Project Planning: Eelgrass
Unsuccessful eelgrass restoration projects are usually the result of improper site selection (Fonseca 1994). Salinity, depth, current and wave energy, water clarity, water temperature, sediment characteristics, and surface water quality are all important factors to evaluate in the selection of a restoration site. Depth and water clarity exert the primary controls over eelgrass zonation and the degree of colonization by epiphytes. The parameters of the transplant site must closely match that of the donor, or reference, site if restoration is to be successful (Kenworthy and Fonseca 1977, Phillips 1980a, Fonseca and Fisher 1986, Fonseca et al. 1987a, Fonseca et al. 1998).
Because of these issues, it is essential to carefully consider and prioritize potential sites for eelgrass restoration. The site selection process should generate a list of sites that offer the chance for success in terms of acreage restored and the degree of habitat function restored.
A considerable number of potential locations for eelgrass restoration exist along the Gulf of Maine’s coast. Evaluation of site-specific factors (e.g., water quality and clarity, navigation constraints, fisheries, transplant and seeding costs) can be used to rank potential restoration sites.
Defining project goals and objectives
As with restoration of other coastal habitats, eelgrass restoration project goals and objectives must be clearly defined and consistent (Fonseca 1994, Pastorok et al. 1997, Short et al. 2000). Eelgrass restoration projects that lack clearly defined goals and objectives are less likely to achieve success, and it may be impossible to gauge success in the absence of a clearly defined project plan.
Project goals refer to the ecosystem attributes to be restored, such as water quality and clarity, hydrodynamics, epiphyte or macroalgae communities, or finfish and shellfish resources. Project objectives are more precise. They may include the specific characteristics of water quality, hydrodynamics, or plant and animal communities to be restored. Performance indicators are developed during the life of the project and represent measurable characteristics such as the percent cover of eelgrass transplant units or the number of stems per transplant.
An example of a goal for a restoration project in the Gulf of Maine could be to restore eelgrass to a particular area that has undergone considerable improvement in water quality in recent years. The project objective might be to reestablish native eelgrass to cover of 60 percent of the designated study area within three years post-construction.
Baseline data collection
Detailed site characterizations are needed to formulate site-specific restoration plans and to develop success criteria for individual projects. Examples of baseline data that may be collected during pre-restoration baseline surveys include:
- water quality (ammonium, nitrite/nitrate, phosphorus, dissolved and particulate organic carbon, chlorophyll a, turbidity, total suspended solids [TSS]),
- light attenuation,
- current/wave energy,
- epiphyte load,
- use of the site by fish or macrocrustaceans, and
- benthic invertebrate communities.
For more information, consult the Monitoring page.
The cost of a restoration project depends on site-specific conditions and the proposed restoration and monitoring activities (see cost analysis on the Rhode Island Habitat Restoration Web Portal). Federal, state, and private funding sources are available to support eelgrass restoration in the Gulf of Maine. These funds are available to state and local agencies, and non-government organizations (NGOs). In partnership with the National Oceanic and Atmospheric Adminstration (NOAA), the Gulf of Maine Council on the Marine Environment provides grants for habitat restoration. A list of other funding opportunities is available here. Restore America’s Estuaries (RAE), a non-profit organization dedicated to preserving estuaries throughout the United States, has developed a directory called Funding for Habitat Restoration Projects: A Citizen’s Guide. The guide is intended to help individuals, organizations, and agencies access federal assistance in support of community-based habitat restoration.
Permitting and regulatory considerations
Eelgrass beds can be restored by encouraging natural recolonization or by actively transplanting. Transplants may be individuals taken from healthy donor beds or seedlings reared under laboratory conditions. In some cases, seeds can be planted or broadcast. Seeding can be used alone or in combination with transplant techniques. Several technical guidance documents have been published to assist restoration practitioners in selecting transplant sites and choosing appropriate restoration methods.
This approach to eelgrass restoration focuses on water quality improvement in the study area with the assumption that once suitable conditions are established, eelgrass will naturally recolonize. It may require a long-term coordinated effort to upgrade municipal sewage systems and a program to identify and curtail point and non-point discharges from industrial, residential, and agricultural areas in the coastal zone.
Transplanting eelgrass is a proactive approach to restoration involving the relocation of viable seedlings grown in aquaria, or mature plants taken from healthy donor beds to the restoration site, once suitable conditions have been established for eelgrass survival. This is not a new technique; the earliest recorded transplant effort involving eelgrass was documented by Addy (1947a, 1947b) from Massachusetts and several locations in the mid-Atlantic. However, transplant methods have been refined in recent years. A specialized transplant methodology known as Transplanting Eelgrass Remotely with Frames (TERF) was developed by Dr. Fred Short of the University of New Hampshire. The TERF method uses clusters of plants tied temporarily with degradable crepe paper to a weighted frame of wire mesh.
Transplanting is very labor intensive, as it requires divers to plant the individual units by hand. Often, trained volunteers can be involved to defray the considerable time and labor costs associated with eelgrass transplant projects.
Eelgrass transplant techniques, along with cost and labor estimates, are documented by Fonseca et al. (1982a, 1982b, 1982c, 1984, 1985, 1987a, 1987b). Fonseca (1994) reviewed all aspects of eelgrass restoration, including planting guidelines and monitoring programs for the Gulf of Mexico, but this information is applicable to eelgrass restoration in general.
Descriptions of planting methods, including seeding, stapling, use of anchored and unanchored sprigs, plugs, peat pots, and transplanting of individual mature plants are provided by Phillips (1980a), Fonseca (1994), and Fonseca et al. (1998). Fertilization of transplants to accelerate growth and bed coalescence is described by Fonseca et al. (1987, 1998) and Kenworthy and Fonseca (1992). The outcomes of fertilization in eelgrass restoration projects have been inconclusive (Fonseca 1994).
Eelgrass can be propagated in estuarine waters by application of seeds. In Chesapeake Bay, eelgrass seeds have simply been broadcast by hand off a small motorboat; the success rates are documented by Orth et al. (1994). Researchers in Great South Bay, New York, developed a method of seeding that involved attaching seeds to a biodegradable tape. The tape is then planted just below the sediment surface at the desired restoration site (Churchill et al. 1978).
Recently, Steve Granger, a research scientist at University of Rhode Island Graduate School of Oceanography has developed a boat-pulled sled that deposits seeds below the sediment surface. His colleague Mike Traber has developed a procedure to encase seeds in a Knox gelatin matrix. This prevents or reduces seed predation and loss of seeds to waves and currents. Gelatin-encased seeds are injected into the sediment from the sled using a food-processing pump similar to those used to make jelly donuts. A metal flange mounted on the back of the sled sweeps sediment over the furrows created by the pump, covering seeds in one inch of sediment. Test plantings were conducted at two locations in Narragansett Bay in fall 2001. The investigators were able to plant a 400-square-meter area in less than two hours, exceeding initial expectations. Ongoing research efforts include monitoring the growth of eelgrass in the newly seeded areas and the evaluation of alternative gelatin agents (CICEET 2002).
Design considerations of particular importance for eelgrass beds include transplant spacing, light attenuation, and patterns of current flow in the vicinity of the transplant site. Careful attention must be paid to the spacing of individual planting units in order to achieve site coalescence. Eelgrass transplant projects conducted in the eastern Gulf of Mexico have achieved coalescence in as little as nine months or as long as three to four years, depending on planting distance between individual units. In high-energy areas, beds may never fully coalesce. Separation of planting units by one half meter is ideal, but it results in greater impacts to donor beds. Trade-offs between rapid transplant coalescence and impacts to donor beds must be considered on a project-specific basis.
Light availability is one of the most important determinants of eelgrass health. Generally, eelgrass requires 15 to 25 percent of the light available at the water’s surface. Because of this, eelgrass rarely occurs at depths exceeding five meters. A predictive model developed by Fred Short of the University of New Hampshire allows the comparison of various restoration alternatives. The model requires inputs of baseline data such as light attenuation, turbidity, water temperature, and nutrient levels. Model output indicates the amount of eelgrass biomass that can be produced at various depths.
An appropriate current regime is critical for eelgrass transplant success. If current velocities are high in the vicinity of the transplant site, transplant success will be poor due to loss of transplant units, and coalescence may never occur. If current velocities are low, sedimentation may occur and suffocate the newly transplanted beds.
Potential obstacles to restoration
Eelgrass restoration projects may encounter a variety of obstacles. Many of these obstacles can be avoided or minimized through careful pre-project planning and post-construction monitoring.
Grazing by waterfowl
Grazing by waterfowl is a potential problem in eelgrass restoration projects. Ducks and geese may eat newly transplanted shoots and leaves in restored eelgrass beds. Various types of nets and cages have been deployed in eelgrass transplant projects to protect the new transplants from direct grazing by waterfowl and other animals.
Bioturbation by crabs
When eelgrass is newly transplanted, the shoots are highly susceptible to bioturbation effects, especially by green crabs (Carcinus maenus), a non-native species that has become abundant in the Gulf of Maine. Caging may help minimize the presence of adult green crabs in the project areas. However, larvae and juvenile crabs are able to recruit into the beds. Careful attention to site selection and monitoring crab density and the degree of disturbance are the best solutions to this potential problem.
Direct physical damage to restored eelgrass beds can be caused by dredging, aquaculture, and propeller scarring from recreational and commercial vessels.
Eelgrass restoration projects in shallow coastal habitats can potentially conflict with historic and cultural resources, including Native American sites of significance.
Equipment sources and contacts
Comprehensive literature reviews and technical manuals are available to assist restoration practitioners in project planning. Experts can be contacted at federal and state environmental resource agencies, non-profit organizations, and academic research institutions. The people listed on the Contacts page are available to answer questions.
Anadromous fish habitat (riverine)