by reef organisms that otherwise would not come in contact with surface 

spills.

For further reading 

Bak, R.P.M.1987.Effects of chronic oil pollution on a Caribbean coral reef.Marine Pollution Bulletin 18:

534–539.

Bak, R.P.M.and J.H.B.W.Elgershuizen.1976.Patterns of oil-sediment rejection in corals.Marine 

Biology 37:

105–113.

Ballou, T.G., R.E.Dodge, S.C.Hess, A.H.Knap, and T.D.Sleeter.1987.Effects of a dispersed and 

undispersed crude oil on mangroves, seagrasses, and corals. API Publication No. 4460, API Health 

and Environmental Sciences Department. Washington, D.C.: American Petroleum Institute. 198 

pp.

Benson, A.A.and L.Muscatine.1974.Wax in coral mucus:energy transfer from corals to reef

fishes. Limnology and Oceanography 19:810–814.

Birkeland, C., A.A.Reimer, and J.R.Young.1976.Survey of marine communities in Panama and

experiments with oil. EPA Report EPA-60013-76-028. Narragansett: U.S. Environmental Protection 

Agency. 177 pp.

Burns, K.A.and A.H.Knap.1989.The Bahía Las Minas oil spill:Hydrocarbon uptake by reef building corals. Marine Pollution Bulletin 20:

391–398.

Cook, C.B.and A.H.Knap.1983.The effects of crude oil and chemical dispersant on photosynthesis in the brain coral, Diploria strigosa. Marine Biology 78:

21–27.

Cram, S., C. Ponce de León, P. Fernández, I. Sommer, H. Rivas, and L. M. Morales. 2006. Assessment of Trace Elements and Organic Pollutants From a Marine Oil Complex into the Coral Reef 

System of Cayo Arcas, Mexico. Environmental Monitoring and Assessment 121:127–149.

Dodge, R.E., B.J.Baca, A.H.Knap, S.C.Snedaker and T.D.Sleeter.1995.The effects of oil and

chemically dispersed oil in tropical ecosystems: 10 years of monitoring experimental sites. MSRC 

Technical Report Series 95-014. Washington, D.C.: Marine Spill Response Corporation. 93 pp.

Dodge, R. E., S. C. Wyers, H. R. Frith, A. H. Knap, S. R. Smith and T. D. Sleeter. 1984. The effects of 

oil and oil dispersants on the skeletal growth of the hermatypic coral Diploria strigosa. Coral Reefs 

3:191–198.
–33–

Chapter 3. Oil Toxicity To Corals 

Downs, C. A., E. Mueller, S. Phillips, J. E. Fauth. and C. M. Woodley. 2000. A molecular biomarker 

system for assessing the health of coral (Montastrea faveolata) during heat stress.Marine Biotechnology 2:

533–544.

Downs, C. A., R. H. Richmond, W. J. Mendiola, L. Rougee, G. K. Ostrander. 2006. Cellular Physiological Effects of the M. V. Kyowa Violet Grounding on the Hard Coral Porites Lobata. Environmental Toxicology and Chemistry 25:

3171–3180.

Elgershuizen, J.H.B.W.and H.A.M.deKruijf.1976.Toxicity of crude oils and a dispersant to the

stoney coral Madracis mirabilis. Marine Pollution Bulletin 7:22–25.

Epstein, N., R.P.M.Bak, and B.Rinkevich.2000.Toxicity of third generation dispersants and dispersed Egyptian crude oil on Red Sea coral larvae. Marine Pollution Bulletin 40:

497–503.

Fucik, K.W., T.J.Bright, and K.S.Goodman.1984.Measurements of damage, recovery, and rehabilitation of coral reefs exposed to oil.

In J.Cairns and A.L.Buikema, eds., Restoration of Habitats 

Impacted by Oil Spills, Butterworth, London, pp.115–133.

Guzmán, H.M., K.A.Burns, and J.B.C.Jackson.1994.Injury, regeneration and growth of Caribbean reef corals after a major oil spill in Panama.

Marine Ecology Progress Series 105:231–241.

Guzmán, H.M., J.B.C.Jackson and E.Weil.1991.Short-term ecological consequences of a major

oil spill in Panamanian subtidal coral reefs. Coral Reefs 10:1–12.

Guzmán, H. M. and I. Holst. 1993. Effects of chronic oil-sediment pollution on the reproduction of 

the Caribbean reef coral Siderastrea siderea. Marine Pollution Bulletin 26:276–282.

Harrison, P.L., J.C.Collins, C.G.Alexander, and B.A.Harrison.1990.The effects of fuel oil and

dispersant on the tissues of a staghorn coral Acropora formosa: A pilot study. In: Scientific Input to 

Oil Spill Response, Proceedings of Second National Workshop on Role of Scientific Support Co-ordinator, HMAS Cerberus (Hastings, Victoria), March 26–30, 1990, pp.

51–61.

Jackson, J., J.Cubit, B.Keller, V.Batista, K.Burns, H.Caffey, R.Caldwell, S.Garrity, C.Getter, C.

Gonzalez, H. Guzmán, K. Kaufmann, A. Knap, S. Levings, M. Marshall, R. Steger, R. Thompson, and 

E.Weil.1989.Ecological effects of a major oil spill on Panamanian coastal marine communities.

Science 243:37–44.

Johannes, R. E. J. Maragos and S. L. Coles. 1972. Oil damages corals exposed to air. Marine Pollution Bulletin 3:

29–30.

Keller, B.D.and J.B.C.Jackson, eds.1993.Long-term assessment of the oil spill at Bahía Las

Minas, Panama, synthesis report, volume 1: Executive summary. OCS Study MMS 93-0047. New 

Orleans: U.S. Department of the Interior, Minerals Management Service, Gulf of Mexico OCS 

Region. 129 pp.
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Oil Spills in Coral Reefs: Planning and Response Considerations

Kennedy, C. J., N. J. Gassman, and P. J. Walsh. 1992. The fate of benzo[a]pyrene in the scleractinian corals Favia fragrum and Montastrea annularis. Marine Biology 113:

313–318.

Knap, A. H., J. E. Solbakken, R. E. Dodge, T. D. Sleeter, S. Wyers, and K. H. Palmork. 1982. Accumulation and elimination of (9—14C) phenanthrene in the reef-building coral (Diploria strigosa).

Bulletin of Environmental Contamination and Toxicology 28:281–284.

Knap, A. H., T. D. Sleeter, R. E. Dodge, S. C. Wyers, H. R. Frith, and S. R. Smith. 1983. The effects of 

oil spills and dispersants use on corals: A review and multidisciplinary experimental approach. Oil 

and Petrochemical Pollution 1:157–169.

Kushmaro, A., G.Henning, D.K.Hofmann, and Y.Benayahu.1996.Metamorphosis of Heteroxenia 

fuscescens planulae (Cnidaria:Octocorallia) is inhibited by crude oil:A novel short term toxicity

bioassay. Marine Environmental Research 43:295–302.

Lane, A. and P. L. Harrison. 2000. Effects of oil contaminants on survivorship of larvae of the 

scleractinian reef corals Acropora tenuis, Goniastrea aspera and Platygyra sinensis from the Great 

Barrier Reef.In:Proceedings of the 9th International Coral Reef Symposium, Vol. 1, pp.403–408.

Lewis, J.B.1971.Effects of crude oil and oil spill dispersant on reef corals.Marine Pollution Bulletin 

2:59–62.

Loya, Y.and B.Rinkevich.1979.Abortion effect in corals induced by oil pollution.Marine Ecology 

Progress Series 1:77–80.

Loya, Y.and B.Rinkevich.1980.Effects of oil pollution on coral reef communities.Marine Ecology 

Progress Series 3:167–180.

Martinez, M.D.C.G., P.R.Romero, and A.T.Banaszak.2007.Photoinduced toxicity of the polycyclic aromatic hydrocarbon, fluoranthene, on the coral, Porites divaricata. Journal of Environmental 

Science and Health, Part A, 42:1495–1502.

Neff, J. M. and J. W. Anderson. 1981. Response of Marine Animals to Petroleum and Specific Petroleum Hydrocarbons. New York: John Wiley & Sons, 177 pp.

Negri, A. P. and A. J. Heyward. 2000. Inhibition of fertilization and larval metamorphosis of the 

coral Acropora millepora (Ehrenberg, 1834) by petroleum products oil contamination along oil

tanker routes off the United Arab Emirates (The Arabian Gulf and the Gulf of Oman).Marine Pollution Bulletin 7:

420–427.

NOAA.1995.Barge Morris J. Berman spill, NOAA’s scientific response. HAZMAT Report 95-10. Seattle: Hazardous Materials Response and Assessment Division, National Oceanic and Atmospheric 

Administration. 63 pp.

Peters, E.C., P.A.Meyers, P.P.Yevich, and N.J.Blake.1981.Bioaccumulation and histopathological effects of oil on a stony coral. Marine Pollution Bulletin 12:

333–339.
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Chapter 3. Oil Toxicity To Corals 

Poulsen, A., K.Burns, J.Lough, D.Brinkman, and S.Delean.2006.Trace analysis of hydrocarbons

in coral cores from Saudi Arabia. Organic Geochemistry 37:1913–1930.

Ray, J. P. 1980. The effects of petroleum hydrocarbons on corals. In: Petroleum and the Marine Environment, Proceedings of Petromar 80, Graham and Trotman Ltd., London.

Readman, J.W., I.Tolosa, A.T.Law, J.Bartocci, S.Azemard, T.Hamilton, L.D.Mee, A.Wagener, M.

Le Tissier, C. Roberts, N. Downing, and A. R. G. Price. 1996. Discrete bands of petroleum hydrocarbons and molecular organic markers identified within massive coral skeletons. Marine Pollution 

Bulletin 32:437–443.

Reimer, A. A. 1975. Effects of crude oil on corals. Marine Pollution Bulletin 6:39-44.

Rinkevich, B.and Y.Loya.1977.Harmful effects of chronic oil pollution on a Red Sea scleractinian

coral population.In D.L.Taylor (ed.), Third International Coral Reef Symposium, Miami, Vol. 2, pp.

585–591, University of Miami, Florida.

Rinkevich, B.and Y.Loya.1979.Laboratory experiments on the effects of crude oil on the Red Sea

coral Stylophora pistillata. Marine Pollution Bulletin 10:328–330.

Rinkevich, B.and Y.Loya.1983.Response of zooxanthellae photosynthesis to low concentrations

of petroleum hydrocarbons. Bulletin of the Institute of Oceanography and Fisheries 9:109–115.

Shafir, A., J.Van Rijn, and B.Rinkevich.2007.Short and long term toxicity of crude oil and oil dispersants to two representative coral species. Environmental Science & Technology 41:

5571–5574.

Rougée, L., C. A. Downs, R. H. Richmond, and G. K. Ostrander. 2006. Alteration of Normal Cellular 

Profiles in the Scleractinian Coral (Pocillopora Damicornis) Following Laboratory Exposure to Fuel

Oil. Environmental Toxicology and Chemistry 25:3181–3187:

Te, F. T. 1991. Effects of two petroleum products on Pocillopora damicornis planulae. Pacific Science 

45:290–298.

Villaneuva, R. D., M. N. E. Montano, and H. T. Yap. 2008. Effects of natural gas condensate - water 

accomodated fraction on coral larvae. Marine Pollution Bulletin 56: 1422–1428.

Wyers, S.C., H.R.Frith, R.E.Dodge, S.R.Smith, A.H.Knap, and T.D.Sleeter.1986.Behavioural

effects of chemically dispersed oil and subsequent recovery in Diploria strigosa (Dana).Marine 

Ecology 7:23–42.
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Oil Spills in Coral Reefs: Planning and Response Considerations

Shipwreck of the F/V Swordsman 1 aground on a coral reef at 

Pearl and Hermes Atoll, in the Western Hawaiian archipelago, 

June 2000. (USFWS)
–37–

Chapter 4. Response Methods For Coral Reef Areas

Chapter 4. Response Methods For Coral Reef Areas

Key points

•	 Vessel accidents can hurt coral reefs as a result of spilled oil, groundings and other physical

impacts, anchor damage, and release of ballast water or hazardous materials.

•	 All potential response options should be evaluated to determine whether the ultimate benefits from the response action outweigh the costs (or impacts) of the action.

•	 Remote locations, lack of response equipment, and waste disposal issues limit options for spill

response in some coral regions.

•	 Mechanical cleanup and salvage efforts should avoid causing additional impacts to coral.

•	 In-situ burning can remove large amounts of oil rapidly, removing up to 90% or more of the oil.

•	 Dispersants are chemicals that break up of oil slicks by enhancing formation of small oil droplets that more readily disperse into the water column.

•	 In-situ burning and dispersing oil at sea can help reduce shoreline impacts and mortality of

birds and other wildlife.

•	 Deciding whether or not to use dispersants involves difficult trade-off considerations.

The goal of spill response in coral areas is the same as in any other habitat—to minimize damages caused by the accident and any associated spillage. All potential response options should 

be evaluated to determine whether the ultimate benefits from the response action outweigh the 

costs (or impacts) of the action.Choosing response methods carefully, with an understanding of

the sensitivities of the reef environment, will minimize any additional impacts incurred from the 

cleanup.

Variables such as location, weather, and availability of equipment for salvage, lightering, or 

cleanup will determine which options can be considered during a response in coral reefs. In the 

best-case scenario, modern response equipment will be available and salvage or lightering may 

be able to prevent any oil from spilling. Contingency plans may already be in place and specific 

response techniques can be evaluated and prepared, even if they turn out to be unnecessary. At 

the other end of the spectrum, response may be constrained by a remote site where equipment 

such as booms, skimmers, and sorbents may not be readily available. It may take long periods of 

time for salvage vessels to reach the scene and attempt to pull a damaged vessel off a reef (see

Rose Atoll case study).Even when containment and collection of spilled oil is feasible, storage and

disposal of collected waste products may limit cleanup operations.
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Oil Spills in Coral Reefs: Planning and Response Considerations

General response considerations

In addition to toxic impacts from spilled oil, vessel accidents can hurt coral reefs in other ways, 

including groundings and other physical impacts, anchor damage, and release of ballast water or 

hazardous materials (Figure 4.1).

Ballast Water 

Discharge

Cargo Spill - 

Chemicals

Oil Spill

Grounding

Figure 4.1. Overview of possible impacts at a vessel accident, including ballast water discharge, potential oil or chemical spillage, physical impacts to reef structures from grounding, and physical and chemical impacts from residual debris.

Physical impacts

Vessel traffic, anchor deployment, dragging lines, and physical contact by response workers 

can detrimentally impact coral reefs and associated habitats. Responders working near coral reefs 

should take care to avoid physical damage to coral, especially in shallow waters. Using floating 

lines, especially for salvage, but also for boom deployment and other operations, prevents damage 
–39–

Chapter 4. Response Methods For Coral Reef Areas

to coral structures from dragging heavy lines over the reef itself. Response methods such as skimming and placement of certain types of booms will need to be limited to deeper waters (greater

than 3 meters) to avoid direct physical impacts to coral.In areas where coral is exposed at low

tides, workers should avoid walking on reefs.

Ship groundings frequently damage reefs, and are discussed in more detail in Chapter 5.

Physical damage from a ship grounding may be the main impact to coral, especially when the ship 

is successfully refloated or lightered without spillage. Removal of a grounded vessel can add to 

the detrimental impact on the reef, especially if new channels have to be opened or constructed 

to remove the vessel (see the Rose Atoll case study).Even small pieces of debris can continue to

damage the reef habitat; in some cases, dissolution of iron as the debris corrodes can have longterm impact (again, see the Rose Atoll case study).

Ballast water

To lighten and remove a grounded vessel from a coral reef, ballast water may be discharged.

Ballast water may contain spores, eggs, larvae, or other life stages of marine life not indigenous

to the reef ecosystem at the wreck site and, thus, may introduce these non-native organisms into 

areas where they can significantly alter the existing community structure. Response options can 

include treatment of ballast water before discharge with ozone, chlorine, or heat.

Hazardous cargo

Stricken or stranded vessels may release hazardous cargoes into a coral reef area. These can 

include many substances that are bulk-transported aboard ships:bulk organic (petro) chemicals,

pesticides or herbicides, ores (such as copper), bulk acids and bases (such as sulfuric acid or caustic

soda), and cement (as at the M/V.S. Zakariadze in Puerto Rico).Other items that have spilled

include ammonia used in refrigeration of catch on fishing vessels, shipping containers, fishing 

gear (longlines, traps, or set nets), and decomposing animal matter such as bait or fish.Response

options for these situations should be developed on a case-by-case basis.

Multiple aspects of an incident can require simultaneous attention. For example, the bulk 

carrier Igloo Moon stranded on a coral reef near Miami, damaging the coral reef. It was also at risk 

of spilling its cargo (butadiene), oil (bunker and diesel fuel), and potentially contaminated ballast

water. The response sequence resembled a medical triage, in which activities were organized to 

maximize risk reduction.The coral reef was injured by the initial impact and subsequent vessel

extraction, but presumably a much larger and longer-lasting disaster was prevented by careful 

treatment and discharge of the carrier’s ballast water and cargo, and fuel lightering.
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Oil Spills in Coral Reefs: Planning and Response Considerations

Booming and skimming

Advantages/disadvantages 

Physical containment and collection of spilled oil on water using booms and skimmers is the 

primary cleanup method used at most spills. High current speeds, heavy wave action, or shallow 

water may limit the effectiveness of either booms or skimmers and necessitate consideration of 

alternative cleanup strategies. Skimming operations will most likely be conducted outside the reef 

in deeper waters to prevent oil from coming over the reef crest. It may be difficult to anchor collection booms on the reef slope because of great depth.

Booms should be anchored in a way that does not damage coral, and tended regularly

to maintain effective positioning and avoid damaging shallow coral. Sorbent booms can be 

deployed to catch oil leaching from shorelines, but must be tended and changed frequently so 

they do not become a source of oiling themselves. In some circumstances, oil can be collected via 

vacuum pumps, if it is concentrated nearshore on water, provided there is appropriate access for 

the mechanical equipment.

Once the oil is collected, adequate short-term storage is necessary, as well as a disposal plan 

for the waste oil and other waste products. Disposal issues can be significant, especially in remote 

areas, and lack of available collection facilities can limit skimming operations. At the Morris J. 

Berman barge oil spill in Puerto Rico, the pools of a large swim stadium were put into service for 

temporary waste oil collection and water separation.

Skimmer and boom guidelines

•	 Limit collection and skimming operations to water deeper than 3 meters.

•	 Tend booms regularly so they do not harm shallow reefs.

•	 Do not damage coral when anchoring booms.

•	 Route boat traffic away from shallow reefs and seagrass beds to avoid propeller damage and

increased sedimentation.

In-situ burning

In-situ burning is a response technique in which spilled oil is burned in place. It has been 

adapted and used in settings as varied as the open ocean and in marsh areas.
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Chapter 4. Response Methods For Coral Reef Areas

Advantages/disadvantages 

In-situ burning can remove large amounts of oil relatively rapidly. Estimated removal efficiencies of 90 percent and above (of contained oil) far exceed those for mechanical or chemical

response methods.Burning requires less equipment, logistical support, fewer personnel, and produces less waste material than other cleanup techniques. In remote locations where many coral 

reef spills occur, these offer significant advantages logistically and environmentally. As long as oil 

has not emulsified (if the water content is greater than 25 percent, it will not burn) the response

window for burning on water can last several days.

In order to sustain burning oil, the slick must be at least ~2–3 mm thick.Either the spilled oil

must be present in that thickness in the slick or natural collection area, or specialized (and expensive) burn boom can be deployed to collect and retain the oil for burning.

In-situ burning is less

effective if winds are greater than 20 knots and seas are greater than 2–3 feet.

In-situ burning produces large amounts of highly visible smoke and other combustion byproducts, which can be a significant deterrent to its use, especially in areas near human populations.

The smoke plume presents both a human and animal (e.g., marine mammals) health risk,

primarily from fine particulate material that may aggravate respiratory conditions. The smoke is 

also a problem of perception: a massive black plume appears formidable and menacing. However, 

the remoteness of many potentially affected coral reef areas may minimize this concern. Special 

Monitoring of Alternate Response Techonolgies (SMART) air monitoring protocols, developed by

NOAA, the U.S. Environmental Protection Agency, the U.S. Coast Guard, and the Agency for Toxic 

Substances and Disease Registry, can be deployed when burning is conducted near population 

centers to monitor particulate levels and provide real-time feedback to the responders. This feedback helps responders determine safe boundaries beyond which smoke levels do not pose health 

risks to people.

Burning in coral reef areas

To our knowledge, there have been no intentional large-scale in-situ burns in coral reef habitats. During World War II, many ships and aircraft that were attacked near corals released oil and 

were set ablaze, particularly in the Indo-Pacific region. For understandable reasons, the environmental impacts of these events were not documented. During the 1968 Witwater spill in Panama, 

small patches of heavy oil apparently were burned as a shoreline oil removal technique, but this 

was a limited and small-scale application.
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Oil Spills in Coral Reefs: Planning and Response Considerations

Environmental impacts

There are no studies of in-situ burning in coral regions.Burning is a still a relatively rarely used

spill response method, and studies on its environmental effects and toxicology are limited. The 

Newfoundland Offshore Burn Experiment (NOBE) provides much of our current information on

burning oil at sea. Crude oil was intentionally released, ignited, allowed to burn, and extensively 

studied, including water-column toxicity to marine organisms, and associated physical effects 

from the burn.

The results from NOBE experiments and other studies indicate that crude oil burn residue

has a low inherent toxicity to test organisms, and incurred no additional toxicity compared to 

unburned oil. Extrapolation of these results to tropical areas and coral reefs should be done cautiously, however.

In some instances the physical characteristics of burned oil residue could be a concern, especially if the density is significantly increased from that of the source oil. There have been some 

observations from both controlled burn experiments and from actual ship fires that burn residue 

can sink under specific circumstances. Recent studies have predicted that residues from about 

half of international crude oils would tend to sink in seawater, but only after cooling. It may be 

possible to collect the burn residues while they are still hot and buoyant. Nets deployed under 

the burn area might allow capture of sinking residues.Based on the previously mentioned studies, the inherent toxicity of the material is believed to be low; but the physical impacts of contact 

(such as fouling or smothering) may be a concern.Given the alternative of much greater volumes

of unburned oil impacting nearby resources, the tradeoff offered by burning seems reasonable; as 

always, however, the risk assessment of different response options must take place on a case-bycase basis.

Water temperatures under a burning slick can reach near boiling in the top few millimeters in 

a static situation. However, water only a few centimeters below the slick remains unaffected. If a 

fire boom containing a burning oil slick is being towed or if underlying water is moving, then there 

is no appreciable rise in water temperature.

In-situ burning guidelines

•	 Burning may be effective on many oil types, except emulsified oil (water content of greater

than 25%).Burning medium to heavy oils may produce residue that sinks.

•	 Oil must be 2–3 mm thick to sustain a burn—it can be collected in natural containment areas,

or in special fire boom that can be towed on water.
–43–

Chapter 4. Response Methods For Coral Reef Areas

•	 Weather conditions are conducive for burning when winds are less than 20 knots and seas are

less than 2–3 feet.

•	 SMART air monitoring protocols can help delimit areas where smoke plumes do not present a

health risk for people.

Dispersants

Dispersants are chemicals containing surfactants, like those in soaps and detergents, which 

have both a water-soluble and an oil-soluble component. When applied to oil slicks, they reduce 

the surface tension of the oil and promote the formation small oil droplets that “disperse” throughout the water column. Dispersants are sprayed directly on floating oil as a fine mist, either from 

aircraft or boats. Oil also disperses naturally, especially lighter fuels and oils spilled in areas with 

heavy wave action; however, the droplets are generally larger and can recoalesce and re-float.

Dispersants have been used on a number of tropical oil spills, but the follow-up data are 

scarce, especially on potential impacts to coral reefs. Regional contingency plans that pre-approve 

the use of dispersants generally place greater restrictions on their use in nearshore waters. Currently, some regions are considering conditions under which dispersants may be safely and effectively used close to shore. This involves understanding the toxicity and fate of dispersed oil and 

balancing possible tradeoffs when oil may impact sensitive shorelines such as mangrove forests.

Advantages/disadvantages 

Dispersing oil may reduce the damaging effects of surface slicks on birds, sea turtles, and 

marine mammals and help prevent oil from stranding on tourist beaches or impacting sensitive shoreline habitats such as mangroves, marshes, or enclosed lagoons. Dispersants treat large 

slicks quickly, reducing the formation of emulsions, and accelerate the biodegradation of oil in the 

water column. Dispersants are an important cleanup tool, and offer a response method that can 

be deployed during weather conditions that preclude mechanical recovery methods. Dispersion 

is the primary response option in many countries and a secondary option in several others. Many 

tropical islands, atolls, and reefs are too remote to deploy mechanical protection and cleanup 

methods, but dispersant use may still be an option if pre-planning efforts have stockpiled dispersants in readily available locations.

Under the proper conditions, lighter fuel oils to medium crude oil can be easily dispersed, 

but heavier bunker oils are much more difficult to disperse. Weathering increases oil viscosity and 

may cause formation of water-in-oil emulsions, which are less amenable to dispersion. A moderate amount of turbulence is needed to mix dispersed oil into the surface waters. Vertical mixing 
–44–

Oil Spills in Coral Reefs: Planning and Response Considerations

and diffusion then dilute and disperse the oil further into the water column. Test applications of 

dispersants can be used to determine the viability of response-scale applications at a given spill.

Dispersant use in coral reef areas

During the past three decades, dispersants were among the countermeasures used to combat 

several spills impacting tropical coasts. However, we have little documentation of these events, 

especially the benefits or impacts to coral reefs and adjacent habitats (see case studies for Ocean 

Eagle, Bahía las Minas, and field studies).

The fate of dispersed oil has been studied in several

Northern Hemisphere offshore and nearshore locations, but there have been very few studies in 

tropical areas near coral reefs. Field and laboratory research studies provide the following picture.

A common misconception is that dispersed oil sinks to the bottom. In fact, wave action 

and currents rapidly dilute and disperse the plume of dispersed oil and transport it away from 

the treated site. The subsurface plume may move in a different direction and speed than the 

untreated surface slick. Within several hours the plume grows and oil concentrations greatly 

decrease. Within a day or two, dilution, spreading, and transport reduce the concentration of dispersed oil by a factor of 100, 1,000, or even 10,000.

Dispersed oil degrades via natural processes, including biodegradation. Laboratory studies 

indicate that, in cooler water systems, dispersed oil biodegrades much more quickly than undispersed oil (on time frames of a few days to several weeks).

Although no comparable work has

been done in tropical settings, it is likely that dispersed oil degrades much faster than in temperate 

areas because of warmer temperatures.

Given the right oceanographic conditions, dispersant use may be appropriate near submerged coral reefs (i.e., where water depth increases quickly, and subsurface currents are likely

to carry dispersed oil away from the reef).NOAA has modeled such situations for potential spills,

when dispersants were considered as a response tool near a coral reef. Usually, these determinations are made after considering the potential shoreline impacts and evaluating local weather and 

oceanographic conditions at the time of the spill.

In the Caribbean and some parts of the Pacific, shorelines adjacent to coral reefs contain mangrove forests, which are highly sensitive to oil. At many tropical oil spills, the most severe impact is 

to mangroves, sea turtle nesting areas, or other sensitive shoreline habitats. Recovery of severely 

impacted mangrove forests takes decades and often has associated impacts, including shoreline 

erosion, decimated marine life nursery areas, or chronic leaching of oil from contaminated sediments (see Bahía las Minas case study).

When conditions are appropriate to minimize impacts to

coral, using dispersants or in-situ burning on floating oil can be an effective and environmentally 

advantageous cleanup strategy that reduces long-term impacts.
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Chapter 4. Response Methods For Coral Reef Areas

Toxicity of dispersed oil

Toxicity studies screen dispersant products and provide data for planning dispersant use 

during spills. In tropical areas, there is continued reluctance towards using dispersants nearshore 

(closer than 3 miles) because of concerns about possible detrimental impacts to coral and associated reef inhabitants. In Chapter 3, we discuss methods used for laboratory studies of oil toxicity 

and how these impact the resulting data. As with coral toxicity studies on oil alone, laboratory 

protocols should be carefully evaluated before applying toxicity lab results to real-life dispersed oil 

scenarios. As discussed earlier, most laboratory toxicity tests have been conducted under artifical 

light;studies have shown that oil toxicity under natural light (that includes ultraviolet radiation)

can be at least an order of magnitude higher. Table 4.1 summarizes relatively recent studies on 

toxicity of chemically dispersed oil.

Table 4.1. Laboratory studies of toxicity of chemically dispersed oil to coral.

Response Exposure References

Reduced photosynthesis in zooxanthellae 

(reversible)

20 ppm, dispersed crude oil, 

8 hr, flow-through system

Cook and Knap 1983

Varied with exposure: stress responses to 

tissue death

2 and 4 ppm, dispersed fuel oil WAF

6–48 hrs, semi-static system

Harrison et al. 1990

Varied with exposure: Larval mortality 7 dilutions, dispersed heavy fuel oil WAF, 

96 hrs, at 12 hr intervals, static exposures in 

glass vials on reef flat

Harrison et al. 2000

Varied with exposure: Unsuccessful larval 

settlement to death

5–5000 ppm (nominal conc.), dispersed 

crude oil WAF, 2-96 hrs, static system

Epstein et al. 2000

Inhibitited fertilization and larval metamorphosis0.035 ppm, dispersed crude oil (1% CEWAF), 

4 hrs, static system

Negri and Heyward 2000

Varied with exposure: 50–100% solutions 

caused 100% tissue death; most survived at 

5% solution

0.5–100% CEWAF dispersed crude oil with 

6 different dispersants, 24 hrs, static exposure, flow-through post-exposure

Shafir et al. 2007

Field studies provide more realistic guidance about dispersed oil toxicity in larger systems.

Table 4.2 summarizes field studies from Bermuda, the Arabian Gulf, and Panama on impacts to

coral from chemically dispersed oil. Coral follows the pattern of most other organisms: its sensitivity to dispersed oil depends on the dose (the concentration and the length of exposure).

Very

high dispersed oil concentrations and long exposures can kill coral, whereas lower doses and 

short-term exposure show few, if any, impacts, many of which are reversible. Thus, dispersants 
–46–

Oil Spills in Coral Reefs: Planning and Response Considerations

and dispersed oil may be less damaging in real field conditions than had been suggested by older 

laboratory toxicity tests. These results highlight the importance of evaluating toxicity in the context of realistic exposures, which can be estimated from oceanographic models.

Table 4.2. Field and mesocosm studies examining impacts of chemically dispersed oil to corals.

Response Exposure References

Delayed sublethal impacts 5 days, 1–2 ppm, crude oil Legore et al. 1989

Coral stress symptoms (reversible) 24 hrs, 20 ppm, crude oil Knap et al. 1983

Coral death, invertebrate death 24 hrs, 12–20 ppm, Prudhoe Bay crude Ballou et al. 1989

No effects on growth parameters 6 hrs, 6–50 ppm, Arabian light crude Dodge et al. 1984

Dispersants guidelines

•	 Dispersants are applied using spraying systems, mostly aerial or from vessels, at a specific

treatment rate, (e.g., 5 gallons per acre of oil, or dispersant:oil ratio of 1:20).Multiple applications may be needed over several days.

•	 The window of opportunity for effective use of dispersants is small:it depends on the oil type,

and narrows with oil weathering and increases in viscosity and emulsification.

•	 Dispersant use is not likely to be 100% effective and thus will not eliminate the need for other

response methods, or the effects of the undispersed oil.

•	 Available dispersants are much less toxic than older formulations;most toxic impacts are from

the oil itself.

•	 Dispersant trade-offs center on potential impacts to water-column and shallow benthic organisms versus impacts to birds, mammals, turtles, and shoreline resources (such as mangroves).

•	 Recommendations from the National Research Council (ASTM 1987) on dispersant use around

coral reefs:

– Whenever an oil spill occurs in the general vicinity of a coral reef, dispersant use should be considered to prevent floating oil from reaching the reef.

– Dispersant-use decisions to treat oil already over a reef should take into account the type of oil 

and location of the reef.

– Coral reefs with emergent portions are high-priority habitats for protection during oil spills.
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Chapter 4. Response Methods For Coral Reef Areas

– The use of dispersants over shallow submergent reefs is generally not recommended, but the 

potential impacts to the reef should be weighed against impacts that might occur from allowing 

the oil to come ashore.

– Dispersant use should be considered to treat oil over reefs in water depths greater than 10 m if 

the alternative is to allow the oil to impact other sensitive habitats on shore.

– Chemical Dispersion is not recommended to treat oil already in reef habitats having low-water 

exchange rates (e.g., lagoons and atolls) if mechanical cleanup methods are possible.

For further reading

A. In-situ Burning

Blenkinsopp, S., G.Sergy, K.Doe, G.Wohlgeschaffen, K.Li, and M.Fingas.1996.Toxicity of the

weathered crude oil used at the Newfoundland Offshore Burn Experiment (NOBE) and the resultant burn residue. Spill Science & Technology Bulletin 3:

277–280.

Blenkinsopp, S., G.Sergy, K.Doe, G.Wohlgeschaffen, K.Li, and M.Fingas.1997.Evaluation of the

toxicity of the weathered crude oil used at the Newfoundland Offshore Burn Experiment (NOBE)

and the resultant burn residue. In Proceedings of the Twentieth Arctic and Marine Oilspill Program 

(AMOP) Technical Seminar, Vancouver, British Columbia, June 11–13, 1997, pp.677–684.

Buist, I.A., S.L.Ross, B.K.Trudel, E.Taylor, T.G.Campbell, P.A.Westphal, M.R.Myers, G.S.

Ronzio, A.A.Allen, and A.B.Nordvik.1994.The Science, Technology and Effects of Controlled

Burning of Oil Spills at Sea.MSRC Technical Report Series 94-013.Washington, D.C.:Marine Spill

Response Corporation. 382 pp.

Daykin, M, A. Tang, G. Sergy, D. Aurand, G. Shigenaka, and Z. Wang. 1994. Aquatic toxicity resulting from in-situ burning of oil on water. In Proceedings of the Seventeenth Arctic and Marine Oilspill 

Program (AMOP) Technical Seminar, Vancouver, British Columbia, June 18–10, 1994, pp.

1165–1193.

Daykin, M. M., P. A. Kennedy, and A. Tang. 1995. Aquatic toxicity from in-situ oil burning. Ottawa, 

Ontario: Environment Canada, Emergencies Science Division, Environmental Technology Centre 62 

pp.

Gulec, I. and D. A. Holdway. 1999. The toxicity of laboratory burned oil to the amphipod 

Allorchestes compressa and the snail Polinices conicus. Spill Science and Technology 5:135–139.

S. L. Ross Environmental Research, Ltd. 1998. Identification of Oils that Produce Nonbuoyant Insitu Burning Residues and Methods for their Recovery.

Prepared for American Petroleum Institute

and Texas General Land Office by S. L. Ross, Ottawa, Canada. 50 p.
–48–

Oil Spills in Coral Reefs: Planning and Response Considerations

B. Dispersants

American Society for Testing and Materials (ASTM).1987.Ecological considerations for the use of

chemical dispersants in oil spill response - coral reefs.pp.909–923, 932–938 and 941–961, Annual 

Book of Standards, v. 11.04. Philadelphia: ASTM.

Aurand, D. 1995. A research program to facilitate resolution of ecological issues affecting the use 

of dispersants in marine spill response.In P.Lane (ed).The Use of Chemicals in Oil Spill Response.

ASTM 1252, American Society for Testing and Materials, Philadelphia, pp.172–190.

Ballou, T.G., S.C.Hess, R.E.Dodge, A.H.Knap, and T.D.Sleeter.1989.Effects of untreated

and chemically dispersed oil on tropical marine communities: A long-term field experiment. In 

Proceedings of the 1989 International Oil Spill Conference, San Antonio, February 13–16, 1989, pp.

447–454.

Cook, C.B.and A.H.Knap.1983.Effects of crude oil and chemical dispersant on photosynthesis

in the brain coral Diploria strigosa. Marine Biology 78:21–27.

Dodge, R. E., S. C. Wyers, H. R. Frith, A. H. Knap, S. R. Smith, and T. D. Sleeter. 1984. The effects of 

oil and oil dispersants on skeletal growth of the hermatypic coral Diploria strigosa. Coral Reefs 3:

191–198.

Epstein, N., R.P.Bak, and B.Rinkevich.2000.Toxicity of third generation dispersants and dispersed Egyptian crude oil on Red Sea coral larvae. Marine Pollution Bulletin 40: 497–503.

George-Ares, A. and J. R. Clark. 2000. Aquatic toxicity of two Corexit dispersants. Chemosphere 40:

897–906.

Green, D.R., J.Buckley, and B.Humphrey.1982.Fate of chemically dispersed oil in the sea:

A report on two field experiments. Technology Development Report EPS-4-EC-82-5. Ottawa, 

Ontario: Environment Canada. 125 pp.

Harrison, P.L., J.C.Collins, C.G.Alexander, and B.A.Harrison.1990.The effects of fuel oil and

dispersant on the tissues of a staghorn coral Acropora formosa: A pilot study. In Scientific Input to 

Oil Spill Response, Proceedings of Second National Workshop on Role of Scientific Support Co-ordinator, HMAS Cerberus (Hastings, Victoria), March 26–30, 1990, pp.

51–61.

Knap, A. H., T. D. Sleeter, R. E. Dodge, S. C. Wyers, H. R. Frith, and S. R. Smith. 1983. The effects of 

oil spills and dispersant use on corals. A review and multidisciplinary experimental approach. Oil 

and Petrochemical Pollution 1:157–269.

Lane, A. and P. L. Harrison. 2000. Effects of oil contaminants on survivorship of larvae of the 

scleractinian reef corals Acropora tenuis, Goniastrea aspera and Platygyra sinensis from the Great 

Barrier Reef.In:Proceedings of the 9th International Coral Reef Symposium, Vol. 1, pp.403–408.
–49–

Chapter 4. Response Methods For Coral Reef Areas

Legore, S., D. S. Marszalek, L. J. Danek, M. S. Tomlinson, J. E. Hoffman, and J. E. Cuddeback. 1989.

Effect of chemically dispersed oil on Arabian Gulf corals: A field experiment. In Proceedings of the 

1989 International Oil Spill Conference, San Antonio, February 13–16, 1989, pp.375–380.

Lessard, R. R. and G. Demarco. 2000. The significance of oil spill dispersants. Spill Science and 

Technology Bulletin 6:59–68.

Mackay, D., S. Chang, and P. G. Wells. 1982. Calculation of oil concentrations under chemically 

dispersed slicks. Marine Pollution Bulletin 13:278–263.

National Research Council (NRC).1989.Using Oil Spill Dispersants on the Sea. Washington, D.C.:

National Academy Press. 335 pp.

National Research Council. 2005. Oil Spill Dispersants: Efficacy and Effects. National Academy 

Press, Washington, DC. 377 pp.

Negri, A. P. and A. J. Heyward. 2000. Inhibition of fertilization and larval metamorphosis of the 

coral Acropora millepora (Ehrenberg, 1834) by petroleum products oil contamination along oil

tanker routes off the United Arab Emirates (The Arabian Gulf and the Gulf of Oman).Marine Pollution Bulletin 7:

420–427.

Shafir, A., J.Van Rijn, and B.Rinkevich.2007.Short and long term toxicity of crude oil and oil dispersants to two representative coral species. Environmental Science & Technology 41:

5571–5574.

Singer, M.M., S.Jacobson, M.Hodgins, R.S.Tjeerdema, and M.S.Sowby.1999.Acute toxicological consequences of oil dispersal to marine organisms. In Proceedings of the 1999 International Oil 

Spill Conference, Seattle, March 8–11, 1999, pp.1031–1033.

Swannell, R. P and F. Daniel. 1999. Effect of dispersants on oil biodegradation under simulated 

marine conditions. In Proceedings of the 1999 International Oil Spill Conference, Seattle, March 8–11,

1999, pp.169–176.

Thorhaug, A. and 12 authors. 1991. Dispersant use for tropical nearshore waters: Jamaica. In Proceedings of the 1991 International Oil Spill Conference, San Diego, March 4–7, 1991, pp.

415–418.

van Ouenhoven, J.A.C.M.1983.The Hasbah 6 (Saudi Arabia) blowout:The effects of an international oil spill as experienced in Qatar. In Proceedings of the 1983 International Oil Spill Conference, 

San Antonio, February 28–March 3, 1983, pp.381–388.

Wells, P. G. 1984. The toxicity of oil spill dispersants to marine organisms: A current perspective. In 

T.E.Allen (ed), Oil Spill Chemical Dispersants: Research, Experience and Recommendations. STP 840.

Philadelphia:American Society for Testing and Materials.pp.177–202.

Wyers, S.C., H.R.Frith, R.E.Dodge, S.R.Smith, A.H.Knap, and T.D.Sleeter.1986.Behavioral

effects of chemically dispersed oil and subsequent recovery in Diploria stirigosa (Dana).Marine 

Ecology 7:23–42.
–50–

Oil Spills in Coral Reefs: Planning and Response Considerations

Coral transplanting as part of restoration activities in Pago Pago, American Samoa, 

1999 (NOAA OR&R).
–51–

Chapter 5. Coral Reef Restoration 

Chapter 5. Coral Reef Restoration 

Key points

•	 Ship groundings on coral reefs physically damage the reef framework, increasing erosion and

reef degradation.

•	 Reef crust and loose rubble should be stabilized as soon as possible after they are physically

damaged.

•	 Damaged coral reefs may take decades to centuries to fully recover.

•	 Coral transplanting can expedite coral recolonization of damaged areas, especially in protected areas.

•	 Massive corals survive transplanting better than branched corals, but are very slow-growing.

Soft corals are difficult to transplant successfully.

•	 Physical surroundings affect how fast coral regrows.

•	 The recovered reef may be different from the original.

•	 Recovery is more likely after acute rather than chronic disturbances.

•	 Delaying restoration may significantly increase restoration costs, increase recovery time, and

decrease likelihood of full recovery.

Most work to restore coral reefs to date has focused on restoring physical injuries caused by

vessel groundings rather than injury resulting from oil or chemical exposure.Grounding impacts

are, in many cases, the main injuries inflicted on coral reefs from“potential”spills or spills of small

to moderate quantities of oil. The initial grounding itself and subsequent attempts to free the 

vessel may physically damage the reef framework and resident marine organisms. Direct grounding damage is often later exacerbated by associated mobile debris. Grounding of vessels of all 

types on reefs continues to be a significant source of injury to coral reefs around the world.

Accretive and destructive (or erosive) forces act continuously upon coral reefs in relative

steady state. Damage to a coral reef framework opens the door for destructive forces to gain 

ground and degrade the reef. Once this reef framework, or “crust,” is breached, for example by 

the hull of a grounded vessel, ship propellers, anchors, or towlines, the unconsolidated material 

beneath the surface is exposed. The breached area, if not repaired, will expand over time, especially during storms or hurricanes. Furthermore, the exposed coral rubble can be mobilized during 

storms and cause collateral reef damage. Structural restoration of the damaged reef framework, 

including stabilizing loose rubble, is essential before either natural or enhanced recovery of the 

live reef community can occur. Reef framework restoration should be conducted as soon as 
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Oil Spills in Coral Reefs: Planning and Response Considerations

possible after a vessel grounding to minimize mortality of reef biota and risk of additional injury

during storms. Delaying restoration may significantly increase restoration costs, increase recovery 

time, and decrease likelihood of full recovery.

Restoration through prevention

Even under the best restoration efforts, coral reefs, once injured, may take decades, if not

centuries, to recover.In some cases, injured reefs may never recover.The best strategy is to

prevent reef injury in the first place through effective vessel management.Designating“areas to

be avoided” by large commercial vessels is one way to help maximize vessel safety and minimize 

physical and biological damage to reefs in areas such as National Marine Sanctuaries. However, 

large commercial vessels are a small component of a chronic problem. In the Florida Keys National 

Marine Sanctuary there are over 580 reported groundings a year, with 40-50% of these on coral 

and the rest on seagrass and hard-bottom habitats. A significant number of these incidents result 

in small spills of refrigerants, lube oils, and diesel fuels. Improved navigational technology and 

education for mariners can also help prevent vessel groundings. Part of the settlement with the 

Responsible Party for a container ship grounding in the Florida Keys included the installation of 

navigation buoys along the outer reef edge.It was estimated that if this system (installed in 1999)

had been in place, it would have prevented 56% of the groundings that occurred along the Florida 

Keys reef system between 1984 and 1999. Nevertheless, it is likely that groundings, like oil spills, 

will continue. Consequently, restoring the physical and biological integrity of damaged coral reefs 

will continue to play an important role in the maintenance of healthy coral reef ecosystems.

Coral transplanting

Coral recruitment onto either intact reef framework or structurally restored reef framework 

may be limited due to scarcity of coral larvae or due to chronic anthropogenic disturbances and 

influences that inhibit successful settlement of larvae. In such cases, transplanting coral can help 

expedite coral recolonization of damaged reef areas.

Transplanted corals often survive and grow in low-energy areas, although damage and 

mortality from wave action is common in less protected locations. Staghorn corals and other 

branching corals of the genus Acropora show good survival and rapid growth after transplanting, 

but their branching growth form and small area of attachment seem to make them particularly 

vulnerable to damage from strong wave action. Thus, using staghorn corals for transplanting may 

be limited to more sheltered areas. Coral species with massive growth forms are more resilient 

to wave action but are very slow-growing, which may make them less suitable for transplanting 
–53–

Chapter 5. Coral Reef Restoration 

where rapid recolonization is desired. Soft corals are more difficult than hard corals to relocate 

without injuring the delicate holdfast tissue, which often eventually kills the transplant.

If coral for transplanting is not available from the damaged area, such as coral broken off or 

mobilized from vessel groundings, extreme caution must be exercised to prevent injury to donor

populations. In addition to transplanting, reattachment of broken or toppled corals using quicksetting lime cement or epoxies has been used to successfully restore some species of damaged 

corals, as described by Hudson and Goodwin (1997).

Coral reef recovery rates

Corals are long-lived and recover slowly from disturbances, whether these are natural, such 

as hurricanes, or human-caused, such as ship groundings or exposure to pollutants. How fast and 

how well a coral reef recovers depends on the extent and type of damage, the location, species 

affected, suitable habitat, and many other parameters. Severe and repeated impacts delay recovery, while ongoing pollution and other chronic stresses may postpone it indefinitely.

Recovery is commonly measured using percent coral cover, species diversity, mean colony 

height, and overall coral color and health. Disturbed areas are compared with nearby areas that 

have not been impacted, or with data collected from the same area before the disturbance. Coral 

on damaged reefs recover by regenerating from partially damaged colonies, by reestablishing 

broken coral fragments, and through settlement of coral larvae carried by ocean currents.

If corals are injured but not killed, survivors regrow as the primary recovery mechanism.If

most of the coral is killed, recovery will depend almost entirely on recruitment and growth of 

propagules from elsewhere, which will be much slower. A physically damaged reef recovers more 

slowly, and may need restoration. For example, vessel groundings fragment coral skeletons, 

producing loose rubble and fine sediments that inhibit successful recolonization of hard corals.

When destruction is localized and small-scale, coral reef communities usually recover in less than 

ten years, if major sectors of the community are left intact and the area involved is not already

marginal for coral growth.Reefs damaged by major natural disasters may take up to 20 years or

longer for full recovery of affected areas. Where destruction has been particularly severe, complete 

reef recovery may take several decades or perhaps over a century.Corals of the Great Barrier Reef

devastated by Crown of Thorns starfish may require 20 to 40 years for full recovery if the bulk of 

hard coral cover has been lost. Recovery may be delayed indefinitely if starfish infestations recur or 

if reefs are subsequently impacted by other natural or human-induced disturbances.

Recovery may also be delayed if the exposed substrate is resettled by fleshy seaweeds instead 

of coral or coralline algae. The situation can be exacerbated further if the algae are alien species.
–54–

Oil Spills in Coral Reefs: Planning and Response Considerations

Given the right environmental conditions, a seaweed may be able to gain a foothold at a grounding site and then spread outwards over previously unimpacted reef.

Recovery time depends on the type and intensity of the disturbance. From observing coral 

communities in the Great Barrier Reef over a 30-year period, Connell et al.(1997) found that coral

assemblages usually recovered from acute disturbances, though rates were slower if disturbances 

altered the physical environment than if they simply killed or damaged corals. In contrast, corals 

did not recover from chronic disturbances of either natural or human origins, or from gradual 

declines. Thus, recovery was more likely if disturbances were acute rather than chronic, since 

recovery will be continually interrupted or set back by repeated, chronic disturbances.

When a coral ecosystem has completely collapsed or the reef environment has changed permanently, making conditions unsuitable for coral, there may be no significant recovery. In areas 

that are marginal for coral growth, disturbances may result in algae replacing coral completely.

Where recovery does occur, the reef may differ from the original in species composition, biological 

assemblages, and reef building capacity.

Physical characteristics such as exposure can significantly influence the process and rate of 

recovery for impacted reefs. For example, areas decimated by lava flows in Hawai’i took about 20 

years to recover in exposed areas and more than 50 years in sheltered areas. For reefs in Hawai’i 

and the Eastern Pacific, which are physically controlled coral communities, recovery rates are 

related to the degree of exposure to sea and swell. Exposed areas require less time for recovery 

since coral is naturally less abundant in exposed areas and less growth is required for a reef to 

completely recover to background conditions. Growth rates of some corals are higher in exposed 

areas, which may be related to differences in circulation or food supply. However, recovery patterns may be different in more biologically accommodated coral reef communities, such as those 

in the Caribbean and Red Sea.

In a review of coral reef recovery rate, Zengel and Hinkeldey (2000) made these key points:

•	 Early-successional coral communities generally recover in about 10-20 years or less following

relatively small-scale or localized, acute disturbances that do not change the suitability of the 

site for coral recruitment, growth, and survival.

•	 Coral communities that are more mature, in late-successional to climax stages, may require

several decades to a century or more to recover, especially if long-lived, large-sized, persistent 

species are lost.

•	 Branching Acropora stands, particularly those in the Caribbean and Florida, can show variable

recovery times, from relatively fast to much longer, depending on the nature and extent of the 

disturbance.
–55–

Chapter 5. Coral Reef Restoration 

•	 There is some evidence that coral communities in the Western Atlantic region may be less

likely to recover, or may recover more slowly, than corals in the Indo-Pacific region.

•	 Coral communities at greater depth may recover more slowly than those in shallow waters.

•	 Severe disturbances that kill or remove all or most corals, or that cover large spatial areas result

in longer recovery times.

•	 Severe disturbances that alter the physical environment or landscape result in substantially

longer recovery times.

•	 Recovery is more likely and more rapid following acute (short-term) vs.chronic (long-term)

disturbances.

•	 Recovery from an acute disturbance can be hindered by pre-existing or co-occurring chronic

disturbance; likewise, several disturbances or “multiple stressors” can interact, limiting recovery.

•	 In some cases, disturbance can result in a “phase shift”to a macroalgae community, limiting or

precluding coral recovery.

Recovery from oil exposure

Coral communities may recover more rapidly from oil exposure alone than from mechanical 

damage. Coral reefs exposed to crude oil and chemically dispersed crude oil in field experiments 

conducted in Panama showed recovery, with no significant differences between the exposed and 

control sites, after ten years. Short-term bioassays of corals exposed to oil have revealed temporary effects followed by recovery generally within one week.

Recovery of coral reefs after oil exposure, however, may depend partly on the recovery of 

associated communities that may be more seriously affected, such as mangroves and seagrass 

beds.As described in the case study, the 1986 Bahía las Minas oil spill in Panama impacted mangrove and seagrass communities, as well as corals.

Death and injury of these habitat-structuring

organisms physically destroyed habitats. The secondary biological effects of erosion and redeposition of oily sediments included greatly increased levels of injuries and decreased growth and

sexual reproduction for surviving subtidal reef corals in Bahía Las Minas compared to coral reefs

outside the bay.The entire Bahía Las Minas ecosystem became more vulnerable to subsequent

natural or anthropogenic disturbances. It has been estimated that recovery of the dominant reefbuilding corals may require at least a century or more to reach the size of many of the colonies 

killed by this spill.
–56–

Oil Spills in Coral Reefs: Planning and Response Considerations

For further reading

Connell, J. H., T. P. Hughes, and C. C. Wallace. 1997. A 30-year study of coral abundance, recruitment, and disturbance at several scales in space and time. Ecological Monographs 67:

461–488.

Cubit, J.D., C.D.Getter, J.B.Jackson, S.D.Garrity, H.M.Caffey, R.C.Thompson, D.Weil, and M.J.

Marshall. 1987. An oil spill affecting coral reefs and mangroves on the Caribbean coast of Panama.

Proceedings of the 1987 International Oil Spill Conference, April 6–9, 1987, Baltimore, pp.401–406.

Dodge, R. E., A. H. Knap, S. C. Snedaker, and T. D. Sleeter. 1995. The Effects of Oil and Dispersed 

Oil in Tropical Ecosystems: 10 Years of Monitoring Experimental Sites. MSRC Technical Report 

Series 95-014. Washington, D.C.: Marine Spill Response Corporation, 82 pp. + app.

Done, T. J. 1999. Coral community adaptability to environmental change at the scales of regions, 

reefs and reef zones. American Zoologist 39:66–79.

Endean, R. 1976. Destruction and recovery of coral reef communities. In: Biology and Geology of 

Coral Reefs, Volume III: Biology 2.O.A.Jones and R.Endean (eds.), Academic Press, New York, pp.

215-254.

Gittings, S.R., T.J.Bright, A.Choi, and R.R.Barnett.1998.The recovery process in a mechanically

damaged coral reef community: recruitment and growth. Proceedings of the Sixth International 

Coral Reef Symposium, Townsville, Australia, August 8th–12th, 1988, pp.225–230.

Grigg, R. W., and J. E. Maragos. 1974. Recolonization of Hermatypic corals on submerged lava 

flows in Hawaii. Ecology 55: 387–95.

Guzmán, H.M., K.A.Burns, and J.B.C.Jackson.1994.Injury, regeneration and growth of Caribbean reef corals after a major oil spill in Panama.

Marine Ecology Progress Series 105:231–241.

Hudson, J.H.and W.B.Goodwin.1997.Restoration and growth reate of hurricane damaged pillar

coral (Dendrogyra cylindrus) in the Key Largo National Marine Sanctuary, Florida.Proceedings of the 

Eighth International Coral Reef Symposium, Panama, June, 1996, pp.567–570.

Hughes, T.P.and J.B.C.Jackson.1980.Do corals lie about their age? Some demographic consequences of partial mortality, fission and fusion. Science 209:

713–715.

Jackson, J.B.C, J.D.Cubit, B.D.Keller, V.Batista, K.Burns, H.M.Caffey, R.L.Caldwell, S.D.Garrity, C. D. Getter, C. Gonzalez, H. M. Guzmán, K. W. Kaufmann, A. H. Knap, S. C. Levings, M. J.

Marshall, R.Steger, R.C.Thompson, and E.Weil.1989.Ecological effects of a major oil spill on

Panamanian Coastal Marine Communities. Science 243:37–44.

Loya, Y. 1976. Recolonization of Red Sea corals affected by natural catastrophes and man-made 

perturbations. Ecology 57:278–289.

Maragos, J. E. 1992. Restoring coral reefs with emphasis on Pacific reefs. In: Restoring the Nation’s 

Marine Environment, Gordon W.Thayer, (ed.), Maryland Sea Grant Books, College Park.
–57–

Chapter 5. Coral Reef Restoration 

Maragos, J. E. 1994. Reef and coral observations on the impact of the grounding of the longliner 

Jin Shiang Fa at Rose Atoll, American Samoa. Honolulu: U.S. Fish and Wildlife Service, Pacific Island 

Office. 27 pp.

Pearson, R. G. 1981. Recovery and Recolonization of Coral Reefs. Marine Ecology Progress Series 4:

105–122.

Schmahl, G. P., D. R. Deis, and S. K. Shutler. 2006. Cooperative natural resource damage assessment and coral reef restoration at the container ship Houston grounding in the Florida Keys 

National Marine Sanctuary.In:Precht WF, editor.Coral reef Restoration Handbook.Boca Raton,

Florida:CRC Press.p.235–56.

Shafir, S., J.Van Rijn, and B.Rinkevich.2007.Short and long toxicity of crude oil and oil dispersants to two representatives coral species. Environ. Sci. Technol. 41:

5571–5574.

Wilkinson, C. R. 1999. Global and local threats to coral reef functioning and existence: review and 

predictions. Marine Freshwater Research 50:867–78.

Zengel, S. and H. Hinkeldey. 2001. Coral reef recovery: literature review and recommendations for 

damage assessment and restoration planning. Silver Spring, Maryland: Research Planning, Inc.; 46 

p.

A helicopter brings response personnel to the grounded barge 

Morris J. Berman off San Juan, Puerto Rico, 1994 (NOAA 

OR&R)
–58–

Oil Spills in Coral Reefs: Planning and Response Considerations

Oiled coral exposed at low tide, Bahía Las Minas, 

Panama (Carl Hansen) 
–59–

Chapter 6. Coral Case Studies

Chapter 6. Coral Case Studies

Introduction

By studying past oil spills in coral reef environments, we get a good idea of some of the complexities and variability of these types of incidents. We have searched for case studies of oil spills 

impacting coral reefs that were well documented both during the incident and response, and also 

were re-visited after the spill to determine long-term outcomes. Unfortunately, many incidents are 

poorly documented, especially those dating back several decades. We describe several case studies representing oil spills from the Pacific, Caribbean, and Arabian regions. Some events caused 

devastating, long-lasting impacts, while others appeared to have caused little long-term impact to 

corals. Some spills, such as the Ocean Eagle and Morris J. Berman, did not impact coral because the 

oil did not reach areas rich in coral. However, these incidents illustrate many of the other response 

limitations that may be present on tropical island incidents, such as limited availability of salvage 

and response equipment and limited storage capacity for collected oil. The Rose Atoll incident 

illustrates an unfortunate but not uncommon type of spill, especially in the Pacific—a freighter or 

fishing vessel runs aground in bad weather on a remote atoll. Response options are almost nonexistent, and salvage vessels must travel for several days to weeks to reach the site. The ship often 

breaks up before the salvor can reach the scene, spilling cargo and fuel and causing repeated 

physical damage as wind and waves toss the wreck about on sensitive coral structures.

For several spills that were not well documented, and where limited follow-up research was 

conducted after the spill, we often do not know whether corals were impacted or for how long 

(e.g., R. C. Stoner and Zoe Colocotronis).At the time, these response efforts and associated studies

focused on oiled beaches and shorelines that represented a valuable economic resource, while 

paying less attention to offshore, underwater habitats. Our most extensively documented case 

study is that of Bahía las Minas, Panama where several biological habitats were studied intensively,

and followed for many years after the spill.Bahía las Minas provides an excellent example of the

tradeoffs that are encountered in many tropical environments between different nearshore habitats, such as mangroves, and subtidal seagrass beds or coral reefs and how these respond differently to oil contamination.

We have included descriptions of two field experiments that, while not representing actual 

oil spills, do provide good information on oil spill impacts in a controlled, non-laboratory setting. Lastly, several restoration case studies give current examples of how reefs that have been 
–60–

Oil Spills in Coral Reefs: Planning and Response Considerations

physically damaged from ship groundings can be given a boost towards eventual recovery by the 

developing technologies of reef restoration.

Spill case studies

R. C. Stoner, Wake Island/September 1967

On September 6, 1967, the tanker R. C. Stoner grounded 200 meters southwest of the harbor 

entrance at Wake Island. Wake Island, in the North Pacific Ocean, consists of three islets forming an 

atoll enclosing a shallow lagoon. The tanker was fully loaded with over 6 million gallons of refined 

fuel oil, including 5.7 million gallons of aviation fuel; 168,000 gallons of diesel oil; and 138,600 gallons of Bunker C.

There was an immediate release of fuel after the grounding, believed to be primarily aviation fuel.

On the following day, a “considerable quantity”of Bunker C was also observed,

and gasoline vapor odor was detected through September 8.

The heavy cargo load and rough seas hampered efforts to refloat the vessel, and on September 8 the stern of the ship broke off. An estimated 600,000 gallons of the mixed fuels covered the 

surface of a small boat harbor, up to 20 cm thick. The strong southwest winds concentrated the 

spilled oil in that harbor and along the southwestern coast of Wake Island.

Response

Oil recovered from the small boat harbor by pumps and skimmers was moved into pits near 

the shore and burned each evening; over 100,000 gallons were disposed of in this fashion. The oil 

was blocked from entering the central lagoon area of the Wake Island group by an earthen causeway.

Impacts

Large numbers of dead fish were stranded along the southwestern shoreline. The Federal 

Aviation Administration (FAA) cleared the area closest to the spill of dead fish.In addition to the

massive fish kill (approximately 1,360 kg collected), dead turbine [sic] molluscs, sea urchins, and a 

few beach crabs were also reported. About 2.4 km of shoreline beyond the FAA-cleaned zone was 

also oil-contaminated; another 900 kg of dead fish were present but not removed. Other dead 

invertebrates included cowries, nudibranches, and grapsoid crabs.

In this assessment, corals in the area were mentioned only in passing and apparently were 

not surveyed either formally or informally for impact. Discussion of corals was completely in the 

context of the associated fish communities. Given the mixture and quantities of fuel spilled, and 

the massive mortalities manifested in fish and reef-associated invertebrates, there almost certainly 
–61–

Chapter 6. Coral Case Studies

was an impact to the coral animals themselves. Gooding did note that, on a survey conducted 

11 days after the grounding (after a typhoon had passed through the area), the only remaining

visible impact in the inner harbor was black oil impregnated in coral. He stated that only cursory 

observations were made on reef invertebrates and, given external challenges to impact assessment described in the account (typhoons, tropical storm, harassment by black-tipped sharks, skin

irritation to divers from exposure to fuels in water), effects to coral was presumably not included in

survey objectives.

For further reading

Gooding, R. M. 1971. Oil pollution on Wake Island from the tanker R. C. Stoner. Special Scientific 

Report--Fisheries No.636.Seattle:NOAA/National Marine Fisheries Service.12 pp.

Ocean Eagle spill, Puerto Rico / March 1968

Morris J. Berman, Puerto Rico / January 1994

These two spills are grouped together primarily because they had similar locations, along 

the northern shoreline of Puerto Rico; and both reported a lack of impacts to coral reefs. The two 

considerations are linked. The northern coast of Puerto Rico has many large hotels and recreational beaches, but few coral reef areas. The circumstances of the two spills were otherwise rather 

different. The Ocean Eagle grounded on March 3, 1968 in San Juan Harbor, after which it broke in 

two and spilled 83,400 bbl of Venezuelan light crude oil. The Morris J. Berman was a barge laden 

primarily with a No.6 fuel oil that drifted ashore about 300 meters off Escambron Beach after its

towing cable parted on January 7, 1994.

Response

At the Ocean Eagle, chemical treatments then called an “emulsifier” were spread on thick oil on 

the water surface. These treatments were described as effective, apparently functioning similarly 

to dispersants. The Berman barge was eventually pulled off its grounding site and scuttled in 

deeper waters offshore. Shoreline cleanup was extensive, and included manual cleanup and washing. Submerged oil mats were collected by divers.

Impacts

Impacts of concern, as noted above, were similar for both incidents. Nearly all of the large 

tourist hotels and beaches in San Juan are concentrated along the north-central shoreline of 

Puerto Rico, where much of the oil in both incidents came ashore. Although many of these 
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Oil Spills in Coral Reefs: Planning and Response Considerations

recreational areas were heavily impacted, sensitive natural resources such as coral reefs and mangroves that would be a major concern elsewhere in Puerto Rico are not found in abundance here.

Widespread mortalities, primarily among fish and benthic invertebrates, were noted during both 

the Ocean Eagle and the Morris J. Berman spills; however, except for a small number of soft corals 

at the Berman grounding site, there is no mention of adverse effects to corals. This should not be 

construed as the absence for potential effect, but rather as a semi-fortuitous consequence of spill 

location and circumstance.

For further reading

Cerame-Vivas, M. T. 1968. The wreck of the Ocean Eagle. Sea Frontiers 15:222–231.

NOAA.1992.Oil spill case histories 1967–1991, Summaries of significant U.S.and international

spills.Report No.HMRAD 92-11.Seattle:NOAA/Hazardous Materials Response and Assessment

Division.

NOAA.1995.Barge Morris J. Berman spill, NOAA’s scientific response. HAZMAT Report 95-10.

Seattle:NOAA/Hazardous Materials Response and Assessment Division.63 pp.

SS Witwater spill, Panama / December 1968

On December 13, 1968, the 35,000-barrel tanker SS Witwater broke apart on the Caribbean 

coast of Panama and released around 20,000 barrels of Bunker C and marine diesel oil.The spill

occurred within three miles of the then-new Smithsonian Tropical Research Institute laboratory at 

Galeta Point.

Response

Response methods included pumping and in-situ burning of oil that collected in a small bay.

Little documentation is available about how the burning was conducted, though it appears to 

have been without booms, and was considered successful in removing some oil and in limiting 

environmental impacts.

Environmental impacts

A follow-up study conducted two months after the spill found that coral reefs were the least 

affected of all the communities studied and no ill effects to corals (mainly Porites furcata, P. asteroides, Siderastrea radians, and Millepora complanata (a hydrocoral)) were observed.

Since the reefs

are subtidal, they had no direct contact with the oil, and a higher-than-normal low tide caused by 

high winds may have protected coral from impacts. The incident highlighted the dearth of baseline information on Caribbean intertidal reef flat communities. A substantial effort was invested by 
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Chapter 6. Coral Case Studies

the Smithsonian lab to compile those data, which were then used to provide background information for experimental tests of effects of oil, reported in Birkeland et al.

(1976).

Black and red mangroves were more severely impacted, with visible sediment contamination,

oil coating on roots and pneumatophores, and die-off of seedlings. Sandy shorelines had heavily 

oiled subsurface sediments, to depths of 30 cm.

For further reading

Birkeland, C., A.A.Reimer, and J.R.Young.1976.Survey of marine communities in Panama and

experiments with oil. EPA Report EPA-60013-76-028. Narragansett: U.S. Environmental Protection 

Agency. 177 pp.

Rützler, K. and W. Sterrer. 1970. Oil pollution. Damage observed in tropical communities along 

the Atlantic seaboard of Panama. Bioscience 20:222–224.

Zoe Colocotronis / March 1973

On March 18, 1973 the tanker Zoe Colocotronis intentionally dumped 37,000 barrels of Venezuelan crude oil in order to lighter the vessel from the reef on which it grounded. Oil was carried 

ashore to beaches near Cabo Rojo in Bahía Sucia, Puerto Rico and into several areas containing

mangrove forests.

Response 

Response efforts included booming, digging sumps, and pumping collected oil into tank 

trucks. The U.S. Coast Guard Atlantic Strike Team helped with beach cleanup.

Impacts

Oil impacts killed approximately 2.5 acres of mangrove forest, including red and black mangroves. Numerous dead invertebrates washed ashore, including sea cucumbers, conchs, prawns, 

sea urchins, and polychaetes. Thalassia seagrass beds offshore were heavily impacted with oil and 

sediments were contaminated. Impacted Thalassia beds suffered die off and subsequent erosion, 

followed by recolonization after approximately one year.

Oil could well have impacted the numerous coral reefs near the spill site. Most of the attention seems to have been focused on the shoreline and nearshore subtidal impacts, including 

seagrass and mangroves. To our knowledge, no one looked at potential oil impacts to coral reefs.
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Oil Spills in Coral Reefs: Planning and Response Considerations

For further reading

Nadeau, R.J., and E.T.Bergquist.1977.Effects of the March 18, 1973 oil spill near Cabo Rojo,

Puerto Rico on tropical marine communities. In Proceedings of the 1977 International Oil Spill Conference, New Orleans, March 8–10, pp.

535–538.

Page, D. S., D. W. Mayo, J. F. Cooley, E. Sorenson, E. S. Gilfillan , and S. A. Hanson. 1979. Hydrocarbon distribution and weathering at a tropical oil spill site. In Proceedings of the 1979 International 

Oil Spill Conference, Los Angeles, March 19–22, 1979, pp.709–712.

T/V Garbis spill, Florida Keys / July 1975

On July 18, 1975, the tanker Garbis spilled 1,500 to 3,000 bbls of crude oil into the waters 

approximately 26 miles south-southwest of the Marquesas Keys, Florida. The oil was blown ashore 

along a 30-mile stretch of the Florida Keys, east of Key West. The only published description of this 

spill and its impacts are found in Chan (1977), although the 1976 M.S.thesis of that author at the

University of Miami further detailed effects and recovery. The source of the spill, the Garbis, was 

identified after the publication of both documents.

Environmental impacts

In addition to documenting early impacts, Chan established a series of sites to be monitored 

over a year following the spill. Since no pre-spill information was available, effect and recovery 

were judged through comparison with unoiled, biologically similar locations.

Several habitats were impacted, including killing of echinoderms, pearl oysters, and oiled red 

and black mangroves. However, a notable lack of spill effect was found in coral reef areas. Reefs 

were surveyed by divers immediately following the spill, and subsequently in August and November 1975 and January 1976. Chan attributed this lack of impact to the fact that the reefs were 

completely submerged during the spill and to calm seas that minimized water column contact 

with the oil.

For further reading

Chan, E.I.1977.Oil pollution and tropical littoral communities:Biological effects of the 1975

Florida Keys oil spill. In Proceedings of the 1977 International Oil Spill Conference, New Orleans, 

March 8–10, pp.539–542.

Bahía Las Minas, Panama / April 1986

On April 27, 1986, about 240,000 barrels of medium weight crude oil (70 percent Venezuelan

crude, 30 percent Mexican Isthmus crude) spilled from a ruptured storage tank at a petroleum
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Chapter 6. Coral Case Studies

refinery at Bahía Las Minas, on the central Caribbean coast of Panama.Of this amount, an estimated 60,000–100,000 barrels spilled into the waters of Bahía Las Minas.

This was the largest

recorded spill into a sheltered coastal habitat in the tropical Americas. The spill was located close 

to the Galeta Marine Laboratory of the Smithsonian Tropical Research Institute, and extensively 

studied.

Response

Six days after the release began, 137 bbls of Corexit 9527 chemical dispersants were applied 

in one bay and along the northern breakwater at the mouth of the Panama Canal. The dispersants 

appeared to be ineffective due to the weathered state of the oil and the calm seas. Researchers 

later concluded that this limited use of dispersant chemicals could not explain the widespread 

subtidal biological impacts reported.

Impacts

The area where this spill occurred was not pristine before the 1986 incident. Nevertheless, 

the incident was shown to have widespread lethal and sublethal impacts in all environments 

examined, including the coral reefs and reef flats. In coral reefs, the cover, size, and diversity of live 

corals decreased substantially on oiled reefs after the spill. Sublethal impacts included decreased 

growth, reproduction, and recruitment.

Follow-up studies reported an extensive mortality of both intertidal reef flat corals (Porites 

spp.) and subtidal reef corals (Diploria clivosa, Porites astreoides, and Siderastrea siderea) that was

attributed to the spill. S. siderea was particularly vulnerable, with patches of recent coral death 

disproportionately common on heavily oiled reefs one year after the spill.

A longer-term follow-up study found higher percentages of recently injured corals at heavily

oiled reefs. However, there were peaks immediately after the spill and also during another period 

spanning 3-5 years post-spill. The latter impacts were attributed to a series of diesel fuel spills at 

the electrical generation plant in Bahía Las Minas.

Coral growth studies in four native species after the spill initially found reductions in growth 

for P. astreoides, D. strigosa, M. annularis, and no effect in S. siderea. The lowest annual mean 

growth rates were measured for 1986, the year of the spill. S. siderea and P. astreoides grew more 

slowly during the first three years after the spill than they had before. At heavily oiled reefs, 

growth after the spill declined significantly for S. siderea but not for P. astreoides.

Guzmán et al.(1991) compared cover of common coral species at six reefs before (1985) and

after (3 months post) the oil spill at Bahía Las Minas.At one heavily oiled reef, total coral cover

decreased by 76 percent in the 0.5-3 m depth range and by 56 percent in the >3–6 m range.Cover
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Oil Spills in Coral Reefs: Planning and Response Considerations

decreased less at moderately oiled reefs and either increased or did not change at the unoiled reference reefs. The branching species Acropora palmata nearly disappeared at the heavily oiled site, 

but increased by 38 percent at the unoiled reefs. This same survey found average colony size and 

diversity decreased significantly with increased oiling.

For further reading

Guzmán, H. M. and I. Holst. 1993. Effects of chronic oil-sediment pollution on the reproduction of 

the Caribbean reef coral Siderastrea siderea. Marine Pollution Bulletin 26:276–282.

Jackson, J., J.Cubit, B.Keller, V.Batista, K.Burns, H.Caffey, R.Caldwell, S.Garrity, C.Getter, C.

Gonzalez, H. Guzmán, K. Kaufmann, A. Knap, S. Levings, M. Marshall, R. Steger, R. Thompson, and 

E.Weil.1989.Ecological effects of a major oil spill on Panamanian coastal marine communities.

Science 243:37–44.

Keller, B.D.and J.B.C.Jackson, eds.1993.Long-term Assessment of the Oil Spill at Bahía Las

Minas, Panama, Synthesis Report, Volume 1: Executive Summary. OCS Study MMS 93-0047. New 

Orleans: U.S. Department of the Interior, Minerals Management Service, Gulf of Mexico Outer 

Continental Shelf Region. 129 pp.

Gulf War Spill, Arabian Gulf / January 1991

During the waning days of the Gulf War in 1991, oil was deliberately discharged by the Iraqi 

military.This resulted in the largest oil spill in history, an estimated 6.3 million barrels.Between 19

and 28 January 1991, oil was released from two major sources:three Iraqi tankers anchored in the

Kuwaiti port of Mina Al-Ahmadi, and the Mina Al-Ahmadi Sea Island terminal area.

Impacts

Given the magnitude of this release and the previous coral reef impacts noted at other tropical spills, there were dire expectations of severe impacts to nearshore and offshore reefs in Kuwait 

and Saudi Arabia. However, to date the extent of coral reef damage directly attributable to the 

Gulf War spill has been remarkably minor. Surveys of nearshore and offshore reefs conducted in 

1992 included a reef at Qit’at Urayfijan that was very likely covered by oil released from at least one

tanker and the Mina Al Ahmadi terminal. While the reef is never exposed to the atmosphere, crude 

oil was assumed to have flowed over it for days. This reef was clearly impacted, mostly in shallower 

water, with coral death in large colonies of Platygyra as well as in most of the Porites. New growth, 

however, was observed in nearly all dead portions of coral.

In contrast, conditions at Getty Reef, close to a visibly oiled beach and directly downstream 

from known release points, showed no evidence of recent coral kills or even stress among Porites, 
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Chapter 6. Coral Case Studies

Platygyra, Cyphastrea, Leptastrea, Psammocora, Favia, and Favites, and the associated fish community was especially robust. Other environmental impacts from the war, such as reduced water 

temperature and lowered ambient light from oil fire smoke, may have obscured actual effects of 

oil on coral.

Vogt (1995) established six 50-m study transects nearshore and offshore the Saudi Arabian

shoreline to document effects and recovery from the spill. On the basis of video recordings made 

along these transects between 1992 and 1994, Vogt concluded that live coral cover had significantly increased and that the corals offshore from Saudi Arabia had survived the largest spill on 

record “remarkably unscathed.”

For further reading

Reynolds, R. M. 1993. Physical oceanography of the Gulf, Strait of Hormuz, and the Gulf of 

Oman—Results from the Mt. Mitchell expedition. Marine Pollution Bulletin 27:35–59.

Vogt, H. P. 1995. Coral reefs in Saudi Arabia: 3.5 years after the Gulf War oil spill. Coral Reefs 14:

271–273.

Rose Atoll National Wildlife Refuge, American Samoa / October 1993

On October 14, 1993, the Taiwanese fishing vessel Jin Shiang Fa ran aground on the southwestern side of Rose Atoll, a remote coral reef in eastern American Samoa. The grounding resulted 

in the spillage of 100,000 gallons of diesel fuel and 500 gallons of lube oil and 2,500 pounds of 

ammonia onto the reef.

Rose Atoll is a National Wildlife Refuge that supports giant clams and a special reef composed 

of coralline algae. The atoll is inhabited by green sea and hawksbill turtles and was considered one 

of the most remote and pristine coral reefs in the world. It is a unique coral habitat in Samoa, in 

that crustose coralline algae (identified as primarily Hydrolithon onkodes and H. craspedium) dominate instead of hermatypic corals. Common reef-building corals include Favia, Acropora, Porites, 

Montipora, Astreopora, Montastrea, and Pocillopora.

Response

Because of its remote location, and safety concerns, response options at Rose Atoll were very

limited.A salvor was underway (from Singapore) but the grounded ship broke up in heavy seas

before the salvor arrived. Most of the larger pieces of wreckage and debris were removed, but the 

stern and associated debris were left in place. A post-spill analysis by a U.S. Coast Guard responder 

on-scene early in the incident suggests that one option (not pursued at the time) could have been
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Oil Spills in Coral Reefs: Planning and Response Considerations

an intentional release of oil when wind and currents were favorable to carry the oil away from the 

atoll into deeper waters. Instead, when the vessel did break up under storm conditions, winds 

were onshore, and most of the oil came directly onto the reef and into the lagoon.

Impacts

All of the petroleum products and ammonia were released into the marine environment, over 

a period estimated as six weeks. Oil was reportedly forced down onto the reef structure by wave 

action, as was oily debris from the wreck.

Although the injury to the corals from the grounding was judged to be “moderate to high,”it

was not possible to ascertain causal factors in a more specific way.Several possibilities for injury

pathways were identified:

•	 Fuel and other contaminant toxicity.

•	 Mechanical damage from the grounding and subsequent debris impacts.

•	 Anoxia due to mortalities in the reef community.

•	 Smothering and scouring from sediments created by the wreck.

•	 Competition from opportunistic algae and cyanobacteria that was being stimulated by dissolved iron being released during corrosion of the remaining debris.

•	 Bleaching from direct and indirect impacts of the incident.

Surveys conducted in the weeks following the grounding indicated that the reefs at Rose 

Atoll had sustained substantial injuries from the physical impact of the vessel and the contaminant releases.

The grounding caused major physical damage to the reef framework, gouging large

grooves into the atoll and grinding reef into rubble, both during the initial grounding and subsequently as the ship rocked back and forth with the movement of ocean swells. Calcareous sediments generated from the grounding formed large berms, smothering and scouring thousands 

of square meters of adjacent reef.The vessel eventually broke up within a few weeks after the

grounding, before a salvage operation could take place.

The wreckage covered an estimated 9,000 square meters of reef flat. A large amount of shiprelated debris was also released onto the reef and spread over an estimated area of 175,000 square 

meters.The movement of this debris is believed to have further injured coral reef organisms and

associated biota through abrasion, breakage, entanglement, smothering, and burial. Additionally, 

observations indicate the large volume of decomposing dead marine organisms and organic ship 

debris created a widespread zone of anoxia at the wreck site, which persisted for several months 

after the grounding and killed some of the surviving sedentary reef organisms in the area. Furthermore, U.S.

Fish and Wildlife Service (USFWS) researchers concluded that iron dissolving from
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Chapter 6. Coral Case Studies

the debris was stimulating cyano-bacteria populations (blue-green algae) on the reef crest and

neighboring back reef and patch reefs, and causing them to spread to other parts of the atoll that 

were not directly affected by the grounding.

Because of the lack of recovery after five years, the USFWS conducted additional removal of

over 100 tons of debris in 1999. Monitoring showed slight recovery through 2002, but dissolved 

iron was still elevated and causing a persistent cyanobacterial bloom. It was determined that 

substantial recovery of the crustose coralline algae would not occur until the metallic debris was 

removed. With funding from the USCG Oil Spill Liability Trust Fund, the USFWS removed another 

100 tons of debris between 2004 and 2007.All debris from the atoll collected from 1999–2007 was

surface-transported and dumped at a U.S. Environmental Protection Agency approved offshore 

dumpsite located three nautical miles north of Rose Island.

Monitoring began in 2005 and will be conducted biennially for ten years, until 2015. This case 

study indicates how complicated spill response is in remote areas and the importance of monitoring to determine whether recovery is occurring and what factors may be limiting recovery.

For further reading

Burgett, J.2002.Summary of Algal Community Changes Observed on the Southwest

Arm of Rose Atoll from 1995-2002. USFWS, Honolulu.

Capune, W. K. 1995. Jin Shiang Fa case study:what could have been done? In Proceedings of the 

1995 International Oil Spill Conference, Long Beach, February 27–March 2, 1995, pp.

1017–1018.

Green, A., J.Burgett, M.Molina, and D.Palawski.1998.The impact of a ship grounding and associated fuel spill at Rose Atoll National Wildlife Refuge, American Samoa. Pago Pago: U.S. Fish and 

Wildlife Service. 64 pp.

Maragos, J. E. 1994. Reef and coral observations on the impact of the grounding of the longliner 

Jin Shiang Fa at Rose Atoll, American Samoa. Honolulu: U.S. Fish and Wildlife Service, Pacific Island 

Office. 27 pp.

Field Experiment Case Studies

Tropical Oil Pollution Investigation in Coastal Systems (TROPICS), Panama

December 1984; September-November 1994; June 2002

In 1984, the American Petroleum Institute (API) sponsored a multi-year experiment in which a

representative tropical system (comprised of mangrove, seagrasses, and coral) was exposed to oil
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Oil Spills in Coral Reefs: Planning and Response Considerations

and chemically dispersed oil. The experimental design simulated a severe, but realistic, scenario 

of two large spills of crude oil in nearshore waters. The original experiment and its findings were 

detailed in Ballou et al.(1987).The original research team revisited the site in 1994, and collected

follow-up data. The sites were again surveyed in 2002 by a team that included one of the original 

researchers.

Although the studies encompassed oil and chemically dispersed oil effects in mangrove, seagrass, and coral systems, we discuss only oil impacts to corals here.

Treatment

Experimental sites were selected on the Caribbean coast of Panama, with the nearshore half 

of each site occupied by mangrove forest, fronted by a subtidal seagrass bed and a coral reef.

Water depth over seagrass averaged about 0.5 meters and over coral reef, 0.63 meters. Coral reefs 

were dominated by Porites porites and Agaricia tennifolia. Each of the three sites was treated with 

oil, dispersed oil, or remained as an untreated reference. The oiled site was treated with 953 liters 

of Prudhoe Bay crude oil (the amount of oil that would strand from a 100- to 1000-bbl spill) that

was released onto a boomed area of the water surface and allowed to remain for about two days.

Tides and winds distributed the oil over the study area, and after the exposure period free-floating 

oil was removed with sorbents.

Monitoring

Chemical and biological monitoring was conducted at five post-spill periods over 20 months.

Chemical monitoring, conducted hourly for the first 24 hours, confirmed that sediments and biota 

were exposed to rising and then rapidly declining dispersed and undispersed oil. For coral reefs, 

detailed transects were surveyed to measure abundance of epibiota living on the reef surface.

Four measurements were taken: total organisms, total animals, corals, and total plants. Growth 

rates of four coral species (P. porites, A. tennufolia, Montastrea annularis, and Acropora cervicornis)

were also measured.

Impacts

The only statistically significant effect documented over the first 20 months at the oiled 

site was a decrease in coral cover. No significant changes in growth rates of four targeted corals 

were noted. Ten years later, neither coral cover nor coral growth showed oil impacts. The authors 

contrasted the finding of no impact from oiling alone to that described by Guzmán et al.(1991)

at Bahía Las Minas, where significant effects of oil alone were found in several of the same species
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Chapter 6. Coral Case Studies

studied at TROPICS. Dodge et al. implied that these differences may have been due to the size of 

the spill at Bahía Las Minas and continued chronic exposure.

Ward et al.(2003) reported that, as of 2002, eighteen years post-oiling, coral cover has

increased significantly since 1994, but there were no significant differences among treatments, in 

both the historical transects and additional Porites photo-quadrats.

For further reading

Ballou, T.G., R.E.Dodge, S.C.Hess, A.H.Knap, and T.D.Sleeter.1987.Effects of a Dispersed and 

Undispersed Crude Oil on Mangroves, Seagrasses, and Corals. API Publication No. 4460. Washington, 

D.C.: American Petroleum Institute, Health and Environmental Sciences Department. 198 pp.

Dodge, R.E., B.J.Baca, A.H.Knap, S.C.Snedaker and T.D.Sleeter.1995.The effects of oil and

chemically dispersed oil in tropical ecosystems: 10 years of monitoring experimental sites. MSRC 

Technical Report Series 95-014. Washington, D.C.: Marine Spill Response Corporation, 93 pp.

Ward, G., B.Baca, W.Cyriacks , R.Dodge and A.Knap.2003.Continuing long-term studies of the

TROPICS Panama oil and dispersed oil spill sites. In Proceedings of the 2003 International Oil Spill 

Conference, Vancouver, BC. 9 pp.

Arabian Gulf field experiment/Field dates unknown, reported 1989 

This large-scale field experiment conducted on Jurayd Island, off the coast of Saudi Arabia, 

tested responses of corals to dispersed oil under realistic spill conditions. The design included 

exposure to crude oil only (Arabian light) among its four exposure scenarios, at exposures of 24

hours and 120 hours. Study plots were established over existing coral reefs that were comprised 

mostly of Acropora spp. (more than 95 percent), with scattered colonies of Platygyra sp., Goniopora 

sp., and Porites sp. The plots measured 2 meters by 2 meters, located over approximately 1-meter 

depth at low tide, and anchored in place.

Treatment

The stated intent of the experiment was to simulate conditions of a typical Arabian Gulf oil 

spill and not to overwhelm the corals with “extraordinary and catastrophic stresses.” As such, oil 

was added to test plots to produce a slick of 0.25 mm in thickness, a total of 14 liters in the 24-hour 

oil-only treatment; and 0.10 mm and 5.63 liters in the 120-hour experiment. Water concentrations of hydrocarbons were measured by infrared methods and no water column elevations were 

detected in the oil-only plots.
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Oil Spills in Coral Reefs: Planning and Response Considerations

Monitoring

The oil-only plots were visually inspected at the end of the 24-hour and 120-hour exposures, and they appeared normal. These areas were monitored for one year, and no extraordinary 

changes occurred relative to the unoiled plots (seasonal changes in degree of bleaching, however,

were noted across all monitored plots).Though dispersed oil appeared to delay the recovery from

seasonal bleaching, this was not observed in the oil-only plots.

Growth rates, expressed as skeletal extension along branch axes, showed no correlation to 

treatment in the 24-hour exposure. There was some indication that growth rates were depressed 

with 120-hour exposure, but LeGore et al. cautioned that these were not definitive. In summary, 

after one year of monitoring coral showed no visible effects after exposure to surface oil for 24 

hours and for 120 hours.The authors concluded that healthy reef corals can tolerate brief (1 to

5-day) exposures to floating oil with no observable effect.They did note the potential for seasonal

susceptibility to exposure in this region in the wintertime when low water temperatures stress 

corals.

For further reading

LeGore, S., D. S. Marszalek, L. J. Danek, M. S. Tomlinson, J. E. Hofmann and J. E. Cuddebak. 1989.

Effect of chemically dispersed oil on Arabian Gulf corals: A field experiment. In Proceedings of the 

1989 International Oil Spill Conference, San Antonio, February 13–16, 1989, pp.375–381.

Restoration Case Studies

M/V Wellwood Grounding, Key Largo/August 1994 

On August 4, 1984, the M/V Wellwood, a 400-foot freighter, ran aground on Molasses Reef in 

the Key Largo National Marine Sanctuary, causing massive destruction to living corals and underlying reef framework. Subsequent surveys indicated that the grounding fractured 644 square 

meters of underlying reef framework, with a 1,282-square meter area losing 70 to 100 percent 

of its live coral cover. Limestone rubble and fine sediment mobilized after the grounding posed 

further risk of reef injury and delayed recovery.

Restoration

Small-scale pilot studies conducted at the grounding tested the feasibility of stabilizing fractured reef framework, transplanting hard and soft corals into the major damage area, and rebuilding reef topography. Grouting with quick-setting underwater cement restabilized a selected area 
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Chapter 6. Coral Case Studies

of fractured reef framework. Loose sand, gravel, and attached algal epiphytes were removed from 

the site so that the cement could bond properly.

A test coral transplantation plot was established in an area with only moderate fracture 

damage to the reef framework. In preparation, loose sediment, rock debris, and attached dead 

soft coral skeletons were removed from the area, but attached dead hard corals were left in place.

Representative hard and soft corals from a nearby reef were transplanted to the pilot site. Corals 

were secured into holes in the reef framework with quicksetting underwater cement, as was used 

in framework repair.

Recovery

Transplanted hard corals survived, but soft corals were killed at high rates from heavy ocean 

swells generated by Hurricane Kate in late 1985. Observations indicated soft corals were twisted 

off at the holdfast base. High mortality of gorgonian corals was observed in areas surrounding the 

grounding site following the hurricane, some of which may have been caused by debris from the 

site.

Following the pilot studies, areas flattened by the hull of the ship were partially reconstructed.

Divers and airlift bags moved sections of dislodged reef framework and intact head corals back 

into damaged areas and cemented them permanently into the reef framework. Observations to 

date suggest that a limited number of gorgonian corals have recruited to cement surfaces, but the 

material does not sufficiently mimic natural reef rock to warrant its general use.

For further reading

Gittings, S.R., T.J.Bright, A.and Choi, R.R.Barnett.The recovery process in a mechanically damaged coral reef community: Recruitment and growth. Proceedings of the Sixth International Coral 

Reef Symposium, Townsville, Australia, August 8th-12th, 1988, Volume 2, pp.225–230.

Hudson, J.H.and R.Diaz.1988.Damage Survey and Restoration of M/V Wellwood Grounding Site, 

Molasses Reef, Key Largo National Marine Sanctuary, Florida, Proceedings of the Sixth International 

Coral Reef Symposium, Australia, 1988, Vol.2, pp.231–236.

M/V Alec Owen Maitland and M/V Elpis, Florida Keys/Fall 1989

On October 25, 1989, the 155-foot M/V Alec Owen Maitland ran aground on shallow coral reef 

in the Florida Keys National Marine Sanctuary. More than 1,600 square meters of formerly pristine 

coral reef dominated by fire coral and gorgonians were totally or partially destroyed by the time 

the vessel was removed from the grounding site. On November 11, 1989, the 143-meter freighter 
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Oil Spills in Coral Reefs: Planning and Response Considerations

M/V Elpis also ran aground nearby in the sanctuary. The ship’s propellers caused two large craters.

The grinding of the ship’s hull against the reef created a large rubble field.

Restoration

Following these incidents, efforts were made to repair damaged coral reef resources through 

structural and biological restoration at 3–4 m depth.At the M/V Alec Owen Maitland grounding 

site, 40 specially designed pre-cast concrete reef modules or slabs, called “Reef Replicating Units,” 

were placed in blowholes created by the ship. The reef replicating units, which weighed nearly 

ten tons each, had upper surfaces textured to somewhat resemble those of living reefs and were 

intended to provide a hard surface for larvae of coral and other stationary reef organisms, such as 

sponges, to settle and grow.

Blowholes created by the grounding of the M/V Elpis at 10 m depth were filled to grade with 

rock and rubble from berms adjacent to the craters.The rock and rubble was covered with large

limestone quarry boulders and voids were filled with sand transported by barge to the site. The 

objective was to recreate a stable foundation to facilitate recruitment of coral colonies.Following

structural stabilization of the reef framework, debris was removed from the site.

Structural restoration at both grounding sites was completed in 1995, and biological restoration efforts were commenced in 1996. The biological restoration efforts were intended to enhance 

or“jump-start”natural biological recovery processes at the sites.This included transplantation of

hard and soft corals, as well as sponges and sea fans, onto the hard surfaces of the concrete reefreplicating units at the Maitland grounding site and onto the limestone boulders at the Elpis site.

Monitoring

A monitoring program to assess the health and recovery of the areas affected by the groundings before, during, and after restoration has been in place since 1993. The program includes 

monitoring for structural integrity, survival, and growth rates of transplanted organisms, and 

recruitment of new coral colonies and fish populations. Initial monitoring results indicate that the 

reef framework has been restored, although it will take several years to determine whether the 

reef organisms will continue to survive and successfully repopulate these areas.

Columbus Iselin, Florida Keys/August 1994

On August 11, 1994 the University of Miami’s 170-foot research vessel Columbus Iselin ran 

aground on a coral reef off Looe Key, in the Florida Keys National Marine Sanctuary. No damage to 

coral or other resources was reported as a result of the diesel fuel released. However, the coral reef 

framework was seriously damaged by the grounding and subsequent salvage operations.Before
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Chapter 6. Coral Case Studies

restoration was started, Hurricanes Georges and Irene and the Groundhog Day storm increased 

the area of initial injury by displacing reef rock destabilized by the grounding.

Restoration

In order to prevent further damage from loose, dead coral rubble created by the impact of the 

vessel, NOAA conducted an extensive rubble removal project in the summer after the grounding.

Several tons of rubble and ship debris were removed and barged away.

Four coral reef spurs damaged in the grounding were physically reconstructed in the summer 

of 1999. Using cranes, several layers of five-ton quarried limestone boulders were lowered into the 

grounding excavation from the deck of a barge. These boulders were held in place by a matrix of 

composite rebar and tremie concrete. A special, non-separating, underwater concrete was then 

pumped into the filled excavations. Special fiberglass reinforcing rod and stainless steel anchor 

rods anchored in the boulders provided additional linkage between the concrete and the boulders. Each spur surface was then dressed with smaller limestone boulders to minimize the concrete surface.

Before pumping in the concrete, divers scrubbed biofouling from the limestone boulders to

enhance concrete adhesion. Various-sized limestone rocks and small boulders were placed on the 

surface of the poured concrete to mimic natural reef outcroppings and to provide more suitable 

habitat for recruitment of corals and other reef biota. Finally, adult coral colonies were transplanted and embedded into the restored reef framework. This was the first successful structural 

restoration of a spur and groove reef. The success of this restoration effort indicated that quarried 

limestone boulders and pumped concrete are suitable materials for rebuilding reef framework.

It also supported the conclusion that coral transplanting is an effective technique to help speed 

recovery of coral communities.

For further reference

Hudson, J.H., Restoration Biologist, Florida Keys National Marine Sanctuary, Key Largo, Florida,

personal communication, June 13, 2000.

http://www.sanctuaries.nos.noaa.gov/special/columbus/project.html

Fortuna Reefer, Puerto Rico/July 1997

The 325-foot container ship Fortuna Reefer ran aground on July 24, 1997 on fringing coral reef 

off the west coast of Mona Island (Isla de Mona) in Puerto Rico.Mona Island is a pristine natural

reserve. The remoteness of the grounding site hampered salvage efforts and the vessel remained 

aground for eight days. Though the vessel never released oil to the environment, the grounding 
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Oil Spills in Coral Reefs: Planning and Response Considerations

and subsequent salvage activities damaged the reefs substantially. Much of the damage was 

attributed to tow and anchor lines.

Restoration 

An expedited settlement for natural resource damage, pursued under the Oil Pollution Act 

of 1990, enabled NOAA and other state and Federal resource agencies to initiate an emergency 

restoration in September 1997 that was completed within a two-and-a-half month period after the 

grounding.The objectives of the emergency restoration were to quickly reestablish the physical

structure of the coral reef community and to reduce coral mortality.

The 6.8-acre grounding site was dominated by a well-established reef of branching elkhorn 

coral, Acropora palmata, at a depth ranging between 3 and 9 meters. Restoration consisted of 

immobilizing loose branches of elkhorn coral by securing them to the reef buttress and to existing 

elkhorn coral framework using stainless steel wire and nails. Several stabilization methods were 

tested. Due to the density and hardness of the reef structure, the method selected consisted of 

drilling holes into the reef, driving nails into the holes, and wiring corals to the reef. Stainless steel 

materials were used to minimize corrosion and increase the longevity of the repair effort. Other 

materials tested, such as plastic tie wraps, did not perform as well in the wave surge. The timely 

removal of injured coral from sand areas prevented them from being smothered and also minimized abrasion damage to broken coral pieces from swell and wave motion. Upon completion, 

1,857 coral fragments had been stabilized.

Monitoring

Monitoring stations were established to track the success of the restoration effort. Monitoring 

will include tracking survival of transplants and success of the transplant materials and techniques 

employed.

For further reference

Helton, D., Rapid Assessment Program Coordinator, National Oceanic and Atmospheric Administration, Damage Assessment Center, Seattle, personal communication, March 2000.

http://www.darp.noaa.seregion/fr.htm#anchor205215
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Chapter 6. Coral Case Studies

Table 6.1. Summary of Case Studies and Oil Impacts

Spills

Name Spill Location Spill Response Impacts

R.C. Stoner 

September 1967

Wake Island Ca. 6 million gallons of refined 

fuel oil 

Oil pumped into pits and 

burned

Fish kill 

Crustaceans 

Invertebrates

(Coral unknown)

Ocean Eagle 

March 1968

Northeast Puerto Rico 

(few coral reefs)

83,400 bbls Venezuelan crude 

Chemical “emulsifier” spread 

on oil

Fish

Benthos 

No coral effects

Morris J. Berman 

January 1994

Northeast Puerto Rico 

(few coral reefs)

Ca. 800,000 gallons No. 6 fuel oil 

Skimming and lightering 

Extensive shoreline cleanup

Fish 

Benthos 

No coral effects

S.S. Witwater 

December 1968

Caribbean coast of Panama 

(subtidal reefs)

20,000 bbls Bunker C and diesel 

oil 

Oil pumped and burned in-situ

No coral effects 

Mangroves 

Sandy shorelines

Zoe Colocotronis 

March 1973

Reef off Puerto Rico 37,000 bbls Venezuelan crude 

Booming, digging sumps, 

pumping into trucks

2.5 acres mangrove 

forests 

Invertebrates 

Seagrasses 

(Coral unknown)

T/V Garbis 

July 1975

Florida Keys 

(submerged coral reefs)

1,500–3,000 bbls crude oil No coral effects 

Echinoderms 

Black oysters 

Mangroves

Bahía Las Minas 

April 1986

Caribbean coast of Panama 60,000–1000,000 bbls Venezuelan crude oil 

Chemical dispersants (Corexit 

9527)

Widespread lethal, sub-lethal 

effects to coral and other 

environments

Gulf War Oil Spill 

January 1991

Arabian Gulf 6.3 million bbls crude oil Minor coral damage

Rose Atoll 

National Wildlife Refuge 

October 1993

American Samoa 100,000 gallons of diesel fuel 

500 gallons of lube oil 

2,500 pounds of ammonia 

No response: oil spilled onto 

the reef

Moderate to high coral injury 

Massive die-off of coralline 

algae and many reef-dwelling 

invertebrates Impacts still 

visible 4 years later
–78–

Oil Spills in Coral Reefs: Planning and Response Considerations

Table 6.1. Summary of Case Studies and Oil Impacts, cont’d.

Field Experiments

Name Spill Location Experiment Impacts/Conclusions

TROPICS 

December 1984 

Sept.-Nov. 1994

Panama Exposure of representative 

tropical system (mangrove, 

seagrasses, and coral) to oil 

and chemically dispersed oil.

Decrease in coral cover

Arabian Gulf Jurayd Island, Saudi Arabia Tested responses of corals to 

dispersed oil under realistic 

spill conditions

Conclusion: healthy reef 

corals can tolerate brief (1–5 

day) exposures to floating oil 

with no observable effect.

Restoration Case Studies

Name Spill Location Restoration Impacts/Conclusions

M/V Wellwood Grounding 

August 1984

Molasses Reef 

Key Largo National Marine 

Sanctuary

Grouted fractured reef with 

underwater cement Transplanted corals

Transplanted hard corals 

survived (soft corals killed by 

hurricane)

M/V Alec Owen Maitland 

October 1989

Florida Keys National Marine 

Sanctuary

Structural and biological reef 

restoration with concrete 

“reef replicating units” Monitored since 1993; initial 

results indicate successful 

restoration M/V Elpis 

November 1989

Transplanted corals, 

sponges, sea fans

Columbus Iselin 

August 1994

Looe Key 

Florida Keys National Marine 

Sanctuary

Four coral reef spurs rebuilt 

Adult coral colonies embedded in restored reef

Coral transplanting is an 

effective technique to help 

speed recovery of coral communities

Fortuna Reefer 

July 1997

Isla de Mona 

Puerto Rico

1,857 coral fragments transplanted and stabilizedEmergency restoration to 

quickly reestablish the physical structure of the coral reef 

community and to reduce 

coral mortality.
–79–

Chapter 6. Coral Case Studies

Glossary

acroporid coral – canopy-forming species of coral belonging to the family Acroporidae.These are

the dominant species of corals found worldwide.

Anthozoa – a class of Cnidaria that includes the stony corals, soft corals, sea anemones, zoanthids,

gorgonians, and corallimorpharians.

Anthropogenic – caused by humans.

Apron reef – the initial stages of a fringing reef;it is discontinuous and covers a small area.

Atoll – a horseshoe-shaped or circular array of coral reefs containing a lagoon in the center, and

capping the perimeter of a submerged volcanic island.

Back reef – shoreward side of a reef, including the area and sediments between the reef crest and

land.

Barrier reef – a reef running roughly parallel to shore and separated from it by a lagoon of considerable depth and width; it may lie a great distance from a continental coast and is often 

interrupted by passes or channels.

Benthic – bottom-dwelling;living on or under the sediments or other substratum.

Bioenergetic – metabolic processes that are responsible for supplying energy to an organism.

Black band disease (BBD) – coral disease containing a photosynthetic cyanobacterium that kills

coral tissue by a lack of oxygen and exposure to hydrogen sulfide produced by the bacterium.

Bleaching – the process during which symbiotic zooxanthellae are expelled from host coral tissues.

Broadcast spawning – method of reproduction utilized by some corals in which gametes are

released into the water column.

Brooding – method of reproduction in some corals in which fertilization and larval development

occur internally.

Calcareous – made of calcium carbonate.

Cnidaria – a phylum of invertebrate coelenterate animals having a simple, two-layered body plan;

includes jellyfish, hydroids, soft corals, sea anemones, and corals.

Coral – a general term used to describe a group of benthic cnidarians;usually indicates the presence of a calcium carbonate skeleton secreted by the animal.

Coral reef – a wave-resistant structure resulting from skeletal deposition and cementation of hermatypic corals, calcareous algae, and other calcium carbonate-secreting organisms.

Coralline algae – heavily calcified, encrusting red algae.
Corallite – a skeletal cup secreted by a coral.

Corallivore – an organism that eats coral.

Coriolis Effect – a rotational effect generated by the movement of a fluid over the Earth’s rotating

surface.

Cyanobacteria – one to many-celled aquatic organisms, formerly known as blue-green algae, that

photosynthesize and produce oxygen.

Extension rate – accretion or lengthening of a branching coral caused by calcification.

Flow-through exposure – a laboratory setup in which organisms are held in continuously flowing

water—in contrast to static exposure, in which organisms are held in a given volume of water 

with no exchange.

Fringing reef – a reef that grows adjacent to the shoreline.

Gametes – the sexual products of an organism such as eggs and sperm.

Gonochoric – each colony is either male or female.

Habitat – place or environment where a particular species lives.

Hermatypic – reef-building coral.

Histological – referring to tissue structure.

Lagoon – a warm, shallow, quiet waterway separated from the open sea by a reef crest.

Leeward – the side of an island or reef that faces away from the prevailing wind.

Massive – when referring to coral types, describes a skeleton formed as a solid block rather than

being branched or plate-like. Most massive corals are mound-shaped.

Mass spawning – simultaneous release of gametes by multiple species usually involving a large

number of individuals.

Natural recruitment – the way a population reproduces itself.

Nominal exposure – oil exposure concentrations based on the proportions of oil added to water

(without actually measuring how much oil was ultimately mixed into the water).

Octocorals – anthozoans of the subclass Octocorallia, commonly called soft corals, sea fans, and

whips.

PAH – polynuclear aromatic hydrocarbon.

ppm – parts per million.

ppt – parts per thousand.

Patch reef – clump of coral colonies unattached to a major reef structure that has a defined reef

slope, crest, and reef flat.
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Chapter 6. Coral Case Studies

Photic zone – the vertical zone in the ocean extending from the surface to that depth permitting

photosynthetic activity.

Planula – a planktonic larval form produced by some anthozoans.

Polyp – an individual of a solitary cnidarian or one member of a cnidarian colony.

Pulse exposure – to simulate a spill-type release in a flow-through laboratory setting, an initial

and relatively high concentration of a contaminant is allowed to dissipate under continuous 

water flow.

Reef crest – shallowest seaward margin of reef.

Reef slope – reef seaward of reef crest.

Scleractinia – order of the Phylum Cnidaria, usually producing calcareous skeletons with six-part

symmetry.

Sessile – immobile because of attachment to a substratum.

SST – sea surface temperatures;considered elevated when they are at least 1 ̊C higher than the

summer maximum.

Sublethal – toxic effect that does not cause death, but impairs the organism in various ways

(includes in corals reduced ability to retract polyps, impaired feeding ability, impaired ability to

clear sediment, impaired settlement of larvae).

Vegetative reproduction – asexual reproduction, such as through budding or fragments.

WAF – water-accommodated fraction.

WSF – Water-soluble fraction.

Weathering – changes in the physical and chemical properties of oil due to natural processes,

including evaporation, emulsification, dissolution, photo-oxidation, and biodegradation.

White band disease (WBD) – coral disease affecting only acroporid corals, it appears in a band

form, and kills coral tissues as it spreads over the entire coral structure.

Windward – the side of an island or reef that faces the prevailing wind.

Zooxanthellae – a group of dinoflagellates living symbiotically in association with one of a variety

of invertebrate groups (e.g., corals).

Coral Websites

http://coralreef.noaa.gov/

NOAA’s main coral website. Links to bleaching predictions for Florida Keys, coral health and monitoring program, NOAA, Marine Sanctuaries, U.S. Coral Reef Task force.
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Oil Spills in Coral Reefs: Planning and Response Considerations

http://response.restoration.noaa.gov

NOAA website that includes response guidance such as dispersant and in-situ burning use, SMART 

monitoring, spill case histories, and spill response software tools.

http://www.osdpd.noaa.gov/ml/ocean/coral_bleaching.html

NOAA’s bleaching hot spot website with satellite data.

http://coralreefwatch.noaa.gov/satellite/

NOAA’s satellite bleaching research website.

http://www.darrp.noaa.gov

NOAA’s damage assessment and restoration program. Includes descriptions of several coral restoration sites, including Fortuna Reefer, Elpis, and Alec Owen Maitland incidents.

http://sanctuaries.noaa.gov/

NOAA’s National Marine Sanctuaries home page with links to existing and proposed sanctuaries.

Includes link to Columbus Iselin restoration site.

http://floridakeys.noaa.gov/welcome.html

Florida Keys National Marine Sanctuary.

http://www.epa.gov/owow/oceans/coral/

EPA’s coral reef home page.

http://www.coral.noaa.gov/

NOAA’s coral health and monitoring program.

http://www.dep.state.fl.us/coastal/programs/coral/

State of Florida Coral Reefs.

http://hawaii.gov/dlnr

State of Hawai’i.

http://www.coralreefnetwork.com/default.htm

Hawai’i Coral Reef Network.

http://www.reefrelief.org/

Reef Relief- nonprofit reef protection organization.

http://www.unep-wcmc.org/GIS/coraldis/cd/damage.htm

Global coral disease database.

http://www.unep-wcmc.org/marine/data/coral_mangrove/index.html

Coral reefs and mangroves of the world. Joint page from numerous government and non-government data sources.

http://www.gbrmpa.gov.au/

Great Barrier Reef Marine Park Authority.Links to published papers, and numerous sources of information on coral and associated habitats.

U.S. DEPARTMENT OF COMMERCE • National Oceanic and Atmospheric Administration • National Ocean Service

July 2010

U.S. DEPARTMENT OF COMMERCE

Gary Locke, Secretary

National Oceanic and Atmospheric Administration

Dr. Jane Lubchenco, Under Secretary of Commerce 

for Oceans and Atmosphere and NOAA Administrator

National Ocean Service

David Kennedy, Acting Assistant Administrator

for Ocean Services and Coastal Zone Management