An eelgrass bed, as seen from the water's surface.
An eelgrass bed, as seen from the water's surface.
Courtesy: NOAA

Eelgrass (Zostera marina)

Appearance: Grows in clumps; can form extensive underwater beds or meadows. The green leaves are 1/4-inch wide and can be up to 3 feet long.
Habitat: Found in brackish to entirely salt water of protected inlets and bays. Grows in sandy, silty, or gravelly substrates in the subtidal zone.
Seasonal appearance: Blooms early spring and summer.

Description

Eelgrass is a flowering underwater plant with 1/4-inch wide leaves that can reach lengths of 3 feet. Eelgrass beds are always completely submerged, and their roots, known as rhizomes, anchor the grass to sandy or muddy bottoms. Eelgrass is a true flowering plant, not a seaweed or an algae, and it is sometimes misidentified as smooth cordgrass, a plant that grows at the edge of the shore in the intertidal zone and is commonly submerged at high tide.

An underwater view of an eelgrass bed.
An underwater view of an eelgrass bed.
Courtesy: NOAA

Life History and Growth

In Rhode Island, eelgrass grows in distinctive clumps, known as beds, in nearshore waters at depths ranging from 15 feet. From spring through late summer, eelgrass produces hundreds of seeds, which float with the current until they sink to the bottom. Uprooted eelgrass can sometimes be found in bright green, tangled clumps or as individual strands along the shore. Dead eelgrass appears brown or almost black and, when left out of water for a period of time, it becomes dry and papery.

Eelgrass is one of Rhode Island's most important and vital habitats for a wide range of fish and wildlife, including flounder, bay scallops, and crabs. At the base of the food chain, many species of commercially valuable fish feed on, or take shelter in, these beds during some stage in their life cycle. Eelgrass beds filter excess nutrients out of the water and help prevent shoreline flooding and erosion by stabilizing sediment and buffering wave action. Because it requires specific amounts of light and clean water, the presence of eelgrass is an indicator of healthy water quality.

Special Notes


Adapted from The Uncommon Guide to Common Life on Narragansett Bay. Save The Bay, 1998.