Eelgrass is a keystone species in shallow estuarine and coastal marine habitats. Eelgrass is a long and slender-leaved plant that flowers and is pollinated underwater. Eelgrass habitat ranges from the Canadian Maritimes to North Carolina. It requires adequate light conditions and relatively low turbidity in the water column. Eelgrass filters and traps sediment, improves water quality, provides nursery habitats for many species of fish and invertebrates, and helps sustain migratory waterfowl—particularly American Brant (Maine Coastal Program, 1991; Short and Burdick, 1994). Eelgrass makes important contributions to the estuarine food web.

Eelgrass loss
Scientists estimate that 50 percent of the eelgrass in the North Atlantic has disappeared over the last century. Reasons include nutrient overloading that deprives the plants of light; competing algae that outgrow and shade eelgrass seedlings; boat propellers, anchors, and dredging activities that dislodge the plants; drag fisheries that scour the bottom; and wasting disease that causes widespread die-offs. Eelgrass restoration has been conducted at some sites in New Hampshire and Maine restoration (Short et al., 2002), and many other sites are considered candidates for restoration. Restoration methods include transplanting native plants and reseeding areas that once supported eelgrass.

Non-point source pollution and dredging
Point and non-point source runoff from agricultural, residential, and urban areas affect subtidal habitat in the Gulf of Maine. Runoff may reduce water quality and negatively affect subtidal habitats. Dredging affects water quality by increasing turbidity and possibly suspending and redistributing pollutants. This can destroy benthic habitats such as shellfish beds and eelgrass beds. Docks and piers limit the light reaching the bottom and initiate fragmentation and decline of eelgrass beds.

Very little subtidal habitat restoration is currently being conducted in the Gulf of Maine. However, this is an emerging concern, and there is a need for identification of projects, funding, and monitoring. As national efforts to improve coastal water quality achieve their goals, the opportunity arises for reintroduction of eelgrass, as well as other types of subtidal habitat restoration.