Science for Solutions 

NOAA'S COASTAL OCEAN PROGRAM 

Decision Analysis Series No. 12 

ines for t e Conservation and Restoration 

e United States 

ters 

Mark S. Fonseca, 

Judson Kenworthy, and 

Gordon W. Thayer 

November 1998 

U.S. DEPrnTMENT OF COMMERCE 

National Oceanic and Atmospheric Administration 

Coastal Ocean Office - 
The Decision Analysis Series has been established by 

NOAA's Coastal Ocean Program (COP) to present documents for coastal decision makers which contain analytical 

treatments of major issues or topics. The issues, topics, and 

principle investigators have been selected through an extensive peer review process. To learn more about the COP or 

the Decision Analysis Series, please write: 

NOAA 

Coastal Ocean Office 

131 5 East-West Highway 

Silver Spring, Maryland 2091 0 

phone: 301 -71 3-3338 

fax: 30 1 -7 1 3-4044 

web: http://www.cop.noaa.gov 

Cover photographs (clockwise from top right): Propeller scarring in the Florida Keys National Marine 

Sanctuary (courtesy C. Kruer); 250 -day old eelgrass (Zostera marina) plantings on a wave-swept shoal 

near Beaufort, NC (M. Fonseca); Alaskan eelgrass bed adjacent to a restoration site (courtesy US Army 

Corps of Engineers); eelgrass planting in San Diego Bay, California (courtesy G. Robilliard). 
Science for Solutions 

NOAA COASTAL OCEAN PROGRAM 

Decision Analysis Series No. 12 

Guidelines for the Conservation and Restoration 

of Seagrasses in the United States 

and Adjacent Waters 

Mark S. Fonseca, 

W. Judson Kenworthy, and 

Gordon W. Thayer 

National Oceanic and Atmospheric Administration 

National Marine Fisheries Service 

Southeast Fisheries Science Center 

Beaufort Laboratory 

101 Pivers Island Road 

Beaufort, North Carolina 285 16-9722 

November 1998 

U.S. DEPARTMENT OF COMMERCE 

William H. Daley, Secretary 

National Oceanic and Atmospheric Administration 

D. James Baker, Under Secretary 

Coastal Ocean Office 

David Johnson, Acting Director 
This publication should be cited as: 

Fonseca, Mark S., et al. 1998. Guidelines for the Conservation and Restoration of Seagrasses in 

the United States and Adjacent Waters. NOAA Coastal Ocean Program Decision Analysis Series 

No. 12. NOAA Coastal Ocean Office, Silver Spring, MD. 222 pp. 

This publication does not constitute an endorsement of any commercial product 

or intend to be an opinion beyond scientific or other results obtained by the 

National Oceanic and Atmospheric Administration (NOAA). No reference shall 

be made to NOAA, or this publication furnished by NOAA, in any advertising 

or sales promotion which would indicate or imply that NOAA recommends or 

endorses any proprietary product mentioned herein, or which has as its purpose 

an interest to cause directly or indirectly the advertised product to be used or 

purchased because of this publication. 
Note to 

Guidelines for the Conservation and Restoration of Seagrasses in the United States and A4acent Waters was 

developed by Mark Fonseca of NOAA's Beaufort Laboratory, along with Jud Kenworthy and Gordon 

Thayer, with hnding &om NOAA's Coastal Ocean Program. The document presents an overview of 

the current state of seagrass conservation and restoration in the United States, discusses important 

issues that should be addressed in planning seagrass restoration projects, describes different planting 

methodologies, proposes monitoring criteria and means for evaluating success, and discusses issues 

faced by resource managers. 

The Coastal Ocean Program (COP) provides a focal point through which NOAA, together with 

other organizations with responsibilities for the coastal environment and its resources, can make significant strides toward finding solutions to critical problems. By working together toward these solutions, we can ensure the sustainability of these coastal resources and allow for compatible economic 

development that will enhance the well-being of the Nation now and in hture generations. The goals 

of the program parallel those of the NOAA Strategic Plan. 

A specific objective of the COP is to provide the highest quality scientific information to coastal managers in time for critical decision making and in formats usehl for these decisions. To help achieve 

this, the COP inaugurated a program of developing documents that would synthesize information on 

issues that were of high priority to coastal managers. As a contribution to the Decision Analysis Series, 

this report provides a critical synthesis of the methods for planning, planting, monitoring, and evaluating seagrass restoration projects. A list of available documents in the Decision Analysis Series can be 

found on the inside back cover. 

As with all of its products, the COP is very interested in ascertaining the utility of the Decision 

Analysis Series, particularly in regard to its application to the management decision process. Therefore, 

we encourage you to write, fax, call, or E-mail us with your comments. Please be assured that we will 

appreciated these comments, either positive or negative, and that they will help us direct our hture 

efforts. Our address and telephone and fax numbers are on the inside fiont cover. My Internet address 

is COASTALOCEAN@COP.NOAA.GOV. 

David ~oh;lson 

Acting Director 

NOAA Coastal Ocean Program 
Table of Contents 

LIST OF FIGURES AND TABLES ................................. ix 

What Are Seagrasses? ....................................... 1 

Defining Seagrass Habitat ................................... 8 

Spatial Scale and Its Role in Defining Seagrass Habitat .............. 12 

Vulnerability and Susceptibility of Seagrass Ecosystems .............. 15 

Historical Impacts and Losses ................................ 16 

A Short History of Seagrass Mitigation and Restoration ............. 21 

Management Context for Mitigation and Restoration of Seagrass 

Ecosystems .......................................... 24 

Pitfalls in the Mitigation and Restoration Process .................. 26 

Regional Breakdown of Permit Activities Dealing with Seagrass 

Mitigation .......................................... 27 

Northeast (NE) Region (Maine through Virginia) .............. 28 

Southeast (SE) Region (North Carolina through Texas 

including the U . S.Virgin Islands and Puerto Rico) .......... 28 

Northwest (NW) and Alaska Regions (Oregon. Washington 

and Alaska) ...................................... -30 

Southwest (SW) Region (California. Hawaii 

and Pacific Territories) .............................. 30 

Comparative Analysis of Seagrass Planting Efforts .................. 30 

Are Planted Seagrass Beds Functionally Equivalent to 

Naturally-Occurring Beds? .............................. 46 

Pre-Project Planning Considerations: Importance of Genetic 

Diversity in Seagrass Populations .......................... 53 

More Pre-Project Planning Considerations: Seagrass Bed Spatial 

Requirements and Planting Site Surveys ..................... 59 

Planning for Execution of a Planting Project ...................... 61 

Identification of Project Goals ............................... 61 
vi Guidelines for the Conservation and Restoration af Seagrasses 

Pre-Construction Planning .................................. 61 

Southern California .................................... 64 

Chesapeake Bay ....................................... 64 

Connecticut ......................................... 64 

Assessment of Interim Losses ................................ 66 

Pre-Impact and Pre-Planting Surveys: Identifjring Presence. Absence 

and Reasons for Absence of Seagrass Coverage ................ 67 

Minimum Size to Just* Pre-Planting Monitoring ................. 70 

Planting Site Selection and Off-siteVs . On-Site planting ............. 70 

Engineered Sites ........................................ -71 

Channel Plantings. Effects of Structures and Other Human 

Activities ........................................... 72 

Constraints Imposed by Physical Setting on Planting Operations ....... 73 

Emersion Effects ......................................... 77 

Bioturbation ........................................... 79 

Sediment Thickness ...................................... -81 

Sediment Stability: Erosion and Burial of Seagrass Shoots ............ 81 

Possibility of Natural Recolonization ........................... 82 

Nutrient Requirements for Transplanting ........................ 83 

Light Requirements for Transplanting .......................... 90 

Salinity and Temperature Requirements for Transplanting ............ 96 

Micropropagation and Laboratory Culture of Seagrass for Planting ...... 99 

Wild Stock Selection, Availability, and Performance ................ 101 

Long-Term Management .................................. 105 

Planting Contingencies by Ecological Region .................... 106 

Northeast Region .................................... 106 

Mid-Atlantic Region ................................. 107 

Gulf of Mexico and the Florida East Coast .................. 107 

South Florida and the Caribbean ......................... 108 

Conterminous West Coast .............................. 108 

Alaska ............................................ 109 

Hawaii and Pacific Territories ............................ 109 

Methods .............................................. 111 

Plug Methods ....................................... 113 

Staple Method ...................................... 114 

Peat Pot Method .................................... 115 

Other Methods ..................................... 122 
Contents vii 

Fertilizer Effects ........................................ 125 

Spacing of Planting Units .................................. 126 

Quiescent Settings ................................... 126 

Wave-Exposed or High Current Speed Settings ................ 126 

CHAPTER 4: MONITORING AND EVALUATING SUCCESS ............ 129 

Terminology .......................................... 129 

Monitoring Specifications ............................... 130 

Survival ........................................... 130 

Areal Coverage ...................................... 130 

Number of Shoots .................................... 131 

Monitoring Frequency .................................... 132 

Interpretation of Monitoring Data ............................ 134 

Real Cost of Seagrass Transplanting ........................... 135 

No-Net-Loss ofwetlands .................................. 139 

Seagrass Ecosystems ...................................... 139 

Value and Function of Seagrass Habitat ......................... 140 

Loss of Seagrass Habitat .................................... 140 

Mitigation as a Management Tool ............................. 140 

Special Planning Considerations .............................. 142 

Preserving Genetic Diversity ................................ 142 

Site Surveys Prior to Impact ................................ 143 

Identrft Project Goals ..................................... 143 

Permit Corodination Protocols .............................. 143 

Interim Loss Assessment ................................... 144 

Site Surveys ............................................ 144 

Site Selection .......................................... 144 

Obtaining Transplant Stock ................................. 145 

Planting Methods ........................................ 145 

Evaluating Project Success .................................. 146 

Monitoring Planted Beds .................................. 147 

Interpreting Results .................................... .-. 147 

Cost Estimates .......................................... 148 

Conservation, Mitigation, and Restoration ...................... 148 
viii Guidelines for the Conservation and Restoration of Seagrasses 

Staple Method ......................................... 203 

Peat Pot Method ........................................ 205 

Core Tube Method ...................................... 205 

APPENDIX D: SUGGESTED MINIMUM COMPONENTS OF 

PROPOSALS AND REPORTS ............................. -207 

A . Mitigation Proposal .................................... 207 

B.Time Zero Report ..................................... 208 

C . Progress Reports ...................................... 208 

D . Final Project Report .................................. -208 

APPENDIX E: EXAMPLE PROPELLER AND MOORING SCAR 

RESTORATION PLAN ................................... 209 

APPENDIX F . COMMENDATIONS FOR FURTHER ]READING ....... 221 
Figures and Tables 

Figure 1.1. Seagrass species ...................................... 4 

Figure 1.2. Cumulative bottom covered ............................. 9 

Figure 1.3. Survey of percent planting unit survival .................... 11 

Figure 1.4. Survey of percent area covered .......................... 11 

Figure 1.5. Faunal abundance in planted seagrass ...................... 44 

Figure 1.6. Aerial photograph of seagrass bed ......................... 44 

Figure 1.7. Change in seagrass bed cover ........................... 48 

Figure 2.1. Decision flow diagram for seagrass planting ................. 62 

Figure 2.2. Assessing interim loss of seagrass habitat functions ............. 68 

Figure 2.3. Computation of replacement ratio ....................... 68 

Figure 2.4. Seagrass cover and physical setting ....................... 76 

Figure 2.5. Site selection process ................................. 78 

Figure 2.6. Ruppia in culture ................................... 102 

Figure 2.7. Recovery of donor beds .............................. 104 

Figure 3.1. Comparison of plugs, cores, peat pots and staples ............. 113 

Figure 3.2. Staple method of seagrass planting ....................... 116 

Figure 3.3. Planting technique using flat biodegradable sticks ............ 118 

Figure 3.4. Planting technique using round biodegradable sticks .......... 118 

Figure 3.5. Peat pot method of seagrass planting ...................... 120 

Figure 3.6. Line planting technique .............................. 123 

Figure 3.7. Remote planting method ............................. 124 

Figure 3.8 Computing row spacing .............................. 127 

Figure 4.1. Sequencing of the seagrass planting success criteria ............ 133 

Table 1 . 1. List of seagrass species .................................. 3 

Table 1.2. Chesapeake Bay SAV habitat requirements ................... 17 

Table 1.3. Percent of seagrass planting documents by literature source ........ 32 

Table 1.4. Percentage of seagrass field planting documents by region ...... .-. 33 

Table 1.5. Area and number of planting units by region and seagrass species ... 34 

Table 1.6. Percentage of transplanting methods by region ................ 36 

Table 1.7. Percentage of transplanting methods by seagrass species .......... 37 

Table 1.8. Experimental parameters in field planting studies ............... 38 

Table 1.9.Ten most common monitoring parameters ................... 39 

Table 2.1. Submersed aquatic vegetation habitat requirements ............. 98 
Executive a 

Seagrass ecosystems are protected under the federal "no-net-loss" policy for 

wetlands and form one of the most 

productive plant communities on the 

planet, performing important ecological functions. 

Seagrass beds have been recognized as 

a valuable resource critical to the health 

and function of coastal waters. Greater 

awareness and public education, however, is essential for conservation of this 

resource. 

Tremendous losses of this habitat have occurred as a result of development within the coastal zone. Disturbances usually kill seagrasses rapidly, and recovery is 

often comparatively slow. 

Mitigation to compensate for destruction of existing habitat usually follows when 

the agent of loss and responsible party are known. Compensation assumes that 

ecosystems can be made to order and, in essence, trades existing functional habitat for the promise of replacement habitat. 

While ~lanting seagrass is not technically complex, there is no easy way to meet 

the goal of maintaining or increasing seagrass acreage. Rather, the entire process 

of planning, planting and monitoring requires attention to detail and does not 

lend itself to oversimplification. 
xii Guidelines for the Conservation and Restoration of Seagrasses 

The success rate of permit-linked mitigation projects remains low overall, but this 

appears to result from failures in the planning process as much as any other cause. 

To prevent continued loss of habitat under compensatory mitigation, decisive 

action must be taken by placing emphasis on improving site selection, compliance, generating desired acreage, and maintaining a true baseline. 

Seagrass planting is no longer experimental, but planting will not succeed unless 

managers appreciate and emphasize the extreme importance of site selection, care 

in planting, and incorporation of plant demography into the planning and planting processes. 

Seagrass beds can be restored, but preservation is the most cost-effective course 

of action to sustain seagrass resources. Although techniques and protocols exist 

that produce persistent seagrass beds, they are often applied inconsistently, which 

has resulted in large-scale failures. 

A logical and ecologically defensible goal is to attain replacement of the lost seagrass species with an area of bottom coverage that compensates for interim lost 

resource services and a comparable shoot density. Seagrass plantings that persist 

and generate the target acreage have been shown to quickly provide many of the 

functional attributes of natural beds. 

When destruction of the impact site requires planting in another location (i.e., 

off-site) it is often difficult to find a site elsewhere with suitable biological and 

physical parameters required for seagrass growth and persistence. 

As more information is made available to managers regarding the function of seagrass ecosystems and the difficulties involved in mitigating for their loss, fewer 

permitted impacts are occurring with more emphasis placed on impact avoidance 

and minimization. 
CHAPTER 1 

Background 

S eagrasses are unique marine flowering 

plants of which there are approximately 60 species worldwide (den Hartog 

1970, Phillips and Menez 1988). With the 

exception of some species that occur in 

the rocky intertidal zone, they grow in 

shallow, subtidal or intertidal unconsolidated sediments. Thus, they bind millions 

of acres of shallow water sediments in the 

coastal waters with their roots and rhizomes while simultaneously baflling 

waves and currents with their lea6 canopy (Ginsberg and Lowenstam 1958, 

Taylor and Lewis 1970, den Hartog 1971, Fonseca et al. 1983, Fonseca 1996a). In 

this manner the canopy inhibits resuspension of fine particles and traps water-column-borne material (Ward et al. 1984, Short and Short 1984), clearing the water column. This cleansing effect extends to water column nutrients as well. Nutrient 

uptake by seagrass blades and their associated epiphytes and macroalgae as well as 

roots incorporate dissolved nutrients into plant biomass, which can improve water 

quality (Harlin and Thorne-Miller 1981). The bding effect of the canopy on sediment stabilization is enhanced by the presence of a robust root and rhizome mat, 

although the relative contribution of the mat has not been isolated fiom canopy baffling in its role of sedment stabilization (Fonseca 1996a). The physical stability, 

reduced mixing and shelter provided by the complex seagrass structure provides the 

basis for a highly 

of seagrasses and 

productive ecosystem (Wood et al. 1969). Overall the importance 

their role in many coastal ecosystems has been extensively docu- 
2 Guidelines for the Conservation and Restoration of Seagrasses 

mented (see reviews by Thayer et al. 1975, Phillips 1982, Zieman 1982a,Thayer et al. 

1984, Zieman and Zieman 1989) and the nature of their general function and high 

resource value are no longer an issue. 

Seagrasses occur in all coastal states of the U.S. with the apparent exception of 

Georgia and South Carolina where fi-eshwater inflow, high turbidity and tidal amplitude combine to prevent their occurrence. There are at a minimum thirteen species 

of seagrass currently recognized to occur in U.S. waters (Table 1.1). The presence of 

a fourteenth species, Zostera asiatica on the West Coast remains a subject of debate 

(Phillips and Wyllie-Echeverria 1990). We will not include in this discussion seagrass 

species occurring in U.S. possessions in the Pacific Ocean because little is known 

about their status; through NMFS Southwest Regional Office reports, we know that 

Enhalus acoroides and Halodule uninervis occur on Rota Island and Saipan Island in the 

Pacific Territories. Also, Phillips and Menez (1988) list Halophila ovalis and Halophila 

minor (fifieenth and sixteenth species) as species that occur in Hawaii. Halophila hawaiiana is also reportedly present on Hawaii (IS. Bridges, Univ. Hawaii, pers. corn.). 

Drawings of the major U.S. species are given in Figure 1.1. One species, Halophila 

johnsonni was only recently described as a separate species despite its occurrence in 

the heavily-studied region of southeast Florida. Because of its limited distribution, 

this species is currently under consideration for listing as a threatened species as 

defined by the Endangered Species Act. Another species, Zostera japonica was recently introduced to the Pacific Northwest . It is spreading and tends to colonize shallow intertidal flats, converting them fi-om their historical ecological status as mudflats 

to intertidal eelgrass habitat (Harrison and Bigley 1982, Pawlak 1994). 

Although recognized for their value where they occur, the distribution of seagrass is not as well known as it should be for proper management (Wyllie-Echeverria 

et al. 1994a). Moreover, knowledge of population-level temporal dynamics is only 

rudimentary at best. We know that at least 90 percent of the southeast United States 

seagrass acreage (-1.1 million hectares) exists in the Gulf of Mexico (Orth andVan 

Montfi-ans, 1990). But nationally, the distribution and abundance of two genera in 

particular have been overlooked. The full extent and function of the reported 

-400,000 hectares of seasonal Halophila beds off the west coast of Florida (Iverson 

and Bittaker 1986) is unknown. Similarly the distribution of the Hawaiian Halophila 

is not reported. Also, very little is known about local distribution (distribution meaning localized, specific locations of beds, not the range of a species) of a unique West 

Coast dominant, the rocky intertidal Phyllospadix spp., although work has been done 

regarding its population ecology (Turner 1985,Turner and Lucas 1985). The distribution of seagrass on the West Coast, including both Alaska and Hawaii, has not been 

systematically compiled to the degree seagrasses have on the east and Gulf coasts 
- 

Table 1.1. List of seagrass by family, genus and species, and common names (if given) that are found in the 

United States and adjacent waters. Species marked with (?) are not llly documented as occurring in U.S. - 

waters. 

Family, Genus, and Species Common Namea 

Hydrocharitaceae 

Enhalus acoroides Royle 

Halophila decipiens Ostenfeld 

Halophila engelnranni Ascherson 

Halophila hawaiiana Doty and Stone 

Halophila johnsonii Eiseman 

Halophila minor (Zollinger) den Hartog? 

Halophila ovalis (R. Brown) Hooker f.? 

Thalassia testudinuni Konig 

Potarnogetonaceae 

Halodule wrightii Ascherson 

Halodule uninervis? 

Phyllospadix scouleri Hook 

Phyllospadix torreyi S.Watson 

Phyllospadix serrulatus Ruprecht et Ascherson 

Ruppia niaritima L. 

Syringodiumfil$mle Kutz 

Zostera japonica Ascherson et Graebner 

Zostera n~arina L. 

Zostera asiatica? 

paddle grass 

star grass 

Hawaiian seagrassa 

Johnson's seagrass 

unknown 

unknown 

turtlegrass 

shoalgrass 

Scouler's seagrass 

Torrey 's seagrass 

surfgrass 

widgeon grass 

manatee grass 

Japanese eelgrass 

eelgrass 

Asian eelgrass 

a Italics on common names indicate suggested common names; R. Phillips, Battelle Laboratories, Richland,Wa., pen. corn. 
Figure 1.1. Drawings ofniost seagrasses found in US. waters (takenjoni Phillips and Menex 1988 and Fonseca 1994). 

All scale bars are set at 2mi and thus vary with seagrass species. A=Zostera marina; B=Zostera japonica; C=Ruppia 

maritima; D=Halodule wrightii; E=Syringodium &forme; FEThalassia testudinum; G=Halophila engelmanni; H=Halophila decipiens; GHalophila johnsonni; ]=Phyllospadix serrulatus; K=Phyllospadix torreyi; 

L=Phyllospadix scouleri. 
Figure 1.1. continued. 
Figure 1.1. continued. 
Chapter 1: Background 7 -. 

Figure 1.1. continued. 

although the general range of species' distributions has been reported PyllieEcheverria and Phillips 1994). 

Historically, emphasis been placed on aspects of seagrass primary and, to a lesser degree, secondary production attributes (see descriptions in Zieman 1982a, 

Phillips 1984, Thayer et al. 1984). Extensive information is available regarding light 

and nutrient requirements of seagrasses (Kenworthy and Haunert 1991, Dennison et 

al. 1993, respec&ely). Seagrasses are flowering plants and much attention has been 

paid to the mechanics of pollination and seed dispersal (see review by Cox 1993 and 

references therein) but much less is known about the role of seeding in bed maintenance or colonization of new areas (Kenworthy et al. 1980, Harrison 1993, Orth et 

al. 1994). With the exception of some recent studies (Duarte et al. 1994, Durako 

1994) and previous transplanting data sets (Fonseca et al. 1987c), demographic studies have been sorely neglected in this country yet this is a topic area where managers 

ask many questions: How quickly will a seagrass bed recover fi-om a given impact? 

Is planting necessary? Given intrinsic recovery rates and transplanting success, how 

do we compute replacement ratios or estimate interim loss? Should we be concerned about genetic diversity of the population? These questions are only now 

being addressed. 
8 Guidelines for the Conservation and Restoration of Seagrasses 

Seagrass beds exist in a wide variety of physical settings that lead to different 

coverage patterns. The problem is coming up with a consistent definition of what 

constitutes a seagrass bed. Although small patches may themselves have significant 

resource value, how does one assess the collection of patches and determine the 

boundaries of a seagrass habitat? Seagrasses exhibit a variety of growth strategies and 

coverage patterns which occur &om rocky and soft-bottom intertidal habitats to 

depths of at least 40 meters. Some species can rely heavily on seeding to ensure yearto-year survival (e.g., H. decipiens and possibly H. engelmanni) meaning that surveys 

during winter months would need to include sediment seed bank assessments to 

accurately define the presence of a seagrass bed. Moreover, some species, such as 2. 

marina, can exist either as perennials or annuals, again requiring very different assessment strategies, varying between seed bank and vegetative material depending upon 

time of year. Clear knowledge of seagrass population ecology is a requirement for 

effective management and planting; that is, one-time snapshot inventories are a very, 

very poor basis upon which to delineate seagrass habitat. 

Seagrass beds move. Depending on the species and the physical setting, the rate 

at which portions of the seafloor switch &om vegetated to unvegetated may vary on 

the scale of days or decades, meaning that the amount of open seafloor required to 

maintain patchy seagrass beds is greater than the coverage by the seagrass itself at any 

one point in time (Figure 1.2), sometimes by a factor of two (i.e., over time, the 

movement of seagrass beds means that they will soon occupy at least twice the 

presently unvegetated bottom evident at any one survey time). Thus, if unvegetated 

areas among existing patches of seagrass are converted to channels, the long-term 

(within four years, unpubl. data) baseline acreage of seagrass in the vicinity of the 

converted habitat, will decline. Therefore, seagrass habitat must be recognized as 

including not only continuous cover beds, but chronically patchy habitat; a policy 

that requires considering the (presently) unvegetated spaces between seagrass patches as seagrass habitat as well. Management of seagrass resources therefore depends on 

understanding the spatial and temporal dynamics of seagrass coverage. 

One of the biggest problems regarding delineation of seagrass habitat relates to 

the choice of sampling scale during the process of inventory, especially prior to a 

planned impact to a seagrass bed (see section, "Spatial Scale and its Role in Defining 

Seagrass Habitat," below). Scale is roughly defined here as the variation of pattern as 

a function of the range and resolution of examination. The scale at which assessments of seagrass coverage take place varies tremendously, depending on some 
Chapter 1: Background 9 

covariate of acreage, interest and time available to conduct surveys. In contrast, after 

a planting is installed, monitoring of seagrass planting is less prone to scale problems 

as direct count methods are usually employed and statistical sub-sampling protocols 

can be instituted to ensure adequate sampling intensity. However, assessment of 

existing natural seagrass and post-coalescent seagrass planting takes place at many 

spatial scales and this leads to very different values of seagrass abundance. If aerial 

photographs are used, the altitude of the airplane, the camera lens, film, solar angle, 

water turbidity, and wind waves affect the ability to detect seagrass beds, particularly at the lower end of their depth distribution. Similarly, if one chooses to survey a 

potential impact site from the deck of a small boat then wavelets, reflectance, turbidity and an individual's search image all influence ability to assess seagrass abundance. Aerial photography such as that recommended by the NOAA Coastal 

Change Analysis Program (C-CAP) (Dobson et al. 1995), has a minimum mapping 

unit of 0.03 ha. At that resolution roughly 37 percent of the permits issued for alterSampling Dates 

SITE - c chl ------"' 

cmi ------. hihl ---- 

--. 

hih2 

mm12 -- nrhl - st1 

Figure 1.2. Plot ofthe cuniulative area of bottom covered in 50 x 50ni survey areas over tinie. Y-axis 

= cunrulative cover assessed by adding new square nieters ofcover to that not previously covered in any 

survey. X-axis = santpling dates. Each line type represents a dgerent 50 x 50m site. 
10 Guidelines for the Conservation and Restoration of Seagrasses 

ation of submerged aquatic vegetation habitats could not be detected. Fortunately, 

those that could be detected with 0.03 ha resolution accounted for ~99 percent of 

the acreage impacted (Rivera et al. 1992). Inherently patchy seagrass beds would be 

even more difficult to detect and quantift at a spatial resolution less than 0.03 ha 

using C-CAP techniques. These scales < 0.03 ha are spatial scales that questions of 

planting unit (PU) spacing and groupings of PU must be addressed (see section on 

"Spacing of Planting Units"), and persistent seagrass patches can be produced at 

these smaller scales. 

Fonseca (1989a) suggested that at the 1:24,000 scale of aerial photography when 

the ratio of average seagrass patch diameter to the distance between patches exceeds 

50: 1, seagrass habitat continuity no longer fosters cognitive recognition by a viewer 

as constituting seagrass habitat. He suggested that above that ratio the area should no 

longer be considered continuous seagrass habitat. Clearly this ratio is scale dependent. If a ratio of 50 shoot widths to the distance between shoots were used, then 

many seagrass beds on the West Coast and in the northeast where individual plants 

are very large (> 2 m length) would no longer be considered seagrass habitat even 

though the unit area biomass might be comparable to other seagrass beds in the 

country. Unfortunately, we are not aware of any quantitative description of how bed 

boundaries are interpreted (i.e., when a bed is drawn as one large polygon or many 

small polygons). However, variation in seagrass bed form can easily be visually detected &om low-level aerial reconnaissance (Figure 1.3), and appears to be correlated 

with exposure to waves and currents. Under wave and current conditions beds can 

take extreme forms; Molinier and Picard (1952) and Fonseca (1996a) described vertical walls of Posidonia and Zostera, respectively, revealing the extent to which seagrass 

could reduce erosion and enhance sediment accumulation. Seagrass patterns also 

change, revealing areas of seagrass coverage loss and gain at meter scales within short 

time periods (months) (Figure 1.4) attesting to the consistent ability of seagrasses to 

stabilize sediments. For at least 20-30 years af?er Molinier and Picard's work, little in 

the way of a quantitative association of seagrasses' effects on water motion and, conversely, the effect of water motion on seagrass bed development took place. During 

this time, interest in the physical processes occurring in seagrass beds was confined 

largely to qualitative descriptions of their geological role and, to a lesser degree, the 

implications of this geological stability on animal utilization. - 

It is unlikely that there will be a universal standard for defining seagrass habitat. 

Different seagrass species form beds that occupy too great a diversity of habitats and 

exhibit such a range of life history strategies that a universal definition would almost 

certainly be restrictive and unworkable. Further, published data on seagrass biomass, 

density, and structural complexity (e.g., surface area) have tended to be collected f?om 
Figure 1.3. Aerial photograph ofntixed Halodule wrightii, Ruppia maritima, Syringodium filiforme, and Thalassia 

testudinum beds on the western ntargin of Tanpa Bay, Florida. In the foreground at the bayward edge ofthe shoal are what 

appear to be wave-sculpted beds while further landward, in shallow water are nlore continuous cover bed. Reduction in wave 

energyfront both the shelving shoal and the grass itself is thought to be responsible for the resultant seagrass bed landscape 

pattern. Taken front Fonseca (in press). 

RSP e e 0 NO CHANGE 0 0 0 LOSS + + + GAIN SAND 

Figure 1.4. Change in seagrass bed cover in a wave-exposed, patchy seagrass bed near Beau$rt, NC. Dark circle=m2 areas 

with no change in cover (6-month period), + = areas ofseagrass gain, = areas of loss and no syntbols = areas of unchanged 

sand. 
12 Guidelinesfor the Conservation and Restoration of Seagrasses 

seagrass beds that form large unbroken meadows. Limited comparative information 

on bed spatial heterogeneity is available fkom the full range of habitats or landscape 

patterns that seagrasses form. Therefore, if we used published data to set boundary 

dehitions of seagrass beds, it is quite likely they would tend to define only certain 

seagrass species (i.e., commonly studied species such as Z. marina, etc.) in certain settings (e.g., relatively wave-protected and low current speeds which yield extensive, 

non-patchy habitat). Further, because data collection has been historically biased 

toward beds in lower energy environments, the more fkagrnented, patchy nature of 

higher energy seagrass beds would be an element of seagrass bed structure that would 

not be captured in such a universal definition. On-site, direct surveys of local undisturbed seagrass beds in similar physical settings, or better, pre-impact surveys of the 

status of a seagrass bed remain over time the best guidelines for delineating seagrass 

habitats. 

What we suggest is that managers must have some historical perspective. Onetime surveys are completely inadequate data (i.e., see Figure 1.2) upon which to base 

management decisions that could have effects for years. Bed form migration (sensu 

Patriquin 1975, Marba et al. 1994, Marba and Duarte 1995), presence of seed banks, 

annual populations, recent nonpoint source anthropogenic impacts (e.g., decreased 

water clarity), and even deliberate removal of seagrasses all combine to cast doubt on 

the veracity of one-time surveys (i.e., see Figure 1.2). For evaluations of extant beds, 

even seemingly straightforward information such as shoot density can be misleading. 

Data such as shoot density are sometimes inversely related to shoot size, meaning that 

shoot densities of even less than one shoot m-2 may be significant, especially if that 

shoot is very large. Conversely, populations of Halophila spp., of which there may be 

in excess of halfa million hectares in the Gulf of Mexico and Indian River Lagoon 

(Iverson and Bittaker 1986, Continental Shelf Assoc. 1991, Kenworthy l992), return 

almost exclusively &om seed every spring (Williams pers. corn.). As with other 

species that rely heavily upon seeds for seasonal recovery, surveys taken during 

months where aboveground biomass is all but absent and that do not incorporate 

seed bank surveys would erroneously conclude the area did not support seagrass. 

SPATIAL SCALE AND ITS ROLE IN DEFINING 

SEAGRASS HABITAT 

If physical processes have the potential to affect habitat heterogeneity in seagrass 

communities then there is the potential for affecting associated fauna (Fonseca and 

Fisher 1986). Seagrass beds composed of isolated, dune-like patches of -2 m in 

diameter can coalesce within several growing seasons upon elimination of waves and 

tidal currents (pers obs). Despite the clear relationship of water motion to seagrass 
Chapter 1: Background 13 

bed form, we have only begun to evaluate their spatial (or temporal) organization 

(Virnstein 1995), otherwise seagrass beds have consistently been treated as a "black 

box" at the landscape scale. To build on information accumulated on ecosystems and 

apply this information to seagrass systems, research emphasis must include not only 

the normative 1 m scale study, but scales that are relevant to mechanisms that contribute to the formation, maintenance, and hnction of whole systems, such as sediment transport pathways or an organism's range. 

If the pattern of distribution observed in seagrass beds is the result of physical 

processes whose effects vary with the spatial scale of examination, then it follows that 

the influence of bed pattern on such things as faunal abundance will, in turn, vary 

with spatial scale as well (sensu Bian and Walsh 1993, Fonseca 1996). Therefore, 

knowing the range of these scales is potentially valuable if, afZer gathering empirical 

evidence, one can infer structural attributes at other scales of interest, especially scales 

that may be less expensive to derive (eg, aerial photography). 

Resource managers must realize that a relationship between ecological phenomena and the spatial scale of a survey is real and sometimes intuitive. At the least, 

such relationships are a statistical reality that can strongly affect interpretation of field 

survey data (Rossi et al. 1992, Cao and Lam 1997). The notion that interactions at 

one scale (spatial or temporal) affect that which is expressed on another scale provides the basis for hypothesizing scale-dependent effects. Therefore, spatial and temporal patterns seen in seagrass ecosystems are the result of physical processes acting 

both on individual plants and the local population level (individual patch). 

Responses of individual plants to water motion and associated phenomena (e.g., sediment particle size) may be cumulative and affect seagrass landscape patterns perceived at coarser scales of resolution. To summarize, examples of the importance of 

deriving scale dependence in seagrass beds include identification of: 

1. The scale at which samples taken in the landscape are independent of one 

another and improve sampling stratification, 

2. Their effect on animal utilization and distribution, and 

3. The relevant scales over which sedimentary processes are controlled provid- - 

ing a better prediction of alterations in current patterns, interception (or lack 

thereof) of wave energy, and sedimentary processes as the result of altering 

the seagrass landscape. 

One result of recent research on seagrass landscape patterns is that there are 

ranges of spatial scales over which estimates of coverage vary as the result of the scale 

of sampling resolution chosen by the investigator (Fonseca l996b). Moreover, for 
14 Guidelinesfor the Conservation and Restoration of Seagrasses 

seagrass beds in North Carolina and Tampa Bay that experience relative wave exposure values (see "Constraints Imposed by Physical Setting on Planting Operations," 

below) greater than 3 x lo6 (on a scale that runs f?om 0 to - 6 x lo6) any estimate 

of seagrass coverage will differ depending on the size 'of the sampling unit and/or the 

distance separating those sample units at scales < 10m (Fonseca 1996b). This means 

that interpretation of any factors related to seagrass bed coverage sampled within this 

range of 1-10 m will be different among any studies that sampled at different spatial 

scales (i.e., samples taken 1 m apart versus, for example, 5 m apart). Therefore, comparisons among studies or surveys, even of the same bed, will differ to some degree 

simply because different size quadrats were used and not necessarily as the result of 

actual differences in the factor being compared. Of course, comparisons between 

studies can be different because different numbers of samples (which approximates 

statistical power) are taken. Finally, this has implications for the integrity of sampling 

schemes because any samples taken in this range of scale dependence will not be statistically independent, casting doubt on the validity of among-study or among-survey comparisons which were conducted at different spatial scales. This can create 

problems for interpretation of planting success. 

Scale dependence in sampling has not only spatial but temporal considerations. 

We raise this caution regarding temporal scale dependence because in our section 

titled "Comparative Analysis of Seagrass Planting Efforts" we found that many projects changed assessment frequency during the course of the monitoring period. In 

fact, we too recommend a change in assessment protocol depending on whether it 

is being conducted before or after coalescence of planting units. Therefore, statistical comparisons should be made with caution between data collected &om pre- and 

post-coalescence because such comparisons of one site over time likely violate rules 

of sample independence. Because many planting projects cannot escape problems 

with sample independence over time, the use of simple descriptive measures (such as 

area covered and persistence) as standard measurement protocols becomes very 

important to minimize problems with comparative analysis among studies or among 

dates within studies. 

Another problem with spatially heterogenous (i.e., patchy as opposed to continuous) seagrass beds is the perception of their comparative ecological function. 

Spatially heterogenous seagrass environments in North Carolina have been classified 

as "scattered" (Caraway and Priddy 1983) versus continuous cover beds that are 

termed "dense." This unfortunate classification inferred a lower resource value 

despite the fact that the former landscape pattern covers many thousands of acres of 

estuarine seafloor in North Carolina, has shoot densities and primary production 

equivalent to continuous cover beds, has significantly hlgher below-ground biomass 
-- . 

Chapter 1: Background * 15 

than continuous beds, and often supports equal densities of some economically valuable species such as pink shrimp (Murphey and Fonseca 1995). 

VULNERABILITY AND SUSCEPTIBILITY 

OF SEAGRASS ECOSYSTEMS 

Why are seagrasses so often impacted by human activity? One of the reasons is 

their location in the coastal zone. Because of their relatively high (compared to phytoplankton) light requirements (Kenworthy and Haunert 1991) they occur in shallow, nearshore waters, a situation that makes them extremely susceptible to damage 

by human activity such as nutrient loading (Short and Burdick 1996), light reduction (Dennsion et al. 1993, Kenworthy and Fonseca 1996), and propeller scarring 

(Sargent et al. 1995). As our utilization of the coastal zone grows so will the damage 

to seagrass ecosystems unless proactive steps are taken to avoid those impacts and successfully mitigate when impacts occur. Because they are now universally recognized 

to be valuable habitats, efforts to mitigate their losses have been underway for many 

years. 

It is critical that one recognizes that seagrass mortality, whether mechanically 

induced, such as dredging, or physiologically induced from reduction in light (e.g., 

docks, turbidity), often happens rapidly; time scales for loss can range to as little as 

weeks or months. Recruitment, however, does not typically keep pace, yet if the site 

were capable of supporting continued cover, seagrass may recolonize within a few 

growing seasons (Kenworthy et al., 1980, Harrison 1987, Fonseca et al. 1990,Thayer 

et al. 1994). Recovery via natural recruitment is a demographic process with 

tremendous spatial and temporal variation (eg, 0 to > 10,000 seeds m-' for 2. marina) and is very difficult to predict. It is clear, however, that seed set and successful 

germination are often requisite for rapidly (1-2 growing seasons) balancing anthropogenically induced seagrass mortality. In contrast, vegetative encroachment may 

take many years (Johannson and Lewis 1992) or even longer, as is suggested by the 

lack of seagrass recovery in portions of the northeast U.S. &om the "wasting disease" 

loss of the 1930's (sensu Short et al. 1993). The point here is that there are fundamentally different time scales involved in population-scale losses and their recovery. 

Only recently have investigations begun to assess the population-scale proceaes of 

seagrass bed formation and maintenance (Orth et al. 1994). In fact, scientists have no 

clear idea what constitutes a population for these plants or what population processes are at work (i.e., existence of metapopulations, sensu Orth et al. 1994). At a minimum, documentation of distribution together with elucidation of demographic 

process must be a research priority. 
16 Guidelines for the Conservation and Restoration of Seagrasses 

We have mentioned environmental constraints to seagrass planting (see review 

by Phillips 1982), but there are many other management constraints that determine 

the effectiveness of seagrass planting. One is the degree of philosophical alignment 

among federal, state and local agencies whose jurisdictions include seagrass habitat. 

The U.S.Army Corps of Engineers, whose fbnction includes issuance of dredge and 

fill permits, sometimes cannot follow recommendations fi-om other agencies to conserve seagrass habitat (Mager and Thayer 1986). Conflicts between preservation of 

seagrass (and many other wetland habitats) and implementation of public-interest 

development projects must be balanced by resource agencies but often results in the 

loss of seagrass habitat (sensu Race and Fonseca 1996). The loss of seagrass habitat is 

sometimes addressed by proposing in-kind mitigation. In addition, maintenance 

dredging projects, particularly those associated with national security, are often considered exempt fi-om mitigation requirements although in instances of very long 

dredging cycles (years to decades), mitigative actions are sometimes implemented to 

minimize immediate impacts. It has been our experience that as more information 

is presented to managers regarding the fbnctions of seagrass ecosystems and the difficulties involved in mitigating for their loss, fewer permitted impacts are occurring 

in seagrass beds. 

Although the loss of seagrasses due to dredging has been significant (Taylor and 

Saloman 1968, Onuf 1994), it is likely that the majority of seagrass habitat loss does 

not result directly &om dredge-and-fill activities. More recently, direct impacts from 

mooring scars (E Short, Jackson Est. Lab., Durham. NH, pers. corn.), propeller scars 

(Sargent et al. 1995), jet skis (Kreuer pers. com.) and vessel wakes (pers. obs.) are 

emerging as a major source of seagrass habitat loss. For some species of seagrass such 

as Thalassia which is slow spreading (Fonseca et al. 1987c), physical damage is 

extremely long-lasting (Zieman 1976, Durako et al. 1992). Short et al. (1993) and 

the Chesapeake Bay Program (1995) recognized improvement of wastewater treatment, surface run-off, restrictions on certain fish and shell6sh harvesting techniques, 

and regulation of boat trafk as key elements in protecting seagrass beds. Although 

scallop harvesting has been shown to damage seagrass beds (Fonseca et al. 1984) as 

has raking (Peterson et al. 1984) and prop-dredging for clams (Peterson et al. 1987), 

other fishery techniques such as trawling for bait-shrimp with specially-designed 

gear can have little apparent effect on seagrass although by-catch mortality is severe 

(Meyer et al. in review). Work by the Chesapeake Bay Program (1995) also lists 

(blue) crab dredging (scraping) as a significant impact on eelgrass beds. Fishing gear 

impacts to seagrass beds must be examined on a gear-by-gear basis. 
Chapter 1 : Background 17 -. 

Reduction in water quality, including water clarity, is another significant agent 

of seagrass loss (Dennison et al. 1993, Gallegos 1994, Onuf 1994, Gallegos and 

Kenworthy in press). Burkholder et al. 1992 and Dennison et al. (1993), like Batiuk 

et al. (1992), provided general guidance on maintaining water chemistry to support 

healthy seagrass beds. In doing so, Dennison et al. (1993) essentially determined the 

converse of health standards; they defined some critical water chemistry conditions 

at which harm would come to seagrass beds (Table 1.2). These data, and those promulgated by the Chesapeake Executive Council (1989) and the Chesapeake Bay 

Program (1995), are perhaps the only quantitative water chemistry information for 

managers to evaluate the health of seagrass environments at this time. They are likely usefd for most temperate seagrass ecosystems and likely describe levels that would 

be too high for typically oligotrophic tropical and sub-tropical waters, particularly 

those dominated by carbonate sediments (sensu Fourqurean et al. 1995). However, the 

correlation between human development of the shoreline and seagrass decline is 

clear (Short and Burdick 1996). 

Although seagrass beds are dynamic systems, with some beds persisting essentially unchanged for decades, others change with the season (den Hartog 1971, 

Zieman andWood 1975, Phillips 1980a, Fonseca et al. 1983, Duarte and Sand-Jensen 

1990). Some changes in seagrass communities can be attributed to the life histories 

of individual seagrass species (e.g., Halophila spp.). However, natural perturbations 

Table 1.2. Chesapeake Bay submersed aquatic vegetation habitat requirements. For each 

parameter, the maximal growing season median value that correlated with plant survival is 

given for each salinity regime. Growing season defined as April-October, except for polyhahe (March-November). Salinity regmes are defined as tidal fresh = 0-0.5 o/oo, 

Oligohaline = 0.5-5 o/oo, Mesohaline = 5-18 o/oo, Polyhaline = more than 18 o/oo. 

(Taken from Dennison et al. 1993). 

- - --- 

Light Total Dissolved Dissolved 

attenuation suspended inorganic inorganic 

Salinity coefficient solids Chlorophyll nitrogen phosphorus 

regime (K, m-') (mdl) a(%/l) (uM) (W 

Tidal freshwater 2.0 15 15 - 0.67 - 

Oligohaline 2.0 15 15 - 0.67 

Mesohaline 1.5 15 15 10 0.33 

Polyhaline 1.5 15 15 10 0.67 
18 * Guidelines for the Conservation and Restoration of Seagrasses 

greatly influence the distribution of seagrass species. Disease has been widely implicated in the loss of seagrass beds since the pan-Atlantic decline in the 1930's 

(Rasmussen 1973, Short et al. 1987, Muehlstein 1989). Through this time, seagrass 

declines attributed to disease have added significantly to fluctuations in seagrass distribution. Physical disruption &om storms and shifting channels redefine seagrass bed 

distribution and composition. Seasonal disturbances, such as low tides which expose 

and desiccate beds (Phillips 1980a,Thayer et al. 1984), and catastrophic events, such 

as hurricanes (Eleuterius and Miller 1976, Livingston 1987), can dramatically restructure seagrass beds both in terms of bed size and seagrass species composition. We 

have found that reductions in seagrass bed coverage as the result of storms is a positive fbnction of how exposed to wind-generated waves a bed is prior to a storm; 

rapid loss of coverage can occur within a period of hours (unpubl. data), reiterating 

the fact that one-time surveys of seagrass coverage can be misleading as to the potential distribution of seagrass in a water body. 

Biological disturbance of seagrass beds by a variety of organisms can also be 

extensive. Overgrazing by herbivores such as urchins has also affected spatial distribution and standing stock of seagrass beds (Camp et al. 1973). Ice scour (Robertson 

and Mann 1984) and extreme cold (Lalumiere et al. 1994) have been shown to control 2. marina distribution in the sub-kctic. Also, excessive epiphytic load (SandJensen 1977), burrowing shrimp (Suchanek l983), vagile macrofauna (Valentine and 

Heck 1990,Valentine et al. 1994), green algae (den Hartog 1994a), and lugworms 

(Philippart 1994) have all been shown to limit seagrass distribution (but see Reusch 

et al. 1994; fertilizer enhancement of eelgrass by blue mussel biodeposition). Rays 

too have been implicated in many seagrass planting failures (Merkel 1988a, Mote 

Marine Laboratory and Mangrove Systems Inc. 1989, Fonseca et al. 1994) and may 

even contribute to the maintenance of natural bed patchiness (Townsend and 

Fonseca in 1998). These are, however, natural processes. Similarly, some dieoffs of 

seagrass such as the "wasting disease" of the eelgrass (2. marina) in the North Atlantic 

during the 1930's (Short et al. 1988) and the current demise of T. testudinum in 

Florida Bay have been attributed to a pathogenic form of a marine slime mold, 

Labyrinthula zosterae (Robblee et al. 1991), among other factors. In nature, however, 

the outbreak of this fbngi has not been easy to classifjr as a cause of seagrass decline 

as opposed to being a by-product of some other environmentally- or anthropogenically-derived decline in the quality of the seagrass habitat (sensu den Hartog 1996). 

When human impacts are added to the natural stresses imposed on seagrass beds, 

disastrous losses of seagrass can occur. Such losses have been documented in Australia 

(Kirkman 1981, Cambridge and McComb 1984) and southeast Asia (Fortes 1988). 

In the U.S., large scale losses have been documented in the Chesapeake Bay (Orth 
Chapter 1: Background 19 

and Moore 1981) and in the Gulf of Mexico (Livingston 1987). Significant impacts 

to seagrass beds in Tampa Bay were documented by Taylor and Saloman (1968), 

eventually reaching over 50 percent of the historical seagrass cover in Tampa Bay 

(Haddad 1989). Similarly, 35 percent of the seagrass acreage in Sarasota Bay has been 

lost as well as 29 percent of that in Charlotte Harbor, Florida, and 76 percent of that 

in Mississippi Sound (Eleuterius 1987). Pulich and White (1991) reported a loss of 

90 percent in Galveston Bay, Texas. Thom and Hallum (1991) report similar ranges 

of losses &om Puget Sound. Large losses of seagrass have also been reported &om San 

Francisco and San Diego Bays (Kitting and Wyllie-Echeverria 1992), the Laguna 

Madre (brown tide, Onuf 1994), and large-scale damage &om propeller scarring has 

been reported in Florida (Sargent et al. 1995). 

Loss of seagrass cover leads to several undesirable and difficult-to-reverse conditions. First, the sediment binding and water motion baing effects of the plants 

themselves are lost (Fonseca et al. 1983, Fonseca and Fisher 1986) allowing sediments 

to be more readily resuspended and moved (eg, Florida Bay, Thayer et al. 1994). The 

physical ramifications include increased shoreline erosion and water column turbidity. Seagrass planted in areas with these conditions may not survive due to light limitation &om the elevated turbidity. Loss of seagrass, of course, eliminates all important, associated habitat functions (IGkuchi 1980, Peterson 1982). 

Much of the documented seagrass loss is due to human-induced reductions in 

water transparency (Kenworthy and Haunert 1991, Bulthuis 1994; these losses are 

ofien not included with other wetland or even seagrass loss statistics). Only in the last 

few years has it become clear that seagrasses typically require light intensities reaching the leaves of at least 15-25 percent of the light which has penetrated to just 

beneath the water surface (Dennison and Alberte 1986, Gallegos 1994, Gallegos and 

Kenworthy 1996). Moreover, the length of time over which a seagrass plant spends 

at photosynthetically-saturating light intensities too has been shown to be correlated 

with growth and survival (Dennison and Alberte 1985, 1986, Zimmerman et al. 

199 1). However, water transparency standards have historically been based on 

requirements of phytoplankton which may need only -1 percent of incident light 

(Kenworthy and Haunert 1991), meaning that there is ofien no legal mandate for 

requiring improvement of water transparency to support seagrasses. This absence of 

technical and legal mandates makes the task of demonstrating the need for restoration of water quality to support seagrasses difficult. 

There are many factors that act to reduce water column transparency (sensu 

Dennison 1987, Dennison et al. 1993, Gallegos 1994, Gallegos and Kenworthy 

1996). Excess suspended solids and nutrients which enter the water column as the 
- 

20 Guidelinesfor the Conservation and Restoration of Seagrasses - 

result of poor watershed management combine to reduce transmitted light below 

that of natural fluctuations, increasing vulnerability to local population extinctions. 

Suspended solids and water color changes reduce water transparency directly. 

Nutrient additions, such as &om septic systems (Burkholder et al. 1992, Short and 

Burdick 1996), accelerate growth of light-absorbing algae in the water column as 

well as benthic macroalgae (den Hartog 1994a,b) and that growing epiphytically on 

seagrass blades (Sand-Jensen 1977), all of which combine to reduce light availability 

to seagrasses. Moreover, the seagrass canopy has intrinsic light attenuation effects 

through mutual shading (Dennison 1987, Enriquez et al. 1992) by the individual 

plants. 

When losses have occurred due to decreased light availability, often only changes 

in watershed management (such. as controlling storm water and sewage discharges) 

can reverse the trend of decline. Such a reversal in decline is rare but has occurred 

(Johansson and Lewis 1992). Transplanting into areas experiencing seagrass loss due 

to decreased water transparency without independent improvements in water quality will only result in the death of the transplants. This is especially problematic in 

areas where water turbidity may be due to sediment resuspension which arises as a 

result of seagrass already lost and is therefore not necessarily a current watershed 

management problem. 

Reduction in water transparency is not the only anthropogenic source of seagrass loss (see Phillips 1982 for an early, detailed review). Thermal effluents &om 

electric power plants have caused extensive losses such as those documented at the 

Turkey Point station in Biscayne Bay, Florida (Zieman and Wood 1975) as well as that 

associated with the Stock Island (Key West) station (pers. obs.). In the past, dredgeand-fill-associated losses were commonly associated with private sector development 

but more recently, many losses can be ascribed to public interest projects, such as the 

replacement of the Florida Keys Bridges (Mangrove Systems Inc. 1985a,Thayer et al. 

1985). In addition, the rapidly increasing number of small boats in coastal waters has 

resulted in the aforementioned widespread damage &om propeller scarring (Sargent 

et al. 1995). Because of the chronic nature of propeller scarring, hull impacts, and, 

more recently jet ski scour, such damage is likely very difficult to repair by planting 

(e.g., ferry boat landings in Puget Sound, R.Thom, Battelle Pacific Northwest Lab., 

Sequim,Wa.), Sargent et al. (1995) recommend a four-point plan to reduce scarring 

in moderately and severely scarred meadows (defined under their criterion) which 

includes (1) education of the public as to the nature and scope of scarring impacts, 

especially in the Thalassia testudinum beds which are very slow to recover &om 

impacts, (2) installing channel markers as aids to navigation, (3) enforcing state and 

federal statutes that address propeller scarring and caused by propulsion systems 

dredging, and (4) establishment of limited-motoring zones in areas where, due to the 

extreme shallowness of beds, impacts &om propulsion systems would be unavoidable. 
Chapter 1: Background 21 

A SHORT HISTORY OF SEAGRASS MITIGATION 

AND C ST ORATION 

Addy's (1947) basic logic was to match planting and harvest site environments, 

and this remains a fundamental tenet in almost all seagrass planting today. Aside from 

early interest by Phillips (1960), almost 30 years elapsed before serious attention to 

planting seagrass developed. It was not until Eleuterius (l975), van Breedveld (1975), 

Thorhaug (1976), and Churchill et al. (1978) that documents again began to emerge 

presenting seagrass planting in a guideline format. But even though suitable planting methods have long existed, the track record for successful mitigation of impacts 

to seagrass beds remains variable (see review by Phillips 1982). Some spectacular failures of seagrass planting (Stein 1984) have created a lasting impression that restoration of seagrass beds is still an experimental management tool. Yet there have also 

been many successful plantings (e.g.,Thayer et al. 1985). Seagrass beds have often 

been successfully planted and have come to perform much as naturally-propagated 

beds (Hornziak et al. 1982, McLaughlin et al. 1983, Fonseca et al. 1996b). Still it has 

not been clear what factors are the most important to address to ensure planting success. We had previously thought that seagrass planting was, as Ronald Phillips put it, 

"a two-edged sword (R. Phillips, Battelle Labs, Richmond, Wa., pers. comm.), providing a means of ameliorating habitat losses but perhaps encouraging habitat 

destruction through the mere existence of a possible remedial technique. In our 

opinion a more conservative trend has emerged. As resource managers and developers have become educated as to the value of seagrass systems and the realities of their 

costly repair, more emphasis appears to now be placed on impact avoidance and minimization. 

Much emphasis was placed on technique development in the late 1970s and 

early 1980s (see reviews by Phillips 1980, 1982, Lewis 1987, Fonseca et al. 1988, 

Thom 1990), but relatively little attention was given to developing a management 

fi-amework within which these techniques could be effectively implemented. As a 

result, most seagrass mitigation projects failed to achieve the goal of 1:l habitat 

replacement (i.e., oaet a net loss of seagrass habitat: sensu Fonseca et al. 1987c, 

Fonseca 1989a, but see Merkel 1988a,b), nor have they consistently addressed 

whether functional equivalency has been achieved (often a permit requirement). 

Phillips (1980b) published seagrass planting guidelines that relied on elevation in 

the tidal zone, current speed, salinity, soil type (sandy, combination, or cohesive) and 

seagrass species. Decision keys for each coast of the U.S. were compiled. However, 

with additional research some of Phillips' (1980b) threshold criteria should be 

changed. He accepted current speeds up to 1.82 m s-' whereas we would strongly 

caution against planting in current speeds exceeding 0.5 m s-' (see below). Further, 
22 * Guidelines for the Conservation and Restoration of Seagrasses 

Phillips indicated that planting in sandy sediments was a cause for rejection of a 

planting site, but we have found excellent success in sandy sediments (Lewis 1987, 

Fonseca et al. 1987a,b,c). Zimmerman et al. (1991) argue that factors increasing root 

and rhizome anoxia such as cohesive soils recommended by Phillips put seagrass (at 

least when using bare-root planting methods) under severe physiological stress, a factor to be especially avoided during planting operations. Similarly, Merkel(1992) recommended planting on sandy sediments on the West Coast and avoiding consolidated clays and mudstones (although he [correctly] noted that rhizome extension is 

slower in coarse sediments). More recently, detailed information on habitat requirements for seagrass (and other submerged aquatic vegetation, SAV) has emerged, but 

only in well-studied areas. Notable is the work ongoing in the Chesapeake Bay. 

Batiuk et al. (1992; see also Dennison et al. 1993) provide a detailed synthesis of water 

quality requirements for SAV (Table 1.2). Based on experimentation and strong correlative evidence of these water quality parameters and SAV distribution, they also 

developed a series of target water quality conditions that would have to be met to 

expand SAV distribution by allowing it to colonize greater depths. This study should 

serve as a model approach to investigate seagrass restoration efforts in other areas.The 

applicability of these data to other areas is discussed in greater detail under the section entitled "Light Requirements for Transplanting." 

Merkel (1992) has developed a field manual for planting eelgrass on the West 

Coast that includes planning protocols and detailed guidance on planting execution 

that is otherwise generally lacking in the literature. Aspects of Merkel's report will 

be reviewed throughout this document. Fonseca (1989a, 1992) published what were 

essentially Agency checklists for planning and evaluating seagrass planting; the design 

of those checklists were the basis for the more comprehensive, yet regionally-specific 

guidelines published later (Fonseca 1994). The planning, planting, and monitoring 

sections of this document were adapted &om Fonseca 1994: "A Guide to Planting 

Seagrasses in the Gulf of Mexico." Lockwood (1990) published criteria for placing 

- marinas in eelgrass habitat that extolled impact minimization as the only guideline 

for mitigation. Based on case reviews of seagrass mitigation projects (Thayer et al. 

1985),Thayer et al. (1990) published a preliminary decision matrix that incorporated site selection criteria as well as environmental conditions required for the growth 

of specific seagrass species. 

In general, studies of seagrass restoration and management have only recently 

become a focus of attention (e.g., Chesapeake Executive Council 1989) and more 

recently, funding. NOAA's Coastal Ocean Program has focused on these issues for 

both seagrass and saltmarsh through its Estuarine Habitat Program, C-CAP, and 

Decision Analyses Series. In conducting our study, we have found the information 

base for seagrass management difficult to locate. For example, a survey of published 
Chapter 1: Background 23 

literature since 1985 using BIOSISTM revealed that there were 655 published works 

on seagrass. This search of the open literature reveals that over the last five years most 

of the focus in seagrass research has been on aspects of the plant's physiology. This is 

typical of seagrass research over the last quarter century where interest in plant physiology and seagrass bed-associated fauna have dominated the open literature. Crossreferencing "seagrass" with "restoration" found nine references while "mitigation" 

provided one reference. From the literature we accumulated directly &om journals 

and solicitation of colleagues, we found that approximately half was found outside 

the open literature.The literature on the subject of seagrass bed restoration and mitigation is found in the grey literature and is ofien not subject to the rigors of peer 

review (but see Batiuk et al. 1992). Another large body of information lies in unpublished project reports, the quality of which are highly variable. We feel that the trend 

to generate information on seagrass restoration and mitigation for dissemination in 

forums other than the open literature has been one of the major reasons that seagrass 

restoration and mitigation is perceived as an experimental tool, when it could be an 

established management practice. 

What are the problems managers face in restoring seagrass beds? Chief among 

these problems is the tendency to plant seagrass in areas where there is no prior history of their existence (Fredene et al. 1985; unless of course the site was created for 

the purposes of planting seagrass). The chronic absence of seagrass &om a site, especially when there are propagule sources nearby, usually indicates that the site cannot 

consistently support seagrasses. Ensuring suficient light, moderate nutrient loads 

(Batiuk et al. 1992, Dennison et al. 1993, Kenworthy and Fonseca 1996, Short and 

Burdick 1996) and protecting plantings &om disturbance are major considerations 

for developing a persistent seagrass bed. Planting stock must be chosen so that there 

are sufficient young shoots and growing meristems to make up for mortality, a ratio 

that changes dramatically depending on what portion of a seagrass bed is examined, 

the species, as well as time of year. Most seagrasses are comparatively short-lived and 

have high natural mortality rates, and suitable growing conditions are needed to allow 

new shoot generation to compensate for this mortality. Thus, development and incorporation of seagrass demographic information into the management process is a 

high priority area for research. There are many other caveats that must be imposed 

to expect successfd restoration of seagrass beds. These will be discussed later both in 

general terms and specifically by region around the country. 

Having argued that seagrass mitigation is no longer experimental and should be 

considered an established management tool, why then place such a priority on conservation? The reason is that while techniques and protocols exist that can produce 

persistent seagrass beds, the history of the field shows that guidance and protocols are 

often inconsistently applied. This has resulted in spectacular large-scale planting fail- 
24 Guidelinesfor the Conservation and Restoration of Seagrasses 

ures (e.g., the aforementioned Port of Miami expansion project: a multi-million dollar -200 acre seagrass mitigation which produced only a few acres; Stein 1984). The 

fact that much information on this subject is conveyed through the grey literature, 

which does not always circulate widely, has resulted in repetititve mistakes, such as 

selection of inappropriate planting sites. 

Scientists and managers are always faced with uncertainty in decisions regarding 

ecosystem management. As pointed out byvitousek (1994) for global environmental change issues, scientists know with certainty that changes are occurring and that 

they are human-caused. What scientists cannot do is always predict the particular 

consequences of a given human activity on the environment. However, some trends 

are obvious and the consequences of inaction can be logically derived. It is irrefbtable that extensive loss of seagrass resources have occurred in this country (see previous section), but what are the management options for halting and reversing this 

decline? 

We have compiled this synthesis of seagrass restoration in an attempt to identifjr reasons for failures and successes which will then allow managers to improve the 

odds of success in restoring seagrass ecosystems. By acting to mitigate, restore and 

maintain these resources, managers can o&et collateral decline of many ecological 

functions which we as a society hold important (erosion control, water filtration, fisheries production, and associated aesthetics). However, as the human population 

grows it is highly likely that losses of these unique plant communities will continue 

(e.g., Sargent et al. 1995). There are no ecological substitutes for their role in coastal 

ecosystems. 

The critical role that seagrasses play in many coastal environments, coupled with 

their extensive losses, have created widespread support for their conservation and 

restoration. The "no-net-loss" policy promulgated by the Executive Branch provided an additional impetus to consider seagrass conservation and restoration. 

Meanwhile, numerous policy changes have occurred at the state and local levels over 

the last ten years to support no-net-loss of habitat. Therefore, as an informationbased system of judging the value of seagrass ecosystems has emerged over the last 

decade, the question is no longer whether seagrasses should be protected, but how? 

When all avenues of protection have failed (eg, sequencing; the US Army Corps of 

Engineers-EPA sequence of first seeking impact avoidance and minimization, and 
Chapter 1: Background 25 

then compensatory mitigation, the latter being composed of some combination of 

enhancement, restoration, creation and under rare circumstances, simply preservation), then active planting may be the only option to avoid a permanent net loss of 

seagrass. 

In order to proceed with discussions of management issues, some terminological clarification is needed. We will utilize the terminologies of Fonseca (1994) which 

are reprinted in amended form in Appendix A. Particularly, we wish to draw the 

reader's attention to the differentiation among the terms "restoration" and "mitigation."They are not interchangeable terms. Mitigation refers to activities related to 

permits (particularly sec. 404 of the Clean Water Act) and embodies a sequence of 

avoidance, minimization and ultimately, if needed, compensatory mitigation, whereas restoration is simply returning a site to a previous condition. Restoration as used 

here does not apply to permit-associated planting projects. We will also differentiate 

the terms "transplanting" and "planting." Transplanting is a subset of planting in that 

here it refers to harvesting of existing plants whereas planting can involve cultured 

plants, seeding, or any number of methods. The terms restoration and mitigation set 

very different constraints on the establishment of performance criteria and the evaluation of compliance (i.e., success). Lewis (1989) defines and differentiates restoration and mitigation as follows: 

RESTORATION -"Returned from a disturbed or totally altered condition to a 

previously existing natural, or altered condition by some action. Restoration refers 

to the return of a pre-existing condition." 

MITIGATION - "...the actual restoration, creation, or enhancement of (functionally equivalent, authors' note) wetlands to compensate for permitted wetland 

losses." 

The term "mitigation" can be used without any modifiers but is often applied 

to situations more aptly termed "compensatory mitigation." Restoration is a term 

which generally applies only to planting activities which are not being counted 

against the destruction of existing habitat. Rather, restoration embraces the concept 

that anything we can do to right a past loss, a loss for which there may be no litigative recourse to seek damage recovery, is a plus to set against the Nation's balance 

sheet for no net loss, but not against that of a project with a pending permit to eliminate seagrass. From a management perspective, restoration for the sake of restoration 

only (properly planned and professionally executed), should be vigorously pursued 

because it will, if one utilizes the above definition, bring a community back toward 

previously existing conditions (i.e., it generally cannot make the situation worse). 
26 Guidelines for the Conservation and Restoration of Seagrasses 

PITFALLS IN THE ~&ITIGATION AND 

RESTORATION PROCESS 

Compensatory mitigation is a process of questionable merit (Race and Fonseca 

1996). Unlike restoration projects which are not necessarily initiated under the 404 

permit process, the circumstances under which a compensatory mitigation are initiated have a large potential to make matters worse, because compensatory mitigation 

usually involves the destruction of existing habitat. The existing habitat is or has been 

traded for the promise of replacement habitat. With restoration, we are dealing with 

a past loss for which the responsible party may or may not be identifiable. With compensatory mitigation, the agent of loss and the responsible party are known and 

sometimes a decision (likely controversial) might be made to trade existing habitat 

for replacement habitat. Of course when a injury occurs to a seagrass bed outside of 

the permit process the loss of seagrass habitat occurred without a secure means of 

mitigating for its loss. However, whether an injury is deliberate or not, if existing 

habitat is lost, an often tangled negotiation process follows to determine the means 

by which compensation for that loss will be made. In many instances, the negotiation process can be prolonged, delaying restoration and resulting in larger impacts 

than might occur if restoration had begun sooner. 

There are, however, a number of management decisions that can be made within 

the permit process to ameliorate a loss in habitat and better approaches the goal of 

no-net-habitat-loss. Mitigation in its broader definition typically also includes impact 

avoidance and minimization (the latter term unfortunately implying an acceptable 

net loss of acreage). In practice, avoidance and minimization are sometimes difficult 

to achieve. The existence of techniques to transplant seagrass has often been used to 

justiG the destruction of existing, productive habitat (pers. obs.). But as pointed out 

earlier, this approach has consistently produced a net loss of habitat. This net loss of 

habitat occurs for a number of reasons, and the permit-associated activities that destroy seagrass beds in the first place typically are long lasting (i.e., creation of channels, bridges, bulkheads). Those activities also ofien do not allow enough area for onsite planting to o&et the loss of habitat. If planting is considered at a location not 

on the original impact site (off-site restoration or mitigation), that site would preferably not be an area that itself has lost seagrass to some other impact. This is a subtle 

point that is often overlooked because of the often costly (in time and effort) site history data that must be obtained to make a quantitative evaluation of no-net-loss. The 

problem works like this: if one permits a loss of seagrass for some form of coastal 

development (eg, -1 acre) and plants an equivalent area (+1 acre) onto a site which 

had previously lost seagrass (e.g., -1 acre) but was not associated with the project at 
- 

Chapter 1: Background * 27 

hand, then the net change in habitat is: (-1 + -1) +1 = -1 acre. All that was accomplished was the repair of the original problem at the planting site, but it does not 

address the loss at the new, most recently impacted site. While there would be no net 

loss &om immediate, present day acreage, the lack of consideration of past losses 

results in a net loss on a recent historical time scale. The critical question here is at 

what point in the past do we choose to represent baseline seagrass acreage? 

Moreover, what if a site chosen for planting does not currently support seagrass? In 

the absence of site history information, one must then ask why it does not presently support seagrass. This often indicates some inherent difficulty in colonization or 

persistence of seagrass. The events influencing the colonization process are sometimes difficult to document because they are often aperiodic, acute events (e.g., 

extreme low tides, storms, migrating rays excavating the bottom). Naturally unvegetated seafloor should not be substituted for vegetated bottom as this typically creates only a transient seagrass bed and alters, not necessarily improves, existing habitat hnctions. The take-home message is that if one contemplates off-site compensatory mitigation, there are usually few, if any sites available that: (a) can support seagrass growth, and if they do; (b) do not involve habitat substitution; or (c) do not satis@ the no-net-loss goal.This is not to say that previously damaged sites should never 

be used for mitigation or restoration, they just must be accurately represented in any 

no-net-loss accounting. As pointed out by Short (Jackson Estuarine Lab., Durham, 

N.H., pers. com.) in reference to the above description of trade-offs, if no mitigation 

is done on a previously damaged site, one ends with a -2 acre net loss of habitat 

instead of -1 acre of loss. 

Under a Memorandum of Understanding with the U. S. Army Corps of 

Engineers, the National Marine Fisheries Service, Office of Habitat Protection, comments on development permit requests under Section 404 of the Clean Water Act 

and Section 10 of the Rivers and Harbors Act. While seagrass restoration has been 

conducted on an experimental scale along all coasts and within all coastal regions of 

the U. S., actual mitigation of impacts resulting &om Corps of Engineers-permitted 

activities has been relatively small, and has been greatest in the NMFS Southeast and 

Southwest Regions. A summary of NMFS-recommended and acted upon mitigation actions by NMFS Region, based on reports received &om NMFS Regional 

Offices as of early 1996, is provided below (note that these regions do not match the 

ecoregions described later in the text). 
28 Guidelines for the Conservation and Restoration of Seagrasses 

NORTHEAST (NE) REGION (Maine through Virginia) 

Seagrass mitigation in the Northeast Region of NMFS is in its infancy and, 

while permits have been reviewed which deal with seagrass habitat, few actions are 

ongoing. In 1991 NMFS began recommending seagrass mitigation for projects without practicable and feasible alternatives that would damage seagrass habitat. At the 

time of this report mitigation actions have been considered in New Jersey, Maine, 

and New Hampshire, but site selection and test planting for a 3-acre mitigation in 

the Piscataqua River (N.H.) is the only ongoing permit-related mitigation which 

NMFS has been involved in making recommendations. This has included not only 

transplanting but also consideration of alteration of bottom topography to achieve 

appropriate planting depths for eelgrass. Proposals are currently being discussed for 

a 10-30 acre eelgrass mitigation in the upper Penobscot Bay (Maine). 

In addition to supporting the experimental transplanting work that is ongoing 

in each of the NE states, the NMFS Regional Office has taken a proactive approach 

to seagrass habitat protection. This has included involvement in the development of 

seagrass management policies, development of seagrass survey guidelines, encouragement for interagency mapping of seagrasses including involvement of the NOAA 

Coastal Change Analysis Program (C-CAP) mapping efforts, and the convening of 

information transfer and education meetings for state and federal agencies on seagrass 

ecology and transplanting technology. 

SOUTHEAST (SE) REGION (North Carolina through Texas including 

the U. S. Virgin Islands and Puerto Rico) 

In the SE Region Habitat Protection Offices reported seagrass mitigation in 

North Carolina, Florida, and Texas. In each state the permits were obtained or under 

consideration primarily for channel maintenance or development related to onshore - construction. In Texas, however, permit activities relate primarily to petroleum pipeline construction and mitigation of illegal prop-dredging activities. With the exception of Texas there has been little or no monitoring or follow-up to assess the degree 

of success of the projects. In addition to permit-related activities noted below, field 

offices of the NMFS have participated in similar management activities noted for the 

NE as a means of educating state and federal agencies and potential developers of the 

ecology and sensitivity of seagrass species and habitats. 

Between 1985 and 1994 the Habitat Protection Field Office in Beaufort, North 

Carolina, recommended seagrass mitigation on 5 permits. The direct seagrass dam- 
- 

Chapter 1: Background 29 

age (i.e., removal of habitat) ranged &om 0.23 to 2.0 acres, and the ratio of seagrass 

planted to that lost ranged &om 1 : 1 to 3: 1. However, in one case there was no onsite or in-kind alternative, and oyster reef creation was accepted as an alternative. The 

seagrasses involved were Zostera marina and Halodule wrightii primarily, but Ruppia 

maritima also was recommended to be transplanted in one instance. During the 9- 

year period between 1985 and 1994, a total of 3.25 acres of seagrass habitat were permitted to be destroyed with a requested mitigation of 4.74 acres of seagrass transplantation. Evaluation of the mitigation sites has been carried out in two cases, one 

demonstrating success and one demonstrating failure. 

Florida has the largest extent of seagrasses in the contiguous U.S., followed by 

North Carolina and Texas (see earlier discussions). Between 1978 and 1994 a total 

of 167 acres of seagrass habitat have been requested for mitigation by the NMFS 

Habitat Protection Field Office in Panama City, Florida. These permit requests have 

generally been the result of new channel construction and port development and 

have ranged in mitigation acreage &om 0.09 to -200 acres. This latter was the result 

of a permit for additional development of the Port of Miami. Thalassia testudinum, 

Halodule wrightii, and Halophila engelmanii have been involved in the recommended 

mitigation. Based on reports &om the Panama City Field Office, the degree of success of these permit-related mitigation has been generally poor and in many cases, 

unknown. 

The Galveston, Texas Field Office of the NMFS Habitat Protection Division 

reported that there have been 6 major seagrass mitigation activities, almost all in the 

Laguna Madre, between 1985-1991. A total of 107 acres of seagrass habitat have 

either been recommended for creation or restoration. These have included filling of 

unused pipeline channels and associated re-contouring of the bathymetry to downgrading of dredge material islands. In some instances, natural recovery of the site(s) 

has been recommended while in others transplanting has occurred. The species 

involved in natural recovery have been Halodule wrightii, Halophila engelmanni, and 

Ruppia maritima, whereas Halodule has been the species of transplant choice. In most 

instances, oil companies have hired private concerns to monitor the mitigation sites 

or staff &om the Galveston Field Office have had the opportunity to visit the mitigation sites. It appears that site selection and proper bathymetric contouring has 

occurred because the Field Office reports that with the exception of 22 acres, there 

has been a mitigation site coverage by seagrasses of between 40-99 percent within a 

3 year period by either natural or transplanted methods. Some planted seagrass sites 

in Florida and Texas are currently being evaluated by National Marine Fisheries 

Service staff for seagrass and faunal recovery. 
30 * Guidelines for the Conservation and Restoration of Seagrasses 

NORTHWEST (N'W) (Oregon, Washington) AND ALASKA 

While research on experimental restoration approaches have been or are being 

carried out in these two NMFS Regions, both Regional Offices have been involved 

to only a very limited degree in seagrass mitigation and restoration. For a summary 

of eelgrass transplanting projects in the Pacific northwest see Thom (1990). 

SOUTHWEST (S'W) (California, Hawaii, and PaciJic Territories) 

Similar to other field and Regional Offices in the SE and NE, the Southwest 

Regional Office has participated in seagrass habitat management at both the permit 

as well as research and educational levels. They have held state-federal seminars 

involving the scientific community in discussions on the ecological value, sensitivity, 

and restoration of seagrasses. In 1991 an eelgrass mitigation policy was drawn up and 

adopted by NMFS, the U.S. Fish and Wildlife Service and the California Department 

of Fish and Game that includes recommended transplanting approaches, monitoring 

approaches, and measures of success that should be considered (see local evidence for 

seagrass function in Hohan 1986). 

From 1976 through 1993 the SW Region recommended eelgrass mitigation on 

25 permits in California while 2 were recommended for Enhalus acoroides and 

Halodule uninervis on Rota Island and Saipan Island in the Pacific Territories. With 

the exception of 6 permits, most mitigation projects have not exceeded 0.1 hectare; 

the remaining 6 ranged fi-om 0.8-3.8 hectares. Twenty sites have been visited where 

the mitigation activity had been completed, 11 of which are considered a success by 

Regional Office staff while 4 have shown a continued decrease in seagrass coverage 

and the remainder have shown no change in coverage. Overall, the success rate of 

seagrass planting in this region has been high (Hoffman pers. corn.). 

At this time we are not aware of any previous analysis of seagrass planting effort 

in the U.S. that used a comparative method. Therefore, we documented the status of 

seagrass planting projects &om around the country by soliciting information on 

planting activities &om many individuals of whom we were aware had conducted 

seagrass planting. In addition, we requested that all National Marine Fisheries 

Service Regional Offices provide us with listings of all seagrass mitigation projects 

for which they had reviewed permits under their statutory authority. We also conducted site visits, especially on the West Coast where we were less familiar with plant- 
Chapter 1: Background 3 1 

ing activities in order to collect additional planting information. Finally we then 

compiled all references on this subject which we could acquire; this included review 

of all literature cited by reports and papers we collected. 

This is not a complete survey and is complete only through 1995. We undoubtedly have missed some individuals and/or planting projects. Some persons did not 

respond to our queries. Again the absence of this work fi-om the peer-reviewed literature made it difficult to find the information. The value of this survey then is 

heuristic, but addresses questions such as "where has effort generally been expended"? What data have been collected?What techniques have been used? How were 

sites selected and how was compliance and/or performance of planting5 determined? 

How consistently has planting technology been applied? 

We also broke down the survey by ecoregions which we have defined for the 

purpose of isolating practices and caveats peculiar to different parts of the country. 

Ecoregion is also the basis for the creation of modules where recommendations for 

planning, planting and monitoring are specifically discussed for each ecoregion. In 

addition, our original intent was to collect information on coverage rates and shoot 

addition of individual planting units (PU) fi-om around the country. Any differences 

in species' coverage and shoot addition rates would aid in the definition of ecological regions for management. However, as our information collection progressed, it 

became clear that there were insufficient data firom most parts of the country to conduct these coverage and shoot rate change analyses. Therefore, we have divided the 

coastal regions of the country based on our knowledge of growing season. The 

ecoregions for this report are as follows: 

NORTHEAST - Maine through New Jersey: known species present = Zostera marina 

and Ruppia maritima. 

MID-ATLANTIC- - Delaware through North Carolina: known species present = 

Halodule wrightii, Ruppia maritima and Zostera marina. 

GULF OF MEXICO AND THE FLORIDA EAST COAST - Mexico to Cape Sable and 

north of Jupiter Inlet to Cape Canaveral: known species present = Halodule wrightii, 

Halophila decijiens, Halophila engelmanni, Halophila johnsonni, Ruppia maritima, Syvingodium_fil$orme, and Thalassia testudinum. 

SOUTH FLORIDAND THE CARIBBEAN - South ofJupiter Inlet to Cape Sable and 

P.R. and USVI: known species present = Halodule wrightii, Halophila decbiens, 

Halophila engelmanni, Halophila johnsonni, Ruppia maritima, Syringodium _fil$orme, and 

Thalassia testudinum. 
32 Guidelines for the Conservation and Restoration of Seagrasses 

CONTERMINOUS WEST COAST - California to Washington: known species present 

= Phyllospadix scouleri, Phyllospadix serralatus, Phyllospadix torreyi, Ruppia maritima, 

Zostera japonica, Zostera marina. 

ALASKA - Zostera marina and Phyllospadix spp.(at least l? serralatus). 

HAWAII AND PACIFIC TERRITORIES - known species present = Halophila hawaiiana 

(K. Bridges, pers. corn.). 

We compiled a collection of 138 documents ranging fEom published, peerreviewed papers to project reports. Some of these documents were reviews or guidelines of how to transplant seagrass; some were feasibility studies; some were laboratory or mesocosm experiments directed at enhancing transplant technology. Each document was categorized several ways. We first determined where the document originated. Roughly 46 percent of the documents were found in the white literature, 29 

percent were unpublished reports, 22 percent in grey literature and -3 percent were 

theses (Table 1.3). All together, these papers reported on the fate of over 686,000 

planting units of seagrass, totaling -78 ha of field acreage, that have been monitored. 

Over time the publication rate of documents concerning seagrass planting have 

increased.We found less than 1 percent of the documents published prior the 1960s. 

In the 1960s we found 2 percent of the documents; in the 70s 21 percent; in the 80s 

46 percent; and so far in the 90s, 28 percent of the documents. At this rate the 1990s 

will produce the greatest amount of documents on the subject of seagrass planting. 

Some of this increase in publication rate may be that more recently created docuTable 1.3. Percent of documents on seagrass planting compiled by literature type. 

Literature Type Percent of Documents of this Type 

White Literature 

Report 

Gray Literature 

Theses 

White literature = peer reviewed journal articles. 

Report = not peer reviewed. 

Gray literature = not in a library circulated journal, may or may not be peer reviewed. 

Theses = masters thesis or doctoral dissertation. 
Chapter 1: Background 33 

ments are easier to locate, but it seems more likely that interest in the subject has 

grown. 

The purpose of the documents varied widely. The largest group 'was fieldresearch-oriented which comprised -57 percent of the total. Next were review documents (29 percent), followed by laboratory experiments (-10 percent), and a rniscellaneous group (6 percent), which included feasibility assessments, economic analyses, project summaries, and recovery assessments. In addition, there were three planting-associated theses. Most laboratory experiments and review documents were 

published in the peer-reviewed literature, while only half of the documents presenting new planting data were in the peer-reviewed literature. 

Of the ecoregions we constructed, most documents originated &om either the 

West Coast (-26 percent) or the Gulf of Mexico (also -26 percent) (Table 1.4). 

South Florida and U.S. Caribbean territories produced -19 percent, mid-Atlantic 

region -18 percent, the northeast U.S. -9 percent, and Alaska -2 percent. Studies 

&om other countries (Australia, France, Great Britain, Italy) were also reviewed but 

not utilized in computation of summary statistics. 

The greatest number of planting units have been installed in the South Florida 

ecoregion (Table 1.5), followed by the northeast,West Coast, and mid-Atlantic states 

(the latter three regions being almost equal in number of planting units install), the 

Gulf of Mexico, and lastly, Alaska. 

Table 1.4. Percentage of complied documents on seagrass planting presenting field transplanting studies, listed by ecoregion. Values are percent of total. Table does not include studies from outside the U.S., guidelines, reviews, or studies involving freshwater planting. See 

section on "Regional Breakdown of Permit Activities Dealing with Seagrass Mitigation," 

above, for regional boundaries. 

Region Percent of Documents Found in Region 

West 26 

Gulf 25 

South Florida 19 

Mid-Atlantic 18 

Northeast 9 

Alaska 2 
- 

Table 1.5. Reported area of planted seagrass in square meters and number of planting units deployed in field 

studies by region and species. 

Region Species Area M2 No. PUS 

Zostera marina 

Cyniodosa manitorunta 

Halodule beaudetteib 

Halodule wrightii 

Ruppia maritinla 

Syringodiuni filforme 

Thalassia testudinum 

Zostera marina 

Halodule wrightii 

Ruppia maritinla 

Zostera marina 

Zostera marina 

Halodule wrightii 

Syringodiuni fily I orme 

Thalassia testudinuni 

Phyllospadix torrqi 

Zostera niarina 

Alaska = entire coast ofAlaska (Ak.) 

Gulf Coast = Gulf of Mexico to Cape Sable, F1. and the Florida East Coast North ofJupiter Inlet to Cape Canaveral (Tex., 

La., Miss., Ala., Fl.) 

Mid- Atlantic = Delrnarva Peninsula to North Carolina @el.Va., Md., N.C.) 

Northeast = Maine to New Jersey (Maine, R.I., N.H., Mass., Con.. N.Y., N.J.) 

South Florida = South ofJupiter Inlet to Cape Sable, Puerto Rico and the U.S.Virgin Islands (Fl., PR., U.S.V.I.) 

West = Washington to California ma., Ore., Calif.). 

aProbably Syringodiumfil$orme. 

bProbably Halodule wrightii. 

PU = planting units. 

? = Insufficient data to calculate the area. 
-. 

Chapter 1: Background * 35 

The use of different planting methods by ecoregion and seagrass species was also 

evaluated (Table 1.6). We constructed fourteen categories of planting methods, one 

of which was an "other" category that contained a number of methods not widely 

used and includes studies [a category of "unknown"] where the method of planting 

was not described. Of the fourteen categories, plugs or staples were the most common; -40 percent of the plantings were done using one of these methods.The next 

most common was bare root-unanchored sprigs (15 percent), anchors of some sort 

(8 percent), followed by turfs (7 percent) and peatpots, biodegradable mesh, seedlings 

and seeds (all at -5-6 percent each). Unusual or unknown methods accounted for 

[were employed in] -2 percent of the plantings. Grids, seed tapes, bagged plants and 

attachment to boulders, with and without mesh grids, and passive seagrass fi-agment 

capture were used in the remaining -4 percent of the plantings. The Gulf of Mexico 

ecoregion had the greatest number of planting categories (1 I), followed by the West 

Coast (lo), south Florida (7), and the mid-Atlantic states (5). 

We also compiled the fi-equency of planting methods used by seagrass species 

(Table 1.7). Thalassia testudinum, Zostera marina and Phyllospadix spp. have been transplanted mostly using techniques that involve removal of the native sediment fi-om the 

root-rhizome matrix (in the case of Phyllospadix, there may have been no sediment 

to remove in the first place). The remaining three species listed in Table 1.7 have 

been transplanted using sediment-fi-ee and sediment-included methods in about 

equal proportion. Three species, H. wrightii, T testudinum, and Z. marina accounted 

for 95 percent of the planting units put in the bottom (26,21, and 48 percent, respectively). S.jli$orme composed the remaining 3 percent of the PU while two other 

species composed -0.00013 percent of the total number (one paper reported Halodule beaudetti and Cymodocea nodosa as occurring in the Gulf of Mexico but we SUSpect these were either H. wrightii and/or Ruppia maritima). Acreage of planting by 

species closely followed percentages for PU (Table 1.9). Some seagrass species that 

have broad distribution have received comparatively little attention to that given 

Halodule, Thalassia and Zostera. For example, few studies have been done regarding 

Phyllospadix spp. planting (Phillips et al. 1992), and these involve attachment to large 

rocks. Aside &om Phillips et al. (1992), little else is known regarding Phyllospadix spp. 

planting techniques even though this species ranges along the entire U.S. West Coast 

(Phillips 1979, Wyllie-Echeverria and Phillips 1994). Turner (1 985) provided important data regarding inherent stability and recovery of natural stands that have at-least 

heuristic value for restoration in that the dynamic aspect of the community can be 

recognized and incorporated into planning (see Chapter 2, Planning). Similarly 

Ruppia maritima, which occurs in every ecoregion, and Halophila, of which there may 

be (based on an incomplete survey) half a million hectares off the West Coast of 

Florida alone (Iverson and Bittaker 1986), have received virtually no study as to their 
Table 1.6. Percentage of all transplanting methods by ecoregion. Values are percent of total. This table does 

not include studies from outside the U.S., guidelines, reviews, or studies involving freshwater planting. - - 

Method Region 

Plug 

Peatpot 

Turf 

Mesh 

Grid 

Seedling 

Seeds 

Anchor 

Sprig 

Seed Tape 

Staple 

Boulder 

MBoulder 

Other 

Alaska Gulf 

25 29 

6 

19 

6 

3 

3 

6 

11 

6 

3 

Mid-Atlantic Northeast South Florida West 

20 43 25 12 

15 8 

Alaska = entire coast ofAlaska (Ak.); Gulf Coast = Gulf of Mexico to Cape Sable, F1. and the Florida East Coast North 

of Jupiter Inlet to Cape Canaveral (Tex., La., Miss,Ala., Fl.) 

Mid-Atlantic = Delmarva Peninsula to North Carolina (Del.,Va., Md., N.C.) 

Northeast = Maine to New Jersey (Maine, R.I., N.H., Mass., Conn., N.Y., N.J. 

South Florida = South ofJupiter Inlet to Cape Sable, Puerto Rico and the U.S.Virgin Islands (Fl., P.R., U.S.V.I.) 

West =Washington to California (Wa., Ore., Calif.). 

Planting methods are defined as follows (categories are mutually exclusive): 

Plug = tubes as coring devices are used to extract the plants with the sediment and rhizomes intact. 

Staple = U-shaped metal staples with attached bare root (no sediment) planting units. 

Sprig = bare mot planting units (without staples or anchors). 

Anchor = any structure used to keep the planting units in the sediment. 

Turf= large square sods of seagrass that are ussually extracted with a shovel and planted as is. 

Peatpot = a plug of seagrass that is transplanted into a biodegradable compressed peat container. 

Biodegradable Mesh = seagrass sewn to a biodegradable mesh fabric and attached to the sediment surface as a planting 

unit. 

Seedling = a newly sprouted seed with one short shoot. 

Seed = seeds with no sign of shoots sprouting. 

Plastic Mesh Grids = similar to biodegradable mesh except these are plastic (non-biodegradable). 

Seed Tape = method of planting seeds using tape that has seeds sticking to it; the tape is then rolled out along the sediment surface. 

Boulder = Phyllospadix torreyi is attached to boulders. 

MBoulder = P torreyi is attached to mesh and then attached to boulders. 

Other = rarely used methods and includes studies where the method was not stated in the document. 
Table 1.7. Percentage of transplanting methods by seagrass species. Dashed line separates methods that transport associated sediments (above line) from those that do not (below line). 

Method Species 

Plug 

Peatpot 

Turf 

Mesh 

Grid 

Seedling 

Seed 

Anchor 

Sprig 

Seed Tape 

Staple 

Boulder 

MBoulder 

Unknown 

Hw = Halodule wrightii 

Pt = Phyllospadix torreyi 

Rm = Ruppia maritima 

Am = Zostera marina 

Tt = Thalassia testudinum. 

Sf = Syringodiumfilijorme. 

Planting Methods are defined as follows (categories are mutually exclusive): 

Plug = tubes as coring devices are used to extract the plants with the sedment and rhizomes intact. 

Staple = U-shaped metal staples with attached bare root (no sediment) planting units. 

Sprig = bare root planting units (without staples or anchors). 

Anchor = any structure used to keep the planting units in the sediment. 

Turf = large square sods of seagrass that are usually extracted with a shovel and planted as is. 

Peatpot = a plug of seagrass that is transplanted into a biodegradable compressed peat container. 

Biodegradable mesh = seagrass sewn to a biodegradable mesh fabric and attached to the sediment surface as a planting 

unit. 

Seedhg = a newly sprouted seed with one short shoot. 

Seed = seeds with no sign of shoots sprouting. 

Unknown = the method was not stated in the document. 

Plastic mesh grid = similar to biodegradable mesh except these are plastic. 

Seed Tape = method of planting seeds using tape that has seeds sticking to it; the tape is then rolled out along the sediment surface. 

Boulders = I? torreyi is attached to boulders. 

MBoulders =I? torreyi is attached to mesh and then attached to boulders. 

? = insdcient data to calculate a percentage. 
Table 1.8. List of experimental parameters and the percentage (in descending order) that were incorporated as 

a data collection or as independent variables in field transplant studies. Pre-survey = the site selected as a trans-. 

plant site was surveyed prior to transplanting for its suitability to sustain a transplant. 

Experimental Parameters Percent of Documents Using this Parameter 

Pre-survey of site 62 

Planting method 45 

Post-survey of site 27 

Depth 26 

Cost analysis 22 

Fertilization type 21 

Season 21 

Faunal study 18 

Planting unit spacing 17 

Tidal zone 15 

Energy regime 14 

Donor survey 12 

Sediment particle size 9 

Enclosure 8 

Shoot numbers 8 

In vitro propagation 8 

Genetics 6 

Light intensity 5 

Bioturbation 3 

Burial recovery 3 

Apicals 1 

Salinity 1 

Planting method = different methods of transplanting were tested for their effectiveness. 

Post-survey of site = the effect of transplanting on the site location was evaluated. 

Depth = effects of different depths on transplanting success was determined. 

Cost-analysis = the total cost of the transplanting was determined. 

Fertilization type = effects of ferthzers on transplanting was evaluated. 

Season =effects of time of year on transplanting was evaluated. 

Faunal study = fauna was sampled in transplanted beds. 

Planting unit spacing = the effects of different spacing of planting units was evaluated. 

Tidal zone = effects of di£ferent tidal zones on transplanting was examined. 

Energy regime = effects of energy regime on transplanting. 

Donor survey = there was a study conducted on the recovery of the transplant donor bed. 

Sediment particle size = effects of different sediment size on transplanting. 

Enclosure = effects of enclosure devices on transplanting. 

Shoot numbers = effects of different planting unit shoot numbers on transplanting success. 

In vim propagation = growing seagrass in the laboratory to be transplanted. 

Genetics = genetic experiments on transplanted seagrass were conducted. 

Light intensity = effects of various light levels on transplanting success. 

Bioturbation = bioturbation effects on transplanted seagrass. 

Burial recovery = effects of sediment burial on transplanted seagrass. 

Apicals = effects of the presence, absence, or Merent numbers of apicals in planting units. 

Salinity = effects of Merent salinity on transplanting. 
Chapter 1: Background 39 

Table 1.9. List of ten most common parameters recorded in monitoring of transplant studies. Some studies considered more than one parameter. 

Monitoring Parameter Percent of Studies with this Parameter 

Irregular frequency monitoring 

Percent survival (PU) 

Shoot counts 

Shoot density 

Percent cover 

Leaf length 

Leaf width 

Rhizome length 

Directm mapping 

Biomass 

Irregular Frequency Monitoring = irregular time intervals were chosen for follow-up monitoring of 

a transplant site. 

Percent Survival = percent of planting units (PUS) that survived were monitored. 

Shoot Counts = direct counts of planting unit shoots was conducted. 

Shoot Density = density of the planting units was monitored. 

Percent Cover = time zero area was known and considered 100 percent cover so that future areal coverage could be compared as a percent of that original coverage. 

Leaf Length = leaf lengths were measured directly. 

Leafwidth = leaf widths were measured directly. 

Rhizome Length = total length of living rhizome. 

Direct Mapping = actual mapping of the planting units for the area covered. 

Biomass = weight of a given area of seagrass. 

ecological role in the coastal zone. Although there has been little in the way of 

focused attention on development of planting techniques for these latter two species, 

we expect that existing methods such as plugs or peatpots may have promise (see 

Chapter 2, Planting). 

There are also some incidental planting of which we are aware. We know that 

Halophila decipiens was transplanted in 15 meters of water on St. Croix, U.S.V.I. in 

1986 (authors unpubl. data) using mini-staples constructed of 130-pound test wire 

leader; planting spread and apparently persisted to the end of the normal growing 

season. Harrison (1990) has also transplanted Z. marina in British Columbia using 

unattached shoots, cores, and by attaching shoots to re-bar (sensu Kelly et al. 1971). 

Phyllospadix was planted in the Monterey Bay Aquarium, California. Indoor small 
40 Guidelines for the Conservation and Restoration of Seagrasses 

tank exhibits had poor survival but plantings lodged under rocks and experiencing 

mild simulated wave conditions in the aviary persisted for several years (Monterey 

Bay staff, pers. corn.). Similarly, Thalassia has been grown in the coral reef exhibit at 

the Smithsonian Institution in Washington, D.C. for several years but with great logistic cost. 

Not only did purposes of these papers vary widely, so did the design parameters 

of the studies. Table 1.8 describes the various parameters that were manipulated for 

documents reporting new field planting data (66 documents total: reviews and lab 

experiments excluded). Twenty-four different parameters were examined. Preliminary surveys of some environmental conditions at the planting site was the most 

common design feature: -62 percent of the papers performed some pre-planting 

evaluation of the site. Slightly less than half of the papers tested planting methods. 

Only -25 percent of the papers continued to survey some environmental conditions 

after plantings were installed, making it very difficult to establish any linkage between 

plant performance and episodic events. Planting depth (a rough surrogate for light 

availability, but also potentially related to frequency of emersion) was at least noted, 

if not a factor tested for influence on plantings in approximately 30 percent of the 

papers. Tidal zone (as opposed to some sea level-normalized depth measure) was also 

noted in 17 percent of the papers, but these data were not as specific as depth data. 

Together, however, water depth and tidal zone considerations were in 47 percent of 

the papers. Cost analyses, comparisons among planting season, and fertilizer effects 

were aspects of project design in -20 percent of the papers. Comparative faunal 

assessments, effects of PU spacing, physical energy on the site, and recovery of plants 

at the donor site were parts of project designs in 12-18 percent of all studies. An 

additional 12 parameters were examined in the papers we reviewed but were never 

included in more than 10 percent of the papers. 

What is interesting here is not so much what was either manipulated or noted 

but the proportions of what was not; that is, data that were considered relevant varied tremendously among studies. Thirty-eight percent of the papers did not consider or at least did not report what information was used to choose a planting site. Of 

those reporting, 33 percent simply used the criteria of no vegetation present which 

when used alone has been previously described as an unacceptable criteria (Fredette 

et al. 1985, Fonseca et al. 1987c, Fonseca 1989a, 1992,1994) because selecting unvegetated areas with no known history of seagrass cover disregards the fact that any one 

of several mechanisms may be at work maintaining that level of patchiness (eg., 

waves, currents, bioturbation). There is a rich body of literature on the role of habitat heterogeneity on ecosystem function that would have to be ignored to recornmend converting naturally unvegetated areas to vegetated. Thus, in addition to being 
- 

Chapter 1: Background 41 

a high-risk planting area, planting in such an environment temporarily substitutes 

one habitat type for another. Therefore, based on our survey, 24 percent used what 

we consider to be an appropriate site selection criteria (the site having been previously vegetated but was now barren, although there are caveats to this criteria; see 

Planning chapter). Approximately 19 percent of the planting were on dredged 

material while 20 percent were on unvegetated spaces adjacent to existing seagrass. 

Few other factors were consistently integrated into design plans. Only 17 percent surveyed fauna after planting. Twelve percent considered the impact of harvesting on donor seagrass beds (i.e., monitored recovery of donor site). Less than 10 percent of the studies manipulated time 0 shoot number in a planting unit (generally as 

an attempt to determine optimal planting unit size). 

Interestingly, two parameters besides percent PU survival that we have long recommended as being critical baseline monitoring data (Fonseca et al. 1982, Fonseca 

1989a71992,1994), number of shoots PU-' and percent cover of the bottom, were 

only in -53 and -47 percent of the papers, respectively. We have recommended these 

forms of data collection because, when combined they describe many aspects of 

planting viability. In contrast, shoot density, a parameter over which there is little 

control, was used as a performance criteria in -51 percent of the studies. Recent 

findings (Fonseca et al. 1996b) also suggest that macroepibenthic faunal abundance 

in planted seagrass beds asymptotes at comparatively (to natural beds) low shoot densities (as little as one third of natural beds), indicating that it might not be relevant to 

require shoot density in a planted bed to equal that of natural beds to support faunal 

densities equivalent to natural (but see performance criteria suggested by Short (1993 

p. 51). Although some lower-than-ambient threshold shoot density may be suitable 

for generating faunal equivalence, lower shoot densities may not provide a sufficient 

buffer to population fluctuations of the seagrasses themselves. Thus, the issue of 

demographic status of the seagrasses of restored vs. natural beds is only beginning to 

be evaluated. - 

Most disturbing was that less than 7 percent of the papers actually provided 

quantitative data on two of the most critical limiting parameters known for seagrass 

planting success, light regime and bioturbation. Although depth and tide zone were 

frequently recognized as important factors, the absence of direct measurements of 

light means that depth and tide zone data are not easily extrapolated because we do 

not know the transparency of the water column. We can look up information on 

tidal amplitude and periodicity, but the interaction of light and tides on seagrass 

growth is only now being modeled (Zimmerman et al. 1994, Dennison and Kirkman 

1996, Koch and Beer 1996), although these papers suggest the interaction of tidal 
- 

42 Guidelines for the Conservation and Restoration of Seagrasses 

amplitude and light availability to accurately predict site suitability based on transmissivity data. 

Apart fi-om those parameters that were monitored and/or manipulated, a total 

of ten parameters were actually utilized as measures of planting performance and/or 

success (Table 1.9). The percentage of PUS surviving was the most common criteria but was reported in only -66 percent of the papers. However, -74 percent of the 

papers varied the fi-equency of monitoring after planting over the course of their 

respective investigations (e.g., contrast fixed interval monitoring with a study that 

conducts monthly sampling for the first year then shifts to biannual monitoring for 

following years). The duration of monitoring in the papers we reviewed ranged fi-om 

zero to eight years with a mean and median of -1.5 years. During these monitoring periods the fi-equency of monitoring was also highly variable, again ranging fi-om 

zero to an equivalent of 30 times y-'. The average fi-equency of monitoring was 4.6 

times y-'. 

Fonseca (1989, 1994) has recommended that early, fi-equent (usually quarterly) 

monitoring be performed for the first year after planting followed by less fi-equent 

(e.g., biannual) monitoring. Despite problems with changing temporal scales in 

analysis (see section "Scale and its Role in Defining Seagrass Habitat"), we continue 

this recommendation because many, but not all (particularly planting with high initial loss of PUS) of our successfid experimental planting followed a sigrnoidal population growth curve; initially high, exponential growth with low mortality followed 

by a balancing of natality and mortality of shoots which leads to an asymptote of 

plant density. Past recommendations for this monitoring strategy (Fonseca 1989a, 

Fonseca 1992, Fonseca 1994) actually agree well with at least the mean monitoring 

time values of the papers reviewed. Similar fi-equencies of monitoring were recommended by Merkel (1992), of time 0,3,6,12,24, and 36 months but with an additional recommended survey at 60 months. Choice of 3 years for monitoring resulted largely fi-om compromise in that permit monitoring is rare (Race and Fonseca 

1996) and shorter monitoring periods increase the possibility of acquiring monitoring compliance. So, for a given planting, how long should monitoring proceed in 

order to judge planting performance? Taken together with the average monitoring 

period of 4.3 y, and the fact that only 10 percent of the papers we surveyed achieved 

an ideal 100 percent cover, indicates that previous suggestions of 3-year monitoring 

by Fonseca (1 989a, 1992,1994) may be a serious underestimate of the time required 

to document project success; times in excess of 5 years may be more appropriate. 

What is probably the most documented parameter in natural beds, seagrass biomass was only measured in -3 percent of the papers, perhaps because it is a destruc- 
-- 

Chapter 1: Background * 43 

tive sampling technique. Also, several measures of the plant's morphology were used 

fi-equently to determine planting performance (Table 1.9). We view these criteria 

suspiciously; seagrasses are often phenotypically plastic, and variation in plant shape 

and size is only loosely linked to functional attributes of seagrass beds'at this time 

(Bell et al. 1991, Fonseca et al. 1996a) alth~u~h'morphology has been linked to significant genetic differences (Fain et al. 1992). We find it disturbing that simple parameters such as survival and coverage were not more universally recorded. From the 

low replication of criteria among studies, it is no wonder that quantitative performance and compliance thresholds, when they appear in mitigation plans, vary so 

tremendously (Thayer et al. 1985). Moreover, some papers used irreproducible units 

such as "scoopfuls" and "bucketfuls" to describe sampling units. Such vague planning 

criteria should not be used by resource managers. 

The results of monitoring efforts have revealed some unexpected trends regarding success. To analyze this, we chose two categories, the final reported percent PU 

survival and the percent of the target area covered that was reported at the conclusion of a paper. Of 53 papers that reported percent PU survival, the median percent 

PU survival was 35 percent; mean 42 percent; standard deviation = 29.9; coefficient 

of variation = 70 with a distribution heavily skewed to lower percent survival (Sk = 

0.35), suggesting adoption [use] of the median value (Figure 1.5). Roughly 5 percent of the plantings reported 100 percent PU survival. We found 27 papers that 

reported percent of the target area covered. The median percent area covered was 40 

percent and was closer to the mean percent area covered of 42 percent; a standard 

deviation = 31.2; but still with a high coefficient of variation = 75 and a distribution 

again skewed to lower coverage amounts (Sk = 0.41) (Figure 1.6). We should point 

out that some of the variance in the data also results fi-om areas such as southern 

California enjoying generally very high success rates (approaching 100 percent). The 

reasons for that success rate may have to do with quiescent settings for planting, high 

experience level and perhaps, comparatively low bioturbation levels. However, on a 

national scale, only approximately 10 percent of the planting achieved 100 percent 

cover within the monitoring period. Thus, these data indicate that replanting is a 

consistent requirement of seagrass operations unless substantial initial overplanting is 

conducted to compensate for anticipated losses. Moreover, low initial survival rates 

may explain why seagrass plantings often produce less acreage than originally 

planned, suggesting that initial PU survival levels should be held to high standards to 

help ensure achieving target acreage. 

An extreme interpretation of these findings would be that based on the median 

survival (a planting should have an overplanting ratio of approximately 3.0). In other 

words, if you wished to ensure that 100 planting units will survive, 300 should be 
% Survival Category 

Figure 1.5. Frequency distribution ofpercent planting unit survival~om the docunlents surveyed nutionally. Y-axis = percentage ofthe survival valuesfalling in the percent survival categories on the Xaxis (1 0% increments). 

% Area Covered Category 

Figure 1.6. Frequency distribution ofpercent area covered by plantingsfront the docunlents surveyed 

nationally. Y-axis = percentage ofthe area covered valuesfalling in the percent area cover categories on 

the X-axis (1 0% increments). 
- 

Chapter 1: Background 45 

planted. Similarly, based on this national average, to ensure the required area of seagrass bed to be generated, a replacement ratio of -2.5 units of area planted to l unit 

of area lost is needed to meet a no-net-loss criteria (i.e., 1:l replacement ratio). We 

conclude that this is an extreme interpretation because many plantings use8 to compile these statistics were conducted on sites that would have been expected to produce patchy seagrass beds in any event. Also, many sites were chosen that violated 

recommended site selection criteria which would skew the distribution toward low 

survival and coverage. If site selection criteria are employed as described later, it is 

possible that these replacement ratios could be made much lower. 

Managers must be cognizant of the different sources of planting failures and 

judge planting proposals under strict criteria. The practice of seagrass bed mitigation 

should not be questioned based on a failure in judgment on the part of someone 

who performed a planting. Such human failures must be separated &om failures of 

the approach as a whole in order to responsibly assess seagrass planting as a mitigative tool (Fonseca et al. 1994).The key is to determine what made some plantings so 

successful and others so marginal. 

Monitoring as recommended in the past (e.g., Fonseca 1989a, 1992,1994) does 

not lend itself to determination of agents of planting loss. Only sophisticated monitoring equipment with high frequency recording capacity could hope to detect environmentally-induced losses. Acute and capricious events such as bioturbation and 

vandalism are even more difficult to determine with complete certainty (although 

use of exclosure cages may go far in suggesting the influence of bioturbation, Merkel 

1988a, Fonseca et al. 1994). Therefore, the agents of loss among these studies cannot accurately be presented as a ranked set. However, based on our observations in 

the field, one might speculate that most failures occur from improper site selection 

(see criteria for site selection, below) and execution. From our experience and conversations with others (not to mention some published findings: Mote Marine Lab. 

& Mangrove Systems Inc. 1989; Merkel 1988a,b; Fonseca et al. 1994), we conclude 

that once a site has been appropriately selected under the criteria described below 

(e.g., previous history of seagrass cover, etc.) the primary agents of loss vary between 

bioturbation, acute storm events, algal smothering, and vandalism. 

These compilations indicate that most of the planting experience is centered in 

the southern and western parts of the U.S. Also only a few species are regularly utilized in mitigation projects. Given the widespread impacts to seagrass ecosystems, 

concern that the absence of these other species &om the literature indicates that 

impacts to those species goes unnoticed. Either that or these plant communities may 

not be receiving sufficient protection under current management practices. These 
46 Guidelines for the Conservation and Restoration of Seagrasses 

survey data also indicate that there has been extensive experimentation with planting methodologies, and it appears that only a few are consistently employed and, 

again, only for a few species.The concentration of planting effort in Florida and the 

West Coast may be due to comparatively high development pressures in these areas. 

Although high habitat loss rates also occur in the mid-Atlantic states ecoregion, the 

proximity of research laboratories that have historically focused on seagrass to those 

estuaries may also explain the concentration of work in that ecoregion. 

ARE PLANTED SEAGRASS BEDS UNCTIONALLY 

EQUIVALENT TO NATURALLY- CCURRING BEDS? 

mat is "functional equivalency"? In a general sense, this means that a restored 

or mitigated system attains functions the same as those of an unimpacted system in a 

similar setting. Seagrass beds have many functions (sensu Wood et al. 1969), some of 

which may be more difficult to restore than others. As is the case with much of biology, the answer to the question of functional equivalency is both "yes" and "no." We 

tend to take the stance that if an area has recovered equal or greater acreage than that 

which was lost, and that area persists with the same seagrass species, a planted seagrass 

bed can become equivalent, but not identical to a natural, unimpacted bed. Our 

stance is not universally accepted. Equivalent means "equal to" but is sometimes 

taken to mean "identi~al.'~ However, since no two samples of any natural ecosystem 

are ever truly identical, some subjectivity comes into play, both in terms of the degree 

of equivalence and the appropriate functions to measure. The problem then is what 

drives the subjectivity? A developer may interpret functional equivalency of their 

mitigation project in far more general terms than a trained biologist. What then are 

the relevant parameters by which to document equivalency? 

According to our comparative analysis of the literature, thirty-three different 

parameters were used to describe success. This indicates the broad definition of hnctional equivalent - practitioners obviously target many different factors and differ 

in their opinions when ranking importance of these factors. Moreover, there is conflicting guidance &om the literature regarding the rate at which planted beds take on 

attributes of natural, undisturbed beds. Brown-Peterson (1993) and Montagna 

(1993) conclude that attributes of planted seagrass beds were sull not equivalent to 

natural ones after 31 and 14-17 years, respectively. Similarly, Smith et al. (1988a) 

found that planted beds did not provide equivalent bay scallop habitat over a growing season. Hoffman (1988) concluded that one-year old 2. marina planting in San 

Diego did not support some fauna at levels exactly equal to that of natural beds, 

although some of differences were small. In contrast, Nessmith (1980), Hornziak et 
.-- 

Chapter 1: Background 47 

al. (1982), Fonseca et al. (1990,1996 a,b), and Wyllie-Echeverria et al. (1994b) found 

that faunal abundance and composition in planted beds approached that of natural 

beds within 2-3 years. 

Much of this discrepancy among studies may be the result of intrinsic differences 

among natural reference sites and planted areas, the organisms chosen to evaluate 

recovery, and different worker's interpretation of what constitutes a difference. 

Because of the tremendous variability among natural beds, we question the efficacy 

of precise numerical comparisons in an interpretation of planting success; comparisons that include estimates of variance might be more appropriate. For example, distance and/or isolation of planted sites fiom natural beds will cause some differences 

(Bell et al. 1988,1992). Brown-Peterson (1993) compared fish communities among 

planted and reference sites but the sites were located on opposite sides of a barrier 

island lagoon. Montagna (1993) compared beds established both by natural recolonization and planting in scraped-down dredged material islands with relatively open 

areas. Thus, there is some question as to whether differences among planted and natural treatments were the result of planting or of innate differences due to the physical setting. However, Montagna (1993) points out that most studies suggesting faunal equivalency have focused on more vagile macrofauna such as fish whereas certain infauna (e.g., clams) may not colonize as quickly. Kenworthy et al. (1980) and 

Hornziak et al. (1982) found rapid colonization of a planted 2. marina site by scallops and meiofauna as did Wyllie-Echeverria et al. (1994b) for salmon prey (largely 

meiofauna). McLaughlin et al. (1983) concluded that recolonization by a wide variety of macrofauna occurred in planted Thalassia beds within only a few years. 

Similarly, Fonseca et al. (1990) found that afier experiencing widespread failure of a 

planted area, the same site then naturally colonized by seed and supported a macrofaunal community not statistically different fiom adjacent planted sites within sixmonths of the onset of seed germination. 

More recently, Fonseca et al. (1996 a,b) found that H. wrightii and S.jlforme beds 

planted on 0.5 m centers in Tampa Bay developed fish, shrimp and crab density and 

composition statistically indistinguishable fiom nearby natural sites within three 

years. One interesting aspect of that work was the relation of animal density to plant 

density (Figure 1.7). The seagrass density at which animal density in planted beds 

equaled (p < 0.05) that of natural beds was only approximately one-third of the mean 

natural bed shoot density. That density can be obtained within one year.They found 

that although linear models could account for approximately 65 percent of the variance of animal density as a function of plant density over time, a non-linear, asymptotic relationship between natural-log transformed animal density and seagrass areal 

shoot density was apparent (Figure 1.7). Although transformation of a straight line 
--- 

48 Guidelines for the Conservation and Restoration of Seagrasses 

Halodule Transplants 

shrimp I natural bed density 

Figure 1.7. Natural-log transformed faunal density plotted against areal shoot density. Open circles=observed points. Closed circles=predicted points using an asynrptotic function. IMical line (VL) 

"shrimp" or 'ffish"=areal shoot density at which densities of these aninralsjrst becanre not sign$cantly dgerent anrong planted and natural versions ofthat seagrass species; "natural bed density"=the studywide average areal shoot density of natural beds of that seagrass species. Taken joni Fonseca et al. 

(1 996b). 

will yield some asymptotic tendencies, they are not enough to account for the pattern observed. The fact that animal density had an asymptotic relationship with 

shoot density implies that monitoring shoot density over time may be an inexpensive diagnostic parameter for determining a threshold planting success in terms of 

fauna. Short (1993) found similarly rapid colonization of 2. marina planting in New 

Hampshire by a wide variety of fauna. Therefore, monitoring shoot density over 

time would be much less costly than direct measures of faunal communities. In order 

to justifjr use of only plant data in assessing some aspects of planting success, however, the temporal relationship among shoot density and faunal community structure 

must be collected &om planted beds across a broad geographic range. 

Although some ecological attributes may return quickly after planting seagrass, 

there is still a measurable period of time until the system has attained full fimction. 

The loss of ecosystem production in the time between when a seagrass bed is dam- 
- 

Chapter 1: Background 49 

aged and functions are restored has long been an issue of concern to managers.This 

loss of production has been termed "interim loss." The manner in which this loss 

has been calculated varies widely, as will be discussed later under sections on planting. We raise the point here because in many instances a reckoning offfunctional 

equivalency among planted and reference sites is made in an attempt to recoup interim loss of various living resources. 

Seagrass species substitution is another issue that has bearing on the question of 

functional equivalency among planted and reference beds. Although much of the 

temperate U.S. is dominated by one seagrass species, 2. marina, subtropical areas and 

more recently the Pacific Northwest must contend with the functional ramifications 

of substituting one seagrass species for another (Pawlak 1994). There are few data to 

guide this decision. Temporary species substitution has been suggested for subtropical species (Fonseca et al. 1987c) where faster-spreading species such as H. wrightii and 

S.$l$orme are planted as predecessors to recover areas previously dominated by the 

much slower-spreading T testudinum. In that circumstance the reasoning was that 

interim loss of ecosystem fimctions could be minimized by establishing any form of 

seagrass coverage. Based on their work in Tampa Bay, Fonseca et al. (1996b) have suggested that differences in macroepibenthic faunal communities among these three 

subtropical species may not be as great as previously inferred (Stoner 1983). One 

reason for the differences among studies could be that Fonseca et al. (1996b) focused 

on unit area of seagrass bed-based surveys while others had compared animal populations among seagrass species weighted by attributes of habitat complexity, such as 

leaf surface area. We acknowledging that such faunal assessments should not be 

construed as indicators of all ecosystem functions (e.g., nutrient cycling, bed stability), the findings of Fonseca et al. (1996b) support the notion that seagrass species substitution to ameliorate interim losses of some ecological attributes may be a legitimate means to an end where that end is eventual replacement of the seagrass species 

that was damaged. 

There is another tack to take in assessing whether planted seagrass beds provide 

resource functions equivalent to those they are intended to replace. On a much simpler level, we are not aware of any study that suggests that a seagrass bed is not a highly productive habitat. Therefore, we may infer that if one can produce a desired 

amount of seagrass habitat which persists over time that many ecosystem functions 

eventually will be restored. Whether a planted bed is the exact replacement for 

another seems to us to be an inappropriate question. It will depend upon what one 

considers to be an important ecosystem function and how much of it must be 

replaced to be considered "equivalent." Utilizing generally accepted significance levels (i.e., p < 0.05) to detect differences among two unique portions of the ecosystem 
50 * Guidelines for the Conservation and Restoration of Seagrasses 

is the most objective and scientifically acceptable means of testing differences. Of 

course, such differences are certainly affected by decisions of sampling gear, its size, 

the bias of that gear towards certain fauna and size classes, and temporal and spatial 

density of sampling. For example, the differences reported by Brown-Peterson 

(1993) and Montagna (1993) may well be within the range of year-to-year and siteto-site variation if longer periods of time were sampled and across wider areas (the 

choice of sampling scale being a powerful determinate of our perception) (e.g., crab 

densities: Fonseca et al. 1996b). Given the spatial and temporal variance in animal 

numbers, we feel it very difficult to justifjr additional planting based on relatively 

small differences in faunal attributes as compared to unplanted areas; using less stringent significance levels may be acceptable as well (i.e., p < 0.10). 

In general, we believe that planting is a success if the acreage is planted, persists, 

and eventually (if not immediately) leads to replacement of the same resource functions of the seagrass species that were damaged. By success we imply functionally 

equivalent to natural beds. Again, we stress that the use of acreage and persistence as 

diagnostic features of planting success needs additional geographic replication. 

As mentioned earlier, this view of assessment of planting success is, of course, not 

universally held. Short (1993) established other criteria for mitigation success for a 

project in New Hampshire. There, based on the recovery observed in his planted 

beds, he suggested that for eelgrass planting to be considered initially successfd, they 

should cover 30 percent of the planted area in one year. In addition, he stipulated 

that 40 percent of the following parameters be attained by planting within one year: 

seagrass primary production, shoot density, leaf area, percent cover, and continuity 

(i.e., meaning that 40 percent of the planting have coalesced). Moreover he stipulated that fish and infaunal assemblages constitute 25 percent of the following ecological parameters: presence of dominant species and total numerical abundance as 

compared to nearby natural beds. The values put forth by Short (1993) appear to 

coincide with finding for Tampa Bay (Fonseca et al. 1996b) in that faunal recovery 

will be closely linked with planting success and persistence. 

Another reason for using plants rather than fauna as a metric of planting success 

is that one can envision scenarios where faunal recruitment to a bed could be inhibited by recent natural events such as storms or local pollution sources that may or 

may not equally affect a reference site. Conversely, we know of no evidence where 

an otherwise unimpacted natural seagrass bed has not supported high faunal density 

and diversity. Thus, if the faunal/seagrass relationship is not necessarily reciprocal, use 

of fauna alone may not be as easily tracked as the plants themselves, which may be 
-- 

Chapter 1: Background 51 

suitable to infer the development of collateral faunal resource functions. At the very 

least, following plants alone is arguably less expensive than faunal data collection and 

may represent the most realistic data collection effort except in heavily subsidized 

restoration efforts. A pragmatic reason for accepting simple measures of acreage and 

persistence is that few planting are well-monitored and enforcement of non-cornpliance with permit conditions is sporadic (sensu Race and Fonseca 1996). The parallel between seagrass presence and fauna we feel is strong enough to accept some 

metric of seagrass alone as a viable indicator of functional recovery. Although additional research must be conducted to strengthen the seagrass-faunal function link on 

a broader geographic basis, our research suggests that monitoring the seagrass itself is 

a very useful option for assessing restoration/rnitigation success. 

Combinations of parameters have also been suggested as an appropriate metric 

for gauging success of seagrass planting (F. Short, Jackson Estuarine Lab., Durham, 

NH.,pers corn.). Combining factors that are known to affect faunal abundance, such 

as shoot size, density and water depth (taken together as a measure of habitat cornplexity), may be a way to provide a better means of indirectly comparing functions 

among planting, impact, and reference sites, especially when they occur in different 

geographic and/or physical settings. Short (rackson Estuarine Lab., Durham, N.H. 

pers. corn.) has proposed canopy volume: 

(shoot density " canopy height; [m/m2= #shoots/m2 " m/shoot]) 

because it is a value that should change more slowly than shoot density alone and 

thus be more tightly coupled to a greater range of ecosystem attributes beyond faunal development (e.g., current speed reduction, change in sediment composition, 

nutrient cycling). Moreover, the canopy volume metric can be obtained with nondestructive methods and, unlike shoot density, would likely not exhibit overcompensation responses with some seagrass species (eg, Syringodium jli$orme: Williams 

1990, Fonseca et al. 1994) which do not accurately reflect long-term recovery from 

injury to a seagrass bed. 

Another factor in assessing bnctional equivalency is habitat size. We do not 

know if there is any relationship between the size or shape of a seagrass bed and its 

functional attributes; this is true for both planted beds and natural beds.This is an area 

of study needing much additional work. From our experience, however, even very 

small patches 1-2 m2 of seagrass in the Beaufort, N.C. area has significantly greater 

numbers of fish, shrimp, and crabs than found in adjacent sand areas (unpubl. data). 

Moreover, Murphey and Fonseca (1 995) found that on a unit area seagrass basis, even 

beds in the range of 30-40 percent cover had penaeid shrimp densities virtually indis- 
52 Guidelines for the Conservation and Restoration of Seagrasses 

tinguishable from that of continuous cover, 100 percent beds. These data taken 

together with years of personal observation of seagrass beds (both planted and natural) have lefi us with the impression that even these very small, isolated patches provide resource functions comprising much of that observed in more extensive, unbroken coverage beds on a unit area basis. Thus, even very small patches of seagrass 

deserve protection. 
CHAPTER 2 

Planni 

A s habitat loss, fiagrnentation and geographic isolation 

of relict habitat has increased worldwide, scientists and 

resource managers, have become justifiably alarmed at the 

rapid loss of species and genetic diversity within remaining 

populations. Seagrass beds are no exception (sensu Ruckelshaus 1994a,Williams et al. 1996). In recent years the genetic status of seagrass beds has begun to be examined and the 

impact of human encroachment on its genetic diversity 

questioned (Alberte 1993,Williams and Davis 1993). However, as is the case in most wild populations, quantitative 

information regarding the genetics of individual plants, let 

alone populations, is scanty; and management decisions at 

the population level are those that most resource managers are likely to make. The 

question remains, however, does reduced genetic diversity actually matter in terms of 

population recovery trajectories and, thus, persistence of seagrass populations? Moreover, do differences in genetic diversity among planted and natural beds signal the 

disintegration of gene complexes specifically adapted to local conditions (S.Williams, 

Univ. California, San Diego, CA., pers. corn.)? Because quantitative phylogenetic 

analysis of seagrasses is only beginning (Procaccini and Mazzella 1996, Waycott and 

Les 1996), it is currently impossible to infer adaptive value for any attributes of seagrasses, including gene complexes. Genetic diversity is generally assumed to be crit- 
54 Guidelines for the Conservation and Restoration of Seagrasses 

ical to the survival of restored populations, but before genetic screening can become 

a management tool, much more research is needed to clarifjr the consequences of any 

changes in genetic structure of seagrass populations as the result of habitat destruction and planting projects. 

Some information is available regarding the role of genetic vs. environmental 

controls of seagrass. Backman (1991) concluded that genetic variation accounted for 

14 percent of morphologic variation, environmental setting 32 percent, and interaction of genetic and environmental factors 35 percent. Based on these findings, 

Backrnan (1991) also suggested differentiating Z. marina into five varieties. However, 

employing similar techniques, Dennison and Alberte (1986) conducted reciprocal 

transplants of a Z. marina population in Massachusetts and found that growth responses were largely environmental and not genetic. 

But for management purposes, maintenance of seagrass populations must be 

based on more than correlative inference of adaptive capabilities. Questions regarding population maintenance and genetic structure therefore must include some comprehension of how connected seagrass populations are along coastal areas. This 

includes some assessment of gene flow, genetic drift, influence of founder effects, 

existence of heterozygote advantages, identification of selection pressures, and determining the existence of metapopulations (sensu Orth et al. 1994). 

The few extant publications differ somewhat in their conclusions regarding 

genetic variation in seagrass beds. Laushman (1993) found that genetic variance of 

Zostera populations was less within bays than among bays. Alberte et al. (1994) asked 

a different question and that is how genetic relatedness is associated with geographic separation; like most spatially dependent data, they found that the closer the eelgrass patches were to each other the more alike they were. Ruckelshaus (1994b) suggested that the role of local extinction as the result of disturbance (eg, sedimentation, storm-induced scour) and subsequent recolonization of such areas may be an 

important source of genetic diversity. Because spatial and temporal variation in disturbance have long been known to have dramatic impacts on genetic diversity (e.g., 

founder effect and subsequent genetic drift: Futuyrna 1986), historical contingency 

is ofien the initial basis for differences in genetic makeup among geographically isolated populations. Without some idea of the historical context of a population, however, it may be difficult to determine what management strategy would best serve as 

a response to detection of lowered genetic diversity, especially in anthropogenicallydisturbed areas. 
- 

Chapter 2: Planning 55 

These population level questions are difficult to answer even in terrestrial environments where direct observation is much easier than in seagrass beds. For example, gene flow among geographically-separate populations is generally considered to 

be significant if only one individual exchanges genetic information with another 

individual in a separate population once each generation. In the case of clonal plants 

such as seagrass, it is not clear what a generation time might be. An individual ramet 

can live for days (eg, Halophila spp.) or years (e.g., Thalassia). However it reproduces 

both by seed which is the result of genetic recombination (which can incorporate 

genetic information &om an individual &om another population: gene flow); and by 

vegetative branching which involves no external genetic input and merely produces 

a second ramet that has the same genetic makeup as its first (i.e., a clone, excluding 

potential somatic mutations). Therefore, in a genetic sense, populations that employ 

a consistent, season-to-season and year-to-year component of vegetative (i.e., asexual) reproduction, a single generation may be composed of changing individual ramets but one genetic constitution. Thus, a single generation could conceivably last for 

decades or longer and for these populations, exchange of genetic material (gene flow) 

might not be needed among geographically isolated populations for many years. 

However, we do not know the appropriate time scales over which to evaluate the 

relationship between genetic diversity and gene flow, one reason being because we 

do not know how long a generation is for these clonal plants. On the other hand, 

most evidence points to interdigitation of genets on small (< 1 m) spatial scales, thus 

gene flow should not be limited across small spatial scales (Ruckelshaus 1995). Local 

gradients in genetic structure might then be assumed to be the product of locally 

abrupt selection gradients (i.e., water depth and light availability, sensu Fain et al. 

19%). 

It is also difficult to determine the size of a population that is interbreeding 

(effective population size; but see Ruckelshaus 1994b). In seagrass beds, Orth et al. 

(1994) reported that seeds typically disperse near their source although many avenues 

for long distance dispersal exist, but others have found evidence for both long- and 

short-distance dispersal (Ruckelshaus 1995). Once a location is colonized (or re-colonized) the degree of subsequent isolation raises questions of founder effects (the initial reduction in local genetic diversity given that the few founders do not represent 

the genetic richness of the parent population) which can result in locally distinct 

genetic structure in a group of plants. A similar scenario of limited gene flow was 

inferred by Alberte et al. (1994), a phenomenon that supports the metapopulation 

theory of Orth et al. (1994). Subsequent long-term reproductive isolation can also 

enhance genetic differences among groups, especially in the aftermath of a founder 

effect. Another means of enhancing local genetic diversity was described by 
56 Guidelines for the Conservation and Restoration of Seagrasses 

Ruckelshaus (1994b) where Zostera presence in an area of the Pacific Northwest 

experienced repeated local extinctions and recolonization which enhanced genetic 

diversity. 

Other potential (though not insurmountable) problems exist in the utilization 

of these data; our knowledge of the appropriate genetic indicators is limited, which 

imposes potentially severe technological limitations. Estimations of population size 

using genetic probes typically requires that the alleles being targeted are not acted on 

by natural selection. Because we do not know what aspects of a seagrass plant's biology are influenced by a given allele, it is conceivable that natural selection could be 

simultaneously altering allele frequencies being tested and, thus, biasing our interpretation of recent selection events. This is particularly a controversy with allozyme 

techniques (Futuyma 1986; p. 98), although these problems can be resolved if appropriate testing of probes is conducted and reported (S. Williams, Biology Dept., San 

Diego State Univ., San Diego, CA., M. Ruckelshaus, National Marine Fisheries 

Service, Seattle,WA., pers. corn.). 

The point here is that without knowledge of how often genes are exchanged 

among populations, the boundaries of populations, the existence or role of metapopulations, the duration of a generation, and the importance of seeds (a product of 

genetic recombination) in maintaining populations (and for the moment ignoring 

niutation), it is very difficult to direct specific management actions (i.e., site-specific) 

based on static surveys of genetic diversity. However, some guidance can be given 

even with preliminary data. If genetic variation were found to be partitioned more 

among sites of known geographic separation (therefore, populations are loosely 

defined as different sampling sites), rather than within sites, it would be advisable to 

equally protect geographically isolated sites (populations), and treat them as a larger, 

continuous resource rather then self-sufficient, isolated populations. 

Following the findings of Ruckelshaus (1994a,b), we suggest that the environmental and geographic context under which surveys of genetic structure and diversity are undertaken are as relevant as the detailed information regarding polymorphic 

loci that emerge &om any given study (sensu Ruckelshaus 1994b). For example, eelgrass beds on the West Coast of the United States exist in a geographically &agmented distribution among various water bodies and have, in the last century, 

experienced high localized losses. The situation on the East Coast is somewhat different. Although localized losses have occurred on the East Coast too, Z. marina populations went through a bottleneck with the wasting disease of the 1930's. These 

historical contingencies represent events known to affect the genetic structure of 

populations (geographic isolation and bottlenecks). It may be that the lack ofhistori- 
Chapter 2: Planning 57 

cal information on many of these populations and the absence of data on effective 

population size and gene flow (particularly human-mediated gene flow such as seed 

transport, may severely bias generalizations regarding erosion of genetic diversity). In 

the Pacific Northwest, such a process was an effective mechanism for the'introduction of an entire species, Zostera japonica, in the last quarter century. 

It is critical to separate naturally low genetic diversity &om an anthropogenically-imposed loss of diversity when attempting to set management standards for protection and maintenance of genetic structure (i.e., one may be setting baseline conditions too low). Another reason for differentiating naturally-low genetic diversity 

fi-om human-induced declines is that some clonal plants with low genetic diversity 

can persist for millennia (Cook 1985). Laushman (1993) suggests that hydrophilic 

taxa (including seagrass) have intrinsically lower heterozygosity, polymorphic loci and 

alleles per locus than non-hydrophytes, meaning that simple identification of low 

genetic diversity may not signal a management dilemma (but see Alberte et al. 1994). 

Thus, it is the detection of the erosion of genetic structure, a measure that requires 

evaluation over appropriate temporal and spatial scales, that will determine the 

response by management (sensu S. Williams, Biology Dept., San Diego State Univ., 

San Diego, CA., pers. corn.). 

Even if genetic differences are seen among populations we still do not know if 

those differences are important to maintaining seagrass populations in areas under 

existing conditions. However, Alberte (1993) has found preliminary evidence of 

reduced genetic diversity of Zostera in impacted, as opposed to unimpacted, areas. 

Similarly,Williams and Davis (1993) have found evidence for reductions in counts of 

polymorphic loci among recently transplanted beds when compared to older, more 

persistent beds in San Diego Bay fi-om which the transplants originated. More 

'Williams et al. (1996) demonstrated ". . . that genetic diversity (percentage of polymorphic loci, allele richness, expected and observed heterozygosity, and proportion 

of genetically u;lique individuals) was significantly reduced in transplanted eelgrass 

beds." Williams et al. (1996) attributed this reduction in genetic diversity to small 

sizes of planting projects, limited geographic range in donor stock collection, and 

failed sexual reproduction, all inferring founder effects. Geographic variability has 

since been shown to contribute greatly to differences in genetic composition among 

planted and natural beds (Williams and Orth 1998). This is a potentially serious 

trend, even though very old (non-seagrass) plant clones of low genetic diversity have 

been shown to exist in nature. The response of decreased genetic diversity in recently transplanted beds observed by Williams and her co-workers (1996) is exactly what 

might be expected of a disintegrating population; one potentially becoming less able 

to respond to the vagaries of environmental variation produced by the comparative- 
58 Guidelinesfor the Conservation and Restoration of Seagrasses 

ly rapid human alteration (as opposed to evolutionary time) of the nearshore environment. Localized extinctions might be expected under these conditions. However, reduced genetic diversity in transplanting might also be expected as it could 

mimic a natural founder effect, and with time, genetic' diversity may increase in these 

planted beds especially as sexual reproduction (seeding) contributes more to these 

beds over time. Thus, it is possible that the small-scale variation in genetic structure 

observed in natural eelgrass beds (Williams et al. 1996) is the result not only of tillering and branching, but deposition of seeds (the product of genetic recombination). 

Thus, we are not yet sure whether reduced genetic structure and diversity are longterm problems. If these planted beds are genetically deficient compared to their parent beds, they may certainly pose short-term problems if managers rely on planted 

beds as donor stock areas to mitigate for losses of natural beds. Planted beds may not 

have the genetic makeup to deal with stressed conditions. Basic research on the phylogenetics of seagrasses is greatly needed. Recent advances by Waycott and Les 

(1996) and Uchiyama (1996) provides guidance on the comparative status of breeding systems which in turn allows us to begin to understand the role of vegetative vs. 

sexual reproduction in species' maintenance (sensu Procaccini and Mazzella 1996). 

All of the above questions aim at resolving the issue as to whether differences in 

genetic diversity, or even its loss, means anything to the short- or long-term survival 

of seagrass populations under planting operations? Do changes in diversity influence 

maintenance of increasingly impacted and fiagmented seagrass habitats? How long 

do these differences persist? Can we collect information on genetic structure over 

spatial and temporal ranges and with sufficient resolution to formulate management 

directives? Without specific, continued funding to support this work, the answer is 

unfortunately, "no." Therefore the question remains as to whether seagrass populations, particularly those currently becoming fiagmented, will have the resilience to 

deal with the environmental changes brought on by human encroachment in the 

coastal zone. It seems to be an extraordinarily risky gamble to assume that present 

rates of habitat loss do not constitute a threat to the genetically-based resilience of 

some seagrass populations. We concur with Alberte et al. (1994) that "Studies that 

examine genetic structure of populations over time in disturbed and undisturbed 

habitats are needed so that the impacts of chronic habitat deterioration on genetic 

stability and resilience of (Zostera marina) can be ascertained." We recommend that 

scientists and managers continue to investigate and take seriously the threat of diminished genetic diversity and population isolation (especially when combined with 

degradation of environmental conditions critical for seagrass growth, such as light) 

that is anthropogenically imposed (sensu Williams et al. 1996). Thus, conservation of 

existing stocks and avoidance of population fragmentation and isolation would be a 

rational approach until a decision process based on data is available. 
Chapter 2: Planning 59 

At present it is our opinion that except for highly impacted estuaries, the major 

short-term problems of maintaining seagrass beds will be providing suitable water 

clarity, appropriate nutrient levels (which also influence water clarity), and minimizing direct physical disturbance (e.g., dredging). Problems of restoring seagrass beds 

are largely ones of appropriate site selection and subsequent bioturbation. No gene 

complex can provide protection against grossly insufficient light, excessive nutrient 

loading, or the depredations of bioturbating organisms in a recently planted bed. 

FollowingWilliams et al. (1996), we suggest that in practice, interim concerns regarding genetic diversity should be met by selecting planting stock &om beds throughout the water body which is closely connected with the planting site. Stock selection (dealt with more completely, below) thus follows recommendations very similar to that ofAddy (1947), especially in light of the fact that Fain et al. (1992) and 

Ruckelshaus (1994b) have both found greater genetic similarity within seagrass populations at similar tidal elevations than among populations. Any proposals to conduct 

surveys of genetic diversity of seagrass beds must contain provisions for periodic resampling to assess the influence of periodic disturbance and seedling colonization 

(Laushman 1993, Ruckelshaus 1994b) on genetic makeup, realizing of course that 

such sampling may have to be conducted for many years to detect the temporal 

sequence of disturbance that actually influences local genetic diversity (sensu 

Ruckelshaus 1994b). 

ORE CT PLANNING CONSIDERATIONS: 

SEAGRASS BED SPATIAL QUIRIEMENTS AND 

PLANTING SITE SURVEYS 

Acquiring pre-impact data on seagrass distribution and environmental conditions at a site is vital to good planning, but there are constraints in obtaining those 

kinds of data. One problem is that site surveys are often done at a single point in time. 

The problems .with one-time surveys of impacted sites have been manifested in many 

ways. One way is when decisions are made to place channels among patchy seagrass 

beds. Typically, a survey such as an aerial photograph will be employed to pick the 

alignment that will minimize impacts to present-day seagrass patches. However, 

because seagrass beds are spatially dynamic in time (i.e., they move: Orth 1977, 

Marba et al. 1994, Marba and Duarte 1995), such an alignment will almost ce&nly 

result in a decision to effect a long-term reduction in seagrass abundance because 

seagrass patches require that today's unvegetated space be available for them to occupy in the future (Figure 1.2). Thus, if a portion of the unvegetated space is removed 

&om among patchy seagrass beds, it is unavailable for colonization. Therefore, when 

the space occupied by present-day seagrass is vacated (via bed migration or mortali- 
60 Guidelines for the Conservation and Restoration of Seagrasses 

ty), there will be insufficient space for colonization and a local net decrease in overall seagrass abundance, even though no seagrass was immediately impacted (sensu, Figure 

1.2). This is the kind of impact that has been mitigated for in the past (Short 1993). 

To demonstrate this effect, we have plotted the cumulative amount of bottom 

area near Beaufort, North Carolina, covered by seagrass in several 50 x 50 m plots 

which we have monitored for almost four and one-half years (Figure 1.2). These 

plots were mapped repeatedly for the presence/absence of seagrass cover with 1 m2 

resolution. Thus, over time, we counted the number of new square meters of bottom space occupied by seagrass each subsequent survey time, but excluding any m2 

locations that had ever had seagrass since the initial survey time (i.e., once a m2 location is scored as having seagrass, it will never be added to this cumulative value again 

in the study period; only locations that had not been previously observed to have seagrass can be added). An important point is that the average percent cover at each site 

was very stable over the survey period. What this graph reveals is that sites that have 

nearly 100 percent cover to begin with, of course, remain at that level over time. 

However, sites that have lower percent coverage (y-intercept value)at any one point 

in time (here in North Carolina, largely the result of wave and tidal current effects), 

have had seagrass occupy twice the number of m2 areas in that 4.5 year period than 

were observed at any one point in time.This cumulative coverage (over time) represents the spatial requirements needed to maintain a representative seagrass bed in a 

given physical setting over time; here at least twice the area of the standing seagrass 

coverage is required to sustain the patchy seagrass cover over a 4.5 year period. 

With enough time, one would expect that ultimately all possible locations 

would eventually have supported seagrass cover; this is evidenced by the "hih2" site 

where cumulative coverage was still increasing at the May 1995 survey time. The 

asymptote of the cumulative coverage lines results at least in part for the tendency 

for m2 areas near to existing patches of seagrass to be lost and recolonized more fi-equently than m2 areas distant &om a patch. What this graph clarifies is that a decision to remove a portion of the unvegetated space among seagrass patches through 

conversion to a channel or some non-seagrass habitat will, in many instances, result 

in the additional loss of seagrass acreage within a four-year period. Also, we hypothesize that depending on the alignment of a channel and the direction of bed migration, the channel may act as an interceptor, creating a large zone of low seagrass abundance in the down-migration direction, much as a snow fence or sand jetty accumulates material leaving the down-flow direction starved for that material. Thus, a 

knowledge of the spatial dynamics of seagrass beds over time is critical to maintaining present-day levels of seagrass acreage, information that is probably critical for the 

Halophila genera in particular. 
- 

Chapter 2: Planning * 61 

PLANNING FOR EXECUTION OF A PLANTING 

PROJECT 

In order to prepare for a seagrass planting project, several factors must be considered. As in Fonseca (1994), the heading for each sub-section below can serve as 

an abbreviated checklist of information needs and subsequent actions which should 

be anticipated. Common to all these considerations is the need for early coordination with State and federal resource agencies. Since many States have a management 

system set up for federal agency review of such plans, early coordination can resolve 

regulatory problems before they become costly. In addition, we present a decision 

flow diagram (Figure 2.1) as a summary of this section. We suggest that readers familiarize themselves with this section before attempting to apply the decision process in 

Figure 2.1. When needed, they should also consider the guidance on how elevation 

affects seagrass survival through the interaction of tides and light regime presented by 

Dennison and Kirkrnan (1996; see section on Emersion Effects, below). 

Although there are many methods to plant seagrass, h-equently the goals of a 

project are not defined. Is the project for restoration or compensatory mitigation? 

Although the differences in project goals have little to do with the execution of the 

planting technique, it is important to recognize that planting in exchange for permitted losses may elicit different responses &om resource agencies than planting for 

the sake of restoration only. For a review which touches on agency concerns, the 

reader should refer to Fonseca (1 989a, 1992,1994). Project goals should identifj the 

species of plants that are to be used. Eventually attaining the same seagrass species as 

what was lost with an equal area of bottom covered is a logical, ecologically defensible goal. 

Because population growth rate varies with geographic location (and planting 

spacing), the timetable for meeting project goals will vary. For example, at --1 m 

spacing, it will typically require two years to reach coalescence of planted areas for a 

shoalgrass bed in the Florida panhandle whereas it may take only six months to reach 

the same level of coverage for the same species in the Florida Keys (Fonseca et al. 

1987c).This time lag should be anticipated for any planting and varies both by ecoregion and initial spacing of planting (Fonseca et al. 1996a). 
DETERMINE SEAGRASS SPECIES 

TOBEPLANTED 

LOCATION DECISION 

1) IS THERE A PREVIOUS HISTORY OF SEAGRASS ON THE 

SELECTED PLANTING SITE? 

I 

2) IS PLANTING TO BE DONE AMONG EXISTING NATURALLY 

PATCHY SEAGRASS? 

I IS THE PLANTING SlTE <0.2 ha? I- NO ARE SEAGRASSES ADJACENT TO 

I YES I I 

THE SlTE AT THE SAME DEPTH 

PLANT SlTE AT DEPTHS (1) 

I 1 rtJES DETERMINED BY CLOSEST NP 

NO- SEAGRASS RFn 

OPTIONS I 

1) CONDUCT PILOT PLANTING (2) 

2) CONDUCT FULL SITE EVALUATION 1 I GUIDELINES AND ( I 

REGIONAL MODULE 

YES 

SEAGRASS LOSS ON THE PROPOSED 

DETERMINE SOURCE OF IMPACT 

FROM CATEGORY(S) BELOW: 

OPTIONS 

1) VERY HIGH RISK WINO 

MONITORING 

2) EXTENSIVE MONITORING 

TO DET. SUITABILITY 4' 

NUTRIENTS 

(eutrophication) 

I MECHANICAL 

PERTURBATION I 

UNKNOWN YES 

PLANT SEAGRASS 

MONITOR PLANTINGS: SEE 

MONITORING GUIDELINES 

Figure 2.1. DecisionJlow diagranlfor seagrass planting with an enlphasis on a nlitigation scenario. 
Chapter 2: Planning * 63 

Early coordination with permitting and commenting agencies is critical. 

Because there are typically several agencies with overlapping jurisdictions, several 

permits may all be required for a single planting (e.g., municipal, county, aquatic preserves, state parks, State and federal agencies). This process should certairily be started months, and preferably a year in advance of the time planting is anticipated. 

Because many states prohibit harvest and/or planting without permits, failure to 

comply with permitting requirements can result in civil penalties. 

Several coordination protocols have been developed. One was designed specifically for siting marinas (Lockwood 1990) while another was designed to assist agencies collect resource information prior to commenting on a permit request (E. 

Nelson, NMFS, Northeast Region, pers. com.). In Nelson's protocol, two tiers of 

information are requested. Tier one relies on the discovery of extant information 

regarding the distribution, quality (e.g., biomass, density), and hnction of the beds 

(e.g., fishery surveys) in question and directs the applicant to a host of potential information sources. Should tier one efforts not provide enough resource information to 

proceed with processing a permit request, then a new, relatively detailed on-site 

assessment is triggered (tier two). The idea of a standardized protocol is essential to 

accurately convey the scope of the potential resource injury to the public stewards 

and to simultaneously treat applicants in a consistent and fair manner. 

There are a number of other policies and/or activities that have been developed 

to aid in seagrass protection and management. Hershrnan and Lind (1994) have summarized the variety of programs in the Pacific Northwest which exist and placed 

them into six categories: 

1. project review occurring at all levels of government; 

2. water quality policies many of which can impact directly on seagrasses; 

3. public land management policies of state, federal and tribal agencies owning 

submerged lands; 

4. restoratiodhabitat development policies implemented by all levels of government; 

5. damage reduction policies; and 

6. inventory and mapping programs which should include, but most fi-equently do not include seagrasses. 
64 Guidelines for the Conservation and Restoration of Seagrasses 

They note that there is little coordination among these processes and that, in fact, 

many lack the necessary geographic scope to effectively protect seagrasses. A major 

finding is that, although federal and state jurisdiction exists over seagrasses, no specific policies for managing seagrasses exist in the Northwest. Although policies exist 

for other portions of the coastal zone of the United States, they often suffer fi-om lack 

of coordination both among and within agencies, as noted by Hershman and Lind 

(1994) for the Northwest. 

Such coordination protocols would be better employed if some broader, statelevel policy regarding seagrasses were in place. To our knowledge there are a limited 

number of published policies that specifically mention or are designed to address the 

protection and/or mitigation of damage to seagrass habitats (Stephan et al. 1997). 

Here we review the Southern California eelgrass mitigation policy, EPAS Chesapeake 

Bay Program, and the State of Connecticut's Coastal Zone Management Program. 

Southern California 

The Southern California eelgrass mitigation policy was adopted in July 1991 

after having been developed by federal and state resource agencies (National Marine 

Fisheries Service, U. S. Fish and Wildlife Service, and the California Department of 

Fish and Game). This policy recognizes the ecological value of seagrasses, specifically eelgrass, and lays out procedures to be used for on-site mitigation performed to 

compensate for adverse impacts caused by projects addressed in Section 404 permits. 

The recommendations for site selection, transplanting techniques, and monitoring 

measures are largely based on published articles of the authors of this study. The 

Southern California policy also recommends criteria for success which are limited to 

the plant component and not to the system as a whole, a point supported by Fonseca 

et al. (1996b). 

Chesapeake Bay 

The EPA Chesapeake Bay Program has developed an awareness of the value of 

seagrasses in the ecology of the Bay, and in July 1989 developed an Agreement 

Commitment Report signed by the states ofVirginia, Maryland, and Pennsylvania, 

the District of Columbia and the Environmental Protection Agency entitled 

"Submerged Aquatic Vegetation Policy for the Chesapeake Bay and Tidal Tributaries." This agreement states that the signers will work together to implement four 

major areas relative to seagrasses. These include assessment of the distribution and 

abundance of the resource, development of protection and restoration guidelines, and 

implement an education component to increase public awareness of the value of the 

resource. The educational component recognizes the need for scientific research to 
-- 

Chapter 2: Planning * 65 

improve our knowledge and understanding of submerged aquatic vegetation to ensure that efforts to protect and restore this resource continue to be effective. It is 

refreshing to see that recognized in a ecosystem or watershed management approach 

such as is being conducted in the Chesapeake Bay. , 

The Submerged Aquaticvegetation Workgroup of the Chesapeake Bay Program 

developed a guidance document for protecting submerged aquatic vegetation &om 

physical disruption (Chesapeake Executive Committee 1995). As part of this guidelines document, the workgroup has summarized policies and activities of the states 

of Maryland and Virginia, the District of Columbia, and four federal agencies that 

directly impact the health of submerged aquatic vegetation in the Chesapeake Bay 

(U. S. Army Corps of Engineers, U. S. Environmental Protection Agency; U. S. Fish 

and Wildlife Service, and the National Marine Fisheries Service) principally as they 

pertain to permit applications under the Clean Water and Rivers and Harbors Acts. 

The reader is referred to this document for specific actions taken by these states and 

federal agencies. 

Connecticut 

The General Statutes of Connecticut, for Sections 22a-90 through 22a-112 for 

the Connecticut Coastal Management Act (revised January 1,1993), presents legislative goals and policies which include insuring that the development, preservation or 

use of the land and water resources proceeds in a manner consistent with the ability 

of these resources to support development, preservation, or use without significantly 

disrupting either the natural environment or sound economic growth. This Act also 

recognizes the need to conduct and sponsor research to improve the information 

base upon which these decisions are made. The Act states that policies include managing estuarine embayments to "protect, enhance and allow natural restoration of 

eelgrass flats except in special limited cases; notably shellfish management. . ." While 

this is the only .direct statement related to seagrasses, the document states that adverse 

impacts include ". . .degrading or destroying essential wildlife, finfish or shellfish 

habitat through significant alteration of the composition, migration patterns, distribution, breeding or other population characteristics of the natural species or significant alteration of the natural components of the habitat. . ." 

Although many other states have developed policies relating to seagrasses, the 

few reviewed here differ &om the other to some extent. However, they are all consistent in that they place an unquestionably high value on the maintenance of seagrass (or SAV) ecosystems, a position that signals the intent of the resource agencies 

to deal seriously with the resource and that allows potential developers a better 

understanding of the serious nature of an injury to these ecosystems. 
- 

66 Guidelines for the Conservation and Restoration of Seagrasses 

Another goal of many seagrass planting is an attempt to recoup interim loss of 

ecosystem functions. This was mentioned earlier as an attribute of functional equivalency. Because the concept of success and functional equivalency are so closely tied, 

planning for successful restoration and/or mitigation requires early incorporation of 

interim loss considerations. The manner in which interim loss has been addressed 

historically has been through adjusting replacement ratios (how much acreage to 

plant per unit acreage lost). However, the manner in which interim ecosystem losses have been computed has not been consistent. Replacement ratios of less than 1:1 

to as high as 5:1 have been proposed (Fonseca et al. in press), based on a number of 

criteria, but that ratio is usually inversely proportional to the degree which a project 

was in the public interest. 

To compute losses though, requires some assessment of not only acreage lost but 

also of how long a time the functions of that acreage were lost to the ecosystem at 

large before it was returned to pre- or un-impacted levels. Depending on how long 

one wishes to amortize a loss will influence how much replanting must be done. In 

theory, if one hectare of seagrass were destroyed today and three hectares were 

replanted tomorrow and reached standards of equivalency in three years, then after 

those three years the planting would have largely compensated for the total loss of 

production; the net loss of production over this three year period would be very low. 

However, thing rarely work this way. First, it is very difficult to consistently locate 

and successfully create new seagrass habitat that meets our site selection criteria 

(which precludes simply substituting naturally unvegetated bottom for vegetated bottom). Finding large acreage for planting in close proximity to the impacted area is 

rare; this means that planting is often done at a site physically removed fiom the 

impact area and any functions affected by spatial elements of ecosystem linkages (i.e., 

geographic setting) are lost. Second, the production that was lost was removed &om 

a specific point in time; ecosystem functions were disrupted and those specific 

resources are not replaced, such as that year's spawn of herring (e.g. as in the Pacific 

Northwest). Further, if there was a greater hiatus between the time of impact and 

recovery, then one could argue that planting conducted longer afier an impact or 

further away fiom an impact have less value than ones conducted sooner or nearer. 

This realization is the basis for new approaches by NOAA to quantitatively standardize the interim loss problem (Fonseca et al. in press). 

The assessment strategy to calculate interim loss is based on four steps of analysis: 

1. documentation and quantification of the injury, 
Chapter 2: Planning a 67 

2. identification and evaluation of restoration options, 

3. scaling of the restoration project to compensate for the injury over time, and 

4. determine the appropriate means of compensation (e.g., monetary or planting). 

The scaling aspect is the portion of the process that helps standardize the way in 

which interim losses are computed, irrespective of the habitat type involved. Interim 

lost services can be considered to be the integral of service lost &om some baseline 

level over time (Figure 2.2). To compare services lost with those recovered by some 

remedial action (such as planting seagrass), the product: 

square m of habitat lost x time = square m-years 

is set against square m-years of services provided by the planting project, but discounted as a function of time since the initial injury (Figure 2.3). Discounting is a 

accepted economic principle, used to transform monetary or service flows over time 

into present value terms for purposes of comparison. Planting that occur longer afier 

an impact are discounted more than plantings conducted shortly after an impact and 

therefore more planting must be done as more time elapses. The NOAA Damage 

Assessment and Restoration Program is currently applying this procedure to seagrasses and it now has been upheld in court (US. District Court, 92-10027-CIVDAVIS). Initial results appear promising but require an empirical assessment of rates 

of recovery by seagrass. These rates are poorly known and experiments have been 

implemented to provide additional data. Population growth and coverage rate information has been useful (sensu Fonseca et al. 1987a,c) and supports previous claims for 

the need to collect these kinds of data as part of any monitoring of seagrass planting (Fonseca 1989a, 1992,1994) 

PRE-IMPACT AND PRE-PLANTING SURVEYS: 

IDENTIFYING SENCE AND REASONS 

FOR ABSENC COVERAGE 

Lockwood (1991) provided guidelines for surveying sites prior to impact and 

how to interpret these data to plan subsequent planting. Essentially, any quantitative 

survey method will work, such as line transects or grid sampling, but some basic 

quantitative standards such as presence/absence of a seagrass species over known areas 

must be met. Sampling for the presence/absence of seagrass should encompass the 

entire impact site on the closest spacing practicable and clearly specift the range over 
Total Resources 

Services 

Interim Lost 

Services 

Post-Incident 

Incident 

TIME 

Baseline 

+ 

Full Recover 

Figure 2.2. Diagraniniatic representation ofthe coniputational process used for assessing interim loss of 

seagrass habitat functions lfoni B.]ulius, DARP/NOAA). 

taken from B. Julius: NOAA-DARP 

Effective 

Discounted Sq. m 

of Services 

Total Discounted 

Initial Effective Sq. m-years of Services 

Service Losses Lost Due to Injury Total Discounted 

Sq. m-years of Services 

Provided by Replacement 

TIME 

Incident Replacement Recover of 

Project Affected Services 

Initiation 

Figure 2.3. Diagranivrtatic representation ofthe discounting process used to compute replacenrent ratio 

for planting seagrass under a mitigation scenario lfonr B.]ulius, DARP/NOAA). 
Chapter 2: Planning 69 

which sampling is to be done and the resolution with which samples are to be taken. 

For example, the following description would be considered adequate for such a 

report: 

On (dates) [representing spring and summer growing conditions], 

five 100-m transects spaced 20 meters apart were swum by divers 

over the site who then recorded the average percent cover seagrass 

[percent of 16, 25 x 25 cm subunits within a 1 m2 quadrat that 

contained a minimum of 1 seagrass shoot] where 1 m2 quadrats 

were assessed on 10-m intervals along each transect). Alternatively, a video camera may be towed over a transect line marked at 1- 

m increments and the cover estimated using a point-grid method 

(e-g., Braun-Blanquet 1965,Virnstein 1995). 

The depth distribution and coverage of each species present should be recorded. If 

seagrass occurs as small isolated patches of grass among open, unvegetated areas, then 

the sum total area occupied by the patches (portion of the sea floor where rhizomes 

overlap) could be recorded per unit seafloor (where the unit area of seafloor is at least 

a minimum of 100 m2). If plants are very large and separated fiom each other then 

the aforementioned quadrat method will be more appropriate for assessing coverage. 

Data on species composition should be used to guide the selection of species for later 

planting. Further, these data can be used to determine the amount of seagrass that 

can be salvaged for planting other sites or potentially stored for replanting onto the 

original site if the disturbance is short-lived. 

Aerial photographs of appropriate resolution can provide useful information for 

evaluating existing seagrass beds. A time series of aerial photographs, (preferably 

-1:20,000 scale) if available, can be particularly useful in determining the dynamic 

nature of a site. Photographs should be used only if taken during the peak biomass 

season for the seagrass in question. Moreover, it is sometimes dificult to accurately 

determine the lower depth limit of seagrass on a site fiom aerial photographs. Lower 

depth limits of seagrass distribution should be verified by on-site inspection, especially if bottom features which are clearly deeper than the apparent lower limit of the 

seagrass in the picture cannot be discerned in the photographs. However: 

If aerial photographs taken over a ten-year period indicate no history of seagrass cover, then the potential planting site should be 

regarded as marginal, or better, rejected. 

Episodic seagrass cover on a potential planting site, either among years or seasons (as 

might be the case with seed recruitment) would suggest that planting there would 

only pulse the system and not provide sustained habitat replacement. As these caveats 
70 Guidelines for the Conservation and Restoration of Seagrasses 

imply, unlike many other wetlands where site engineering is often an option, it is very 

difficult to locate a planting site that will provide self-sustaining seagrass habitat. Also, 

as discussed under the section titled "Spatial Scale and its Role in Defining Seagrass 

Habitat," aerial photography must be taken with sufficient resolution to detect the 

smallest patches of seagrass in the target area; this may require fairly low overflights (< 

1000 feet) which may present significant problems in certain areas where Federal 

Aviation Administration rules prohibit low flights. S. Nixon and B. Kopp (Graduate 

School of Oceanogr., Univ. Rhode Island, Narragansett, RI., pers. com.) have 

employed Geographic Information Service technology to overlay water column light 

transmissivity, water depth, wave exposure and other factors in a site selection process 

that may become a model approach for regional restoration planning. 

Environmental data or pilot test planting results should be collected to provide 

an indication of planting success prior to the commitment of the entire project's 

resources. However, personal observations suggest that some planting may be sufficiently small (-500-1000 planting units) so the cost of collecting environmental data 

and performing pilot planting are equivalent to the cost of planting the entire site 

itself. 

Selecting an appropriate planting site is perhaps the single most important step 

in the entire process. It is also the step that is the most difficult to objectively verifjr. 

. This is because the circumstances contributing to the presence or absence of seagrass 

at a given site vary tremendously (see "Pre-Impact and Pre-Planting Surveys,'' above 

and criteria in Appendix E, p. 21 1). Planting areas may be classified as either on- or 

off-site. When an off-site planting area must be selected, whether it be for restoration or mitigation, it must pass a simple, but exacting, test: "If seagrass does not currently exist at the (chosen) site, what makes you believe it can be successfdly established?" (Fredette et al. 1985). 

The absence of seagrass on what may appear to be an otherwise suitable site 

often indicates some inherent difficulty in colonization or a temporally dynamic site 

(e.g., as the result of disease, E Short, Jackson Estuarine Lab., Durham, NH, pers. 

com.). In the case of disease-induced loss of cover, planting may be considered sim- 
Chapter 2: Planning 71 

ilar to planting among existing seagrass patches in that temporarily fi-eed-up bottom 

space would be used as an inappropriate planting site. Planting among patches of 

existing natural seagrass should also be rejected because this too will only pulse the 

system and not create any long-term increase in seagrass acreage and this space is 

soon required by the spatially dynamic seagrass patches (see sections on "Defining 

Seagrass Habitat" in Chapter 1 and "Constraints Imposed by Physical Setting on 

Planting Operations," below). The take-home message is that if one contemplates 

off-site compensatory mitigation, there are usually few, if any sites available that: a) 

can support seagrass growth and, if they do, b) do not involve habitat substitution, or 

c) do not satisfy the no-net-loss rule. 

One form of off-site planting that meets the criteria discussed above is grading 

down uplands to elevations suitable for planting. Although this entails the trade-off 

of upland habitat for seagrass, if that upland is zoned for development, then its conversion to seagrass habitat type is warranted. Other off-site options include filling of 

dredged areas or areas that have experienced an improvement in water quality (e.g., 

transparency, temperature, etc.). These latter two choices, however, may include areas 

which historically supported seagrasses and thus may not be effective to offset seagrass loss in compensatory mitigation (see section "Pitfalls in the Mitigation and 

Restoration Process"). In the case of on-site planting associated with a particular 

project (i.e., planting back into a portion of the site which suffered a loss of seagrass), 

the activity which originally caused the loss of seagrass must have ceased. 

In many instances seagrass planting takes place on sites that have met the criteria of past seagrass presence, identifiable (and human-induced) agents of loss, and the 

termination of those loss agents (Thayer et al. 1985). Less fi-equent, however, is planting on sites that -have been specifically engineered to accommodate seagrass planting. 

Those that have been contoured to appropriate elevations have had good success; in 

the Laguna Madre, the interiors of dredged material islands were returned to subtidal elevations suitable for seagrass growth and connected to the adjacent sound; both 

planting5 and natural recolonization were successful (Montagna 1993). Work in San 

Diego Bay in the early 1980's featured the creation of a submarine dike that allowed 

placement of dredge material shoreward of the dike, raising the bottom to elevations 

(- -5 m) with suitable light for seagrass growth (pers. obs.). Short (1993) conducted a similar planting in Great Bay, NH. Both projects created viable seagrass habitats 

that are currently supporting extensive seagrass cover, even though portions of the 

New Hampshire site was susceptible to winter ice shear. The drawback to this approach is that naturally unvegetated subtidal seafloor was converted to seagrass habi- 
72 Guidelines for the Conservation and Restoration of Seagrasses 

tat; such habitat substitution may not be an acceptable mitigation tradeoff as implied 

by recent symposia on the important ecological roles performed by unvegetated 

estuarine sediments (Marine and Estuarine Shallow Water Science and Management 

in the Mid-Atlantic Region, Atlantic City, NJ). 

Other engineered sites include those near Beaufort, NC, where seagrass and saltmarsh habitats were created on old dredged material islands for the purposes of both 

stabilizing eroding shorelines and experimentally investigating recovery trajectories 

and linkages among these two habitat types (Fonseca et al. in press.). In this case sites 

that did not receive subsequent dredged material successfdly supported seagrass 

plantings. Thus, sites have been engineered to support seagrass mitigation and have 

enjoyed good planting success. Such attention to site preparation is encouraged 

although the costs in performing such site engineering may often place it outside the 

realm of possibility for small mitigation projects. 

On-site planting often entails planting into permanently modified areas, such as 

in the case of channel dredging, and typically cannot accommodate a replanting ratio 

(planted seagrass area/lost seagrass area) above 1 : 1. Planting along banks of artificially-created channels is logical if the depth of planting does not exceed that at which 

the plants occurred prior to dredging even though a larger potential planting area 

may be created. Channel margins, however, are highly susceptible to subsequent 

grounding events by vessels which will limit replanting options. In addition, many 

channel bottoms at navigational depths will not support seagrass due to insufficient 

light or severe scour &om propwash. Channels, being deeper than the surrounding 

seafloor often act as areas of enhanced deposition, especially of organic material. As 

a consequence, highly reducing sediments and prolonged periods of anoxia may be 

found in channels which are typically highly stresshl, if not lethal conditions for seagrasses. As a general rule, planting in and around channels is very risky. 

As an alternative to dredging access channels, docks are often built to access vessels &om land. Docks, however, have their own suite of potential impacts to seagrass 

beds. Besides actual impacts where dock pilings are installed, unless a dock is narrow 

and high above the water, it will create a substantial shadow that will reduce seagrass 

density and biomass, as seen in Massachusetts (Burdick and Short 1995). At the deeper end of the seagrass bed, plants will be killed as the shadow pushes them below 
--- 

Chapter 2: Planning 73 

compensation irradiance (see section on "Light Requirements for Transplanting,'' 

below). Relationships derived by Burdick and Short (1995) in New Hampshire 

reveal that at those latitudes and tidal regimes, a 1-m wide dock had to be nearly 5 

m high to maintain eelgrass (Zostera marina) bed quality. Burdick and Short (1995) 

also found that plank spacing and width were far less important than height of the 

dock and its compass alignment (north-south docks had less impact than east-west 

docks because their shadow moved further across the bed, thus mitigating the shading effect). Burdick and Short (1995) recommend that T-shaped docks, with a floating dock beyond the outer edge of the seagrass, minimizes collateral disturbance &om 

propwash and boats settling onto or perpetually shading beds when they are moored 

at the dock. Similar findings were reported by Loflin (1995) in Florida. While existence of collateral disturbance (e.g., dispersing of fish and wildlife) are not well-documented in seagrass systems, there is also no reason to expect that such disturbances 

would not occur. These kinds of empirical estimates are greatly needed by resource 

managers nationwide but must be developed on a regional basis. 

Other collateral direct impacts to seagrass beds caused by human activity include 

propeller scarring and mooring chain scars. Sargent et al. (1995) have found thousands of acres of seagrass beds in Florida either destroyed or significantly degraded as 

the result of vessel scarring, which includes not only vessels with propellers but jet 

skis as well (pers. obs.). The source of injuries to seagrass beds is varied, but collateral impacts &om otherwise seemingly benign activities such as foot traffic or mooring a vessel to those actually designed to minimize or avoid impacts to seagrass beds 

(docks) can sometimes result in significant damage. Care must be taken to avoid 

these impacts. 

If sigmficant physical alteration such as dredging has occurred at a site, on-site 

planting ofien cannot provide sufficient acreage to prevent a net loss of habitat. 

Another common, but less obvious physical alteration occurs when bulkheads are 

installed. Many bulkheads are designed as walls to efficiently reflect waves. This wave 

reflection effectively doubles the wave energy seaward of the wall, ofien eroding 

existing offshore beds and creating a situation where they likely cannot be replanted. When physical alterations are subsequently ameliorated, on-site planting is appropriate and offers one of the few circumstances where substantial acreage can be generated, even though historical levels may not be attainable. 
74 Guidelines for the Conservation and Restoration of Seagrasses 

The physical setting will dictate the amount of seagrass coverage per unit seafloor as well as the pattern of that coverage. The organization of the coverage into 

patches is correlated with wave and current climate (Fonseca et al. 1983). Application 

of wave and current data into site layout is given below in the section, "Spacing of 

Planting Units." Physical setting is correlated with sediment stability which can 

severely limit planting success (Fonseca et al. 1985). In general, sites with high wave 

exposure and tidal current speeds are difficult to restore because of frequent disturbance. 

A precise survey of the physical conditions at the planting site will assist in determining the amount of plant material required later. In the case of mitigation projects, a similarly precise survey of conditions prior to any proposed impact is required 

to obtain an accurate estimate of the seagrass habitat to be lost. This will allow accurate computation of planting ratios (mitigated acreage vs. impacted acreage) to be 

computed. For example, if 0.5 acres of continuous cover seagrass bed (i.e., low-energy site) were lost to a project and a high-energy planting site was chosen which 

would typically support patchy beds one would have to: 

1. anticipate planting an acre of bottom to achieve 0.5 acres of cover, and 

2. budget for substantial replanting (as much as 50 percent of the original planting) because planting failures increase with higher currents (Fonseca et al. 

1985). 

We focus on wave and tidal current effects on seagrasses in unconsolidated sediments because we have no quantitative information regarding seagrass growing on 

consolidated sediments (e.g., Phyllospadix spp.) to guide selection of a physical setting. 

We draw the reader's attention though to work by Turner and Lucas (1 985) who outlined spatial and temporal dynamics of a rocky intertidal seagrass community and 

work by Sousa (1979) who noted an inverse relationship between boulder size and 

frequency of disturbance, an important factor to recognize if planting are attached 

to boulders. 

For seagrass growing on unconsolidated sediments, we have some data from 

southern Core Sound, North Carolina, and Tampa Bay, Florida, to indicate a strong 

relationship between wave exposure (described below) and tidal current speed. To 

obtain these relationships in North Carolina, seagrass coverage data was determined 

by mapping 18, subjectively chosen seagrass study sites in Core and Back Sounds, 

Carteret Co. (latitude 34.40-34.50 N, longitude 76.20-76.40 'Wr). These sites were 

chosen based on examination of aerial photographs and ground-truthing to repre- 
-- 

Chapter 2: Planning 75 

sent the full range of seagrass coverage that could be locally identified. These sites 

are also colonized by a mixture of Zostera marina and Halodule wrightii. Carteret Co. 

represents the primary area of overlap of these two seagrasses on the east coast of the 

United States. The occurrence here is marked by different seasonal peaks of abundance (Thayer et al. 1984). 

(1 995) : 

where: 

i = 

v = 

P = 

F = 

Exposure to waves was calculated for each site using methods of the Shore 

Protection Manual (1977) and Keddy (1982) as reported by Murphey and Fonseca 

8 

Exposure = (Vi X Pi X Fi) i=l 

ith compass heading (1-8) 

average monthly maximum wind speed in m s-' 

percent frequency which wind occurred from the ib direction 

effective fetch 

To analyze the effect of both forms of water motion (waves and currents) in 

North Carolina, exposure values (based on mean monthly maximum wind speeds), 

and tidal current speed (peak free-stream speed over seagrass at the lunar maxima) 

were plotted against percent coverage using all the sites &om 4 sampling times covering 2 years. The percent coverage for each site was calculated by dividing the total 

number of one meter square (pixel) observations that had seagrass by the total area 

of the survey plot (2500 m2). Site maps were produced fiom the survey data and each 

pixel registered as containing seagrass plotted as a square. 

These surveys produced significant relationships as seen in Figure 2.4 (Fonseca 

and Bell in press): 

Percent Cover = Exposure index (-0.0135) + 92.525 

r2 =: 0.45 

Percent Cover = Maximum monthly tidal current speed in 

cm s-' (-2.644) + 11 1.044 

r2 = 0.60 

We are not sure how these data may be applied to other areas because to our 

knowledge, seagrass plantings have not been conducted to account for anticipated 
0 1000 2000 3000 4000 5000 6000 

RELATIVE EXPOSURE INDEX in 1000s 

10 

0 

0 10 20 30 40 50 

CURRENT SPEED in cm/sec 

Figure 2.4. Relationship between seagrass cover and physical setting for seagrass beds near Beauirt, NC. (a) Relationship 

between seagrass cover and exposure index (eq. 1 in text) from eighteen, 50 x 50m plots surveyed with In1 resolution. 

(b) Relationship between seagrass cover and tidal current speedfrom eighteen, 50 x 50ni plots surveyed with In1 resolution. 
- 

Chapter 2: Planning * 77 

landscape patterns. We suggest that in areas where currents speeds are less than 15 

cm s-', only wave exposure be considered in predicting coverage. For lack of better 

guidance, but taking into account observations of dune formation even in subtropical areas (Fonseca 1996a), we suggest that the tidal current speed model hold for seagrasses in all settings when currents are greater than 15 and less than 50 cm sec-' (tidal 

current speed > 50 cm sec-' would indicate rejection of the site, Figure 2.5). It 

should be noted that application of these data are extremely experimental but may 

represent an important aspect of planning that might be considered in planting operations. 

Despite the long-standing recognition of seagrass emersion as a factor in its ecology (Johnson andYork 1915, cited in Harrison 1982), until recently little work has 

been done to document direct effect of emersion on the plants. The effects of emersion vary widely around the U.S.; in the southeast and Gulf states, emersion can cause 

significant mortality. In northern states eelgrass beds may be regularly exposed at low 

tide but avoid serious desiccation due to local micrometerological factors, such as fog, 

cool air temperatures, and high local humidity in the immediate vicinity of the seagrass canopy. Moreover, seagrass beds can also trap water in their canopy as the blades 

lay over at low tide by making the path for water drainage extremely long by causing flow to wend through the leaves and stems. Powell and Schaher (1991) reported this phenomena in Florida Bay and it has also been observed in New Hampshire 

(E Short, pers. com.) and elsewhere (authors' pers. obs.). In addition, Bulthuis et al. 

(1984) demonstrated that seagrass beds retain both fine sediments and nutrients while 

trapping water. Limited work by Harrison (1982) on comparative emersion effects 

among Zostera spp., and more detailed studies by Cooper and McRoy (1988), 

Cooper (1989) on isotopic variation with emersion, and Perez-Llorens and Niell 

(1993) on Zostera spp. may constitute the entire body of quantitative work on the 

subject. ~erez- lore ens and Niell (1993) describes perhaps the only work on nonrocky intertidal seagrass where an experiment was designed specifically for the effects 

of temperature and emersion. In that study, photosynthetic rates were significantly 

higher in water than in air, but a narrow-leaved morphotype of Zostera noltii displayed 

higher photosynthetic rates than a broader-leaved morph. Increased temperature 

decreased photosynthesis during the 2-h incubation period for both morphs, 

although the narrow-leaved morph was more resistant. However, emersion time was 

not varied and recovery of photosynthetic capacity was not measured. Adams and 

Bate (1994) removed individual blades for desiccation effects and measured chlorophyll fluorescence. They found that the wider-bladed Zostera was significantly more 
78 Guidelines for the Conservation and Restoration of Seagrasses 

MECHANICAL PERTURBATION 

WAVES TIDAL CURRENT BIOTURBATION 

 NATURAL 

TIDAL CURRENT 

CONSIDER KNOWN? 

I 

COMPUTE 

EXPOSURE 

INDEX (3) 

I 

USE REGRESSIONS 

TO ESTIMATE FINAL 

PERCENT COVERAGE 

0 AND CHOOSE DEVICE 

INPUTTO DECISION MATRIX 

Figure 2.5. Site selection process using physical setting. 

resistant to desiccation than narrower blades of Ruppia, although tests were conducted on blades in isolation and thus did not account for the possible mitigative effects 

of a canopy or moisture content of the sediment on desiccation. 

The findings of Perez-Llorens and Niell (1993) have implications in other 

regions. For example, in the Beaufort, NC area, two seagrass species occur at the 

edge of their distributions - the temperate species, Z. marina and the subtropical 

species, H. wrightii. Zostera marina leaves are approximately 3-5 mm wide whereas H. 

wrightii leaves are 1-2 mm wide. The narrower-leaved species can exist in slightly 

shallower water which receives more Gequent emersion (sensu Perez-Llorens and 

Niell 1993). Thus, the interaction of species and canopy morphology with tidal 

regime may be a significant zonation factor as has been documented for macroalgae. 

If this is the case, then the ability of the narrow-leaved form of Zostera noltii to maintain higher photosynthetic capacity at higher temperatures might result Gom an 

adaptive advantage for narrow leaves in regulating leaf temperature. These findings 

are contradicted by those of Adams and Bate (1994) where narrow-leaved species 

were less resistant to desiccation. Clearly experimental designs that simulate natural 

settings are needed to generate quantitative measures of desiccation tolerance of sea- 
-- 

Chapter 2: Planning 79 

grasses. Knowledge of desiccation tolerance will facilitate selection of appropriate 

seagrass species for a site in an ecoregion where such choices may be possible. 

Despite contradictory experimental findings, exposure to air is ofiexi detrimental to most seagrasses. Human alteration can render many sites too shallow for seagrasses. For example, reduced water depth &om dredge material deposition may 

result in sites where transplants would be exposed at low tides, causing them to desiccate. Sufficient water depth must be maintained to cover the plants even at lowest 

tides. Very short term events (2-3 hours) may substantially alter seagrass abundance 

and distribution. For example, desiccation caused by an extreme low tide at mid-day 

in the summer can determine the upper limit of seagrass distribution in an entire bay 

for the following year (Beaufort, NC, pers. obs). Areas with high turbidity and tidal 

amplitudes are extremely difficult to plant given that desiccation at low tide and light 

extinction at the lower depth limit must both be avoided (E. Koch, Horn Point, MD, 

pers. com., sensu Koch and Beer 1996). Because plantings are generally more stressed 

than established beds, we suggest (as we will for light) that emersion should be avoided. Arranging planting depth for minimum emersion is best planned by surveying 

elevations of nearby beds. 

Dennison and Kirkman (1996) suggest a balance of tidal elevations for seagrass 

survival based on the premise that Secchi depth is equal to the compensation point 

for some seagrasses, while considering tidal range and type. For seagrasses existing 

intertidally (with the possible exception of Pkyllospadix spp.) mean range of astronomical tides (MTRA) must be greater than the mean range of barometrically-driven tides (MTRA > MTRB) for their survival. Also, Secchi depth (Zd) must be 

greater than MTRA (Zd > MTRA). For subtidal seagrasses, Zd > MTRA and Zd 

> maximum depth of seagrass distribution (Z; Zd > Z) for seagrass survival. This 

model has not, to our knowledge, been tested in North America. 

Prior to rooting and coalescence of planting, seagrasses are especially vulnerable to bioturbation (Fonseca et al. 1994). Bioturbation is widespread and has been 

shown to limit distribution of natural beds as well. Ogden et al. (1973) documented the effect of the echinoid Diadema antillarum on the formation of grazing halos in 

seagrass beds associated with West Indian patch reefs. Similarly, Camp et al. (1973) 

andvalentine and Heck (1991) demonstrated the role Lyteckinus variegatus in producing unvegetated areas &om seagrass beds in the northern Gulf of Mexico. Orth 

(1975) attributed the destruction of large areas of eelgrass (Zostera marina) in the 
-. 

80 . Guidelinesfor the Conservation and Restoration of Seagrasses 

Chesapeake Bay to the feeding activity of the cownose ray (Rhinoptera bonasus). 

Suchanek (1983) and Harrison (1987) demonstrated the negative impacts of the burrowing shrimp Callianassa on the seagrasses Thalassia testudinum and Zostera spp., 

respectively. Valentine et al. (1994), however, found that even large animals such as 

rays were apparently unable to create unvegetated patches within existing Thalassia 

testudinum beds, and that only very large rays were capable of producing pits at the 

bed-sand margin that resulted in damage to these seagrasses' rhizomes. They also 

found that sand dollars (Mellita quiquiesperforata) did not disturb these edges whereas 

stone crab (Menippe spp.) burrows were disruptive.They point out that the deep rhizome layer of T testudinum (as compared to Z. marina or H. wrightii as found in the 

Beaufort, NC area) may insulate these plants &om ray and sand dollar disturbance. 

Various waterfowl can graze down seagrasses (eg., Black Brant, redhead ducks, mallards, etc.) (Thayer et al. 1984) and can destroy early stage plantings (Beaufort, NC, 

pers. obs.). If waterfowl grazing is anticipated, then exclosures should be covered on 

top and not just on the sides. Bioturbation has been linked to maintenance of kagmented seagrass landscapes (Townsend and Fonseca 1998). 

Bioturbation is a factor that can require a substantial replanting budget; thus 

some kind of exclusion device is often needed. For example, Fonseca et al. (1994) 

found that in areas of Tampa Bay where currents did not exceed 13 cm/sec, a greater 

than 50 percent loss of planting units occurred due to sediment disturbance, apparently by rays. Fonseca et al. (1994) found that caging of Halodule planting with one 

inch mesh galvanized chicken wire cages (sides and tops) in Tampa Bay made a difference of < 1 percent survival with no cages versus 60 percent survival with cages. 

Merkel (1988a) also found extensive disturbance of seagrass transplants in San Diego 

Bay and used stakes, fencing, and erosion matting in an attempt to improve planting 

survival. Short (1993) constructed gill-net cages with no tops which excluded horseshoe crabs and green crabs and preserved eelgrass plantings in a New Hampshire 

estuary. However, Short (pers. comm.) has also reported that certain polychaete 

worms (e.g., Nereis) will pull the blades of early stage eelgrass planting down into 

their burrows to feed on epiphytes. This lays the short shoot along the sediment surface where it is then subject to other attacks and burial. Short found that decreasing 

planting density &om 0.5 m on center to 0.1 m centers resulted in slower, but still 

complete incorporation ofblades into burrows.We are not aware of a remedy for this 

source of bioturbation. 

Bioturbation events can occur quicMy.We have experienced 100 percent loss 

of Halodule and Syringodium planting units within 24 hours of planting (Florida Keys 

backreef area) due to grazing where chicken wire cages were not used. The lack of 

good pre-project information on bioturbation potential will usually cost one more 
Chapter 2: Planning 81 

in remedial planting than will be saved fi-om planting a minimum of material for a 

test of bioturbation at the onset. 

Insufficient sediment thickness (eg, bedrock too near the surface) has been 

shown to be limiting to the distribution of some seagrasses (Zieman 1982b), particularly Thalassia testudinum. Although not documented for any other seagrass, the potential for exposure of bedrock by currents due to shallow unconsolidated sediments 

should be considered when choosing a site. In relatively quiescent areas, we have 

successfklly established H. wrightii and S.filijorme beds on sites with as little as 15 cm 

of loose carbonate sand over bedrock (Fonseca et al. 1987a). Generally, species with 

shallow root and rhizome systems (e.g., Halophila, Halodule, Zostera) may not be inhibited by thin veneers of sediment. 

SEDIMENT STABILITY: EROSION AND BURIAL 

OF SEAGRASS SHOOTS 

Generally, sediment stability is going to be correlated with wave exposure and 

tidal current speed. The relation between exposure and/or currents and sediment 

stability is difficult to predict given variation in sediment grain size (therefore different erosion thresholds) among sites and the episodic nature of wind events. The 

apparent threshold responses evident in Figure 2.4 suggest, however, that some erosion threshold may be represented by exposure indices near 3 x 106 and tidal current 

speeds of 25 cm sec-'. Merkel (1992) suggests that erosion rates of 0.5 mm day-' and 

burial rates of 0.3 mm day-' are limits for Z. marina survival on the West Coast. These 

data compare favorably with the sediment fluctuation limit of -1 .O mm day-' found 

on the East Coast for both Z. marina and H. wrightii (Fonseca et al. 1985). 

Conversely, there are few data to indicate critical burial depths; those depths 

likely vary among species. However, our preliminary data for H. wrightii (unpubl. 

data) indicate that when 25 percent of the shoot is buried, 75 percent of the plants 

survived, but when 75 percent of the shoot was buried only 5 percent survived. This 

response suggests an exponential decline of survival with percent burial.We are aware 

of no data on North American species that gives guidance on the duration of burial 

time after which recovery of the plants would be expected (but:see Marba and 

Duarte 1995,Terrados et al. 1998). 
82 * Guidelines for the Consevvation and Restoration of Seagrasses 

Prior to planting, measurement of sediment fluctuation relative to numerous 

(minimum of five) fixed datum established on-site is recommended (sensu Fonseca et 

al. 1985, Merkel 1992). The number of datum should be increased to as many as 

practicable, covering all areas of a planting site where differences in sediment erosion 

and accumulation are anticipated. Readings should be taken daily if possible for at 

least one lunar cycle at the same time of day to allow measurements at as many tidal 

stages during a lunar cycle as feasible. Merkel (1992) recommended placing a one 

foot long 1/2-inch diameter PVC pipe halfway into the sediment as a datum and 

measuring sediment elevation relative to the top of the pipe. In areas of moderate 

waves and/or currents, we suggest that the pipe be longer and buried deeper into the 

sediment, up to 50 cm. We also suggest that an inverted T-shaped device for measuring sediment height be used. The cap of the T should be a 25 cm long segment 

of a wooden yard or meter stick bolted through the leg of the T so it can pivot when 

placed on the bottom. In this way the effect of local scour around the pipe on computation of sediment elevation change is minimized. These methods are designed for 

detection of chronic conditions; the reader should keep in mind that extreme, aperiodic events ofien determine limits to distribution of seagrass (sensu Gaines and 

Denny 1993). 

POSSIBILITY OF NATURAI, COLONIZATION 

One question that repeatedly arises is the potential for natural recolonization 

and, thus, avoidance of the cost of planting. The ability of seagrass to recolonize a 

site is very difficult to predict. Rapid recolonization by Z. marina has been observed 

in North Carolina (Kenworthy et al. 1980, Fonseca et al. 1990) and British Columbia 

(Harrison 1987), as has H. wrightii in the Florida Keys (Thayer et al. 1994) and 

Halophila spp. (Kenworthy 1992). Annual populations of 2. marina in Nova Scotia, 

the Gulf of California, and San Francisco Bay require seeding for year-to-year persistence (in fact, planting of vegetative stock using the techniques designed to capitalize on persistent vegetative growth is wholly inappropriate for these annual populations; Fredette et al. 1985). However, it has been our observation that seedling 

recruitment success in some seagrasses (e.g., 2. marina and ?: testudinum) have some 

years with extraordinary seed and seedling production. In the interim, seedling success appears to be minimal. Of course this observation could be confounded by 

grazing, sediment disturbance, etc., and seed production and seedling germination 

could exhibit little interannual variation. However, we do know that seedling 

recruitment to unvegetated areas varies with current regime; high current areas can 

have very low- to nonexistent seedling recruitment while relatively quiescent areas 

have heavy seed sets (Fonseca and Kenworthy 1987). Thus, there is evidence to sug- 
-- 

Chapter 2: Planning 83 

gest that site conditions alone can influence recolonization potential (Orth et al. 

1994). 

Recolonization can also occur vegetatively (rhizome extension) frorri any adjacent seagrass. The proximity of plants and the geometry of the open area combine 

to produce variable recovery scenarios that are currently unquantified. However, 

plants close to a small (several meters wide) open area will, in the absence of seeding 

or fragment colonization (sensu Cambridge et al. 1983), colonize that area more 

rapidly than a larger area, a process very much like that described for patches opened 

in coral reefs and rocky intertidal ecosystems (Connell and Keough 1985). Bioturbation can arrest recovery of open areas (see "Bioturbation" section, above). Therefore, natural recolonization of even small-to-moderately-sized open areas can potentially be arrested, but conversely may be stimulated by the use of bioturbation exclusion devices. It is critical though, that the reason for lack of recolonization be determined. Propagule limitation and inappropriate environmental conditions (i.e., periodic exposure at low tide) can yield similar results: no coverage. We conclude that 

natural recolonization is almost always such a chance occurrence that is strongly 

iduenced by disturbance events, that management practices should not, in the 

absence of some pilot data (e.g., monitoring of a site with planting held in abeyance 

or prior local quantitative observations of recolonization on similar sites), rely on natural recolonization to restore coverage. 

When considering the nutrient requirements of seagrass transplants there are 

three important site-specific questions that require attention. First, are there sufficient nutrients to support the growth and reproduction of transplants? Second, are 

nutrients present in excess of what the seagrasses can utilize, thereby available to stimulate epiphytes, phytoplankton, and macroalgal growth? Finally, are nutrient concentrations toxic to the plants? Recent evidence suggests that NO, may be toxic to 

some seagrass species (Burkholder et al. 1992). Uptake by the plants of this form of 

nitrogen apparently cannot be controlled, possibly leading to a loss of flexural stiffness which makes the plants lay over (leading to the same problems encountered by 

E Short with Nereis bioturbation). In general though, there is very little additional 

information suggesting that any of the major macronutrients (N, P, K) occur in high 

enough concentration to negatively affect seagrasses. This also includes a consideration of organic herbicides in surface and ground waters, which do appear to have a 

negative effect on seagrasses in concentrations observed in the field (Schwarzschild 

et al. 1994). 
-.- 

84 Guidelines for the Conservation and Restoration of Seagrasses 

There is a large body of evidence indicating that mature, well established seagrass beds can be nutrient limited under certain conditions, despite large reservoirs 

of nutrients in the sediments (Short and McRoy 1984, Dennison et al. 1987, Short 

1987). These conditions include periods of time when optimum temperature and 

light regimes coincide to allow very high rates of primary production by the seagrasses (Perez et al. 1991). During these periods seagrasses extract nutrients from the 

available reservoirs faster than they can be regenerated by biogeochemical processes, 

eventually exhausting their resources (Short et al. 1985). The strongest and most consistent evidence for nutrient limitation has been demonstrated for seagrasses growing 

on sediments with sufficient amounts of biogenically derived carbonate to tightly 

adsorb phosphorus (Powell et al. 1989, Short et al.1990, Perez et al. 1991), although 

they may also be limited by phosphorus on siliceous sediments (Murray et al. 1992). 

The largest reservoir of nutrients available for seagrasses are the sediments 

(Kenworthy et al. 1982, Short 1987, Fourqurean et al. l992a). With the exception of 

one genus, Phyllospadix, all seagrasses grow rooted in soft sediments. Results from a 

wide range of studies, including comparisons of porewater and water column nutrient concentrations, sediment organic content, functional anatomy, and physiological 

ecology, all suggest that seagrasses can derive their nutrition fiom both the sediments 

and the water column (for a review, see Short 1987). However, because of relatively higher concentrations of dissolved inorganic and organic nutrients in the interstitial water, seagrasses obtain most of their macronutrients fiom the sediments. 

Fertilization experiments, which have added nutrients to the sediments, confirmed 

this for inorganic nitrogen and phosphorus with several North American species 

including 2. marina, H. wrightii, S.jlijorme, T testudinum, and R. maritima (Orth 1977, 

Orth and Moore 1982, Short 1987, Powell et. al. 1989, Short et al. 1990, Murray et 

al. 1992), as well as for other species such as Cymodocea nodosa (Perez et al. 1991) and 

Heteroxostera tasmanica (Bulthuis and Woelkerling 1981). For Phyllospadix spp. most, 

if not all, of their nutritional requirements must be met by water column constituents. Because of very low nutrient concentrations in the water column, 

Phyllospadix species depend on the flux of nutrients generated by water movement 

and may be nutrient limited more frequently than other seagrasses (but see Koch 

1993). 

The nutrient requirements of some genera have received minor attention. Very 

little is known about the nutritional requirements of the three Halophila species living in the southeastern United States and Caribbean region. All three, H. decipiens, 

H. engelmanni, and H. johnsonni, grow on soft sediments, but the roots only penetrate 

a few centimeters into the substrate. Because rooting depths are much shallower than 

any of the other species, reduced access to the larger sediment reservoir may result in 
-.- 

Chapter 2: Planning * 85 

nutrient limitation. Likewise, Halophila hawaiiana, a seagrass endemic to the Hawaiian 

Islands, and Halophila ovalis, another species common in the Pacific territories, have a 

morphology and rooting depth similar to the other three Halophila species and 

should also have limited access to the sediment nutrient reservoir. 

Sediment reservoirs may also become depleted for species which depend on the 

substrate for their nutrition. This occurs when regeneration rates cannot keep up 

with plant demands, leading to nutrient limitation (Short 1983). Since established 

beds of clonally integrated plants can exhibit nutrient limitation, it is expected that 

young, independently (i-e., not physiologically integrated with a larger clonal unit) 

developing shoots of transplanted seagrasses can experience more severe limitation. 

Young, transplanted shoots have immature root systems, and support by translocation 

of nutrients &om neighboring plants in the clone may be interrupted if (when) the 

rhizome if broken during transplanting. This is exacerbated by the fact that the rhizosphere is usually disturbed during planting. Disturbance may be more severe with 

bare root planting techniques than if cores are utilized. Cores usually retain the sediments intact so that the substrate is planted together with the seagrasses, minimizing 

disturbance to the biogeochemical recycling processes. Considering the previous 

discussion and a very large body of evidence indicating that seagrasses are nutrient 

limited, we expect that the survival and growth of seagrass transplants can be 

improved by addition of nitrogen and phosphorus to sediments (Kenworthy and 

Fonseca 1992). 

Despite the evidence suggesting that seagrasses can be nutrient limited, the few 

studies examining nutrient fertilization of seagrass transplants have demonstrated 

inconsistent results (Orth and Moore 1982, Kenworthy and Fonseca 1992). Reasons 

for this variation include the possibility that the delivery of nitrogen and phosphorus is altered by the presence of flooded, anaerobic sediments. Most commercial fertilizers were developed for terrestrial sediments with a much smaller h-action ofwater 

to solubilize the fertilizer in proportion to a very large fiaction of soil surface to 

adsorb the inorganic ions as they are released. Granulated fertilizers leach nutrients 

rapidly in flooded soils, possibly much faster than can be adsorbed or utilized by the 

plants. Granulated fertilizers are also difficult to deploy in a flooded sediment without a means of containing the granules. Slow release fertilizers show the most prornise, although past evidence has shown variable release rate characteristics with fertilizers containing both nitrogen and phosphorus (Kenworthy and Fonseca 1992). 

Unfortunately, many studies using the slow release forms in field and greenhouse 

experiments did not directly test the release characteristics of the fertilizers nor were 

many of these experiments done on transplants (Pulich 1985, Short et al. 1990, 

Erfiemeijer et al.1994). The majority of the studies were done with established or 
86 Guidelines for the Conservation and Restoration of Seagrasses 

patchy seagrass beds which may not be indicative of the response of transplants. Slow 

release forms of inorganic and urea nitrogen (38 percent N) and phosphorus (41 percent P), which are encapsulated separately, seem to perform more consistently and 

show some promise (eg, OsmocoteTM). Slow release forms are more appealing 

because they are designed to deliver nutrients over an extended period of time in a 

steady dose during the most important and vulnerable time for developing transplants. Research has demonstrated the utility of slow release forms with the delivery of nitrogen and phosphorus in agar-nutrient mixtures (Perez et al. 1991, Murray 

et al. 1992) and improved forms of encapsulated commercial fertilizers (Fred Short, 

Jackson Estuarine Lab., Durham, NH, pers. com.). These studies have suggested that 

slow release forms will stimulate the growth and reproduction of seagrasses as well as 

the nutrient content of their tissue, which is a strong indication that the plants are 

nutrient limited and utilizing the supplemental nutrients provided by the fertilizers 

(Fourqurean et al. 1992b). 

Originally, Kenworthy and Fonseca (1992) thought that by encapsulating the 

nitrogen and phosphorus separately, problems originally encountered with the lack 

of phosphorus release would be overcome. Subsequent work (Fonseca et al. 1994) 

has shown that even phosphorus alone does not always release on schedule although 

nitrogen pellets appear to follow manufacturers' specifications. The point here is that 

fertilizer additions have not always performed as anticipated based on terrestrial 

applications. 

Kenworthy and Fonseca (1992) and Fonseca (1994) recommend that no reduction in planting effort should be enacted in anticipation of fertilizer benefits. However, they also note that no negative effects have been reported meaning fertilizer use 

is either neutral (considering the small additional cost per planting) or positive (accelerating new shoot formation). When employed, fertilizers should be added to the 

sediments at the time of planting and during the growing season of the particular 

species. If peat pot methods are used, a measured dose of fertilizer can be placed in 

the pot prior to installing the seagrass plug. If a coring technique is used, the fertilizer can be installed into the hole where the plants are to be placed after extracting 

the plug of sediment, or placed directly into the core that is to be planted (see 

"Methods" section in Chapter 3). In both cases the fertilizer may be installed into 

some type of porous container such as tissue paper (Bulthuis and Woelkerling 1981) 

or fine mesh screen (Kenworthy and Fonseca 1992). This helps avoid the problem 

experienced by Bulthuis et al. (1992) where bioturbation redistributed buried fertilizers onto the sediment surface, essentially terminating their effectiveness as a source 

of nutrition for the seagrasses. Preferably, the material containing the fertilizer should 

be biodegradable. Pre-weighed fertilizer can be packaged inside small paper envel- 
Chapter 2: Planning 87 

opes, although these can disintegrate in water during handling. The envelope is stapled shut and installed with the planting units. Recommended application rates are 

between 5 and 10 g of balanced N-P slow release fertilizer (including the capsule) 

per planting unit (Kenworthy and Fonseca 1992). I 

For best results it may be necessary to reapply fertilizer within the prescribed 

release period, as long as the time is within the window of the species' growing season. The best way to determine the need for reapplication is to set aside a representative sample of fertilizer packets as controls and periodically recover replicate samples to determine the residual fertilizer, and thus, the release rate (see Kenworthy and 

Fonseca 1992); or simply re-fertilize in accordance with the release schedule given 

for the fertilizer at ambient temperatures. 

Nutrients may also be added with commercially available fertilizer stakes which 

can be purchased at garden and hardware stores (Williams 1990). Stakes are easier to 

work with because the fertilizer is compacted into one single unit rather than several pellets, eliminating the need for a container. These stakes are another form of slow 

release but their specific delivery-rate characteristics in marine and estuarine sediments are unknown. When planting in terrigenous sediments both nitrogen and 

phosphorus fertilizers should be applied. In pure carbonate sediments it has appeared 

as though fertilization only with phosphorus (thereby avoiding the stimulation of any 

other macrophytes or microalgae by added nitrogen) was needed. However, Duarte 

et al. (1995) has shown that iron limitation may play an important role in Thalassia 

and Syringodium growth in carbonate sediments. We speculate that use of iron staples 

as anchors in planting, as recommended later, may inadvertently contribute to overcoming that limitation. 

An important consideration before planting is the status of water column nutrients at a restoration or mitigation site. An excess of nutrients (&om outside the planting, not &om fertilizers installed in the sediment as part of the planting process) can 

lead to the overabundance of chlorophyll in the water column and, eventually, to 

severe light limitation for the seagrasses (Twilley et al. 1985, Dennison et al 1993). 

Excess nutrients can also lead to the growth of nuisance macroalgae which compete 

with seagrasses for space and light. Blooms of macroalgae may actually overgrow seagrasses and smother them (Harlin and Thorne-Miller 1981, Walker and McComb 

1992, Short and Burdick in press), even the large climax species like T testudinum 

(Tomasko and Lapointe 1991). The smaller Halophila species, seedlings of larger 

species, and young developing transplants of all seagrasses are especially vulnerable to 

overgrowth and displacement by macroalgae. 
88 Guidelines for the Conservation and Restoration of Seagrasses 

Nutrient enrichment in the water column and the general degradation of water 

quality are also responsible for stimulating the overabundance of epiphytic algae 

which grow on seagrass leaves (Sand Jensen and Borum 1983, Borum 1985, 

Silberstein et al 1986). Excessive amounts of epiphytes will shade out light and 

diminish the productivity and growth of seagrasses (Bulthuis and Woelkerling 1983, 

Wetzel and Neckles 1986, Neckles et al. 1993). Young, newly-established transplants 

adjusting to the shock of planting are particularly vulnerable to overgrowth of epiphytes; therefore, the nutrient status of the water column is an important consideration when selecting a planting site. 

Generally, it is not practical to measure water column nutrients at the precision 

and kequency necessary to determine if there is a statistically significant excess present. Because inorganic nutrients in the water column are utilized and turned over 

so fast, an excess may not be detected by sampling the dissolved forms of these nutrients in the water column (Tomasko and Lapointe 1991). This is especially pertinent 

for inorganic phosphorus in subtropical-tropical systems of south Florida, Puerto 

Rico, the Virgin Islands and possibly the Pacific territories (although effects of volcanic soils on the sediment chemistry and seagrass growth is poorly understood) 

where carbonate sediments are the primary substrate (Fourqurean et al. 1992a). 

Alternatively, much more practical indicators of nutrient enrichment or limitation are the organisms themselves. There are three reliable indicators that can be used 

as semi-quantitative descriptors of the site-specific nutrient regime. The first is the 

amount of phytoplankton chlorophyll which reflects the concentration of nutrients 

in the water column (Smith et al. 1981,Valiela et al. 1990). Sustained water column 

chlorophyll concentrations in excess of 10-15 mg I-' are usually indicative of nutrient enrichment and a general degradation of water quality (Batiuk et al. 1992, 

Dennison et al. 1993,Table 1.2). At these concentrations chlorophyll can make a significant contribution to water column light attenuation (McPherson and Miller 

1987, Gallegos 1994) and be detrimental to seagrass transplants. 

If long-term data for dissolved inorganic nitrogen and phosphorus are available 

for potential planting sites located in the mid-Atlantic, Northeast, Pacific West Coast 

and Pacific Northwest, then the nutrient criteria provided in Dennison et al. (1993) 

can be used to accept or reject a location. These criteria would apply mainly to sites 

with terrigenous sediments and not with biogenically derived carbonates. Dennison 

et al. (1993) showed that polyhaline regions of the Chesapeake Bay supported 2. 

marina where dissolved inorganic nitrogen and phosphorus were < 0.10 and < 0.67 

uM, respectively. These are medan values derived &om data obtained over several 

years, but only for the growing season of the plants (March to November). At these 
Chapter 2: Planning 89 -. 

same locations median values for chlorophyll a were < 15 ug I-'. Keep in mind that 

these criteria were developed using established seagrass beds that persisted over multiple growing seasons and define upper threshold values. 

The success of newly developing plantings could potentially be improved by 

avoiding sites with similar maximum concentrations as those described by Dennison 

et al. (1993). We suggest that, as a first guess, locations with concentration values -25 

percent lower than the predicted maximum constitute a reasonable starting point to 

introduce planting. These criteria (Table 1.2) are probably reasonable for planting 

sites in the northern Gulf of Mexico andTexas, but are probably much too high for 

comparatively oligotrophic conditions of southeast Florida, Florida Bay, Florida Keys, 

Puerto Rico, the Virgin Islands, and the Pacific Territories. In these oligotrophic 

waters with carbonate sediments, larger amounts of nitrogen and phosphorus are 

normally tied up in plant biomass and sediments. Water column concentrations of 

nitrogen and phosphorus in the ranges reported by Dennison et al. (1993) would 

result in the relaxation of nutrient limitation for phytoplankton and benthic macroalgae, likely leading to eutrophication (Tomasko and Lapointe 1991). Unfortunately, 

there are no comprehensive studies that define nutrient criteria as specific as 

Dennison et al. (1993) for the aforementioned carbonate environments. We recommend that inorganic phosphorus criteria for suitable planting sites in areas of carbonate sediments be established at concentrations an order of magnitude less than 

reported by Dennison et al. (1993) and Tomasko and Lapointe (1991). 

A second indicator of nutrient effects is the tissue Redfield Ratio or C-N-P 

content of the seagrasses themselves (Atkinson and Smith 1983, Short 1987, Duarte 

1990, Fourqurean et al. 1992b, Perez et al. 19%). If seagrasses are present in the vicinity of a planting site, evaluation of their tissue nutrient composition can be used to 

determine the necessity for fertilization or provide some indication that there are 

excess nutrients. In nutrient enriched sites seagrasses have higher than average tissue 

concentrations for the nutrient occurring in extra abundance relative to the composition of plants at sites isolated from enrichment (controls). Deviation in the tissue 

concentration of a particular element can provide a clue as to which nutrient is either 

limiting or in excess. Duarte (1990) suggested that seagrass leaves with median nutrient levels of <l.8 percent N and <0.2 percent P are strongly nutrient limited. If seagrasses in the area at or near the planting site display similar levels, fertilization of 

transplants could be helphl. Likewise, deviations upwards from these values would 

indicate either adequate nutrients or, possibly, nutrient enrichment at the site. The 

advantage of using the plant tissue is that the seagrasses act as a barometer for continuous longer-term monitoring of their environment and reveal the conditions 

without sampling error (Dennison et al. 1993). 
90 Guidelinesfor the Conservation and Restoration of Seagrasses 

A third indicator of nutrient enrichment is the presence of large amounts of 

macroalgae, especially the faster growing species of green algae like Ulva spp. or 

Enteromorpha spp.These non-vascular plants utilize nutrients at a much faster rate and 

have higher turnover than seagrasses, allowing them to out-compete vascular plants 

for essential nutrients (Harlin and Thorne-Miller 1981, Lapointe and Clark 1992, 

Walker and McComb 1992). There are no quantitative criteria defining a threshold 

amount of macroalgae that is detrimental to seagrasses, but if quadrat sampling indicates macroalgal cover in excess of 50 percent of the bottom it is likely that seagrasses 

will be negatively impacted. 

LIGHT REQUIREMENTS FOR TRANSPLANTING 

All seagrasses in the United States with the exception of one genus, Phyllospadix, grow in flooded and chronically anoxic sediments. This section focuses on those 

seagrasses in unconsolidated sediments given to anoxia. Light requirements for the 

intertidal Phyllospadix spp. are unknown, but their distribution is likely more tied to 

emersion limitations (see "Emersion Effects" above). 

To survive and grow in anaerobic sediments, seagrasses require photosynthetically-produced 0, to support the aerobic metabolism of non-photosynthetic root 

and rhizome tissues and the dark respiration of leaves (Smith et al. 1988b). In the 

absence of available 0,, less efficient anaerobic fermentation leads to a demand for 

carbohydrate reserves which may be provided by stored material in the rhizome or 

translocated &om healthy adjoining shoots in the clone (Harrison 1978, Dawes et al. 

1987, Libes and Boudouresque 1987,Tomasko and Dawes 1989). Transplanting may 

disrupt the physiological integration between rhizome and adjoining shoots, limiting 

the ability of healthy shoots to support stressed short shoots (ramets), depending on 

the amount of physiological integration among shoots in the first place (a phenomenon that is now only poorly understood). In mature, well established meadows, 

neighboring shoots attached by the same rhizome may contribute to the survival and 

growth of other shoots by translocating carbon and nutrients which can be utilized 

during periods of time when resources are depleted. This relationship can be especially critical for young, developing plants that have not yet produced enough photosynthetic tissue to be independent of clonal support. Young developing shoots are 

very important when transplanting because they are the basis for survival and expansion of the planting. Therefore, if young shoots are physiologically dependent on 

adjacent, older shoots, the light requirements of transplanted seagrasses require special attention because they are likely to be higher than the requirements determined 

&om established meadows. Moreover, there are cases in terrestrial systems where 
- 

Chapter 2: Planning 91 

young ramets are sacrificed by older ramets should those young ones venture into 

physiologically unsuitable areas. Even if this were the case in seagrass, most planting 

stock consists of fi-agments of the root-shoot-rhizome complex and the integration 

of shoots is broken in any event. Therefore, even if young shoots were to be sacrificed by older ones, the feedback mechanism would not exist when rhizomes are 

fiagrnented during planting, therefore light requirements should still be higher for 

the young shoots. 

When transplanting with mature shoots, either completely removed &om the 

sediment (bare root technique) or left intact in a sediment core (plug), the rhizomes 

are severed. Presumably, the plug method would be less stresshl because of minimal 

disturbance to the rhizosphere. However, in both cases transplant survival and new 

growth depend on the formation of vegetatively reproduced shoots which may have 

less support available than shoots growing in a dense, clonally-integrated meadow. 

Seagrass minimum light requirements have been determined by three approaches: (1) photosynthetic measurements, (2) whole plant carbon balance models, and (3) 

correspondence (correlation analysis) between light availability and maximum depth 

of seagrass growth. Photosynthetic measurements alone are inadequate and have severely underestimated seagrass light requirements (Drew 1979). Carbon balance 

models have improved our understanding of light requirements because they account 

for the additional carbon requirements of non-photosynthetic tissue (Zimmerman et 

al. 1989, Fourqurean and Zieman 1991, Zirnrnermen et al. 1994). Correspondence 

analysis between some statistical average light level (mean or median) and the maximum depth to which seagrasses grow uses a long term response by the plants to 

record the requirement (Dennison 1987, Duarte 1991, Kenworthy and Haunert 

1991, Dennison et al. 1993, Onuf 1994). The third approach is particularly useful 

because it depends on the plants interacting with their environment to reveal their 

actual response, which has usually indicated a higher light requirement than either of 

the first two approaches (Kenworthy and Haunert 1991). Even though a correspondence analysis seems more appropriate to estimate light requirements, it still 

must be adjusted upward for estimating transplanting requirements. The deep edges 

of the beds used as the barometer in the correlation between light and depth of 

growth are formed &om well-established stands and are probably maintained by support &om adjoining shoots. Moreover, the level of resolution in a correspondence 

analysis does not contain enough information about the possible influence of shortterm departures fi-om average light levels (Zimmerman et al. 1994). The survival of 

individual shoots in a transplanting unit is thus potentially vulnerable to short term 

fluctuations in light levels whereas mature beds are buffeted by reserves within the 

clone. For these reasons we recommend that the light environment necessary for the 
92 * Guidelines for the Conservation and Restoration of Seagrasses 

initial survival and growth of transplanted seagrasses exceeds minimum requirements 

for established meadows. 

Another important consideration is the fact that light requirements are not the 

same for all species of seagrass. Large differences occur between genera that are based 

on growth form of individual shoots, clonal architecture, and physiology. In temperate regions, both in the Northeast and on the West Coast, the dominant seagrass, Z. 

marina, has a much different growth architecture than any of the five species found 

in the southeastern United States. Initially, on Z. marina, vegetatively reproduced 

short shoots are arranged morphologically and physiologically close to the parent 

shoot fiom which they are formed. Tbs relationship is only temporary because both 

the parent shoot and its offspring grow away fiom each other quite rapidly. 

Horizontal rhizome growth separates the mature plant fiom the younger shoot and 

the metabolic activity of the rhizome diminishes rapidly as the older nodes age, severing the physiological coupling between ramets in the clone (Kraemer and Alberte 

1993). R. maritima, Z. noltii, and Z. japonica all have a growth architecture and morphology similar to 2. marina and should be as sensitive to light-limiting conditions 

immediately following planting. 

In the southeastern ecoregion, the potential for integrating shoots is greater for 

the three larger and most common subtropical genera, ?: testudinum, S.Jil$orme, and 

H. wrightii. For these species horizontal internode distance is deterministic and adjoining short shoots remain the same distance &om one another, usually throughout 

their entire life span. For all these species, adjoining shoots in a clone have far greater potential for sharing resources and supporting one another than is available for Z. 

marina. In Zostera, horizontal rhizome growth and new shoot formation are not as 

closely coupled and, therefore, clonal integration does not likely make as great a contribution to survival. The individual Zostera shoot in the initial stages of planting is 

independent of the clone sooner and may be more vulnerable to physiological stress 

than either of the three larger subtropical species. 

The fourth tropical genus and the smallest of all seagrasses, Halophila, appears to 

have the lowest light requirement. Halophila decipiens is usually found growing in the 

deepest and most turbid water and is almost never observed in the canopy of the larger species; these are attributes that make its detection by conventional remote-sensing methods unlikely (Dobson et al. 1995). Because it has thin leaves and relatively 

lower root rhizome biomass it was once believed to have been better equipped to 

survive in low light environments (Josselyn et al. 1986). But this conclusion was 

drawn without full consideration of the life history of the plants and the seasonal 

variation in light. Many coastal environments have regular seasonal fluctuations in 
Chapter 2: Planning 93 

light which include periods when light is well above and well below the average. 

Part of the explanation for growing in low light environments is that H. decipiens 

reproduces by seed and avoids the stress of the lowest light periods (usually winter) 

in a temporary seed bank (Kenworthy 1992). Halophila engelmanni has a similar life 

history strategy, but unlike H. decipiens, this species may be found beneath the canopy 

of the larger seagrasses. Very little is known about the life history or physiology of 

H. johnsonii, however, it does grow in high light environments in the intertidal zone 

(Kenworthy 1992). Also, little is known about how these three Halophila species 

would respond to transplanting. However, we have successfully transplanted H. decipiens among existing beds of the same species in 15 m of water on St. Croix, USVI, 

but we are unaware of any other planting with this genera. 

The ability to avoid the stress of low light periods by surviving in a seed bank may 

be important for the persistence of other tropical genera (McMillan and Phillips 

1979) and temperate species Zostera marina, Z. noltii, and Ruppia maritima as well 

(Harrison 1982, Orth and Moore 1983, Hootsmans et al. 1987). Like H. decipiens, 

some temperate species may have annual life history strategies completely dependent 

on seed reproduction for their survival (Keddy and Patriquin 1978, McMillan 1983). 

In these annual populations the plants do not experience a large portion of the seasonal light regime. Even though correspondence analysis has demonstrated higher 

light requirements for seagrasses in general, the averaging processes may include periods of low light that are not actually critical to the survival of the plants. In tropical, subtropical, and temperate regions seagrasses reduce their growth rates significantly during the colder temperatures in winter, and therefore, the light regime during this period may be much less important to the plants. 

Light requirements should be determined based on the time period when the 

plants are responding to solar insolation and not when metabolism is slowed or when 

the population is residing in the sediments as seeds. This suggests that seagrass minimum light requirements determined &om correspondence analysis (Dennison 1987, 

Duarte 1991) exceed the frequently cited value of 10 percent surface light. Recent 

evidence suggests that more realistic values for H. wrightii and S.$lforme are in excess 

of 15-20 percent (Kenworthy 1992, Kenworthy and Fonseca l996), and for planting 

may even be higher (-25 percent). Moreover, light requirements of an individual 

species may vary as a function of the optical water quality indicating a very site specific component (Kenworthy 1992, Gallegos 1994, Gallegos and Kenworthy 1996). 

Pre-restoration monitoring and site selection criteria should incorporate elements of the preceding discussion to improve the likelihood of planting success. 

Most sites d not have long-term data bases &om which to characterize the light 
-- 

94 Guidelinesfor the Conservation and Restoration of Seagrasses 

environment. If they do, then only data collected during the growing season should 

be used to calculate the appropriate statistic for a light level parameter. Regional 

growing seasons (see below: Planting Contingencies by Ecological Region) can be 

determined &om the literature and planting should occur as early as possible in the 

season to take advantage of the optimum light regime. 

Without light data taken over a growing season, the next best parameter is to 

utilize the maximum depth to which seagrasses grow in seagrass beds located in the 

area around the planting site. These reference beds can only be used to establish a 

maximum depth for transplanting rather than a specific light level. The reference site 

should have as similar a fetch (unobstructed over-water distance over which the wind 

blows), sediment composition, and tidal velocities as the planting site to assure that 

suspended sediments and light attenuation by turbidity at the two sites will be similar. Also, there should be as little difference as possible in freshwater discharge and 

water column chlorophyll concentration so that there are no gross differences in 

water color which could mean a different level of light attenuation. The reader 

should keep in mind that only light recordings performed at high 6-equency during 

growing seasons can yield prediction strength. 

The depth to which local seagrasses grow would represent the minimum for an 

established bed and would likely overestimate the depth that transplants could survive. Beers Law describes the decline of photosynthetically-active radiation (PAR: 

the wavelengths of the light spectrum that activate chlorophyll) with depth in the 

water column by the following equation: 

where: 

I. = Incident light just beneath the surface 

Iz = Percent incident light at depth 

e = base e 

-k = diffuse light attenuation coefficient 

z = water depth 

Therefore, we can estimate the percent light reaching a predetermined depth. If 

seagrasses in the area grow to a depth of 2.0 m and the average diffuse light attenuation coefficient is 0.75 (similar to the Indian River Lagoon; Kenworthy 1992), this 

indicates seagrasses require 22 percent surface light at their maximum depth of 

growth. At this location the light reaching shallower depths of 1.75 or 1.55 m is 26 

and 32 percent, respectively. Transplanting at these two shallower depths would 
- 

Chapter 2: Planning 95 

increase the relative amount of light available by 18 and 45 percent, respectively (+4 

and 10 percent, respectively, of the amount of light available at the lower limit). 

Because the decay of light in water is exponential in the upper portion of the water 

column, a small change in depth yields a proportionally larger change in percent surface light reaching that depth. Reducing the depth of planting by 12.5 percent 

increases the amount of light by 18 percent whereas a reduction in depth by 25 percent adds 45 percent more light. This also works in the other direction whereby 

planting at slightly deeper depth would yield considerably less light. Paying close 

attention to depth and its relationship to available light could make the difference 

between success and failure of a planting. 

In some cases planting sites may be isolated &om established reference beds, especially in large-scale restoration efforts where entire lagoons or large portions of 

estuaries are involved. In these instances reference sites with established seagrass beds 

must be carehlly matched with the restoration site for sediment composition, fetch, 

and tidal velocities. Short-term between site-paired comparisons of optical conditions can be made in lieu of a direct correspondence analysis or the availability of any 

long-term water quality data in order to grossly infer the lower depth limit. A paired 

comparison between sites would involve the acquisition of either light or water quality data over the same time period and under the same environmental conditions at 

each site (e.g., no localized storms affecting one site and not the other). Measuring 

equipment and methods must be intercalibrated to avoid detecting differences that 

cannot attributed to the sites. 

One of the best parameters for inter-site comparison is the diffuse attenuation 

coefficient for photosynthetically active radiation (k, PAR). If available, this parameter can be used to calculate percent surface light reaching a predetermined depth 

in the equation for Beers Law (p. 94) so that light available at depth can be used to 

help select planting depth. If at all possible, the technique for estimating k,PAR 

should utilize quantum sensors instead of a Secchi disk (Kenworthy 1992). A Secchi 

disk severely underestimates light attenuation in estuarine water where there are dissolved organics (influencing color). Two types of quantum sensors are available, the 

cosine-corrected flat type sensor that measures downwelling PAR and the spherical 

quantum sensor that measures light fiom all directions (scalar PAR). The spherical 

quantum sensor is the preferred equipment although under most conditions the two 

different sensors will yield similar attenuation coefficients. 

In a short-term paired-site comparison the sensors can be deployed in either a 

continuous or profiling configuration. In a continuous mode, at each site where one 
.-- 

96 . Guidelinesfor the Conservation and Restoration of Seagrasses 

intends to plant seagrass, two sensors should be placed in the water column at two 

fixed depths at least 20-50 cm apart and PAR recorded continuously using a data logger (Zimmerman et al. 1994). A calculation of k,PAR at each site over the same time 

period should be made. Attenuation coefficients should be calculated for time periods between 10 a.m. and 2 p.m. to avoid the errors associated with solar angle and 

path length (Miller and McPherson 1995). If the equipment is available, this method 

is appropriate for small sites, but for larger sites, where intra-site variation may be a 

problem, a profiling method is necessary. This method uses two sensors deployed at 

fixed depths &om a mobile vessel so that more stations can be sampled to examine 

spatial variation. The same calculation algorithm is used as described above, however, for inter-site comparison one must be certain that profiles are obtained at the same 

times for accurate comparisons. Ideally, both the continuous recording and the profiling methods should use a base station with a sensor measuring incident radiation 

to correct for errors &om local cloud conditions (Morris and Tomasko 1993). 

Another method to compare sites is to use a properly calibrated optical water 

quality model (Morris and Tomasko 1993, Gallegos 1994, Gallegos and Kenworthy 

1996). This method estimates light attenuation by summing the additive properties 

of scattering and absorption due to three commonly measured water quality constituents: turbidity (NTU), color (Pt-Co units), and chlorophyll (chl in mg 1-').This 

kind of modeling approach is convenient because once the calibration is completed 

the model uses the water quality constituents that are inherent optical properties and 

not subject to errors of solar angle (i.e., time of day). Thus, measurements can be 

taken at any time of day and the information tells you what particular water quality 

constituent is having the greatest effect on light attenuation. Model calibration requires a minimum of 30 profiles of these 3 constituents and light attenuation for a 

water body. Calibrations have been successfully completed in the Chesapeake Bay 

region (Gallegos 1994) and the Indian River Lagoon (Gallegos and Kenworthy 

1996). 

SALINITY AND TEMPERATURE REQUIREMENTS 

FOR TRANSPLANTING 

Salinity and temperature tolerances of seagrass species must be considered when 

selecting off-site planting locations. Seagrasses exhibit a wide range of tolerances to 

salinity but the effect of periodicity and duration of extremes in salinity on seagrass 

survival are poorly documented (see review by Zieman and Zieman 1989). Matching salinity regimes between the planting site and donor site is therefore strongly recommended. Temperature regimes should be similar as well. Temperature extremes 
-- 

Chapter 2: Planning * 97 

may be problematic if a planting site has been constructed with restricted circulation 

allowing water temperatures to rise above levels found in natural beds. 

Known temperature and salinity tolerances and optimum ranges for seagrasses 

growing in the continental United States are presented in Table 2.1. It is important 

to realize that the stress effects of these variables may be synergistic, but the effects of 

any such synergism on planting survival are poorly known in nature and likely vary 

widely depending on circulation, tidal zone, and geographic location within a 

species' distribution. 

As seen in the data presented in Table 2.1, the tropical seagrasses are more 

stenothermic than temperate seagrass species. Z. marina has the widest temperature 

range (-6.0 to 40.5' C), and is found growing in a variety of temperate to sub-arctic habitats on both the east and west coasts of the United States. The range of 

reported optimal temperatures for this species is also greater than that reported for 

any other species (Bieble and McRoy 1971, Phillips 1984,Thayer et al. 1984, Evans 

et al. 1986, Bulthuis 1987). Data concerning the introduced species, Z. japonica, is less 

readily available, but its distribution suggests that its temperature tolerances are close 

to, if not greater than, that of Z. marina (Baldwin and Lawon 1994). R. maritima and 

H. wrightii also have broad temperature tolerances as witnessed by their distribution 

patterns along the east Coast. Both are wide ranging species, often found in estuarine conditions where temperature conditions vary greatly with water depth, circulation patterns and exposure to periods of desiccation. While these species are often 

found growing in mixed beds with Z. marina, they have higher optimum temperatures (Evans et al. 1986, Orth and Nowak 1990, Zieman 1982a, Zieman and Zieman 

1989). 

Seagrasses growing in the more stenothermal subtropical and tropical marine 

conditions have narrower temperature tolerances than the estuarine species listed 

above (eg., ?: testudinum, S.Jil@rme, Halophila spp.). Information regarding members 

of the Phyllospadix genus is sparse. The distributional patterns of the three United 

States representatives of this genus suggest that they have similar temperature ranges, 

with a low end temperature of 5 and a maximum around 25' C (Drysdale and 

Barbour 1975). Tropical seagrass species are the least temperature tolerant, with maximum ranges of 15 degrees and optimum temperatures close to 30' C (McMilllan 

and Phillips 1979, McMillan 1984, Zieman 1982a, Zieman and Zieman 1989). 

Salinity tolerances of seagrasses follow a similar pattern with R. maritima and 2. 

marina having the broadest tolerances.The coastal and marine species, which live in 

less euryhahne conditions, are more sensitive to changes in salinity. As with other 
98 * Guidelines for the Conservation and Restoration of Seagrasses -. 

physico-chemical requirements, comparisons of temperature and salinity with existing beds provide the best local guidance for placement of planting areas. In the 

absence of nearby vegetation, a minimum of weekly monitoring during both ebb 

and flooding tides should be conducted on a projected planting site to determine if 

values fill within those proscribed in Table 2.1. More intense sampling should be 

conducted (daily) just after several rainfill events, hopefully of differing rainfall 

amounts, to determine the response of a site to fireshwater inflow. Although the tolerance ranges are known, the effects of dosing periodicity of either salinity or temperature extremes on planting survival (or natural beds for that matter) are unknown 

to us. For want of better guidance, we suggest that persistence of borderline values 

for more than five days should be cause for concern about site suitability. 

Table 2.1.Temperature and salinity ranges of seagrass species occuring in the continental United States, 

optimal ranges are in parantheses. 

Species Temperature Range Salinity Range 

Halodule wrightii 

Halophila decipiens 

engelniannii 

johnsonii 

Phyllospadix torreyi 

scouleri 

Ruppia niaritinia 

Syringodiunt Jilgorme 

Thalassia testudinuni 

Zostera n~arina 

. japonica 

a. Baldwin and Lawon 1994 

b. Bulthuis 1987 

c. Dawes et al. 1987 

d. Dawes et al. 1989 

e. Drysdale and Barbour 1975 

f. Evans et al. 1986 

g. Mayer and Iow 1970 

h. McMiUan and Phillips 1979 

i. McMiUan 1984 

j. Phdlips 1960 

k.Thayer et al. 1984 

1. Zieman 1982a 

m. Zieman and Zieman 1989 
Chapter 2: Planning 99 

MICROPROPAGATION AND LABORATORY CULTURE 

OF SEAGRASS FOR TING 

Laboratory culture of plant fiagrnents (micropropagation) for large-scale field 

planting is an active research area (Durako and Moffler 1981, 1984, Lewis 1987, 

1990, Ailstock et al. 1991, Koch and Durako 1991, Durako et al. 1993, Bird et al. 

1994, DeLeon et al. in press.). In the future, large-scale planting may rely on laboratory-reared plants as there are many potential advantages to using this approach. 

However, there are many practical problems that must be overcome first as well as 

questions regarding the general efficacy of the approach. Below we contrast some of 

the argued benefits with what we feel are limitations to the technology. In summary, the advantages of relying on laboratory-cultured plants are as follows: 

1. Donor bed damage reduction: Reduce damage to donor bed by making small field collections and geometrically expanding the numbers of plants 

in the lab to provide planting stock; 

2. Genetic stock improvement: Improve genetic mix of stocks (avoidance 

of founder effects, see section "Pre-Project Planning Considerations," above) 

to go into the field; 

3. Disease/stress resistance: Select for disease-resistant or stress-tolerant 

strains of plants; 

4. Cost reduction: Reduce project costs through mass production of planting units; 

5. Stock availability: Maintain donor stocks to meet the sporadic demands 

of disjunct planting projects; 

6. Bioassay tool: Develop genetically consistent stocks that can be deployed 

and thus used as a bioassay standard of water quality, and potentially, planting-site suitability for subsequent restoration projects. 

Taken together, the above arguments would seem to logically place culture techniques at the forefront of the seagrass mitigation/restoration effort. However, there 

are serious questions regarding many of the proposed benefits of micropropagation. 

The disadvantagess to the above claims are as follows (response by corresponding 

number): 
-. 

1 00 Guidelines for the Conservation and Restoration of Seagrasses 

Donor bed damage reduction: Sustained injury to donor sites &om onetime impacts have been demonstrated to be an issue for only one of the -13 

North American seagrass species, Thalassia testudinum (e.g., Zieman 1976, 

Durako et al. 1992; see following section). Donor bed injury recovery can 

be rapid (Fonseca et al. 1994) especially if a minimum attempt is made to disperse the collection effort. However, some States (e.g., Florida) have placed 

restrictions on harvest of wild seagrass stock for planting projects; this appears 

to fuel the donor-bed impact argument. 

2. Genetic stock improvement: "Improvement" of genetic stocks is currently speculative. A broad knowledge of the existing genetic structure of 

seagrass populations and the factors influencing genetic stock (especially sitespecific; sensu Ruckelshaus 1994) would be requisite to form a comparative 

basis for ccimprovement," which requires stricter definition. Moreover, while 

strain selection is applicable to terrestrial crops where gene flow and population interactions are not an issue, the potential for improvement of genetic 

structure is untested in the management of wild, clonal plant communities. 

3. Disease/stress resistance: The disease/stress resistance of micropropagated plants has not yet been demonstrated, nor has the consequences of trading off natural genetic diversity for selection of, and introduction to nature, 

of a few strains designed to meet specific environmental problems. Moreover, if a bed were developed in a stressed area through selection of resistant 

stock, would such a bed become functionally equivalent to natural beds? 

Introduction of manipulated genotypes remains a significant issue in population ecology, and is many years away &om resolution. 

4. Cost reduction: While large-scale production costs would be less on a 

planting unit basis, only DeLeon et al. (in press) has, to our knowledge, considered a quantitative review of the entire planting cost using micropropagation techniques that includes the overhead and amortization of culturing 

facilities, materials, and labor. Break-even points (i.e., number of planting 

units needed) have not been determined. Moreover, culturing does not 

eliminate out-planting costs which may be similar among cultured or wildharvested planting. 

5. Stock availability: Like (4) above, we are not aware of published data on 

cost break-even points, which are strongly influenced by required fi-equency 

and magnitudes of requests for planting stock needed to support such a facility. 
-- 

Chapter 2: Planning * 101 

6. Bioassay tool: This aspect of seagrass micropropagation offers one of the 

most powerful applications of this technology Having a "standard plant," 

coupled with plant health assessment techniques such as variable fluorescence 

techniques (sensu Adam and Bate 1994) could yield rapid and consistent 

water quality and planting site suitability indices, as evidenced by Durako et 

al. (in press). 

At this time, there are only two seagrass species that have been successfidly cultured: Ruppia maritima and Halophila decipiens (M. Durako, University of North 

Carolina, Wilmington, pers. corn.), two species that have very high sexual and asexual reproduction and thus, high colonization (and likely, donor bed recovery) rates. 

The technology is not currently available to the only species for which there are 

demonstrable, long-term donor bed impacts, T testudinum. 

The choice of species is often dictated by project goals, such as the desire to 

replace in kind the seagrass species that was lost. In subtropical areas where several 

species co-occur, it is sometimes appropriate to temporarily substitute faster-covering species in order to stabilize a planting site (sensu "compressed succe~sion,~~ attributed to M. Moffler). The specific choices of available species are covered under each 

ecoregional below. In general however, the early recommendations of Addy (1 947) 

still hold where matching conditions at donor and planting sites were recommended. 

For seagrass planting projects to eventually be successfid, it is critical that they 

consider physiological requirements and life histories when selecting a planting site 

(see sections dealing with growth requirements, e.g., light, nutrients, temperature, 

salinity, above). For example, species with a slow coverage rate (i-e., T testudinum) are 

very difjticult to restore in the time fi-ame often allotted projects. It can take decades 

for a bed to re-create the dense root system, organic-rich substrate, and nutrient 

cycling capabilities of turtlegrass beds (sensu Zieman 1976). Halophila spp. have very 

different strategies. This species often colonizes disturbed areas rapidly and requires 

relatively little light to grow (Josselyn et al. 1986). Interestingly, although the spatial 

distribution of Halophila spp. indicates an ability to colonize low light environments 

relative to other seagrasses, it only has growth during times of the year when light 

levels are at their highest. This signals a potentially complex interaction between light 

and temperature in effecting Halophila distribution. An individual leaf pair of H. 
102 Guidelines for the Conservation and Restoration of Seagrasses 

Figure 2.6. Ruppia maritima in culture. Courtesy M. Durako. 

decipiens may live for only six weeks, and produce many seeds, a strategy typical of a 

species living in marginal environments. Its shallow root system, however, makes it 

vulnerable to disturbance. Ruppia maritima (widgeon grass) has a wide tolerance of 

salinities and grows in fiesh water, brackish water, or among other seagrasses in full 

strength seawater. Like Halophila, this species has a very high seed production and 

covers the bottom quickly. Finally, H. wrightii, S.fil$orme, Zostera marina and, likely, 

Z. japonica have comparatively moderate coverage rates. Little is known regarding 

coverage rates of other seagrass species in the United States, such as Phyllospadix spp., 

under planting conditions. For the subtropical species, the comparative coverage 

rates are important both for predicting recovery rates (e.g., Fonseca et al. 1987a,c, 

Lewis 1987) and choosing a fast-covering species with which to initiate planting5 

(i.e., "compressed succession": begins with shoalgrass, allow coalescence, and then 

add the slower-growing target species if it were initially different &om shoalgrass). 

For temperate areas where the pioneering species is the same as the climax species 

(i.e., begin with eelgrass and end with eelgrass), coverage rates are useful for recovery rate estimation.Thus, the different growth strategies of seagrasses implicitly define 

the anticipated performance, monitoring, planting schedule and, ultimately, fbnction 

of the restored system. 

Although some data exist to select planting stock by ecotypes (Backman 1991), 

costs of collection are also important. Collection of plants &om areas of high densi- 
Chapter 2: Planning 103 

ty, such as sandy shoals, is often more cost-effective when plants are small. Larger individual plants, such as Zostera, that are sometimes planted singly or with only a few 

in a planting unit (Davis and Short 1997), are sometimes removed more easily &om 

softer sediments. Some seagrasses, such as Halodule and Syringodium, sometimes have 

ramets extending, rootless, into the water column, and these make excellent planting 

stock without having to extract material &om the donor bed rhizosphere (Fonseca 

et al. 1987a,c, Lewis 1987). Thalassia, with its deeper rhizome system, is most easily 

collected at bed margins where the rhizome development is nearest the sediment 

surface. 

At this time virtually all planting material must be obtained &om existing, wild 

vegetative stocks. However, the collection of vegetative material &om existing beds 

is rigorously managed in many states. Collection without appropriate permits may 

result in fines. Because of the evolving nature of this field of restoration science, it is 

imperative that anyone planning seagrass planting carefilly coordinate their actions 

with state and local government. It is not uncommon to find permits required &om 

not only the federal government, but also numerous state agencies. Individual counties and municipalities too may require consultation. Because of the increasing volume of permit requests reaching permitting agencies, obtaining a permit could take 

months. Such a delay must be anticipated in order to collect plants (if approved) and 

plant at the desired time of the year. 

Once planting is permitted, wild stocks are usually used. Zostera marina, H. wrightii 

and S.jlijorme can be harvested &om wild stands with no long-term (> 1 year) impact to the donor site (Williams 1990, Fonseca et al. 1994) (Figure 2.7). However, 

unless specifically created as a donor site, repeated harvest of donor sites 

within a calendar year should not be permitted. It should also be noted that 

wild stock harvesting will cause some interim loss of habitat functions and productivity. Therefore, we recommend that harvesting impacts be composed of numerous, 

individual small collections rather than opening large holes in the seagrass cover. 

Although not currently documented, it is highly probable that Ruppia, Halophila 

spp., and other Zostera spp. would recolonize small harvest patches quickly (< 0.25 

m2 patches returning to normal density within 1 year) because of their high population growth rate and seed production. Harvest &om high current areas ( > -30 

cm/sec) however, could initiate the development of an erosion scarp which would 

spread and damage the donor bed irreparably (sensu Patriquin 1975). Thalassia can 

be transplanted with good survival but slow population growth (Fonseca et al. 

1987a,c, 1989a, Lewis 1987,Tomasko et al. 1991), but harvest damage to those donor 

beds may last for years (Zieman 1976, Fonseca et al. 1987c), and harvest of vegetative 
Excavated vs. Control Halodule Density 

Days Since Excavation 

......... NTREAT - CONTROL 

------. 

0.01 M2 

0,063 M2 ---- 0.25 M2 

Excavated vs. Control Syringodium Density 

- 

100 150 200 250 300 350 400 

Days Since Excavation 

Figure 2.7. Recovery of donor beds harvestedforplanting Halodule wrightii (a) and Syringodium 

filiforme (b). Shoot density ni2 by original excavation size and time since excavation (days). Gunexcavated control. NTREATEtreatment, or size of excavation (M2 = m2); control=no excavation. 

Takenfroni Fonseca et al. 1994. 
Chapter 2: Planning 10.5 .- 

Thalassia stock should be &om bed margins (to minimize rhizosphere disturbance) if 

a salvage operation (&om planned or permitted disturbance) is not available. Another 

means of acquiring Thalassia planting stock is to harvest its seeds which wash up on 

shore (Lewis and Phillips 1980), which has no negative influence on existing beds. 

The impact of harvest of seeds or seedlings of any species &om within existing beds 

or colonizing areas currently has an unknown effect on the maintenance of seagrass 

in those areas. However, given that seed harvest probably gathers only a small percentage of the seed production, we expect the impact to be small. The impact of 

donor bed harvesting on Phyllospadix spp. is largely unknown. 

In general, planting stock should be selected fi-om a site with conditions as similar as possible to the planting site, as near the planting site as possible, and at similar 

or equal water depths, salinity, and sediment type. The concept of choosing plants of 

the same size as those lost, perhaps accounting for potential races of seagrass, was suggested 45 years ago (Addy 1947). Little data have emerged to suggest changing this 

practice although concerns have been voiced regarding the maintenance of genetic 

diversity in "Pre-Project Planning Considerations," above). Until more is known 

about the genetic structure of seagrass ecosystems, harvesting of plants &om as wide 

a geographic range as feasible is recommended. Similarly, matching sediment types 

of the donor site with the planting site (percent silt and clay, and percent organic rnatter content of the sediment) is thought to facilitate transplant success. 

Planting material may become available as salvage prior to the imposition of a 

project. Utilization of salvaged material requires good up-&ont organization so that 

a planting site is available before the plants are destroyed (e.g., turtlegrass, Lewis 

1987). Long-term storage of salvaged plant material to use for future plantings has 

not be scientifically evaluated, but has been accomplished for at least a week (pers. 

obs.). Longer term storage may be possible but may significantly increase handling 

costs. 

In summary then, by use of environmental monitoring data, the most prudent way 

to select planting stock is to match conditions at a donor site with the planting site. 

The temperature, salinity, surface sediment (top 3 cm) particle size and organic content, tidal current speeds and wave exposure of the planting should be as similar as 

possible to that of a donor bed of the same seagrass species. 

Creation of transplanted beds for the sole purpose of providing donor material to 

subsequent operations would be prudent. This would alleviate the problems of stor- 
106 Guidelines for the Conservation and Restoration of Seagrasses 

age costs, relieve some of the time constraints and permitting problems that accompany most projects, and prevent damage to native seagrass beds. However, once these 

beds are planted, they fall under the permit jurisdiction of resource agencies as would 

any seagrass bed. However, experimental beds, such 'as those we have created, total 

many acres and were not created to offset any particular 1oss.These should be made 

available as mitigation/restoration donor site. In any event, planting ofbeds for future 

donor material needs to be organized early and in coordination with permitting 

agencies. Moreover, to avoid net losses in baseline acreage, we recommend that 

planted beds be given special status and be protected fiom any subsequent consideration for permitted impacts. Given that early stage plantings have been found to have 

lowered genetic diversity (see above section), institution of these donor sites should 

be linked to an evaluation of their genetic structure to avoid embedding additional 

lowered genetic diversity into planted populations. 

Northeast Region - Maine through New Jersey: known species present = Zostera 

marina and Ruppia maritima. 

Compared to many other parts of the country, the growing season is shorter 

here. Water temperatures are also comparatively cold and will be a cost factor in 

planting operations especially when using divers. Planting may begin as early as the 

waters are ice-fiee, but to obtain robust planting stock one usually will have to wait 

until April or May, and sometimes as late as June. The drawback to early planting is 

that shoots of Zostera will not yet have flowered. Planting flowering shoots of this 

species will potentially add seed stock, but because the shoots die after flowering very 

little vegetative spreading will result fi-om planting flowering shoots. Thus, as much 

as 30-40 percent more plants might need to be installed when planting early in the 

year to make up for this loss, unless flowers are reliably culled fiom plantings. 

Ice shearing is a significant problem in many locales, depending, of course, upon 

the severity of the winter (sensu Robertson and Mann 1984 and F. Short, Jackson 

Estuarine Lab., Durham, NH, pers. corn.). Coarse, cobble sediment can become especially destructive to planted seagrass when it moves during storm events. Grazing 

by waterfowl (Thayer et al. 1984) and green crab, horseshoe crabs, and various fishes are significant sources of bioturbation (Nereid worms have also been reported to 

injure planting; E Short, Jackson Estuarine Lab., Durham, NH, pers. corn.). Also, 

wide tidal ranges, up to several meters, will force planting to either be done in nar- 
Chapter 2: Planning 107 

row low-tide windows of opportunity or will require divers. In steep catchments, 

periodic rainfall events can become especially concentrated, rapidly driving salinities 

down and elevating turbidity. These aperiodic events, as with storms, may be worthy of attention when selecting sites. 

Mid-Atlantic Region - Delaware through North Carolina: known species present = Halodule wrightii, Ruppia maritima and Zostera marina. 

Planting strategies differ markedly for the species in this region. Halodule is a 

subtropical species, and like the temperate Zostera, is at the edge of its distribution in 

this region (i.e., the northern and southern limits of these two species overlap in 

North Carolina). For Zostera planting may be done fi-om April through November, 

although the farther south one goes in this region, planting later in the year 

(September-November) gets plants into the bottom for the longest time possible 

before the next period of low growth (heat stress in July-August). Spring planting 

of Zostera would still have the flowering problem described for the Northeast 

Region. Fall planting is also the best strategy for Zostera in the Chesapeake Bay 

(Moore and Orth 1982). For Halodule spring planting are best. Ruppia is probably 

best planted in early spring as well (Bird et al. 1994). Sources of bioturbation are 

much the same as elsewhere in the country - rays, crabs, and horseshoe crabs. 

Gulf of Mexico and the Florida East Coast - Mexico to Cape Sable and north 

of Jupiter Inlet to Cape Canaveral: known species present = Halodule wrightii, 

Halophila decipiens, Halophila engelmanni, Halophila johnsonni, Ruppia maritima, Syringodiumj2i$orrne, and Thalassia testudinum. 

Of the seagrass species in this region, the three most commonly used species 

(Halodule wrightii, Syringodium Jilqorme, and Thalassia testudinum) have very different 

intrinsic coverage rates (Fonseca et al. 1987~). Planting should be done in the spring 

although planting will survive (but spreading at lower annual rates) if initiated at 

other times of the year. Fonseca et al. (1994), however, found that a fall planting was 

more successful in high bioturbation areas (no cages used) because it apparently 

avoided the peak of the yearly bioturbation activity. Bioturbation has been reported 

by urchins, sand dollars, rays and crabs. 

Coverage rates of the common species are: Halodule wrightii > Syringodium$liforme > Thalassia testudinum. Any of these species can be planted alone, but H. wrightii 

is considered a pioneering species and should be used to quickly establish cover. This 

may also be planted in alternating rows with the other species. Although T testudinum may be planted alone, its very slow population growth and coverage rates under 
108 Guidelinesfor the Conservation and Restoration of Seagrasses 

transplant conditions make it susceptible to interim erosion. The prolonged lack of 

cover would also likely extend the period of interim loss of fishery resources. If turtle grass is the target species, it should be added once faster-growing species (e.g., H. 

wrightiq have stabilized the bottom. 

Ruppia maritima performs much as shoalgrass when transplanted (Stout and 

Heck 1991, Durako et al. 1993). Its high density of rhizome apicals allows the same 

planting techniques to be employed as used with shoalgrass (Stout and Heck 1991). 

In some areas widgeon grass has reportedly been pinned to the bottom in mats, after 

being intertwined in a biodegradable mat or allowed to grow over mats placed in 

natural beds afier which the mats and intertwined shoots are removed for planting 

elsewhere. Durako et al. (1993a) used cotton mesh bags with Ruppia hgrnents and 

a small stone inside for planting; bags were thrown overboard and allowed to root on 

the bottom by growing through the cotton bag. 

The Halophila species (paddle grass and star grass) are extremely &agile, but can 

significantly reduce currents and wave scour (Fonseca 1989b). Because of their 

growth strategy, with only 3 or 4 leaf pairs on a rhizome in close proximity to the 

rhizome apical, these species would likely be suitable for transplanting using the peat 

pot method described in Chapter 3, although we have not tested this method at 

depths > 1-2 m. We have successfdly transplanted H. decipiens bare root sprigs in 15 

m of water using 60 lb. test wire fishing leader bent into a U-shape as a staple to hold 

the plants to the bottom until they rooted. While few cases of Halophila spp. transplanting have been documented, their pioneering growth strategy and small size 

make them likely candidates for effective use in planting projects. 

South Florida and the Caribbean - South of Jupiter Inlet to Cape Sable and 

Puerto Rico and the U.S.Virgin Islands: known species present = Halodule wrightii, 

Halophila decipiens, Halophila engelmanni, Halophila johnsonni, Ruppia maritima, 

Syringodiumjlijorme, and Thalassia testudinum. 

The same guidance should be used here as for the above section on the Gulf of 

Mexico and Florida east coast. The only difference is that planting can be performed 

at any time of the year with little difference in expected response. 

Conterminous West Coast - California to Washington: known species present = 

Phyllospadix scouleri, Phyllospadix serralatus, Phyllospadix torreyi, Ruppia maritima, Zostera 

japonica, Zostera marina, and potentially, Zostera asiatica. 
Chapter 2: Planning * 109 

Planting should be performed during the springtime (April, May, early June). 

Some specimens can be very large and carefbl handling is required. Planting of 

Phyllospadix spp. has been practiced very little, and we can offer little guidance except 

to review Phillips et al.'s (1992) report (also see Chapter 1,"Comparative Analysis of 

Seagrass Planting Efforts"). Cold water may, as in the Northeast, contribute to high 

planting costs. In some areas such as San Francisco Bay, there are extensive annual 

populations of Zostera which are problematic for transplanting. Transplanting of 

annual Zostera means there will be little vegetative spread (the shoots die after flowering). Seed deposition is the only mechanism that would sustain the transplant and 

this is very risky unless a site is extremely quiescent; even then seed predation remains 

a potential problem. Experimentation with seeding techniques would be appropriate in such settings. Vertical zonation of Phyllospadix spp. in the rocky intertidal must 

be recognized and matched with local distributions. Bioturbation sources include 

crabs, rays, some of these fishes, and sand dollars. Bioturbation in the rocky intertidal 

has not, to our knowledge, been documented for planted seagrass. 

Alaska - known species present = Zostera marina and assumed some Phyllospadix 

SPP. 

Little is known about planting requirements here except that spring planting 

are logically better and that cold water and ice shearing may be particularly problematic. 

Hawaii and Pacific Territories - known species present = Halophila hawaiiana, 

Halophila minor, and Halophila ovalis. 

As with Alaska, little is known here but we are aware of no reports of seagrass 

planting in this region. Planting guidance must be extrapolated &om elsewhere. 
CHAPTER 3 

Plan ti 

ommon to all planting methods are 

some fundamental constraints. As 

mentioned earlier, the basic premise is to 

adjust the ratio of births and deaths of 

shoots so as to effect net population 

growth. To achieve this, it is important to 

ensure the presence of growing rhizome 

apical meristems in individual planting 

units (PUS) as these provide a source of 

new shoots and horizontal growth; one 

means of colonizing of new areas (as opposed to seeds). Visually inspecting arbitrarily selected planting units for an absolute 

minimum of one apical shoot per PU is requisite for asexual reproduction; more than 

one apical is highly recommended. The number of short shoots on a long shoot 

should be maximized whenever possible so as to derive benefits &om the clonal 

nature of the plants. Fonseca et al. (1987a) used an average of 2.6 short shoots per 

long shoot (horizontal rhizome with several short shoots) with turtle grass but 

Tomasko et al. (1991) found higher rates of new short shoot production when the 

short shoot/long shoot ratio increased (up to a ratio of 4). Davis and Short (1997) 

use only two Zostera marina shoots per planting unit in a modified staple method. It 

is also recommended that whenever possible, plants should be collected and planted 

on the same day. Any number of incidents may further shock the plants and inhibit their photosynthetic capacity for prolonged periods after planting. Seagrasses are 

inherently fragile, having evolved in a fluid medium that provides support for their 

structure. When out of the water, they are very susceptible to physical damage. To 

ensure transplanting success, it is critical that seagrasses are kept wet and handled gen- 
112 Guidelines for the Conservation and Restoration of Seagrasses 

tly. Moreover, seagrasses have very little resistance to desiccation. On a breezy, sunny 

day, plants left out of the water in the open can experience permanent leaf damange 

within minutes and protracted loss of photosynthetic efficiency within 1-2 hours 

(author's unpubl. data). Plants must be kept in ambient temperature and salinity water 

at all times! They may be covered with seawater-soaked cloth for short periods if 

transportation is necessary. Stacking of the plants on one another should be minimized. Although they appear and even feel robust, they are easily bruised and broken. 

Numerous methods have been shown to successfidly establish seagrass; however, 

familiarity with handling and planting methods as well as the ability to work in or 

under the water are requisite. The familiarity of an individual with these plant communities is inversely proportional to the difficulty encountered in executing a planting. Candidates for planting projects should be able to identie the species involved 

and, if needed, have the ability to snorkel or SCUBA dive. Planting inexperience is 

one of the most common causes of problems (and added cost) in a project failure. 

Planting strategies can be divided into SCUBA and non-SCUBA assisted operations. In either case, once the required area for planting is selected, the planting area 

should be clearly marked off so its boundaries are visible &om the surface (e.g., poles, 

buoys). Experienced boat operators and SCUBA divers may be required. The decision to utilize SCUBA does not necessarily mean that depths are over one's head. 

Where the water is deep enough to prevent a snorkeling diver from reaching the bottom without breath-holding, a person walking and either handing planting units 

(PUS) to the diver or pre-placing them for installation can greatly reduce physical 

exertion. Various combinations of planting and providing PUS to the planter will 

work effectively. Experimentation will typically improve efficiency by best utilizing 

the skills of the personnel involved. However, when SCUBA is required for planting, many logistical and safety problems are introduced (sensu Merkel 1992). At the 

least, higher wages associated with diving significantly increases planting costs sometimes by an order of magnitude. 

Merkel (1992) gave careful consideration to the role of personnel and the use of 

volunteer labor. For intertidal bare-root (e.g., staple technique) planting he suggested a minimum of 7 persons (1 project coordmator and 6 staq; for subtidal bare-root 

planting he suggested a minimum of 9 persons (1 coordinator, 4 staff on shore, and 

4 divers). Slightly fewer people were recommended for plug planting. As for volunteers, he points out that after the relatively brief learning curve for executing seagrass planting, they often lose interest as the work is tedious and repetitive. Paid staff 

are often more cost-effective. 
Chapter 3: Planting * 1 13 

Plug Methods 

Plugs of seagrass with the associated 

sediment can be harvested using a core 

tube. Core tubes (Figure 3.1) are used to 

extract plugs &om the donor bed and 

transport them in the tube to the planting 

site. The tube (usually 4-6 inch diameter 

PVC) is inserted into the sediment and 

capped, creating a vacuum so that when 

the tube is pulled &om the sediment the 

small plug of seagrass with associated sediment is carried inside. Another cap is 

placed over the bottom to avoid losing 

the plug in transport. Another hole must 

be made at the planting site to accomrnodate the plug. This can be accomplished 

either by removing another core or by 

sofiening the bottom using a wedge. 

Fonseca (1994) described using tree 

Figure 3.1. Coniparisonjom lefi to right of6" diameter plug or core, 

3" diameter core, 9" square peat pot plug and staple unit. Note dij 

ferences in size ofcollection apparatus and niass ofmaterial to be handled among techniques; this is a large part ofthe basis for d# i erences 

in logistic burdens among techniques. 

planting bars of the kind employed in forestry practices for this purpose. To plant the 

plug, the bottom cap is removed fiom the core tube, and then the core tube is inserted into the new hole. The top cap is then removed, letting the plug slide out of the 

tube into the substrate. This method requires handling the caps and core tubes 

between planting and the next harvesting. Because of this handling time, the core 

tube planting was the most expensive (3.53 work-minutes per planting unit) tested 

by Fonseca et al. (1994). Costs for all methods included only work time to harvest, 

fabricate planting units, and plant those units. No transportation time, lodging, capital expenditure for equipment, boats, overhead or profit was included. Basic cost 

may then be computed by multiplying the number of planting units (PU) needed by 

time per PU and then by hourly wage. However, this method has been used extensively and for most species with good results. 

Use of plugs requires that the sediment-root mass be sufficiently cohesive so that 

it remains in the tube when the plug is pulled firom the bottom. The ability to retain 

a plug in the core tube varies inversely with particle size and core diameter, but positively with depth of the plug (filling more of the core tube with sediment; unfortunately with concomitant increase in mass) or root mat thickness. 
-. 

11 4 Guidelinesfor the Conservation and Restoration of Seagrasses 

Staple Method 

The staple method has been used widely since its development in the late 1970's 

(Derrenbacker and Lewis 1982, Fonseca et al. 1982). Plants are dug up using shovels, the sediment is shaken &om the roots and rhizomes in the process, and the plants 

with the roots and rhizomes are placed in flowing seawater tanks (or floating pens) 

for holding until made into PUS. Surprisingly, this handling results in no measurable 

loss in photosynthetic efficiency by at least some seagrass (Zostera marina), even after 

repeated insertion into the sediment. Groups of plants are attached to staples by 

inserting the root-rhizome portion of the group under the bridge of the staple and 

securing the plants with a paper-coated metal twist-tie (Figure 3.2). The twist tie is 

secured around the plants at the basal meristem so that the leaves will extend &om 

under the staple up into the water column when planted. A small strip of paper has 

been used to protect the rhizomes &om the twist-tie by wrapping the group ofplants 

with the paper and securing the twist-tie over the paper strip. The staples are then 

inserted into the sediment so that the roots and rhizomes are buried nearly parallel 

to the sediment surface, as they occur in nature. (Fonseca et al. 1982, 1984). 

Loosening the sediment with a utensil such as a dive knife facilitates placing the roots 

into the sediment. One person may lay out the planting units beforehand at the 

appropriate spacing, while a second person follows and installs them. 

This planting method takes less time than the core tubes, but the intermediary step 

of attaching plants to staples is time-consuming (see below). In calm areas, groups of 

plants may be stapled to the bottom without attaching them to the staples beforehand. When attached to the staples, these plantings have successhlly withstood tidal 

velocities of up to -50 cm/sec (Fonseca et al. 1985). The staple method required 

1.91-2.07 work minutes per PU in a test by Fonseca et al. (1994). The relatively low 

cost and widely tested applicability make this one of the most useful methods available at this time. 

Some criticism has been leveled at the use of metal staples, because the bridge of 

the staples will oxidize before the legs which are deeper in the typically anaerobic 

sediment, leaving two potentially sharp pieces of metal in the bottom (Merkel 

1988b). However, we have deployed thousands of these PUS and, despite repeated 

visits to the sites, have not yet experienced an injury. The use of metal staples 

described here is emphasized for its sediment-&ee approach, reducing the burden of 

carrying associated sediment. Any degradable anchor may be substituted if shown to 

provide similar stabilization of the planting until they root. Two variations of this 

method are described below. 
-.- 

Chapter 3: Planting 1 15 

Merkel (1988a) utilized a popsicle-stick technique where shoots were tethered 

on a short cotton string to a popsicle stick and inserted into the sediment (Figure 

3.3). The stick would then rotate to a horizontal position deep in the sediment and 

resist dislodgement. The bundle of shoots, attached on their lead to the stick would 

then be resistant to erosion. Although we have not tested this technique, Merkel has 

used it extensively (pers. corn.). It would seem that a fine sediment would facilitate 

deployment and lead holes as with peat pots or regular staples would be sufficient to 

install the PU. Also as with any PU, the depth of insertion of the anchor requires 

attention so as not to allow the plants to float out of the bottom or be held too deep 

in the sediment, covering the leaves. Information on fabrication and deployment 

costs are not available for comparison with other methods. 

Another variation on the staple method is the use of a biodegradable anchor. 

Davis and Short (1997) have used bamboo "shish kabob" sticks in place of metal 

anchors (Figure 3.4). The sticks are soaked to enhance their flexibility and bent in 

half. The fibrous nature of the bamboo usually prevents complete breakage, thereby 

forming an inverted "V" or U-shaped staple, much like the prefabricated metal staples. Costs are expected to follow that developed for metal staples although when 

purchased in bulk, skewers can cost as little as $0.006 apiece as compared with $0.01 

apiece for metal staples. These sticks lack the weight of a metal staple but are easily 

moved about if placed on the bottom (i.e., just prior to planting by a diver, pers. obs.) 

and alleviate concerns regarding potential injury &om corroded metal staples. Also, 

Davis and Short (1997) did not attach plants to the staples beforehand: plants were 

pinned to the bottom by the diver who carried both staples and plants.They claim 

a substantial cost saving using this approach. 

Peat Pot Method 

Fonseca et al. (1994) recently modified the method of Robilliard and Porter 

(1976a). Peat pot planting have been found to have the lowest cost per planting unit 

(1.21-1.49 work minutes per PU), despite the fact that substantial amounts of sediment are moved with the plants (Fonseca 1994). As with the coring method, shearing of blades may impair growth of larger plants. Shoalgrass and potentially widgeon 

grass and paddle grass (or any Halophila species) may be most suitable for this method, 

given their relatively high density and generally shorter blade lengths than manatee 

grass. The peat pots used by Fonseca et al. (1994) were 3 inches on a side and are 

readily available. The 3 x 3-inch sod plugger (Figure 3.5 a-g) used in that study can 

usually be purchased locally. The sod plugger is used to cut plugs &om existing beds. 

The plug should then be extruded immediately into a peat pot and placed in a hold- 
Figure 3.2. Staple Method. (All photographs staged on land and in air for denionstration purposes only; eelgrass Zostera 

marina used in this demonstration.) 

(a) Typical shovel-sized sod that is excavated for collection ofplanting stock. 

(b) Seagrass shoots remaining after rinsing sedinrentfronr sod. 

(c) Depending on size ofshootsjonr one (very large, -1m long plants) to fifteen (small, -20-20 cm long plants) are separatedjom the sod. A staple is then placed over the plants where the leah shoots are attached to the rhizomes, separating 

what will beconre the above and belowground portions ofthe planting unit. 

Note: In quiescent settings it may not be necessary to attach shoots to the staples; plants can be separatedfrom sods and stapled into the 

bottom all in one act. Practitioners ofthis method work either in pairs where one person separates out planting stock and hands it to and 

second person who manipulates the staples and inserts the planting unit into the bottom or else planters work alone and develop ways to 

secure and carry staples. For example, VelcroTM straps have been fabricated to be placed along the forearm ofa wetsuit under which many 

staples can be secured yet easily slid outfrorn under the strap as planting progresses. Ifa planting does not require pre-planting attachment to staples, then skip the next three steps. 
(d) (Opposite page) A paper-coated (not plastic) wire twist-tieTM is then placed under the shoot bundle and over the bridge 

ofthe staple and twisted snugly. Care nrust be taken not to crush the rhizonres and/or shoots when tkhtening the twist tie. 

The ~lanting unit is then readyfor transport to the planting site. 

(e) An optional tactic that is sonretinres us$ul with larger plants whose rhixonres are more brittle is the addition ofa paper 

collar around the shoots prior to the addition ofthe twist-tie. 

@ The twist-tie may then be attached. The planting unit is then ready for transport to the planting site. 

Cq) A softened fluidized) spot is usually created in the sediwrent unless the sedinrent is already soji. Because the staple unit 

is small, this can be acconrplished with a dive kniji although free bars work very well. The points ofthe staple are inserted 

into the bottonr, sonretinres at an angle, instead ofperpendicular to the sedinrent surfdce. 

h) The staple is inserted into the sedinrent to the point tvlzere the bridge ofthe staple is just covered, burying the rhizomes 

taking care to make sure the plant bundle renrains under the bridge ofthe staple. Also leaves rirust not be caught under the 

staple and should befree to extend up into the water colunin. 
Figure 3.3. A technique developed by K. Merkel (Merkel G. Associates, Sun Diego, CA) as an alternative to staples.. Bundles of seagrass are tethered to wooden anchors (e.g., popsicle sticks or tongue 

depressors), and inserted into the sedinrent. The stick renrains horizontal in the sedinrent and holds the 

seagrass in place until rooting occurs. 

Figure 3.4. A technique developed by R. Davis and E Short 1997 which substitutes baniboo barbecue skewers (right) for the nietal staple (left). The skewers niay be soaked overnight to increase theirj7exibility, and then broken in halj Thefibers ofthe banrboo prevent the two ends ofthe skewerjonr separating, fornring an inverted Vshaped staple which is used just as the nretal staple. Advantage: 

biodegradable without fornration ofsharp points as sonretinres occurs with nretal staples when the bridge 

portion (nearer the oxygenated sediment surface) nrsts away. Disadvantage: sonretinres not negatively 

buoyant and pre-placement ofplanting units is not always possible. 
Chapter 3: Planting 11 9 

ing tray. Typically, one person cuts plugs while a second person holds out the peat 

pots and arranges them in a floating tray. As the trays fill up, they may be sunk to the 

bottom until moved to the planting site. With either method of handling, all air must 

be squeezed out of the peat pots prior to submergence or the pots will capsize in the 

tray. The tray can be stabilized easily by placing a layer of wet burlap over the plants 

with an aluminum grid laid on top for ballast. The trays should be of a size to facilitate handling (-30 pots per tray). Planting can be accomplished in a number of 

ways. As with most of these methods, the PUS may be laid out by one person while 

others follow to plant them. One person loosens the sediment with a tree planting 

bar while the other person installs the peat pot in the bottom. Once in the bottom, 

the sides of the peat pot should be ripped down to allow rhizome spread. The rhizomes will not penetrate the peat pot wall. Despite their low cost, use of peat pots 

must be evaluated over a wide range of conditions before this technique is universally recommended. One such evaluation was provided by a worker in the midAtlantic region. Adapted &om: "Utilization of Peat Pots in Transplanting Eelgrass" 

Ben Anderson (Delaware Department of Natural Resources and Environmental 

Control) : 

"This describes the methodology being used for the past two years in a program 

of eelgrass (Zostera marina) restoration in the Inland Bays of Delaware. From an operational perspective staple planting would work, but a major draw back was that it was 

extremely labor intensive. Various methods were tried to reduce the time and 

expense of the original three day process. The most successf%l and the method preferred to date was a variation on the above process. Three inch peat pots were used 

to transport and transplant the eelgrass. This method eliminated a whole day in the 

process, the most labor and personnel intensive-that of sorting bundling and anchoring the eelgrass planting units. This new process also shortened the time period that 

the plants were out of their environment and thus eliminated a level of stress that in 

all probability enhanced the success of the transplant and the well-being of the plants. 

"The plants were harvested &-om the donor beds as before with a long-handled 

round nosed garden spade. The shovel passed through the sediments just beneath the 

eelgrass root zone, approximately three inches for these beds. The spade was then 

lifted to the water's surface and the eelgrass, with its intact sediment load, was transferred to a floating mesh box which was used as a sorting platform.The eelgrasdsediment matrix was gently broken apart into units that contained between 15 and 20 

eelgrass shoots. The sediment volume for this size unit was too large to fit into the 

3 inch peat pot; the rhizome sediment volume was reduced by gently cradling the 

roots and sediment in one's hands with fingers slightly spread and lightly massaging 

the sediment mass while allowing the sediment to fall between the fingers until the 
Figure 3.5. Peat Pot. (All photographs staged on land and in air for dentonstration purposes only; Halodule wrightii used 

in this demonstration.) 

(a) A sod plugger is used to take 3 x 3 inch plugsfront existing seagrass beds. 

(b) Sod extruded to show size; note extruder plate inside plugger has been depressed to eject the plug. On leji is a tree planting bar that is used to soften the sedinient (by mixing the sediment with the overlying water;Juidizins) to insert the peat 

pot. 

(c) Tree planting bar softening sedinrent. Wi'zen underwater, a hole does not fornt but aJuidized zone fornrs in the sand, 

allowing the peat pot to be inserted easily into the sedinrent. Taking extra tinre to form a 1argeJuidized area greatly facilitates peat pot installation. Use ofthe bar should just precede the installation oftlze peat pot else the sedinient ntay de-fluidize and harden, preventing installation. 

(d) Peat pot planting nraterial ajer washing away sediment; note snrall amount ofplanting nraterial (Halodule wrightii in 

this case) used in a peat pot unit. 

(e) (Opposite page) Installing peat pot in the sediment, 

13 (Opposite page) A critical step after the peat pot is installed in the sedinrent: the peat pot walls must be torn down to allow 

the rhizonres to spread. Seagrass rhizonres @en do not penetrate peat pot walls. This should be done intnrediately ajer 

inserting the peat pot into the bottont while the sedinrent is stillJuidized. 
Chapter 3: Planting 121 

@ Summary ofpeat pot planting process. 

Frorr~ right to left; a peat pot with fertilizer 

pellets prior to receiving a sod; sod cutter 

with extruder plate down; peat pot with 

sod, and installed peat pot with near wall 

torn down. 

volume of the roodsediment mass would fit into the peat pot. This sediment reduction was best done in the water with hands just below surface. This allows a substantial degree of control in shaping and "feeling" the loss of the sediments until the 

dimension of the sedimendroot volume approximates that of the peat pot. It was 

also important to overfill the peat pot so that a dome was created with sediment and 

roots in order to allow the rhizomes to creep over the peat pot as they grow and not 

allow a point of attachment for algae growth on the peat pot which would thus compete with the eelgrass. The potted eelgrass units are then placed into 9.5 gallon stackable RubbermaidTM plastic storage trays approximately 24 x 16 x 8 inches for transport. Approximately 45 to 55 potted eelgrass units fit each tray. Our experience has 

shown that about 700 potted units can be collected by a three person team in about 

three hours. The team consists of one person on the shovel gathering the plants and 

two persons sorting and packing the peat pots. 

"The trays were kept out of direct sunlight until planting and may be placed 

submersed in a shallow protected cove for a few days without any noticeable harm 
122 Guidelinesfor the Conservation and Restoration of Seagrasses 

done to the plants. The trays have sufficient weight &om the contained sediments to 

remain submerged and can be further stabilized by stakes and rope should conditions 

dictate. After a planting grid was placed on the planting site, peat pots were planted 

by divers, using a small hand garden shovel, at each intersect node in the grid matrix. 

The peat pot was totally buried in the sediments with the "dome" of the eelgrass and 

sediments flush with the existing sediment surface. Any portion of a peat pot 

exposed to the water will invite colonization of algae and thus may compete with 

the eelgrass for resources. When inserting the peat pot into the sediment it may be 

advantageous to "crack" the peat pot sides gently and lightly before planting the pot 

into the hole. This will allow the newly formed roots an easy path into the sediments 

and allow for faster root colonization in its new location. The planting grid was carehlly removed, being carell not to disturb or damage the transplants." 

Other Methods 

A wide variety of methods are reviewed by Phillips (1982), Fonseca et al. (1988), 

and Harrison (1990). These include the use of whole sods, plastic pots, iron rods, 

concrete rings, wire mesh, plastic bags, attachment to construction re-bar, nails, and 

seeds. But of all non-whole plant methods, the use of seedlings is currently receiving 

widespread attention yet has had little actual application. Sowing seeds of seagrass 

has been studied for a temperate species (R. Orth, Virginia Institute of Marine 

Science, Gloucester Point,VA, pers. com.) and large areas (acres) have been established 

in the Chesapeake Bay by this approach. Granger et al. (1996) has experimented 

with pelletization of seeds as well as embedding seeds in biodegradable mesh; these 

experiments are in progress at this time and appear promising. Seeding techniques 

currently hold what we consider the highest promise for large-scale restoration of 

some damaged seagrass species. However, seed predation and stabilization (hydrodynamic regime) are two important issues to consider in use of seeds. Areas of high 

seed predation or high currents/waves may be problematic in application of this seed 

technique, although Granger et al.'s (1996) pelletization method may help overcome 

these problems. With Zostera, seed collection must be performed months in advance 

of a planned project. Given the lead time required for many planting projects, 

though, this should not be an impediment. However, this approach is now feasible 

for only one (Z. marina) and perhaps two other species (R. maritima and T testudinum). Thorhaug (1974) introduced Thalassia seedling planting, and Fonseca et al. 

(1985) and others have all used Thalassia seedlings and a patented turtle grass seedling 

grow-out method has been registered by Lewis (1987). These methods appear to 

work, but are ultimately dependent on wild stock harvest of seeds and may be better suited for quiescent areas. 
Chapter 3: Planting 123 

Meinesz et al. (1992) have successfully used plastic meshes with attached shoots, 

similar to the employment of degradable erosion control fabric by Fonseca et al. 

(1979). However because of their plastic components, both methods are now illegal 

in this country. Further, Fonseca et al.'s mesh was actually not bio- but photodegradable; a feature that was severely compromised in the estuarine sediment. 

Others have attempted planting of freshwater and brackish water species using 

biodegradable mesh bags containing PUS dropped overboard (Durako et al. 1993). 

There has been mixed success and these methods have only been tested in small-scale 

experiments. Stout and Heck (1991) found no survival of bagged ~llisneria tubers 

while staple units had -75 percent survival. Coconut fiber erosion control mats have 

been tested with micropropagated Ruppia maritima (5 planting units per 20x20 cm 

mat; M. Durako, University of North Carolina at Wilmington, Wilrnington, NC, pers 

corn.). Planting units were pinned to the mat with hair pins and mats attached to 

the bottom with erosion-control staples (see Staple Method, above). One advantage 

to this method is that shoots are held erect and are less susceptible to burial. 

Another technique using manila line 

or twine has been mentioned to us independently by K. Merkel (Merkel and 

Associates, San Diego, CA) and the late 

K. Bird (Univ. North Carolina, Wilmington, NC), working on the West and East 

Coasts, respectively. The line method 

simply involves untwisting the line (or 

twine) itself which is a 3-ply, using a very 

loose lay, and inserting shoots between 

the open lays of the line (Figure 3.6). The 

line has enough resilience to close again, 

holding the shoot in place. Coils of line 

with inserted plants can then be quickly 

fabricated and payed out on a planting 

site and stapled to the bottom. Planting 

times are not available but this could be 

a very promising technique, especially in 

quiescent areas. It may be prudent to cut 

the line periodically so that afier it is installed an errant propeller does not wrap 

up large portions of the planting area. 

Figure 3.6. Line planting technique (suggested by several contributors). 

Seagrass shoots are inserted through naturalfiber string, such as baling 

twine and pinned to the bottom (shown here with metal staples). String 

can be coiled in water-filled tubs and paid out over the side $a boat or 

floating tubs allowing rapid installation. We suaest that periodic cuts 

be nrade in the line afer installation so that anyfailures (such as propeller entanglement) are not transnlitted to large nunrbers $plants. 
124 Guidelines for the Conservation and Restoration of Seagrasses 

Another planting method has been developed by (E Short, Univ. New Hampshire, pers. com.) that, like the cotton mesh bag method of Durako et al. (1993), is 

designed to avoid the cost of divers. The TERFS (transplanting eelgrass remotely 

with fiame systems; Figure 3.7) may overcome several'other potential planting problems. One is that this technique is suitable for deployment in contaminated areas 

(e.g., PCBs) that might otherwise not affect plant growth but would make diving 

operations extremely costly, not to mention hazardous. Thus, this method may be 

Fkure 3.7. Retnote planting nrethod (TERFS: Transplanting Eelpass Remotely with Franre Systems, 

developed by E Short, Utziv. New Hanrpshire), desktzed to avoid the cost of divers and for deploynrent 

in contanzinated areas (e.g., PCBs) that m$zt otlzenuise not dect plant growth but cause diving operations to be costly and hazardous. nzis nzetlzod nray also be applied as a bioassay tool. Plants are 

attadzed to tlrefrnt~re with paper ties, thefranre can be retrieved nfter a suitable rootirg finre, leaving the 

plants in tlze sediment. 
Chapter 3: Planting 125 

applied as a bioassay tool. The fiame also may minimize some bioturbation hazards. 

Because the plants are attached to the fiame with paper ties, the fiame can be 

retrieved after a suitable rooting time, leaving the plants in the sediment. Strict cost 

comparisons are not yet available, but these remote techniques are promising for specialized applications. 

For hydrodynamically rigorous settings, planting with large sods may be appropriate. This approach is only now being applied (E. Paling, Murdoch Univ., Perth, 

Western Australia, pers. corn.). Massive sods with their intact rhizospheres may possess sufficient integrity to allow establishment in areas where small cores or bare-root 

plantings are quickly eroded or exposed during sediment migration. Care would 

have to be taken to hlly install sods into the sediment. A sod extending into the 

water column would be highly vulnerable to tidal current-induced erosion or acceleration reaction and lift forces under waves. Costs associated with moving large sods 

are unknown, but may prove cost-effective as compared with other methods. 

A potential advantage to the peat pot method over staples is that slow release 

fertilizer may be added to the pots and installed with the plantings at little additional handling cost (Figure 3.5 g). An innovative technique is needed to add fertilizer 

to the sediment with other planting methods (see section on "Nutrient 

Requirements for Transplanting," above, to aid in guiding choices on application). J. 

Anderson (Ruskin, FL, pers. com.) has developed a pontoon boat system for injecting plant hormones and liquid fertilizer into the margins of prop scars but no data 

are currently available to assess its effectiveness. Previous work by Orth (1977), 

Pulich (1 985), Fonseca et al. (1 987b), Williams (1 99O), and Kenworthy and Fonseca 

(1992) has met with mixed results, due at least in part to suspicious performance of 

the fertilizer. Fonseca et al. (1994) did find slow-release pellets to be empty after the 

prescribed 70-day release period, with all their fertilizer apparently solubilized. They 

observed a significant increase in shoalgrass population growth in sediments which 

contain approximately 1.2 percent carbonate but only in association with phosphorus addition. Additions of nitrogen alone or in combination with phosphorus had 

little or no apparent effect. However, when these experiments were repeated, only 

nitrogen additions had any significant effect. These results are similar to those found 

by Short et al. (1985) and Powell et al. (1989) who found phosphorus-linked stimulation of seagrass productivity in carbonate sediments. Fonseca et al. (1994) and 

Kenworthy and Fonseca (1992) recommend that peat pot plantings of H. wrightii in 

sediments containing > 1.0 percent carbonate may benefit substantially &om initial 
126 Guidelinesfor the Conservation and Restoration of Seagrasses 

additions of slow-release phosphorus fertilizer. The recent findings of Duarte et al. 

(1995) suggest that iron limitation in carbonate sediments may also be significant, 

implying the need for iron additions to planting in carbonate sediments. 

Quiescent Settings 

Much attention has been given to row spacing of planting (Fonseca et al. 1982, 

1984,1985,1987b,c7 Merkel 1988b). The reader is directed to those references for a 

detailed study of the derivation of appropriate spacing. In practice, PU spacing typically ranges &om 0.5 to 2.0 m on center. More rapid coalescence of bottom coverage is logically achieved with higher planting density. The benefit of increased rate 

of coalescence is offset by substantially higher costs due to the number of PUS 

involved. For example, a 100 m X 100 m (1 hectare) planting area planted on 2.0, 

1.0, or 0.5 m centers would require 2,500, 10,000, or 40,000 PUS, respectively. 

Wave-Exposed or High Current Speed Settings 

In areas with currents over 30 cm/sec, or with long fetches (over 1 km), one may 

anticipate that the seagrass beds do not naturally cover the bottom completely 

(Patriquin 1975, Fonseca et al. 1983) (Figures 1.3,1.6,2.4). In these instances, planting at high densities such as 0.5 m centers, in groups of plantings 5 to 10 m on a side 

will probably improve the chance of survival. Experimentation is needed for planting in high energy settings. As a result we offered a generalized planting modification scheme (Figure 2.5). Because percent cover by seagrass decreases nearly linearly 

with both wave exposure and current speed, we devised a decision matrix for calculating row spacing and grouping of plantings based on these models (Figure 3.8). 

These models are based on seagrass beds (mixed H. wrightii and 2. marina) in North - 

Carolina (Figure 2.4); we have evidence to suggest that these models will not predict 

seagrass coverage as well in areas that do not have strong tidal currents. We are confident, however, that the general approach of modifying the arrangement of PUS to 

accelerate bed form development toward expected patchy, rather than continuous 

cover is appropriate. We urge users to modify this approach as might seem appropriate given the wide range of conditions that constitute high-energy settings. 
Chapter 3: Planting 127 

1) Compare % cover estimate from equations on p. 75 

2) Use smaller % cover value of those found using those equations 

3) Compute required area of seafloor to be planted: I note: 1 M is based 

I loss 

Impacted are (1 M) * (1 1% cover) = mitigation 

area 

Ex: 1 M = 5,000 m2 Predicted % cover = 30% 

5,000 * (110.3) = 16.667 m2 of seafloor must be planted in this wave and/or 

current climate to achieve the total 1 M acreage 

not only on area 

directly impacted but 

additional acreage 

computed for interim 

4) Compute a nominal planting unit (PU) density (this is not the total 

number for the project) 

Based on nominal 1 m spacing of PU under quiescent conditions ... 

Im = x then, (x + = Nominal PU density: save for later computations I 

Make observations of local patch sizes: 

Ex: local patch sizes appear to be -1 0 x 10 m 

5) Take the total area of seafloor to be planted (here 16,667 m2) and divide it 

into subunits of the local patch size and multiply by predicted percent cover 

e.g., 30% cover: 

(1 6,667 / 100) 0.30 = 50 subunits (where 50 * 100 = original 5,000 m2 

to plant) 

6) Take the square root of that area: 

SO = 71 

7) Divide by the square root of the number of PU: 

= 130 which is: 71 I 130 = 0.55 m spacing 

8) Multiply the reciprocal of spacing * square root of patch area, square that value 

and then multiply by the number of subunits to compute TOTAL NUMBER OF PU 

FOR THE PROJECT 

J- 

( (1 / 0.55) * 100 ) * 50 = 16,529 PU (note the correspondence between 

this number and the actual area of 

seafloor to be planted) 

Figure 3.8. Conlputing row spacing with strong eJects of waves and/or tidal currents. 
CHAPTER 4 

Monitoring and Evaluating Success 

In order to promote effective restoration and mitigation, one must have an 

unambiguous definition of success. As 

seen in the comparative analysis (above), 

there are many criteria that have been 

used for evaluating planting success (Table 

1.9). It is our opinion that simple measures of seagrass coverage and persistence 

are at this time: (1) the most parsimonious 

indicators of many other seagrass bed 

functional attributes, and (2) constitute the most pragmatic choices of monitoring 

parameters under the present system of resource management. 

Through seagrass planting, one is attempting to establish a viable plant community that performs habitat functions equivalent to ones that were lost. The evaluation of all seagrass ecosystem functions (e.g., sediment stabilization, biomass production, nutrient cycling, secondary production) is almost always beyond the resources 

of any project. However, we have been conducting research with the goal of identi$ng diagnostic parameters which can be inexpensively monitored so as to infer 

with reasonable certainty that specific functional attributes have been restored. Many 

habitat functions (e.g., animal abundance, taxonomic composition, complexity of the 

seagrass canopy, macroalgal abundance) appear to relate simply to coverage and persistence of that coverage; parameters that are inexpensively monitored (Fonseca et al. 

1990, Meyer et al. 1990, Fonseca et al. 1996a,b). Although these findings are limited 

to studies in Tampa Bay, FL, and southern Core Sound, NC, we feel that they provide sufficient basis to guide resource managers in some decisions regarding planting success. However, we stress that validation of the following generalizations should 
-. 

130 Guidelinesfor the Conservation and Restoration of Seagrasses 

be an ongoing process with an emphasis on extending geographic replication. 

Therefore, we define seagrass planting success as: 

the unassisted persistence of the required acreage of seagrass coverage for a prescribed period of time (suggested minimum of five 

years). 

The required acreage is a result of the replanting ratio (habitat acreage restored / 

habitat acreage lost) which is in turn a function of agency policy and the nature of 

the planting site. Fonseca (1989a, 1992, 1994) described what to monitor, how to 

perform the monitoring, and how to interpret the results. The following are modified excerpts &om those publications. 

Monitoring SpeciJications 

No one data type can stand alone in a monitoring program (Fonseca et al. 

1987c, Fonseca l989a). Several factors must be considered and these lead to an ecologically valid characterization of seagrass planting success. Sufficient monitoring 

should be conducted to ensure that any contracted work was performed to specifications. However, in any situation, monitoring of planting performance using standard methods provides the basis for mid-course corrections (Fonseca 1989a) and 

improved planning of subsequent projects. 

Survival 

The number of PUS that survive should be recorded. This may be expressed as 

a percentage of the original number, but the actual whole number is critical as well. 

If a planting site is sufficiently small (-500-1000 PU), all PUS should be surveyed for 

presence or absence (survival survey). The existence of a single short shoot on a PU 

indicates its survival (hopefklly that shoot is associated with a rhizome meristem, otherwise subsequent vegetative growth will not occur). If a site is large, then randomly (not arbitrarily) selected rows or subsections (area in m2) should be sampled. Since 

each row or subsection is actually the level of replication, at least 10 replicate rows or 

subsections should be performed at the level which one wishes to generalize their 

findings (e.g., over the whole planting site). At the very least, stabilization of the running mean of survival should be obtained as a measure of statistical adequacy. 

Areal Coverage 

A random (as opposed to arbitrary) sample of area covered (m2) per planting 

unit should be recorded until coalescence (the point where indwidual PUS grow 
Chapter 4: Monitoring and Evaluating Success 13 1 

together and the PU origin of individual shoots cannot be readily observed).The area 

covered by a PU may be measured by recording the average of two perpendicular 

width measurements (in meters) of the PU over the bottom. These numbers are 

averaged, divided by 2, squared, and multiplied by n: (i.e., n:"r2) to compute the area 

of a circle, and in this case, the PU. This procedure tends to give a higher value than 

use of a quadrat with 25 cm2 resolution, particularly when PU expansion is not uniformly circular. With a quadrat survey, a 50 x 50 cm quadrat, divided into 5 x 5 cm 

grids (string on 5 cm centers across the quadrat fi-ame) is laid over the PU and filled 

grids counted. In this case, the number of 5 x 5 cm grids (or half grids if there are 

only 1 or 2 shoots in the 5 x 5 cm grid) that have seagrass shoots are totaled and converted to meters square of cover for the PU. The quadrat method is more appropriate for seagrasses that propagate by long runners (e.g. shoalgrass), and do not form a 

clearly radial growth pattern (e.g. eelgrass).The number of surviving PUS may then 

be multiplied by the average area per PU to determine the area covered on the planting site. After coalescence, the area of bottom covered should be surveyed using randomized grid samples at the 1 m2 scale width (Fonseca et al. 1985).These data may 

be used to assess persistence of the planting as well as total seagrass coverage. 

For very large seagrass plants whose rhizome mats do not significantly interdigitate (e.g., Zostera marina on the West Coast of the U.S., R. Thom, Battelle Pacific 

Northwest Lab., Sequim, WA, pers. corn.; pers. obs.), post-coalescence techniques 

may actually be more appropriate with the 0.0625 m2 resolution being perhaps better scaled to this plant size and spacing. 

Number of Shoots 

Random samples should be collected to measure the number of shoots per PU. 

The data fi-om pre-coalescence surveys may be used to compare performance relative to other, local planting by plotting the average number of shoots per PU as well 

as shoot density (number of shoots PUW'/area PU-') over time. The comparison may 

be statistical or visual on a graph (which often suffices to detect grossly different population growth rates). Early stage PUS that are still associated with the anchor are artificially clustered by the nature of the PU show an artificially high m-2 shoot density, 

sometimes ten times higher than a reference site. When shoot density of a PU is 

essentially equal to that of reference sites, this indicates that the plants have spread to 

a point where they are occupying area in a way consistent with long-term establishment and that successful colonization has occurred.This is an important indicator of 

planting performance and environmental suitability of a site. Shoot number is recommended in addition to areal coverage because shoot addition is a more accurate 

means of assessing the asexual reproductive vigor of the planting. Also, areal coverage varies with the environmental setting of the planting. For example, in areas of 
132 * Guidelinesfor the Conservation and Restoration of Seagrasses 

high current shoots grow more densely. Without shoot number data, the patchy pattern and low areal coverage in high current environments could be erroneously 

ascribed to poor planting performance instead of a natural pattern of growth. 

Moreover, the size of the naturally-occurring patch& gives an idea of the expected 

form of planted patches (see section on "Spacing of Planting Units," above). 

Survival, areal coverage, and number of short shoots per PU are straightforward 

measures, although they usually require snorkeling or SCUBA diving (a factor that 

is surprisingly not considered, or equipped for, by many attempting these data collections). An individual can be trained to count in a few hours, and can count individual PUS in 5-10 minutes or less at early stages of post-planting growth. 

Monitoring of shoot numbers, area covered per PU, and shoot density should, 

at a minimum, be done quarterly for the first year after planting and biannually thereafter for a minimum of four more years (a minimum total of five years). After PUS 

begin to coalesce and the PU fiom which shoots originated can no longer be discerned, areal coverage and shoot density data should be recorded and counts on a PU 

basis suspended. However, any replanting after the initial planting resets the monitoring clock and monitoring fiequency to time zero. 

However, as suggested by Fonseca (1989a), mistakes may be made in selecting a 

site. Repeated planting may fail. There needs to be some decision sequence to 

break the cycle of replanting in perpetuity before managers lose control of the 

process. We propose the following sequence. For Zostera spp, Halodule, Syringodium, 

Ruppia, and Halophila spp., monitoring should continue for a minimum of three years 

(Figure 4.1). For Thalassia and Phyllospadix, longer periods of time may be required. 

While the time course for monitoring Phyllospadix spp. has not been determined, its 

slow vegetative growth suggests that 5-10 years may be an appropriate length to 

begin with, with comparatively quiescent areas monitored for 5 years while more 

wave-exposed sites monitored for 10 years. For Thalassia, restoration of the rhizome 

mat could conceivably take a century. Because most permits cannot be followed for 

anywhere close to that time, we suggest that 5-10 years may also be appropriate. 

Duration of monitoring may also have to be extended and/or intensified for sites 

susceptible to subsequent human impacts such as propeller scarring. 

If at any time a loss of PUS occurs, then replanting (remedial planting) should 

be done. Because this tends to happen with greater fiequency soon after planting, 

heavy arrows are used (Figure 4.1) to indicate conveyance to Replanting #l; less 
SEQUENCING OF THE SUCCESS CRITERIA 

Year 1 Year 2 Year 3 

""".' ...) 5 y 

monitoring steps 

monitoring steps 

...-..&............................---.......*................*....-.....-................-........-....... / Replant # 2 

monitoring steps 

i 

Figure 4.1. Sequencing ofthe seagrass planting success criteria. Initial planting is done at Time 0. Monitoring is to continue for a minimum five years. Ifat any time a sign$cant loss ofplanting units (PUS) occurs, then replanting (remedial 

planting) should be done. Because this tends to happen with greaterfrequency soon ajerplanting, heavy arrows are used to 

indicate conveyance to Replanting #l; less heavy arrows are used to indicate the lowered expectedfrequency ofremedial planting as time progresses. Any remedial planting on the original planting site itseEfmeans that for those PU, the clock is reset 

to zero. This prevents chronic replanting right up to the end ofthejive year monitoring period. IfPU losses are again experienced, then a second remedial planting may be called for. At this point the dashed lines indicate that ifsome clear and overriding problem is evident with the planting site (e.g., repeated large scale losses due to unfavorable environmental conditions), 

then a decision may be made to select an altogether new site and start over (minus any acreage sustained at the original planting site). However glosses are minimal and actions can be taken to ameloriate the agent of loss (e.g., adding bioturbation 

exclusion devices), then continued remedial planting would be allowed. Only rarely would any additional replantings be 

allowed on the original site after two remedial tries. At that point an altogether new site should be considered. 
13 4 Guidelines for the Conservation and Restoration of Seagrasses 

heavy arrows are used to indicate the lowered expected fi-equency of remedial planting as time progresses. 

Any remedial planting on the original planting site means that for those PUS, 

the clock is reset to zero. This prevents chronic replanting of an unsuitable right up 

to the end of the three-year monitoring period. If PU losses are again experienced, 

then a second remedial planting may be called for. At this point the dashed lines 

(Figure 4.1) indicate that if some clear and overriding problem is evident with the 

planting site (e.g., repeated large-scale losses due to unfavorable environmental conditions), then a decision may be made to select an altogether new site and start over 

(minus any acreage sustained at the original planting site). However if losses are minimal and actions can be taken to ameliorate the agent of loss (e.g., adding bioturbation exclusion devices), then continued remedial planting would be allowed. Only 

rarely should any additional replanting be allowed on the original site after two 

remedial tries. At that point a new site should be considered. Ideally, an alternate 

site would be selected in the initial site-selection process. 

The computations described above allow a direct comparison on a unit area basis 

of planted versus lost acreage. Success may then be based on whether the targeted 

amount of coverage has been generated. This is a quantitative measure which is 

assumed to be diagnostic of ecological function. If the planting project is for mitigation, then compliance may thereby be interpreted as both acreage generated and 

the unassisted persistence of that acreage over time (the three year period). The persistence issue is also critical. If the planting does not persist, then the ecosystem has 

experienced a net loss and the project has not been successful. The population 

growth and coverage data may be compared periodically with published values 

(dependent on species and ecoregion) as a relative indicator of performance. 

Although these data collections may seem involved, they represent some of the simplest and least expensive metrics we found in our survey of planting projects. 

Moreover, without them cost projections cannot be made and cost overruns can follow. In computing costs, it should be recognized that little or no additional care may 

be required once the plants are established. Natural disturbance (rays, storms) and seasonal peaks and troughs in growth are to be expected. 

As an example of how these various monitoring conditions we have added an 

example plan (Appendix E). There, we give specific language for planting site selec- 
-- -

Chapter 4: Monitoring and Evaluating Success 135 

tion criteria, monitoring, replacement ratio computation surveying with the BraunBlanquet (1965) method (also see Appendix E, p. 220). The plan was designed with 

both propeller scars and mooring scars in mind. However, unlike the specialized 

prop scar portion of the plan, the mooring scar part can be generalized to many 

plantings that involve broad, open areas that are not in high energy settings. To use 

the mooring scar part in high water motion areas, apply the decision sequences given 

in Figures 2.1 and then revise that by applying the decision processes &om Figures 

2.5, and 3.8. 

One of the most-asked questions is "how much does seagrass planting cost?" 

Given the wide variety of seagrass growth strategies and environmental settings 

under which seagrass beds occur, this is not an easy question to answer. Prices vary 

widely. Besides the direct influence of project size on cost, the following are some 

factors that we have seen to generally constitute grounds for increased costs (in an 

approximate decreasing order of importance): 

1. inappropriate site selection, 

2. inexperience (inefliciency, poor technique), 

3. high disturbance, e.g., bioturbation (actual losses and therefore costs of replanting or exclusion devices which are inherently costly to construct and 

deploy) , 

4. water depths that require use of SCUBA divers, 

5. low visibility, 

6. soft sediments (especially when wading or walking on the site is required), 

7. rough seas, 

8. cold water planting, 

9. capitalization (purchasing equipment: e.g., boats, motors), 

10. wide profit margins, 

11. amount of site preparation (e.g., creation of subtidal dikes) 

12. excessive frequency of monitoring, and 

13. overly detailed parameters chosen for monitoring (blade width, length, faunal 

assessment). 

Over the years there is a general trend for seagrass planting costs to be similar to 

those for salt marsh planting. A recent review by King and Bohlen (1994) found that 

submerged aquatic plant restoration typically ran between $19,000 and $20,000 acre-' 

(-$47-49,000 ha-'; albeit based almost exclusively on &eshwater work). Thorhaug and 
13 6 Guidelinesfor the Conservation and Restoration of Seagrasses 

Austin (1976) reported the direct cost of planting seagrass to be ~$25,000 ha-' and 

Fonseca et al. (1987a) reported collection, fabrication and planting costs to total an 

estimated $19,000 acre-' (-$46,940 ha*'). The Port of Miami planting project reportedly paid almost $3 million for a +200 acre planting (~$37,000 ha-'; Stein 1984). 

Planting in Tampa Bay in the late 1980's were priced at approximately $2.50 PU-' 

(425,000 ha-') (M.O. Hall, Florida Department of Environmental Protection, St. 

Petersburg, FL, pers. com.) and more recently we have seen planting projects with 

monitoring included at -$49,000 ha-' (K. Fitzpatrick, Sebastian Inlet Tax District 

Commission, Indiatlantic, FL, pers. corn.). Thus, even without corrections for inflation, the price of seagrass planting appeared to have been consistent for nearly the 

last 20 years, varying with species and the density of planting, and other extenuating circumstances, but averaging near $37,000 ha-'. There are large cost discrepancies though. For example, if one takes the costs quoted by Zieman (1982) and correct them to 1997 dollars, the cost per acre is in the neighborhood of -$3l6,OOO ha- 

'.. Therefore, we feel that most of these projects did not accurately compile the real 

costs associated with launching a restoration or mitigation project. To cost out the 

project plan described in Appendix E in 1997 US dollars, we used a 12,580 PU, 

Halodule wrightii peat pot planting that requires boat access. The costs included securing aerial photographs (-$5,465), preparing maps and groundtruthing (-$14,314), 

collecting, preparing and installing (-$64,846), and monitoring with re-fertilization 

and report writing (-$205,650), and contractor profit of 10% (-$20,028), the total 

cost was -$206,000 acre-', or -$510,000 per ha-' (a value closer to Zieman's 1982 

estimate than more recent estimates &om other projects). Our estimate did not 

include costs incurred by any Government oversight. Although there may be many 

ways to reduce cost, the discrepancy between -$37,000 ha-' and over $500,000 ha-' 

means that large variation in costs can be expected and that it is prudent to conduct 

a detailed costing before allowing the loss of a seagrass bed. 

More recently, some effort has been made to guarantee planting success. 

However we caution against such guarantees without specific caveats regarding 

remedial planting (incidently, terrestrial crops are not guaranteed and there is much 

more experience in their production). With a planting guarantee, there are three possible outcomes: 

1. A very successful planting that requires little or no additional planting is 

heavily over-compensated, e.g. $100,000 per acre as opposed to the average 

of -$I5 K acre-' (above: $37 K ha-'). 

2. If extensive replanting is repeatedly required up to the end of the guarantee 

period (if a guarantee limit was set), then no effective mitigation has occurred. 
-- 

Chapter 4: Monitoring and Evaluating Success 13 7 

3. If there is no limit and replanting must continue for some indefinite period, 

then the criteria of success are not met. 

Because planting conditions do vary so widely it is sometimes inappropriate to 

judge each project based on an average cost (see reasons listed above, some of which 

are difficult to control). Rather, we have historically focused on providing managers 

with some estimation power by evaluating the costs to harvest plants, fabricate PUS 

(when a method called for this), and installation of the PUS (Fonseca et al. 1984, 

1985, 1987c, 1994). These numbers have been challenged as being too optimistic 

both by consultants and independent investigators (pers. corn.). 

The reader must be absolutely clear that the data we have reported 

should only be used as a guide from which managers may roughly assess 

costs and from which they can ask questions about what factors are actually contributing to the cost discrepancy they present versus those reported by us in the literature that emphasize only planting costs. These other 

costs must then be added on, such as break times, travel, training, mobilization and demobilization, materials (usually negligible unless exclusion 

cages are employed, etc.) and scrutinized for their reasonableness. Because 

he planting itself cannot be conducted for much less cost than reported 

for planting alone, any reductions in project cost must be found in other 

components of the project (i.e., capitalization costs, profit, etc.). We 

emphasize the heuristic value of these data, recognizing they embody only 

certain aspects of a larger planting program and can only hope that 

resource managers utilize these data in that manner. 

Our planting costs in work-minutes for the three categories of effort listed 

above - collection, fabrication (if appropriate) and deployment of stock - have 

ranged between -2 and 3.5 work-minutes PU-' (Fonseca et al. 1994). For a l-hectare planting on l-m centers, this means between approximately 340 and 595 work 

hours of labor. At a given cost (e.g., $10.00 h-') this gives a fundamental cost of ranging between $3,400 and $5,950 ha-' or an average of -$l,9OO acre-', similar to our 

previously published data (Fonseca et al.1984,1985). 
CHAPTER 5 

he national "no-net-loss" policy for wetlands was adopted to counter tremendous 

losses of these valuable natural resources, with 

mitigation playing a central role in its implementation (White House Office on Environmental 

Policy 1993; Zedler 1996). For the purposes of 

this document, mitigation refers to activities related to permitted habitat conversions and includes 

a sequence of avoiding damage, minimizing damage, and finally, if needed, planting to compensate 

for damage. Compensatory mitigation usually follows the destruction of existing 

habitat when the agent of loss and responsible party are known. Compensation 

assumes that ecosystems can be made to order and, in essence, trades existing functional habitat for the promise of replacement habitat. In addition, the "no-net-loss" 

policy recommends increasing the quality and quantity of wetland resources through 

restoration of historically degraded habitats. Here the term, "restoration" does not 

apply to permit-associated projects, although planting techniques and assessment 

used may be identical. 

Wetland resources include subtidal seagrass beds and their associated interspersed 

unvegetated bottom which perform a number of important ecological functions and 

are among the most productive ecosystems on the planet. There are at least 13 

species of seagrasses in U.S. waters, with seagrasses occurring in all coastal states, with 
140 Guidelines for the Conservation and Restoration of Seagrasses 

the possible exception of Georgia and South Carolina. Conservation, mitigation, and 

restoration attempts have been underway for many years, and despite the wide-scale 

distribution and ecological importance of seagrasses, surprisingly little is known 

regarding some aspects of their distribution, population biology, resistance to various 

disturbances, and rates of recovery following disturbance. 

Seagrasses occur almost exclusively in shallow, soft-substrate habitats where their 

roots bind sediments and their canopies baffle waves and currents. Seagrasses and 

their associated epiphytes are highly productive, produce a structural matrix on 

which many other species depend, improve water quality, and stabilize sediments. 

Because of their requirements for high light levels, seagrasses are restricted to 

shallow coastal areas where anthropogenic disturbances that damage or kill them are 

common. Unfortunately, once seagrasses die, the sediments they helped stabilize may 

be resuspended into the water column, potentially lowering light levels to intensities 

that may not allow seagrasses to recover in this site unless the entire watershed is 

managed to improve water clarity. 

Loss OF SEAGRASS HABITAT 

As human population concentrates along our coastlines, anthropogenic impacts 

to seagrass habitats increase through nutrient loading &om runoff, light reduction 

&om increased turbidity due to phytoplankton blooms, increased boat traffic, and 

more direct vessel impacts such as propeller scarring. 

In recent years, seagrass losses of 30% to 90% have been reported &om the 

Chesapeake Bay and coastal areas ofTexas, Florida,WBshington, and California. In 

some cases, historic losses &om disturbance and disease appear to have been even 

greater. Disturbances kill seagrasses rapidly while recovery is usually very slow. If the 

resource services that seagrass beds provide are to be maintained, lost beds need to 

be restored and processes harming present-day beds need to be minimized or 

restored through improvement of environmental conditions that facilitate recovery. 

Recent legeslation embodied in the Manguson-Stevens Fisheries Management 

and Conservation Act of 1996 recognizes that the long-term viability of living 
- 

Chapter 5: Manager's Summary 14 1 

marine resources depends on protection of their habitat, and requires that each of the 

Fishery Management Councils describe and identift essential fish habitat in fishery 

management plans and avoid or minimize adverse impacts to such habitat. It also 

requires that the Secretary of the Department of Commerce initiate and maintain 

research to identift essential fish habitat, the impact of wetland and estuarine degredation, and other factors affecting the abundance and availability of fish. Also 

required are recommendations on research needed to develop restoration techniques 

for these habitats. Because productivity and recruitment success may be determined 

at different life history stages of a fishery species, the Plans are required to describe 

each of these stages and their connectivity to habitats. The first amendments are due 

to Congress for evaluation and approval in October 1998. 

Seagrasses have been recognized as one of the many habitats that are essential to 

conservation agencies and organizations around all coasts. Many of the management 

organizations have formal and/or informal policies on aspects of management of seagrass habitats. Recently the Atlantic States Marine Fisheries Commission (ASMFC), 

which assists in managing and conserving shared coastal fishery resources of the 15 

Atlantic coastal states &om Maine to Florida, established a "Submerged Aquatic 

Vegetation Policy". The promulgation of this policy was based on the recognition 

that many of the ASMFC managed species are directly dependend upon SAV for 

refuge, attachment, spawning, food, or prey location. Coupled with the Essential Fish 

Habitat component of the Magunson-Stevens Act of 1996, seagrass meadows along 

the Atlantic coast and elsewhere should receive more conservation, protection and 

enhancement measures. 

In the past, mitigation was perceived as an experimental tool rather than an 

established management practice. Given the documented success of mitigation, this 

perception is no longer appropriate. Seagrass planting is now a proven management 

tool. However, planting will not succeed unless managers appreciate and emphasize 

the extreme importance of site selection, care in planting, and incorporation of plant 

demography into the planting and planning process. Many planting failures have 

resulted &om poor site selection or poor planting procedures rather than basic limitations of planting technology. When appropriate procedures are followed, planting 

has been relatively successful (e.g., Southern California sites). Planting of different 

seagrass species has been employed in a variety of habitats, using a wide range of procedures. The relative success of seagrass plantings when using different techniques, 

seagrass species, or habitats has often been difficult to judge rigorously because of the 

absence of standard assessment techniques following planting a problem common to 

habitat restoration in general (Mager and Thayer 1986, Race and Fonseca 1996). 

However, seagrass plantings that persist and generate the target acreage have been 

shown to quickly provide many of the hnctional attributes of natural beds. 
142 Guidelines for the Conservation and Restoration of Seagrasses 

Whether a project focuses on restoration or compensatory mitigation of an 

injured site, carehl and thoughthl planning is crucid to project success. Managers 

need to determine if a seagrass system has been injured, how much area has been disturbed, and what constitutes adequate remediation. These decisions may not be as 

straightforward as they might seem. For seagrass beds that establish seasonally &om 

seed banks, beds that are lush in the summer may appear as bare sand in the winter. 

Thus, if there is no historical or at least seasonal perspective, a manager could look at 

the site in the winter and conclude that no seagrasses are present and no mitigation 

is needed. A similar error could occur when monitoring a planted bed. If the 

responsible party planted a large bed that did well, set seed, and died back (as might 

be natural for this location and species of seagrass), mitigation might be judged to be 

successhl if the bed were checked in the summer of establishment or during the next 

summer when the seed bank had germinated. If the site were checked in the winter, however, mitigation at this same site might be judged to have failed completely 

because only bare sand would be visible. Such instances call for more comprehensive site surveys such as coring for seeds and/or living rhizome and shoot meristems. 

Moreover, some beds migrate over time, meaning larger areas of the seafloor must be 

set aside to maintain the patchy population. 

Methods of seagrass transplantation that are efficient and cost effective in one 

geographic region may be ineffective in another. Managers should consider the life 

history characteristics of local species, and how these species vary geographically, seasonally, and as a consequence of various physical (e.g., temperature) or biological 

(e.g., bioturbators) regimes. 

Continued research is needed to determine how anthropogenic actions may isolate small populations and erode genetic diversity. Managers should strive to potentially maximize genetic diversity by selecting planting stock &om a variety of widely distributed seagrass beds. Collection of all planting units &om one localized bed, 

even if that bed appears robust, may result in a high degree of relatedness among 

transplants; this lack of genetic diversity could depress sexual reproduction or make 

plpted beds more uniformly susceptible to diseases or other disturbances. 

Although populations are difficult to define, managers should also strive to conserve existing stock and minimize geographic isolation of seagrass beds as a long- 
-- 

Chapter 5: Manager's Summary . 143 

term management goal to maintain genetic structure of local seagrass systems. But 

no gene complex can provide protection against insufficient light, excessive nutrient 

loading, or the depredations of bioturbating organisms in a recently planted bed. 

It is important to obtain information about seagrass distribution and the environmental conditions at a site before that site is allowed to be disturbed. If sites are 

illegally injured prior to being assessed, extent of damage is especially difficult to 

assess. Site surveys are a recommended tool but they provide inadequate information if sites are surveyed at only one point in time. This is especially true when dealing with patchy seagrass beds. It is important that managers realize that bare areas 

among patchy seagrass beds are a natural characteristic of these beds and that over 

time seagrasses will move and alternately colonize and vacate these areas. If channels 

are placed in these beds in such a way that they intercept bed migration, unanticipated and persistent losses of seagrass habitat may occur. If possible, present-day beds 

should be evaluated over a sufficient period of time and with appropriate spatial resolution to reveal seagrass movement into bare areas and identifjr currently unvegetated areas that should be protected &om negative impacts. 

Early in the planning phase, the project manager must determine whether the 

project will be for compensatory mitigation or for restoration. These projects could 

have different goals and may be evaluated according to different performance criteria by resource agencies. In any case, attaining the same seagrass species as what was 

lost with a comparable shoot density and equal or greater area of bottom covered 

(depending on time since injury and recovery potential) that compensates for interim lost services is a logical and ecologically defensible goal. 

Because different agencies at the state, federal, county, and municipal levels may 

have jurisdiction over projects affecting wetlands or seagrass beds, delays can be 

avoided by addressing all permitting requirements as far ahead of planting as possible. Coordination protocols developed for Southern California, the Chesapeake Bay, 

and Connecticut provide guidance. A standardized protocol is essential to accurately convey the scope of the potential injury to the public stewards and to simultaneously treat applicants in a consistent and fair manner. 
144 Guidelinesfor the Conservation and Restoration of Seagrasses 

It is essential to profile the injury area and determine the interim loss of ecosystem functions. This determination considers how much acreage will be lost and how 

long it will take to replace the ecosystem services that this area provides. In the past, 

interim loss assessment has been inconsistent, with highly variable replacement ratios. 

NOAAYs Damage Assessment and Restoration Program is now utilizing an economically-based model to standardize interim loss computations using discounting methods and acre-years of lost services as a metric. A qualitative description of the model 

is provided (p. 66 and Appendix E). 

Guidelines for pre-injury and pre-planting surveys allow managers to quantitatively profile seagrass habitat. Surveys can identlfjr species composition, distribution, 

and availability of seagrass to salvage and which could then be set aside for planting 

to other sites or replanting to the original site in the case of short-term disturbance. 

Aerial photographs can establish the historical perspective on the persistence and distribution of coverage on the site. Pitfalls to seagrass habitat replacement over the 

long term include transplanting into unsuitable areas, or into bare areas between 

established seagrass patches. If aerial photographs or other surveys indicate no history of seagrass cover over a ten-year period, then the planting site should be rejected 

as unsuitable, unless some specific actions are taken to improve the site, or, unless mitigating factors such as recently improved water quality can be demonstrated. 

Site selection is the single most important step in the seagrass restoration and 

mitigation process. Important aspects of site selection and seagrass physiology 

include the following: emersion and desiccation effects; bioturbation; sediment thickness; sediment stability; natural recolonization; nutrient limitation or overload; light 

requirements and light attenuation characteristics of the site; salinity and temperature 

tolerances; and waves and current speed (see site selection criteria in Appendix E). 

Planting areas are classified as either on-site or off-site. In some cases grading 

down of upland areas or engineering subtidal areas to create suitable sites may be possible. When destruction of the site requires planting in another location it is often 

very d@cult tojnd a suitable of-impact site location. The seemingly simplistic question 

that must first be asked is "If seagrass does not grow there now what makes you 

believe it can be successhlly established?'' (Fredette et al. 1985). 
- 

Chapter 5: Manager's Summary 145 

Most planting projects currently utilize wild planting stock which almost always 

requires a permit to collect. Managers are cautioned against repeated hahests fiom 

donor sites. Matching the environmental conditions of the donor site to the planting site remains, after 50 years (Addy 1947), the best rule of thumb for donor stock 

selection. In terms of long-term management, some planted beds should be created 

solely to provide donor stock and experimental beds no longer being studied could 

be made available for harvest. 

Successful planting of seagrasses demands that: (1) planting units have intact 

meristems so that they can spread vegetatively, (2) they have enough short shoots per 

long shoot to facilitate growth following planting, and (3) minimization of stress to 

planting units so that they are healthy when planted. For seagrasses to undergo vegetative spread, they must have at least one apical meristem on a rhizome in each 

planting unit. Greater numbers of rhizome meristems is preferable. Spread of planting units will also be enhanced if they have several short shoots per long shoot. 

Minimizing stresses experienced by planting units will reduce the possibility of rhizome meristems being killed, and will facilitate more rapid establishment of transplants. To achieve this, plants need to be collected and planted soon thereafier, preferably on the same day, kept in seawater that is of ambient temperature and salinity, and 

not crowded or piled on each other in ways that cause bruising or breakage. 

A common cause of planting failure is inexperience of persons involved in the 

project. Persons involved in the project need to be able to identifj the species to be 

planted, be familiar with the handling and planting methods, and, in some cases, be 

comfortable snorkeling or SCUBA diving. Planting starts with selecting an appropriate area and marking it with poles or buoys so that its boundaries are visible. 

Waders, snorkelers, or SCUBA divers then begin planting, unless remote methods are 

used. As diving often increases costs considerably, it may be advisable to have workers pre-place planting units so that underwater time can be used most effectively. 

Previous efforts have shown that volunteers often lose interest in planting because it 

becomes tedious and repetitive following the brief learning period; paid staff may be 

more cost effective, but close attention to providing challenge and diversity in tasks 

is recommended. 

Planting can be conducted using any of several methods. The plug method 

involves driving 4-6 inch diameter PVC tubes into established seagrass beds, capping 
146 Guidelinesfor the Conservation and Restoration of Seagrasses 

these tubes to create a vacuum that allows removal of the tube and its contents, and 

then transplanting this plug of seagrass, rhizomes, and sediment into a new habitat. 

Although this method tends to be more expensive than others, it has been extensively used with numerous species with good results. The staple method involves digging up plants and their associated rhizomes using a shovel, shaking sediment &om 

the rhizomes, using twist-ties to attach rhizomes to metal, bamboo, or wooden staples, and planting these seagrasses by pushing the staples into sediments so that blades 

protrude upward and rhizomes are buried in the sediments. In calm areas, staples can 

be placed over groups of plants without securing the plants with twist-ties. This 

method is cost effective, widely used, and generally successful. The peat pot method 

has been used less than the above methods, but shows promise. A sod plugger is used 

to extract 3x3" plugs &om an existing seagrass bed. These are immediately extruded into similar sized peat pots and the peat pots then transplanted into areas that are 

to be established. Once in the bottom, the sides of the peat pots are ripped to facilitate spread of the rhizomes. This method currently has the lowest cost per planting 

unit. Plants can also be collected with a shovel and plants with sediment shaped by 

hand into a peatpot sized mass and put into the pot for planting. Other methods, 

including sowing seeds, have also been tried. Some of these show promise and may 

be desirable for particular habitats or situations; however, most other methods have 

been used less extensively and are less well tested. Several investigators have attempted to improve planting success by adding fertilizers. These efforts have produced 

mixed results. At present, it appears that fertilization, and potentially, hormone treatment, cannot hurt and may improve planting success, especially phosphorus fertilization in carbonate sediments. 

There is a considerable literature on how the spacing of transplants affects coalescence rates, potential disturbance in habitats subjected to different flow regimes, 

etc. In general, a balance will have to be achieved between desired coverage, rate of 

coverage, and the cost of planting at different densities or using different arrangements. Determining spacing requires knowledge of the natural history and physiology of the seagrasses being planted and an understanding of the hydrodynamics 

affecting the planting site. However, decreasing spacing may reduce bioturbation. 

Seagrasses are planted in hopes of restoring all aspects of ecosystem function 

(sediment stabilization, nutrient cycling, etc.) that were lost when natural beds were 

injured. However, management resources are rarely available for monitoring planted beds to be sure that they each recover these functions. Although numerous cri- 
Chapter 5: Manager's Summary 147 

teria have been used for evaluating planting success, studies available to date indicate 

that simple measures of seagrass coverage and persistence are the most parsimonious 

indicators of a functioning seagrass bed, and are the measures that should be favored 

by resource managers. Therefore, successful seagrass establishment should be defined 

as beds that persist, unaided, at, or above, the desired acreage with comparable shoot 

density for a period of five years following planting, or in the case of slow-spreading 

species, on a trajectory for reaching the target acreage in a specified time. Use of 

Habitat Equivalency Analysis is strongly recommended to help identifjr and utlize 

realistic recovery horizons. 

Monitoring planted beds is necessary to: (1) ensure that contracted work was 

performed to specifications, (2) allow for mid-course corrections, and (3) improve 

planning of subsequent projects. Adequate monitoring will involve determination of 

percent survival of planting units, the areal coverage of each planting unit, and the 

number of shoots per planting unit. For small planting, these measures may be taken 

on each planting unit. For larger planting, monitoring will need to be conducted 

using numerous randomly (as opposed to arbitrarily) located sites within the area that 

was planted. Specific recommendations on making these measurements, converting 

measurements into the most useful form, appropriate sizes of quadrats, etc. are provided. Monitoring should occur at least quarterly during the first year following 

planting, and biannually for at least four years after this (i.e., for a minimum of five 

years). If replanting is necessary, this sets the five-year-clock back to zero for the area 

that is replanted. This five-year rule may need to be extended in situations where 

seagrasses spread very slowly. If two replanting following the initial planting fail to 

establish a successful grass bed, then managers should abandon these failed sites or 

portions thereof and find areas more suitable. 

The bottom-line is that the tavget acreage must persist with a comparable shoot 

density for an adequate period of time to assure that the planted seagrasses are well 

established and likely to provide the desired ecosystem functions. Although various 

percent survivorship criteria previously have been used to define planting success, 

these criteria may miss the point that it is not percent survivorship alone, but coverage and persistence that are the critical components of establishing adequate seagrass 

systems, especially since the ultimate metric of success is generating acre-years of seagrass service (i.e., to offset interim lost resource services). 
- 

148 Guidelines for the Conservation and Restoration of Seagrasses 

Costs of successfully establishing seagrass beds vary &om a few thousand to many 

thousands of dollars per hectare depending on site selection, experience of workers 

and managers, extent and rate of subsequent disturbance, water clarity and depth (i-e., 

light avadability and quality), temperature, extent of monitoring following the plantings, and numerous similar factors. Published costs for planting range &om about 

$25,000 to $50,000 per hectare, with an average of about $37,000. These general 

estimates likely greatly underestimate the cost of a particular project because of the 

particular concerns associated with each site, the size of the site, the coverage that 

needs to be achieved, the species of seagrass involved, special logistic costs, monitoring, and profit; the latter &equently overlooked! Values in the range of $200K per acre 

may be more reasonable over the life of the entire project. 

CONSERVATION, MITIGATION, AND RESTORATION 

Despite proven techniques, the success rate of permit-linked mitigation projects 

remains low overall. There is continuing dif6culty in translating mitigation concepts 

into legal principles, regulatory standards, and permit conditions that are scientifically defensible and sound. To prevent continued loss of seagrass habitat under compensatory mitigation, decisive action must be taken by placing emphasis on improving compliance, generating desired acreages, and maintaining a true baseline. 

Seagrass planting is not an experimental technique. Seagrass beds can be 

restored but preservation is the most cost-effective course of action to sustain seagrass 

resources. Planting for mitigation should be treated as the last practicable alternative. 

There must be communication and coordination of efforts between agencies and 

those that would alter seagrass habitat. Seagrass beds have been recognized as a valuable resource essential to the health and hnction of coastal waters, and greater awareness and public education is necessary for conservation of this resource. The problems of restoring seagrass beds are largely those of appropriate site selection, plant 

demography, care in planting, and subsequent disturbance. 

Seagrass habitat conservation must become a national focus because loss can 

occur rapidly when conditions are altered and because recovery occurs at a much 

slower rate. If an area is already stressed due to diminished water quality &om point 

and non-point source runoff, addition of a new channel or increased boat traffic to 

a new marina may push the nearby seagrass population beyond its physiological limits. Once the habitat is lost, turbidity &om nonstabilized sediments may make 

restoration impossible, with concomitant additional reduction in water quality. 
-- 

Chapter 5: Manager's Summary 149 

As more information is made available to managers regarding the fhction of 

seagrass ecosystems and the costs involved in mitigating for their loss, fewer permitted impacts are occurring with more emphasis placed on impact avoidance and minimization. Our ability to wisely manage, conserve, or restore these productive 

ecosystems is limited due to our fi-agmentary understanding of seagrass ecology and 

distribution and inconsistent application of available technology. Managing seagrass 

systems requires that managers understand some basics of seagrass ecology and having historical perspective regarding the particular seagrass beds being affected by their 

management decisions. Why place such a priority on conservation if mitigation is 

no longer experimental? Although techniques and protocols exist that produce persistent seagrass beds, they are applied inconsistently, and have resulted in large-scale 

failures. Key issues to protect existing seagrass habitat include improved wastewater 

treatment, surface run-off control (i.e., watershed management), restrictions on certain shellfish and fish harvest methods, control of boat tratitic, and public education. 
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Acknowledgements 

This has been a nearly five-year effort, with references and changes being added 

right until the very end in July 1998. The field of seagrass planting for restoration 

and mitigation continues to grow and we ask the reader to recognize that this document represents an arbitrary point in time to summarize and reflect on the status of 

the science. 

We would like to thank the many people who took time to answer questionnaires, return phone calls, emails, unearth and fax and mail reports, send reprints, 

share unpublished material and talk to us on the phone and in person right up to the 

last bell. We cannot list you all without fear of omission; the list involves dozens of 

people &om private and public sectors all around the country. We thank you all very 

much. Thanks are extended to the many people who contributed to the nonanonymous peer review: Mike Durako, Robert Hoffman, Curtis Kruer, Robin 

Lewis, Mary Ruckelshaus, Arthur Schwarzschild, Fred Short, Ron Thom, Edward 

Townsend, Susan Williams, Paula Whitfield and Sandy Wyllie-Echeverria. However, 

we did not always concur with the reviewers' recommendations and their views are 

not necessarily those expressed herein. Arthur Schwarzschild drafted the sections on 

temperature and salinity effects. Patricia Hay, drafted the executive summary and 

Chapter 5, the Manager's Summary. 

Special thanks are extended to EdTownsend and Paula'Whitfield for their tireless editorial work and their contributions to our research base over the years. For 

this project, Paula spent days reading all the documents and creating a relational data 

for the comparative analysis. Among many other tasks, Ed and Paula marshalled the 

literature citation effort and conducted extensive editing tasks. Gene Cope facilitated production of the color plates. Patti Marraro edited the references. Erik Zobrist 

graciously provided a last-minute review. Sandy Rodgers calmly and professionally 

performed the editing and typesetting. Finally, thanks are extended to our contract 
190 Guidelines for the Conservation and Restoration of Seagrasses 

monitors, Isobel Sheifer, David Johnson and Mike Murphy of NOAA's Coastal 

Ocean Program for their support and patience in the long production of this document. Funding for this document was provided by the Beaufort Laboratory of the 

National Marine Fisheries Service, NOAA, the NMFS Restoration Center, and a 

grant fiom NOAA's Coastal Ocean Program. 
Appendix A: Glossary 193 

Appendix B: Seagrass species characteristics 199 

Appendix C: Partial list of equipment 

Appendix D: Suggested minimum components of proposals and reports 207 

Appendix E: Example mitigation/restoration plan. 209 

Appendix F: Recommendations for further reading 221 
APPENDIX A 

Glossary 

allele(s): any of the different forms of a gene that occupy the same locus on homologous chromosomes (the latter being the chromosomes that pair during meiosis) 

allozyme: one of several forms of an enzyme which is coded for by different alleles at a given locus on a chromosome; contrast with isozyme 

apical: as in apical meristem; the distal unit of a seagrass plant that gives rise to new 

plant compenents, leading to vegetative expansion 

arbitrary sample: a sample taken without regard to potential bias in the location, 

quality or quantity of the variable being sampled 

areal coverage: coverage of the sea floor by seagrass expressed on a unit area basis 

asyrnptote(s): portion of a graphed curve that levels out with respect to the independent variable 

baseline acreage: the amount of habitat acreage at some past time that is used as 

a reference for computing subsequent changes in habitat abundance 

Beer's Law: a mathematical expression that describes the exponential decay of light 

quantity with increasing water depth as a function of turbidity 

bioturbation: the physical disruption of the sea floor and/or seagrass bed by the 

activity of any number of animals (e-g., rays, crabs, fish). 

clone: here, an assemblage of seagrass shoots formed through asexual reproduction, 

arising &om a sexually-reproduced individual 

compensatory mitigation: the establishment of a wetland area for the purposes of 

offSetting a permitted loss of a like wetland 
194 Guidelinesfor the Conservation and Restoration of Seagrasses 

compliance: the degree to which stated project goals are attained 

continuous cover: a seagrass bed with little or no open areas of unvegetated sea 

floor 

coverage rate: the rate at which planting units colonize the sea floor expressed on 

a unit area basis per unit time 

creation: in reference to wetlands, the conversion of persistent non-wetland area 

into a wetland, contingent upon the status of the non-wetland area having been persistent through 100-200 years 

cultivated seagrass: seagrass plants that are generated under any one of several 

anthropogenically-mediated techniques (e.g., tissue culture, micropropagation) 

donor bed: an existing seagrass bed fiom which transplant material is harvested for 

planting elsewhere 

dredge and fill: the act of dredging or mng of a habitat, particularly in reference 

to the management of this activity under sec. 404 of the Clean Water Act and Section 

10 of the Rivers and Harbors Act 

enhancement: the increase in one or more values of all or a portion of an existing 

wetland by man's activities, often with the accompanying decline in other wetland 

values 

erosion scarp: a point of erosion in a seagrass bed that results in vertical relief and 

often exposes seagrass roots and rhizomes. 

genet: a group (here seagrass shoots) derived by asexual reproduction fiom a single 

original zygote such as a seedling or isolated shoot (usually with a rhizome apical 

where this is required for clonal expansion) 

genotype: the heritable genetic constitution of an individual 

growth strategies: the rate at which individual species of seagrass reproduce by 

either sexual (seed production) or asexual means (tillering of rhizomes across the bottom accompanied by vegetative production of new short shoots) 

habitat: an unspecified spatial scale which has physical, chemical and biological 

attributes conducive to the maintenance and propagation of biota 
-- 

Appendices 195 

habitat functions: services provided to the ecosystem by a given habitat type (e.g., 

shelter, stability, refuge, nursery) 

impact avoidance: avoidance of any alteration of an existing wetland 

impact site: a site containing jurisdictional wetlands which is being, or is going to 

be altered by anthropogenic actions 

in-kind: planting a wetland species that is the same as the one that was damaged 

isozyme: one of several forms of an enzyme that is produced by different (nonallelic) loci; contrast with allozyme. 

jurisdictional wetlands: wetlands under the management jurisdiction of a regulatory agency 

long shoot: a collection of short shoots physically located on the same rhizome 

lower depth limit: the depth to which seagrass can grow which is determined by 

the amount and possibly the quality of available light; i.e., compensation depth 

meristem: as in apical meristem; the portion of a plant that contains tissue which 

divides and gives rise to similar cells and/or plant structures (e.g., tissues, organs, rhizome, roots, leaves) 

metapopulation: a group of conspecific populations co-occurring in time, but not 

in space 

minimization: minimizing the degree of alteration of an existing wetland by modification of a project plan 

mitigation: the actual restoration, creation, or enhancement of wetlands to compensate for permitted wetland losses 

monitoring: collection of habitat attributes (e.g. depth, cover, species composition 

or planted seagrass growth) relative to assessment of site conditions, planting site suitability, or planting performance. 

no net loss: a quantitative evaluation which compares habitat area replaced or conserved with the habitat area lost 
196 Guidelinesfor the Conservation and Restoration of Seagrasses 

off-site: planting of a wetland as some form of mitigation at a location not in immediate proximity to the physical location of the damaged wetland for which it is to 

compensate 

on-site: planting a wetland on an area which has suffered a loss of a wetland habitat 

out-of-kind: planting a wetland species that is not the same species as the one that 

was damaged or lost 

PAR (photosynthetically active radiation): wavelengths of light between approximately 400 to 700 nanometers 

patchy distribution: seagrass beds (areas where rhizomes overlap) and associated 

unvegetated bottom; either distinct, isolated patches of seagrass in a predominantly 

unvegetated sea floor or meandering patterns of unvegetated bottom in a predorninantly vegetated area 

peat pot: in reference to a seagrass transplanting technique where plugs of seagrass 

are removed and placed into commercially available, small cups constructed of compressed peat; the plug and peat pot container are then planted in the sea floor 

permitting agency: a resource management agency (e.g., state, federal) that has 

statutory authority for issuing or commenting on permits dealing with wetlands 

modifications 

phenotypic plasticity: the capacity for marked changes in a phenotype as the result 

of environmental influences upon the genotype during development 

pioneering species: a species of seagrass with a growth strategy than enables it to 

rapidly colonize unvegetated sea floor 

planting performance: attributes of a planted area which can be used as indicators 

of project success; eg, planting unit survival, planting unit population growth and 

coverage rate. 

planting ratio: the ratio of planted, and eventually, persistent seagrass acreage to the 

amount of acreage lost in a given project 

planting unit(s): an individual core, plug, staple, peat pot, sod, etc., and the associated plant material used in a planting operation 
- 

Appendices 197 

plugs: in reference to a seagrass planting technique where hollow tubes are used as 

a coring device into a seagrass bed, thereby harvesting the sediment "plug" in the 

tube with the associated seagrass 

propagule: any portion of a seagrass plant that is capable of colonizing a new site 

after becoming detached fiom an existing plant (e.g., seeds, plant fiagrnent with 

leaves and roots) 

propeller scarring: typically a long, linear fbrrow excavated in the bottom as the 

result of operating vessels in water depths shallower than the drafi of the drive unit 

(propeller); results in excavation of seagrass 

PU: planting unit 

ramet: a member of a clone, assumed to be of identical genetic composition as the 

rest of the clone, and that will continue to survive if separated fiom the clone 

random sample: a sample taken such that each sample unit has an equal (unbiased) 

probability of being selected 

restoration: returned fiom a disturbed or totally altered condition to a previously 

existing natural, or altered condition by some action of man; refers to the return of 

a pre-existing condition 

rhizome: sensu Websters' Collegiate Dictionary: a somewhat elongated, usually horizontal plant stem which produces shoots above and roots below and is distinguished 

fiom roots in possessing buds, nodes and scale like leaves 

rhizome apical: the meristematic region at the terminus of a long shoot that gives 

rise to further rhizome growth and differentiates to give rise to short shoots 

rhizosphere: portions of the sediment occupied by the roots and rhizomes of seagrass 

salvage operation: transplanting seagrass &om an area where activities are planned 

which will destroy that seagrass 

Section 404 permit process: references section 404 of the Clean Water Act which 

provides the statutory authority to specific federal agencies regarding dredge and fill 

activities in the waters of the United States 
198 Guidelinesfor the Conservation and Restoration of Seagrasses 

sediment resuspension: the transfer of sediment &om a resting position on the sea 

floor to the water column as the result of some external action such as wind waves, 

tidal currents, or a vessels' propeller(s) 

short shoot: an individual meristem located on a long shoot which produces leaves 

and roots 

site survey: a quantitative assessment of the amount of plant material to be disturbed, its distribution and the environmental conditions at impact and planting sites 

prior to initiating a project (see also monitoring) 

slow release fertilizer: a fertilizer which releases nutrients over ime at a given temperature 

staple: in reference to a seagrass planting technique where plants are washed fiee of 

sediment and typically are attached to a U-shaped metal bar (staple) which is then 

inserted points down into the sediment, pinning the seagrass to the sea floor 

success (planting): although the definition of this term may be changed with the 

goals of the project at hand, a broadly applicable form is as follows: the unassisted persistence of designated seagrass coverage for a prescribed period of time (suggested 

minimum of 5 years) 

turbidity: the degree of opacity of the water column as a result of dissolved and suspended material in the water column 

unassisted persistence: seagrass beds maintained by natural recruitment and have 

not been assisted by any deliberate anthropogenic manipulation 

unvegetated sea floor: the portion of the estuarine floor which is not colonized 

by rooted submerged aquatic vegetation 

water transparency: a measure of the degree of water clarity 

wild stock (stands): naturally-occurring seagrass beds 
APPENDIX B 

Seagrass Species Characteristics 

(Alphabetical order by scientific name; modified 6om Fonseca 1994; for 

greater taxonomic detail see den Hartog 1970, Phillips and Menez 1988) 

Halophila decipiens: An extremely fi-agile seagrass that is often conhsed with some 

rhizophytlc algae, such as Caulerpa spp. The leaf blades are 10 to 25 mm long and -5 

mm wide and occur in pairs at each rhizome internode (one root per node). The 

blade margin is finely serrated and the end of the blade is rounded. Blades are -1 

cell thick and translucent. Rhizomes are typically 1 mm in diameter. The entire 

plant community can easily be dislodged &om the sediment although because of it's 

high fecundity and rapid rhizome extension rate (Josselyn et al. 1986) it is a ruderal 

or opportunistic species. Plants cannot tolerate burial and will disintegrate beyond 

recognition in 24 h if buried, making the carbon and other nutrients fixed by 

Halophila the most labile of any seagrass. Although diminutive, this seagrass genus can 

significantly enhance sediment stabilization (Fonseca l989b). In general, this genus 

can withstand very low light conditions (-1% of insolation as opposed to -20% for 

other genera) and occurs at great depths (>40 m; Josselyn et al. 1986, Kenworthy et 

al. 1989), or in shallow turbid water, under docks or as an understory to other seagrass species. 

Halophila engelmanni: Similar in an ecological context to H. decipiens but rather than 

having leaf pairs at each rhizome node, there is one stem per rhizome node with 

upwards of 7 leaves on each stem. Blades are more elongated and pointy than H. 

decipiens. 

Halophila johnsonni (threatened species): Also similar in an ecological context to H. 

decipiens and also has a leaf pair at each rhizome node. Blades are more elongated and 

pointy than H. decipiens and veins sweep upwards fi-om the center line of each leaf at 

nearly 45 degrees, but blade margins are not serrated. 
200 Guidelinesfor the Conservation and Restoration of Seagrasses 

Halophila hawaiiana: Again, similar in an ecological context to H. decipiens and also 

has a leaf pair at each rhizome node, Blades are more elongated and pointy than H. 

decipiens although unlike H. johnsonii, leaf tips are more rounded. 

Halophila ova1is:Very similar in appearance to H. decipiens except H. ovalis has 10-25 

leaf veins whereas H. decipiens only 6-9 leaf veins. 

Halophila minor: Smaller than H. decipiens with a maximum length of 14 rnm and 

has only 3-8 pairs of leaf veins. 

Halodule wightii (contrast with Ruppia maritima): This species was once classified under the genus Diplanthera. References fiom earlier than 1975 often refer to 

this species by that name. It has a lower depth limit equal to turtle grass and manatee grass. It also can occur in very shallow water and it is noted for its relative tolerance to desiccation once rooted. It often forms large pancake-like patches reaching 30 m diameter) or extensive meadows on shallow shoals and flats, experiencing 

regular exposure at low tides (the basis for its common name). The fine (1-3 mm 

width) blades occur in groups of two to four on a shoot and vary in length according to depth as does turtle grass. Blade lengths range fiom as small as 5 cm to over 

40 cm. This species forms very dense beds, with upwards of 5000 shoots per m2 

(although 11000 can occur; pers. obs). Flowers are difficult to locate as they occur 

on the base of the shoots near the sediment surface. Rhizomes are fairly shallow, 

rarely being deeper than 5 cm, although roots may extend for 25 cm or more. 

Rhizomes may extend into the water column with attached short shoots which 

appears to be a form of vegetative propagation. These rhizomes may be easily harvested and are efficiently transplanted with the staple method. 

This species can easily be confused with widgeon grass. Four visual clues separate them: (1) widgeon grass produces extensive flowering stalks often reaching a 

meter in length, with numerous seed clusters resembling miniature rattlesnake rattles 

while flowers in shoalgrass are rarely seen; (2) the blade tip of shoalgrass forms a 

miniature three-point crown, with the two leaf margins and central vein of the leaf 

forming the points. Widgeon grass blades taper to a single sharp point; (3) shoalgrass 

rhizomes are usually very straight and white often somewhat zigzagged when 

viewed fiom above and may be green or white; and 4) shoalgrass has two roots per 

node on the rhizome whereas widgeon grass has one root per node. 

Phyllospadix scouleri: Found on rocky substrate and appears much like Zostera; blades 

can be 2 meter long but compared with Zostera, are much narrower, only up to 4 
Appendices 201 

mm wide. Rhizomes can be covered with many fibers. Abundant, but not limited 

to, north of Monterey, California. 

Phyllospadix serralatus: Found on rocky substrate primarily north of southern 

Oregon. Leaf margins show fine serrations. 

Phyllospadix torreyi: Also found on rocky substrate but deeper than the other 

Phyllospadix spp.; abundant but not limited to south of Monterey, California. Blades 

are different &om the others of this genus in that they emerge &om a sheath that is 

wider than the blade itself with only one blade per sheath. 

Ruppia maritima (contrast with Halodule wightii): This species is a favorite food 

of migratory waterfowl, a fact on which its common name is based. This species does 

not usually form a rhizome mat as dense as that of shoalgrass, but does much to stabilize the bottom. This species is set apart &om all other seagrasses in that it can grow 

in both hesh water and hypersaline conditions (> 70 ppt). See shoalgrass for further 

description and contrast. 

Syringodiumcfiliforme: This species is easily distinguished fi-om all the other seagrass 

species. It is nearly cylindrical. Its long erect blades are - 2-3 mm in diameter and 

there are usually only two leaves per shoot. These beds often accumulate a large 

under story of unattached macroalgae. The rhizome system varies in depth, between 

1-10 cm. Flowering produces extensive branching which extends up into the water 

column, similar to widgeon grass grass but not as extravagant. Rhizomes may extend 

into the water column with attached shoots as described for shoalgrass, again presumably as a means of producing vegetative (as opposed to seed) propagules. As with 

shoalgrass, these propagules make excellent transplanting stock with no app 

Thalassia testudinum: This species is one of the most well-known seagrasses in the 

subtropical regions of the U.S. It is a favorite food of the endangered green sea turtle, hence its common name. Its broad (often > 1 cm wide) deep green, strap-like 

blades (usually three to a plant but may often have upwards of five) cannot easily be 

mistaken for any other marine submerged aquatic macrophyte. Leaf length of the 

plants depends on water depth (as is the case with most seagrasses) and varies &om 

-10 to 75 cm. The leaves emerge &om the sediment at the top of a vertical rhizome 

which rarely protrudes above the sediment surface. The thick, fibrous rhizomes fi-om 

which the individual shoots originate are often located in excess of 20 cm into the 

sediment. This species develops flowers which emerge &om the sediment next to the 

short shoot. Once fertilized, a round seed the size of a small acorn will be produced. 
202 Guidelinesfor the Conservation and Restoration of Seagrasses 

Seeds have been successfully used in planting projects. This species is noted for its 

longevity (sometimes > 10 yr. for an individual shoot) and the dense, extensive 

stands. 

Zostera asiatica: Similar in appearance to Z. marina except that there are many more 

roots per rhizome node and sometimes emerge from the side of a short shoot. 

Multiple sheathes can occur on a single shoot which does not occur in Z. marina. 

Zostera marina: The most common temperate seagrass species. Tremendous variation in size is reported from 30 cm to over 200 cm long. This species occurs on 

both coasts of the U.S. The rhizome is brown with roots located only at the rhizome nodes. A single shoot occurs at the end of each rhizome. A sheath encompasses 3-5 strap-shaped leaves. The leaf tip is rounded, sometimes with a very small 

point at the apex. 

Zostera japonica: Appearing to be a smaller version of Zostera marina, this recently 

introduced species occurs as a Z. marina under story or in intertidal areas not colonized by Z. marina. Leaves are narrow, rarely wider than 15 mm and only -30 cm 

long. Also unlike 2. marina, the blade tips may be asymmetrical or have longer margins than the center (like Iialodule). 
APPENDIX C 

Partial List of Equipment 

This Appendix was modified from Fonseca 1994 and Merkel 1992; see Merkel 

for a more detailed list and integrated discussion of how to implement that list using 

his field methods. 

Depending on the location of the sites, access by boat may be required. Local 

knowledge of wind, tide and navigational hazards should be obtained prior to operations. A prominent listing of emergency numbers and emergency procedures 

should be worked out in advance, with particular attention to the needs of SCUBA 

divers. Reliable, seaworthy vessels which can work in a range of sea conditions and 

water depths should be procure. More than one vessel type might be required. If 

you are not hlly knowledgeable in these areas and do not posses basic training in 

navigation and seamanship, retain trained personnel as boat operators, divers, etc. 

Precautions must be taken against injury during heavy lifiing which is typical for seagrass planting. 

STAPLE METHOD 

Paper coated twist ties (e.g., tomato plant tie-up material) 

Dive knife (or similar tool for loosening the bottom to insert the staple) 

Mesh float buckets (for holding plants washed free of sediment) 

Site markers (stakes, buoys, etc. 3/4" diameter thin wall electrical conduit is relatively inexpensive, comes in 10' lengths and can be easily driven into the sediment 

although it must be cleaned out between uses). Conduit is difficult to see and should 

be marked with reflectors. When possible, white PVC pipe should be used. 
-.- 

204 Guidelinesfor the Conservation and Restoration of Seagrasses 

Waterproof tape measures (100 m variety) 

Lead core lines with ribbons on plating intervals if precise spacing is desired or visibility is so poor that a means of orientation is required at depth (line is manufactured 

for gill nets, survey ribbon must be added) 

or 

Polypropylene line with ribbons may be floated on the surface as a planting guideline for surface-oriented (non-diving) operations. Buoys are also helpful for orientation as are 3/4" diameter thin wall electrical conduit poles, over which PVC pipe 

may be slid to mark boundaries. We recommend the conduit because it cuts into the 

bottom, is more stable in the bottom than re-bar and rusts less (make sure the conduit is cleaned out between uses; fill the conduit with water and shake vertically or 

tap on a hard substrate - the pressure of the water will eventually force out the sediment in the conduit). 

Snorkeling or SCUBA equipment (certified divers only). 

If SCUBA diving is required, develop and rehearse a Dive Accident Management 

Plan. Follow emergency procedures as recommended by recognized safety groups 

such as the Divers Alert Network (D.A.N.). An ample supply of SCUBA tanks, extra 

weights (divers work better negatively buoyant here). Dive Flags should be plentiful 

and obvious. 

Tide tables and updated weather forecast. 

First aid kit including sun screen and insect repellent and, for divers, an emergency 

0, kit. 

Redundant communications equipment. 

Appropriate clothing for exposure cannot be overstated. Equipment such as wet 

suits, wool clothing and foul weather gear which can be worn in the water as well 

as a wind breaker. Waders may be preferred by some people but as seagrass planting 

requires much bending over, it is not unusual to overtop waders. 

Warm or cold fluids (depending on season), gesh water, and high energy foods. 

Polarized sun glasses (enhances visual penetration of the surface). 
Appendices 205 

All of the same operational equipment except for the first four items. These should 

be replaced by the following: 

Peat pots (3" square) 

Plugger (same size as peat pot) 

Tree planting bar 

PVC (or equivalent) float collars to support - 30 peat pots in a tray 

Durable plastic trays to contain - 30 peat pots. 

Heavy (- 10 ga.) wire mesh to fit over peat pots in tray to prevent them fiom floating out as any air pockets are displaced by water. 

All of the equipment for staples except for the first four items. Replace with sufficient core tubes so as to fully utilize the capacity of the transport vehicle. 

Surveys 

Transit 

Meter sticks 

Waterproof tape measures (100 m variety) 

Random number table 

Writing tablets (photocopiable underwater paper on clipboards with prepared data 

collection sheets are useful). Pencils or grease pencils tethered to the tablet with a 

generous length of surgical tubing is inexpensive. 

(OPTIONAL - Depending on survey technique) 

Quadrat: 1 x 1 m 1" PVC sand-filled frame with parachute cord (thin braided nylon 

line) on 25 cm intersections. 
APPENDIX D 

Suggested nimum Components of 

Proposals and 

(modified fiom Fonseca 1994). 

A. Mitigation Proposal 

1. Identification of goals 

a. compensatory mitigation or restoration 

b. specifjr replacement ratio and final acreage 

2. Description of impact site survey methodology 

3. Site selection criteria and list of sites 

4. Location and availability of donor material/demonstration of appropriate collection permits 

5. Planting methodology 

6. Spacing and spatial arrangement on site 

7. Monitoring specifications 

a. identification of variables and methods of collection 

b. monitoring and reporting fiequency and duration (suggest minimums of 4 

times in year 1,2 times in year 2, and annually thereafter; this fiequency 

allows implementation of Item 8. 

c. monitoring interpretation criteria 
208 Guidelines for the Conservation and Restoration of Seagrasses 

8. Specifj criteria for remedial planting 

9. Specifj criteria for success (e.g., acreage of seagrass cover to be generated [Ib], 

species, duration of unassisted persistence). 

10. Specifj duration of responsibility and consequences of non-compliance with 

Items 1-9. 

B. Time Zero Report 

1. Results of impact site survey and statistical relevance of the survey methodology. 

2. Documentation of implementation as compared to the descriptions of Items 

1-6 above. 

C. Progress Reports 

1. Results of monitoring as described in Section A, Item 7, above. 

2. Identifj and document any remedial action taken 

3. Provide best professional estimate of likelihood of meeting Item 9, Section A. 

D. Final Project Report 

1. To improve subsequent projects, review operational errors/shortcomings in 

the context of the original work statement. 

2. Identifjr and document compliance with all stated requirements, with particular attention to Section A, Items 1,7b, 8,9, and 10. 
APPENDIX E 

Example Propeller and Mooring 

Scar Restoration Plan 

I. BACKGROUND 

The appropriate scale for the restoration should be determined using Habitat 

Equivalency Analysis (HEA) methodology (Attachment I). 

11. RESTORATION APPROACH 

The restoration of seagrass scars created by vessel impacts represents is a viable 

approach to off-site restoration. Restoration efforts will should on seagrass transplanting of scars in heavily injured Thalassia testudinurn (turtlegrass) seagrass meadows 

such as described by Sargent et al. (1995) within the Florida Keys. Seagrass beds can 

be scarred by many activities, but scars are most commonly made when a vessel is 

moored and the ground tackle gouges the bed or the vessel operates in areas vegetated by seagrasses that are too shallow for the vessel to avoid contact with the 

seafloor. The vessel's hull and/or propeller tears and cuts up the leaves, stems and 

roots of the seagrasses, typically leaving long, narrow, trench-like furrows devoid of 

seagrass. A typical prop scar created by a small vessel (less than 6.5 m in length) is 

approximately 0.25-0.5 m wide and 0.1-0.5 m deep. Larger vessels with twin propellers or inboard engines (greater than 6.5 m in length) can produce deeper (0.25- 

0.75 m) and wider trenches (0.5-1.5 m). While smaller scars may naturally recolonize over several years, some scars, especially in Thalassia seagrass beds experiencing 

moderate tidal currents or wave action, persist for decades and can enlarge &om erosion (Zieman, 1976). The slow growth rate of Thalassia contributes to its comparatively slow recolonization of the bare sediments in scars. 

One technique for restoring slow-growing seagrass species such as Thalassia 

focuses on planting another seagrass species such as shoalgrass, Halodule wrightii 
2 10 * Guidelines for the Conservation and Restoration of Seagrasses 

(Halodule) to achieve a "compressed succession" (Durako et al., 1992; sensu Fonseca, 

1994). The compressed succession is a planting technique intended to achieve a 

more rapid rate of seagrass recovery by temporarily substituting the faster growing 

Halodule for the slower growing Thalassia. This sequence promotes more suitable 

conditions for Thalassia to recolonize the scar while stabilizing the sediment and 

establishing hnctional seagrass habitat. 

111. RESTORATION SITE SELECTION 

There are, however, a number of management decisions that can be made within the permit process to ameliorate a loss in habitat and better approaches the goal 

of no net habitat loss. Mitigation in its broader definition typically also includes 

impact avoidance and minimization (the latter term unfortunately implying an 

acceptable net loss of acreage). In practice, avoidance and minimization are sometimes difficult to achieve. The existence of techniques to transplant seagrass has often 

been used to justify the destruction of existing, productive habitat but this approach 

has consistently produced a net loss of habitat. This net loss of habitat occurs for a 

number of reasons: one reason is that because the permit-associated activities that 

destroy seagrass beds in the first place typically are long lasting (i.e., creation of channels, bridges, bulkheads) and do not allow enough area for on-site planting to o6et 

the loss of habitat. 

If planting is considered at a location not on the original impact site (off-site 

compensatory mitigation), that site would preferably not be an area that itself has lost 

seagrass to some other impact (i.e., if one permits a loss of seagrass for some form of 

coastal development [e.g. -1 acre] and plants an equivalent area [+1 acre] onto a site 

which had previously lost seagrass [a previous loss of -1 acre] but was not associated 

with the project at hand, then the net change in habitat is: [-I + -I)] +1 = -1 acre; 

because only the repair of the original problem was addressed, the new, most recently impacted site then constitutes a net loss of local habitat). 

Moreover, what if a site chosen for planting does not currently support seagrass? 

Selecting an appropriate planting site is the single most important step in the entire 

process. If an off-site planting area must be selected, whether it be for restoration 

or mitigation, it must pass a simple, but exacting, test: "If seagrass does not currently exist at the (chosen) site, what makes you believe it can be successfully established?" (Fredette et al. 1985). In the absence of site history information, one must 

then assume absence of seagrass indicates some inherent difficulty in colonization or 

persistence of seagrass. The events influencing the colonization process are some- 
-- 

Appendices 2 1 1 

times difficult to document because they are often aperiodic, yet acute events (e.g., 

extreme low tides, storms, migrating rays excavating the bottom). Naturally unvegetated sea floor should not be substituted for vegetated bottom as this typically creates only a transient seagrass bed and alters, not necessarily improves, exiting habitat 

functions. There are few off-site compensatory mitigation sites that do not involve 

habitat substitution or can satisfjr the no-net-loss goal. 

Planting sites must meet (at least) the following criteria: 

1) they are at similar depths as nearby natural seagrass beds; 

2) they were anthropogenically disturbed; 

3) they exist in areas that were not subject to chronic storm disruption; 

4) they are not undergoing rapid and extensive natural recolonization by seagrasses; 

5) seagrass restoration had been successful at similar sites; 

6) there is sufficient acreage to conduct the project; and, 

7) similar quality habitat would be restored as was lost. 

In the case of scarred habitat, scarring can be an ongoing impact on seagrass 

meadows and restoration efforts should be conducted at locations that provide protective management, such as restrictions on power vessel operation where restoration 

is less likely to be disturbed by further scarring. Additional sites may be considered 

outside of such management areas where other site characteristics or circumstances 

exist which will minimize the threat of future injury &om vessel groundings. 

Preliminary site selection of scars should encompass the inspection of existing 

high resolution vertical aerial photography or detailed on-site mapping Low level 

vertical photos are required to quantitatively delineate areas. Photographs should be 

inspected, and scars identified and measured to calculate total area. If existing aerial 

photographs are not adequate, new aerial photography should be collected. 

Following preliminary selection, the sites should be verified for the presence of seagrass adjacent to the scar and for plantable unconsolidated sediments within the scar. 

Verification should be conducted by snorkel or SCUBA divers, depending upon 

water depth at the site. Plantable unconsolidated sediments in a scar should be medium to fine grain and at least 10 cm thick. Sediment thickness should be determined 

by inserting a probe into the sediment approximately every 5 m along the length of 

the scar. Scars should be targeted in areas that at the time of the survey appear to be 

susceptible to additional erosion and scar expansion, particularly as the result of disturbance caused by water motion (e.g., waves, tidal currents). 
-- - 

212 Guidelines for the Conservation and Restoration of Seagrasses 

IV. METHODS 

A. Planting Area, Site Marking and Site Preparation 

We present here guidance for propellor scar restoration; planting broader areas 

(e.g. mooring gouged areas) would follow similar procedures. Using a conservative 

estimate for scar width of 0.5 meters, the planned acreage should require delineating 

X linear meters of scar (Area in m2 / 0.5); this estimate is conservative given that -' 

narrower scars translates into a greater linear distance needed to restore. The location of each scar selected for planting should be established using a differentially corrected Global Positioning System (GPS). Each end of the selected scar should be 

identified with a permanent marker for positioning and the distances calculated in a 

Geographical Information System (GIs). Maps delineating the sites and the location 

of scars should be produced with GIs. 

B. Planting Species and Technique 

The selected scars should be planted with planting units of shoalgrass, Halodule 

wightii to achieve a "compressed succession" (attributed to M. Moffler, Durako et 

al., 1992; sensu Fonseca, 1994). The compressed succession is a planting technique 

intended to achieve a more rapid rate of seagrass recovery by temporarily substituting the faster growing Halodule for the slower growing Thalassia. This sequence promotes more suitable conditions for Thalassia to recolonize the scar while stabilizing 

the sediment and establishing functional seagrass habitat. 

C. Planting Methods 

Planting should occur during April and May, months which present optimal 

environmental conditions for planting. The planting method to be used should use 

commercially available "peat pots" (Fonseca et al., 1994). Peat pots (one peat pot = 

one planting unit) are made of an organic, compressed peat material with a surface 

area of 7.6 cm2 and approximately 7 cm deep. A sod plugger of the same dimensions 

as the peat pot is used to extract plugs &om the donor seagrass bed which is then 

extruded into the peat pots (see Fonseca, 1994 and Fonseca et al, 1994 for detailed 

description of method). The donor beds should be located on shallow, sandy shoals 

where Halodule grows at densities of at least 3,000 shoots per m2 yielding planting 

unit shoot densities of at least 17 shoots per planting unit. Donor plugs should be 

extracted at no less than 25 cm between plugs to minimize any effects on the donor 

beds. 
Appendices . 2 13 

Prior to extruding a plug of Halodule, approximately 10 grams of constant release 

(70 day) phosphorus fertilizer (0-39-0, nitrogen-phosphorus-potassium) or an equivalent form should be added to each peat pot. Phosphorus has been shown to be a 

highly limiting nutrient in carbonate sediments such as are found in the Flbrida Keys 

(Powell et al., 1989; Fourqurean et al., 1995). Plugs should then be planted at 1.0 m 

intervals in the scars selected for restoration. 

.5 

V. SEAGRASS TRANSPLANT MONITORING 

Monitoring of the restoration project is necessary to provide data required to 

evaluate the viability of the restoration project based on the performance standards 

identified in SectionVI and to permit timely identification of problems or conditions 

that may require corrective action to ensure the success of the restoration project. 

Restoration monitoring herein should be in accordance with the following terms 

and specifications. 

A. Monitoring schedule and activities 

Field collection of data for performance monitoring should occur for four years 

afier planting. Original plantings should be monitored for three years and potential 

remedial plantings inyear 2 should be monitored for three years for a total monitoring period of four years. Under this schedule the monitoring would be conducted 

as follows: 

Year 1 - day 60,180,365 

Year 2 - day 180,365 

Year 3 - day 180,365 

Year 4 - day 180,365 

The precise dates are weather dependent. At day 60 ofYear 1, each surviving planting unit should receive an additional spike of constant release phosphorous fertilizer 

(0-39-0, nitrogen-phosphorus-potassium) to be delivered to each planting unit. 

Semi-annual refertilization of surviving Halodule planting units should be required at 

each planting unit. Alternatively, bird roosting stakes could be installed - every 5-10 

m along scars; the roosting birds defacate into the water and fertilize the plantings 

with their phosphorous-rich defecant. This has been shown to be an extremely 

effective means of accelerating Halodule growth in shallow water and in prop scar 

restoration (Powell et al. 1989, Progress Report 11, Prop Scar Restoration Pilot Study, 
2 14 Guidelinesfor the Conservation and Restoration of Seagrasses 

December 1995). The drawback is that rows of stakes may be mistaken for navigational aids, drawing additional boaters to run alongside, fkrther scarring the adjacent 

beds. Bird roosting stakes can only be used with appropriate navigational markings 

to discourage such action. 

B. Data Collection 

Monitoring should focus on documenting the numbers of apicals at planting 

time, planting unit survival, shoot density and areal coverage under the following 

schedule and definitions. This monitoring protocol applies to original planting for 

three years (Year 1-3) and to remedial planting under Section VII for three years 

wear 2-4). 

1. Apical counts 

Prior to planting, one planting unit (i.e. peat pot core) out of every one hundred (100) collected should be examined for the number of rhizome apicals. 

2. Survival 

Each scar should be examined for survival of all planting units during each survey in Year 1 (60, 180 and 365 days) or until coalescence. Survival of each species 

should be expressed as a percentage of the original number, but the actual whole 

number should also be reported. 

3. Shoot density 

A separate (fi-om survival) random selection of three (3) planting units of 

Halodule per scar or per 100 planted PU (whichever yield the higher sample size) 

should be assessed for number of shoots per planting unit at each survey time until 

coalescence begins. Mer some planting units begin to coalesce, 3 randomly selected locations per scar or per 100 m (100 PU) should be surveyed for shoot density 

over a 1 meter linear distance along each planted scar at 0.0625 m2 (25 cm x 25 cm) 

resolution. Shoot density should be monitored for three (3) years. 

4. Areal coverage 

The randomly selected planting units (may be same as shoot density selection) 

should be surveyed for coverage at each survey time starting at day 180 ofyear 1. 

Measurements should be taken at a 0.0025 m2 (5 cm x 5 cm) resolution prior to 
Appendices 2 15 

coalescence and over a 1 meter linear distance along a scar at 0.0625m2 (25 cm x 25 

cm) resolution afier coalescence for each seagrass species present at each survey time. 

Areal coverage should be monitored for three (3) years. 

5. Video Tape Transects 

Five 100 meter transects along randomly selected portions of the planted scars 

should be video-tape recorded to establish permanent visual documentation of the 

progression of areal coverage of seagrass through time. A metric tape measure should 

be laid along the central (long) axis of the scar and should be included in the video 

tape to allow physical reference of locations within the scar. Video recordings should 

be taken at each survey time during the monitoring period of three (3) years. 

Observation-based assessment of success may be substituted for 3 and 4 above, if 

quadrats are used in accordance with a Braun-Blanquet survey method (see 

Attachment 11) if the data are obtained fiom the video tape (making the observational data base available for cross-checking). The same number of sample points 

must be obtained with the same spatial extent (i.e., survey each scar). Similarly, 

Braun-Blanquet observations of cover at every meter along each scar may also be 

obtained fiom the video tape to obtain estimates of planting performance. 

C. Reports 

Monitoring reports (up to a total of 9) should include copies of raw data gathered in each survey, an analysis of the data, and a discussion of the analysis. Originals 

of all video tapes recorded since the previous report should be provided with each 

new report. Originals of all video tapes and other photography should be turned 

over to the permitting agency following project completion by the party conducting the monitoring. 

VI. PERFORMANCE STANDARDS 

Although it is the overall objective to restore Thalassia at the selected scar sites, 

performance criteria should be based on the success of the Halodule planting as the 

planting methodology used is designed to expedite the recovery of Thalassia. 

A. Apicals 

A minimum average of one horizontal rhizome apical per unit should be maintained in all original planting and remedial planting. 
2 16 Guidelinesfor the Conservation and Restoration of Seagrasses 

B. Survival 

The survival rate shall be considered successfbl if a minimum of 75% of the 

planting units have established themselves by the end ofyear 1. If it is determined 

that less than 75% survival has occurred by the end ofyear 1, then remedial planting 

should occur during the next available planting period to bring the percentage survival rate to the minimum standard by the next monitoring survey. 

C. Growth 

The third success criteria should be the measured growth rate of bottom coverage. The growth rate should be considered successfbl if, starting after one year, the 

planted seagrass in the scars (restoration sites) is projected to achieve 1.55 acres of 

bottom coverage, with 95% statistical confidence, within the three year monitoring 

period for original planting. If this criteria is not met, then remedial planting should 

occur during the next available planting period. 

VII. REMEDIAL PLANTINGS AND/OR PROJECT MODIFICATIONS 

If data &om a monitoring report establishes that the performance standards 

described in SectionV are not being met or are projected not to be met, remedial 

planting of those affected seagrass species should occur. If there is a recurring problem with survival of plantings or replanting in a particular area, remedial planting 

should occur in another scar within the Sanctuary subject to the approval of permitting agencies. 

Based on past experience in seagrass restoration efforts, it is assumed that 30% 

of the planted area should require remedial planting in Year 2. All original planting 

should be monitored for three (3) years in accordance with Sections V and VI. 

Remedial planting should be monitored for three (3) years subsequent to the date 

of a remedial planting. 

VII. PROJECT PERMITTING 

The seagrass restoration and monitoring outlined in this plan should be implemented consistent with any applicable state or federal permitting requirements. The 

format of the restoration and monitoring plan outlined in this document may be 

amended in order to comply with applicable permitting requirements. 
.-- 

Appendices 21 7 

IX. CONTRACTOR(S) 

The permitting agecny should utilize the services of one or more qualified contractors to implement this restoration and monitoring plan. 

X. PERMITTING AGENCY OVERSIGHT OF SEAGRASS RESTORATION 

PROJECT 

The agency should oversee the implementation and monitoring of the seagrass 

restoration project in order to ensure its implementation in accordance with the 

terms of this plan. Costs which the agency should incur to provide effective oversight are part of the costs of implementing this seagrass restoration and monitoring 

plan. Activities which the agency may undertake in order to provide for effective 

implementation of this plan include, but are not limited to, the following: 

a. actions associated with the identification, selection and hiring of any contractor(~) who should implement any part of this plan, including monitoring or 

remedial actions, 

b. oversight of any field work at the project site, including remedial actions, 

c. inspection of any completed field work, including remedial actions, to determine whether implementation is in accordance with this plan, including any applicable contract or permitting requirements, 

d. review and evaluation of monitoring reports, 

e. identification and direction of any actions needed to bring field work, including remedial actions, into compliance with standards for project performance identified in this plan, 

f. actions to address NEPA and permitting processes, and 

g. actions associated with final site selection. 

XI. REFERENCES 

Durako, MJ., M.O. Hall, E Sargent, S. Peck. 1992. Propeller scars in seagrass beds: 

an assessment and experimental study of recolonization in Weedon Island State 
2 18 Guidelinesfor the Conservation and Restoration of Seagrasses 

Preserve, Florida. p. 42-53 IN Webb, EJ. (ed.) Proc. 19th Ann Conf. on wetlands 

restoration and creation. Hillsborough Cornrn. Coll., Plant City, FL. 

Fonseca, M. S. 1994. A Guide to Planting Seagrasses in the Gulf of Mexico. Texas 

A&M Sea Grant College Program, TAMU-SG-94-601. 26 p. 

Fonseca, M.S.,WJ. Kenworthy, EX. Courtney, and M.O. Hall. 1994. Seagrass planting in the southeastern United States: methods for accelerating habitat development. 

Rest. Eco. 2:198-212. 

Fourqurean, J.W., G.V.N. Powell,WJ. Kenworthy and J.C. Zieman. 1995. The 

effects of long-term manipulation of nutrient supply on competition between 

the seagrasses Thalassia testudinum and Halodule wrightii in Florida Bay. Oikos 72: 349- 

358. 

Powell, G.V.N.,WJ. Kenworthy and J.W. Fourqurean. 1989. Experimental evidence 

for nutrient limitation of seagrass growth in a tropical estuary with restricted circulation. Bull. Mar. Sci. 44: 324-340. 

Progress Report 11, Prop Scar Restoration Pilot Study, December 1995. 

Sargent, FJ.,TJ. Leary, D.W. Crewz, and C.R. Kruer. 1995. Scarring of Florida's seagrasses: assessment and management options. Florida Marine Research Institute, 

Tech. Rep. TR-1. 

Zieman, J.C. 1976. The ecological effects of physical damage &om motorboats on 

turtle grass beds in Southern Florida. Aquat. Bot. 2: 127-139. 

ATTACHMENT I. Assessment of Interim Losses 

Another goal of many seagrass plantings is an attempt to recoup interim loss of 

ecosystem fimctions. This was mentioned earlier as an attribute of fimctional equivalency. Because the concept of success and functional equivalency are so closely tied, 

planning for successfid restoration and/or mitigation requires early incorporation of 

interim loss considerations. The manner in which interim loss has been addressed 

historically has been through adjusting replacement ratios (how much acreage to 

plant per unit acreage lost). However, the manner in which interim ecosystem losses have been computed has not been consistent. Replacement ratios of less than 1:l 

to as high as 5:l have been proposed (pers. obs.), based on a number of criteria, but 
Appendices 2 19 

that ratio is usually inversely proportional to the degree which a project was in the 

public interest. 

To compute losses though, requires some assessment of not only acreage lost, but 

how long a time the functions of that acreage was lost to the ecosystem at large 

before it was returned to pre- or unimpacted levels. Depending on how long one 

wishes to amortize a loss will influence how much replanting must be done. In theory, if one hectare of seagrass were destroyed today and three hectares were replanted tomorrow and, for argument sake, reached standards of equivalency in three years, 

then after those three years, the planting would have largely compensated for the total 

loss of production; the net loss of production over this three year period would be 

very low. However, it rarely works this way. First, it is very difficult to consistently 

locate and successfully create new seagrass habitat that meet our site selection criteria (which precludes simply substituting naturally unvegetated bottom for vegetated 

bottom). Finding large acreage for planting in close proximity to the impacted area 

is rare, meaning that planting is often done at a site physically removed fiom the 

impact area and any functions affected by spatial elements of ecosystem linkages (i.e., 

geographic setting) are lost. Second, the production that was lost was removed fi-om 

a specific point in time; ecosystem functions were disrupted and those specific 

resources are not replaced, such as that year's spawn of herring (e.g. as in the Pacific 

northwest). Further, if there was a greater hiatus between the time of impact and 

recovery or the spatial separation were greater, then one could argue that planting 

conducted longer after an impact or further away fiom an impact have less value than 

ones conducted sooner or nearer. 

The injury assessment strategy to calculate interim loss is based on four steps of 

analysis: 1) documentation and quantification of the injury, 2) identification and evaluation of restoration options, 3) scaling of the restoration project to compensate for 

the injury over time, and 4) determine the appropriate means of compensation (e.g., 

monetary or planting). The scaling aspect is the portion of the process that helps 

standardize the way in which interim losses are computed, irrespective of the habitat type involved. Interim lost services can be considered to be the integral of service lost &om some baseline level over time. To compare services lost with those 

recovered by some remedial action (such as planting seagrass), the product: 

square m of habitat lost x time = square m-years, 

is set against square m-years of services provided by the planting project, but discounted as a function of time since the initial injury. Discounting is a widely-known 

economic principle and is a way of computing value of a commodity (such as a unit 
220 Guidelines for the Conservation and Restoration of Seagrasses 

area of planted seagrass) based on how long it has been since the impact occurred. 

Planting that occur longer after an impact are worth less than planting conducted 

shortly &er an impact and therefore more planting must be done as more time elapses. 

ATTACHMENT 11. Synopsis of Braun-Blanquet Technique (Braun-Blanquet, J. 

1965. Plant Sociology: The study of plant communities (translated, revised and edited by C.D. Fuller and H.S. Conrad). Hafher, London. 

The B-B coverage abundance scale is computed beginning at the zero point and at 

X m intervals along a transect (fkequently enough to get some detailed variation, say 

a absolute minimum of 30 quadrats per transect), place a quadrat (for seagrass I recommend 0.25 m2 , i.e., 50 cm on a side) on the seafloor. Visually inspect the content of the quadrat and assign a cover-abundance scale value to the seagrass coverage. 

The scale values are: 

0.1 = solitary shoots with small cover 

0.5 = few shoots with small cover 

1.0 = numerous shoots but less than 5% cover 

2.0 = any number of shoots but with 5-25% cover 

3.0 = any number of shoots but with 25-50% cover 

4.0 = any number of shoots but with 50-75% cover 

5.0 = any number of shoots but with > 75% cover. 

From the survey of quadrats along a transect, fi-equency of occurrence, abundance 

and density of seagrass (or macroalgae, by species in either case) can be computed as 

follows: 

fi-equency of occurance = number of occupied quadrats / total number of quadrats, 

abundance = sum of B-B scale values / number of occupied quadrats, 

density = sum of B-B scale values / total number of quadrats. 

One might wish to average the fi-equency, abundance and density values of the various transects or consider stratifjhg the data in some way that defines the site in 

some meaninful way. These values can then be used as a comparative basis among 

sites, pre- and immediately post-impact or post-planting as a means of assessing 

recovery. 
APPENDIX F 

Recommendations for Further Reading 

The following community profiles on seagrass published by USFWS: 

Phillips, R. C. 1984. The ecology of eelgrass meadows in the Pacific northwest: a 

community profile. US. Fish Wildl. Serv. FWS/OBS-84/24.85 p. 

Thayer, G. W., Kenworthy, W. J., Fonseca, M.S. 1984. The ecology of eelgrass meadows of the Atlantic coast: a community profile. U.S. Fish Wildl. Serv. FWS\OBS84\02.147 p. Reprinted 1985. 

Zieman, J. C. 1982a. The ecology of the seagrasses of south Florida: a community 

profile. US. Fish Wildl. Serv. FWS/OBS-82/25. 158 p. 

Zieman, J.C., Zieman, R.T. 1989. The ecology of the seagrass meadows of the west 

coast of Florida: a community profile. U.S. Fishwild. Serv. Biol. Rep. 85(7.25). 155p. 

Specific readings on seagrass restoration and management (see references for full citation). 

Batiuk et al. 1992. (Entire document). 

Churchill, Cok, and Riner 1978. 

Durako, M., R.C. Phillips and R.R. Lewis (eds.). 1987. Proceedings of the symposium on subtropical-tropical seagrasses of the southeastern United States. F1. Mar. 

Res. Rep. No. 42. (Entire document). 

Fonseca, et al. 1982; 1984; 1985; 1987c; 1988,1994. 

Fonseca 1989a 1992,1994. 
222 Guidelinesfor the Conservation and Restoration of Seagrasses - -- 

Kenworthy and Haunert 199 1. (Entire document). 

Lewis, R. R. 1987,1989. 

Merkel and Hoffman 1988. 

Merkel 1992. 

Neckles 1994. (Entire document). 

Phillips 1982. 

Thayer 1992 (Entire document). 

Thom 1990. 

Wyllie-Echeverria et al. 1994a. (Entire document). 

Muehlstein, L.K. (1989): review of wasting disease phenomena. 

Phillips, R.C. and C.P. McRoy (1990): handbook of seagrass research method. 
OTHER TITLES IN THE 

DECISION ANALYSIS SERIES 

No. 1. Able, Kenneth W. and Susan C. Kaiser. 1994. Synthesis of Summer Flouder Habitat Parameters. 

No. 2. Matthews, Geoffrey A. and Thomas J. Minello. 1994. Technology and Success in Restoration, 

Creation and Enhancement of Spartina Alterniflora Marshes in the United States. 2 vols. 

No. 3. Collins, Elaine V, Maureen Woods, Isobel Sheifer, and Janice Beattie. 1994. Bibliography of 

Synthesis Documents on Selected Coastal Topics. 

No. 4. Hinga, Kenneth R., Heeseon Jeon, and Noelle E Lewis. 1995. Marine Eutrophication Review. 

No. 5. Lipton, Douglas W., Katherine Wellman, Isobel C. Sheifer, and Rodney E Weiher. 1995. 

Economic Valuation of Natural Resources: A Handbook for Coastal Policymakers. 

No. 6. Vestal, Barbara, Alison Reiser, et al. 1995. Methodologies and Mechanisms for Management 

of Cumulative Coastal Environmental Impacts. Part I - Synthesis with Annotated Bibliography, Part 

I1 - Developnlent and Application of a Cumulative Impacts Assessment Protocol. 

No. 7. Murphy, Michael L. 1995. Forestry Impacts on Freshwater Habitat of Anadrornous Salmonids 

in the Pacific Northwest and Alaska - Requirements for Protection and Restoration. 

No. 8. William F. Kier Associates. 1995. Watershed Restoration - A Guide for Citizen Involven~ent 

in California. 

No. 9. Valigura, Richard A., Winston T. Luke, Richard S. Artz, and Bruce B. Hicks. 1996. 

Atnlospheric Nutrient Inputs to Coastal Areas - Reducing the Uncertainties. 

No. 10. Boesch, Donald E, et al. 1997. Harmful Algal Blooms in Coastal Waters: Options for 

Prevention, Control and Mitigation. 

No. 11. McMurray, Gregory R., and Robert J. Bailey, editors. 1998. Change in Pacific Northwest 

Coastal Ecosystems. 
U.S. Department of Commerce 

National Oceanic and Atmospheric Administration 

Coastal Ocean Office 

131 5 East-West Highway 

Silver Spring, Maryland 2091 0