Vol. 2, No. 2
Eelgrass: Essential or expendable in the Gulf?
Gulf of Maine - Reaching up through the shallows along the Atlantic coastline from North Carolina into the Canadian maritimes are long, thin, bright green blades of Zostera marina, or eelgrass. Some scientists maintain that the plant's value to the ecosystem and to fisheries warrants its preservation. But a question remains whether singling out eelgrass for protection means that other equally valuable marine habitats will suffer.
A type of seagrass that grows in beds anchored to the marine floor by intricate root systems, eelgrass reaches lengths of up to five feet. Protected coastal areas tidal rivers, bays, and estuaries that are completely covered with water and have fine-grained sediments provide the best growing area for eelgrass, which also requires light and water clarity for photosynthesis, and moderate waves and currents that prevent stagnation without uprooting the plants. Beachcombers frequently find dried, black, tangled masses of eelgrass washed ashore, marking the high tide line.
Eelgrass protection proponents say the plants serve as refuge and nursery for juvenile finfish and shellfish, and as food for fish, invertebrates, and waterfowl. They note that the plants produce oxygen needed by other organisms; filter contaminants and absorb nutrients that can cause excess growth of algae; and stabilize sediments with their root systems, helping to prevent erosion.
But while Bob Steneck, a professor at the University of Maine School of Marine Sciences, agrees that eelgrass is an important habitat, he is not convinced it takes precedence over others in all parts of the Gulf. "What I get concerned about is if you are protecting one habitat or one community, then, defacto you are possibly focusing some of the environmental stresses on the others. I don't think there's a compelling biological argument that places the role of Zostera above the roles of [ kelp and cobble beds]," as important habitat, he said.
Seth Barker, who is mapping eelgrass for Maine's Department of Marine Resources, said, "We really, in the Gulf of Maine, consider the question of the relative importance of eelgrass as still an open issue."
Experts debate protection
Steneck asserted that eelgrass received federal protection under the US Clean Water Act which requires that any eelgrass destroyed by human activity be replaced or restored because of its role as essential fish habitat in the mid-Atlantic, not the Gulf of Maine. "Something that could be absolutely essential along much of the east coast may not be essential everywhere," he said. If eelgrass were crucial to the survival of fish in the Gulf, devastating results would have occurred in the 1930s, when 90 percent of the eelgrass beds in the North Atlantic region were destroyed by a marine slime mold known as the mass wasting disease, Steneck stated.
"There is data to suggest that the great dieoff in the 1930s resulted in wildlife loss," argued US Environmental Protection Agency (EPA) marine biologist Phil Colarusso, who organizes an annual meeting of New England scientists and researchers studying eelgrass and working on restoration projects. Populations declined among bay scallops, brant geese, and the eelgrass limpet, which "went extinct as a result," he said, noting, "Since none of these are very commercially important anymore, people tend to discount them."
Colarusso asserted, "We're not sacrificing other habitats to protect eelgrass. We're all for protecting macroalgae and cobble and some of these other habitats." He said Steneck is "taking ecological principles that have been demonstrated all over the globe and saying they don't apply in Maine."
Steneck maintained that the importance of certain habitats does vary in different regions of the Gulf. Along Maine's rocky coast, habitats that are more structurally complex than eelgrass including kelp beds, boulder fields, and cobble beds support more organisms than eelgrass does, making them more valuable than eelgrass for coastal food webs in that region, yet they are not federally protected, he explained. "Zostera's importance as a habitat is likely to be greater from Cape Cod south, where it provides most or all of the habitat complexity in many marine systems," Steneck said.
Threats to eelgrass numerous
According to Fred Short, a University of New Hampshire scientist who is a consultant for eelgrass restoration projects in New Hampshire, Maine, and Massachusetts, the decline of eelgrass by 50 percent along the North Atlantic Coast during the past century has been caused by numerous factors, particularly "nitrogen loading," in which nitrogen-rich nutrient runoff from agricultural land, discharge from sewage systems, and leaky septic systems flows into coastal waters, in effect fertilizing them. This increases the growth of phytoplankton and other vegetation, blocking the light eelgrass needs for photosynthesis, and, as it decomposes, robs the water of oxygen needed by other organisms a process called eutrophication.
Boat propellers and recreational ski-craft stir up sediments in the water, and these also block light. Propellers, mooring chains, and some types of fishing gear can uproot or crush eelgrass, and dredging and shoreline development of terminals and piers can tear up eelgrass beds.
Eelgrass is also vulnerable to the long-term effects of docks, moored boats, and other structures that shade the plants from the light they need.
Researchers lack information on how eelgrass is affected by chemically pressure-treated wood, lobster pounds, and pipelines laid under or along the surface of the ocean floor, but Colarusso said people can reduce known threats by making sure that sewage and septic systems are functioning properly; using fertilizers and pesticides sparingly, especially before a heavy rain; using dinghies to access boats rather than building piers and docks or dredging deeper channels; and orienting piers to reduce the amount of shade they throw over eelgrass beds.
To help people build eelgrass-friendly piers, Short produced a CD ROM, funded by the Waquoit Bay Estuarine Research Reserve, Sea Grant, the National Oceanographic and Atmospheric Administration (NOAA), Massachusetts Coastal Zone Management, and UNH. Dock Design with the Environment in Mind outlines guidelines for building eelgrass-friendly docks.
Doug Burdick, environmental specialist at the Maine Department of Environmental Protection, said that while effects on eelgrass are considered as part of an extensive permitting process used for larger waterfront development projects, most privately-owned piers are reviewed under a shorter process that does not directly address eelgrass.
Steneck believes regulatory protection of eelgrass is well-intentioned, but said, "sometimes the regulations can move us in an imprudent direction." He recalled Maine Governor Angus King as citing eelgrass protection as the deciding factor in the state's decision two years ago to shelve a cargo terminal proposed for Sears Island in Penobscot Bay. Richard Bostwick, Supervisor of Environmental Studies within the Maine Department of Transportation's Office of Environmental Services, said "Eelgrass was one factor out of many that put [the original proposal] over the edge and helped put the project on hold."
In most cases, according to Colarusso, projects are modified rather than relocated to avoid damage to eelgrass beds, however the state is now planning to upgrade the existing port at Mack Point, across the harbor from the proposed cargo terminal site. Steneck worries that the new location may endanger a cobble bed that serves as a lobster nursery ground.
Restoration piecemeal, but progressing
Scientists in the Gulf of Maine use aerial surveys to inventory eelgrass beds, while in the US, eelgrass restoration projects involving transplanting of seedlings and shoots are under way in several areas, as researchers can find funding for them. Eastern Canada is not working on eelgrass restoration, according to Glyn Sharp, Marine Plant Biologist for the maritime region of Canada's Department of Fisheries and Oceans (DFO), who stated, "In general our areas are very stable." But, Sharp pointed out, "DFO does have a fish habitat protection act, so if people wanted to dig a big canal or fill in big shallow areas of Zostera, the alarm would go off. It's not a free-for-all."
Eight acres/about three hectares of eelgrass beds have been restored in New Hampshire so far with help from EPA funds, and the New Bedford Harbor Trustee Council provided a grant for eelgrass restoration in New Bedford harbor as part of a harbor cleanup, Short said, noting that small-scale transplanting took place in Maine on a trial basis in the mid-1980s.
"We're getting better at it. I would say we're very successful now. We've developed a site selection model that allows us to go into an area and determine how suitable it is for planting," said Short. But while restoration appears to be working, it can be problematic. Ice, exposure, and predators such as crabs and worms threaten newly planted eelgrass shoots, and hiring specially trained divers to transplant shoots harvested from more prolific areas is expensive. Short said that he and other researchers are working on developing cheaper methods that stewardship groups can undertake. Ultimately, he said, "We want to create an overall visible impact on the estuarine system."
More information on eelgrass
Eelgrass and Fisheries in the Gulf of Maine
The Importance of Eelgrass
Dock Design with the Environment in Mind: Minimizing Dock Impacts to Eelgrass Habitats
Information on other essential habitats for commercially important species is available from Bob Steneck via e-mail at firstname.lastname@example.org or by calling the University of Maine Sea Grant office at (207) 581-1435.