Eelgrass Bed (S1)
Eelgrass beds are a type of subtidal natural community that occur exclusively below mean low tide, although upper reaches may be briefly exposed during the lowest spring tides. Common eel-grass (Zostera marina) is the dominant rooted vegetation. Associated species include a diverse array of rooted, epiphytic, and suspended marine algae.
This continually submerged aquatic community performs important ecological functions including supporting eelgrass and fish populations, providing refuge for fish and invertebrates that retreat from exposed intertidal flats and estuarine marshes at low tide, and serving as a spawning and nursery area for numerous species of aquatic animals.
The upper limits of eelgrass populations are determined in large part by ice scour in winter and desiccation in summer. Maximum depth, conversely, is regulated by light penetration, with no eelgrass growing below a minimum tolerance threshold. Light penetration is a function of both water depth and concentration of suspended particles in the water. In the northeast, eelgrass can grow to a depth of 6 m (20 ft.) where water transparency is high.
Substrate is sand or mud comprised of silt and clay particles.
A good example of this community can be seen in New Hampshire's Great Bay estuary.
Eelgrass beds occur as part of a larger subtidal system.
Eelgrass bed beneath the waters of Great Bay (photo by Ben Kimball)
Eelgrass bed beneath the waters of Great Bay (photos by Ben Kimball)