Eelgrass
Zostera marina
Eelgrass is a flowering plant that grows submerged in salt water. They form meadows or beds near the shore, and provide a complex habitat for many animals from small invertebrates to fish and birds. These beds also help protect the coastline by protecting against storm waves and stabilizing the substrate with their roots. Eelgrass are also sensitive to pollution and serves as an indicator species of water quality.
Originally published: July 11, 2007
Last updated: January 22, 2026
Eelgrass (Zostera marina) at Cape Cod National Seashore. Credit: Holly Plaisted, NPS
SPECIES IN DETAIL
Eelgrass
Zostera marina
CONSERVATION STATUS: Safe for Now
Geographic Distribution
Widely distributed on the US Pacific & Atlantic coasts, coast of British Columbia, Canada north to Alaska’s Seward Peninsula, and in Europe.
Habitat
These flowering salt-tolerant plants grow in the sandy mud of tidal flats and creeks in sheltered bays, inlets, salt ponds, and at the mouth of estuaries. The blades of the plants are either submerged or partially floating.
Physical Characteristics
The thick white rhizomes are branching with numerous roots and a leaf spaced at nodes 1.0-3.5 cm (0.39-1.4 in) apart. In shallow waters the dark or emerald green leaves of the eelgrass plant are ribbon-shaped with rounded tips and are up to 0.9 m (3 ft) in length. The leaves are longer and wider in deeper waters at a maximum depth of usually no more than 6 m (20 ft). Flowers are enclosed in transparent leaf sheaths.
Reproduction
Eelgrass has an asexual and sexual stage of their reproduction. Each plant has male and female flowers but they aren’t mature at the same time. Male plants release pollen into the water which are carried to a female plant and fertilized. Shoots form and are carried away by the ocean currents. The seeds within these shoots are released into the water and sink to the sea floor before maturing.
Behavior
In intertidal waters the plants have a seasonal biomass cycle building up in the spring and summer, flowering from June into August, and then dying back in the fall to become detritus in the winter.
Adaptation
Leaves and rhizomes contain air spaces that help keep the blades buoyant. Seeds are also buoyant.
Conservation
In 1930 “Wasting Disease” decimated almost all of the eelgrass beds on the Atlantic coasts of North America and Europe. As a consequence beaches and sandbanks eroded away, fisheries closed, and some wildlife species disappeared. The partial recovery of these beds is now threatened by 21st century human-caused impacts.
Eelgrass beds are threatened by commercial, industrial, and residential development that replaces wetlands and by urban runoff that pollutes the wetlands.
Special Notes
Historical uses for eelgrass include food, roofing material, basket weaving, medicine, fuel and mulch. Eelgrass has also been used in paper making, as packaging material, and as a gelling agent.
SPECIES IN DETAIL | Print full entry
Eelgrass
Zostera marina
CONSERVATION STATUS: Safe for Now
Widely distributed on the US Pacific & Atlantic coasts, coast of British Columbia, Canada north to Alaska’s Seward Peninsula, and in Europe.
These flowering salt-tolerant plants grow in the sandy mud of tidal flats and creeks in sheltered bays, inlets, salt ponds, and at the mouth of estuaries. The blades of the plants are either submerged or partially floating.
The thick white rhizomes are branching with numerous roots and a leaf spaced at nodes 1.0-3.5 cm (0.39-1.4 in) apart. In shallow waters the dark or emerald green leaves of the eelgrass plant are ribbon-shaped with rounded tips and are up to 0.9 m (3 ft) in length. The leaves are longer and wider in deeper waters at a maximum depth of usually no more than 6 m (20 ft). Flowers are enclosed in transparent leaf sheaths.
Eelgrass has an asexual and sexual stage of their reproduction. Each plant has male and female flowers but they aren’t mature at the same time. Male plants release pollen into the water which are carried to a female plant and fertilized. Shoots form and are carried away by the ocean currents. The seeds within these shoots are released into the water and sink to the sea floor before maturing.
In intertidal waters the plants have a seasonal biomass cycle building up in the spring and summer, flowering from June into August, and then dying back in the fall to become detritus in the winter.
Leaves and rhizomes contain air spaces that help keep the blades buoyant. Seeds are also buoyant.
In 1930 “Wasting Disease” decimated almost all of the eelgrass beds on the Atlantic coasts of North America and Europe. As a consequence beaches and sandbanks eroded away, fisheries closed, and some wildlife species disappeared. The partial recovery of these beds is now threatened by 21st century human-caused impacts.
Eelgrass beds are threatened by commercial, industrial, and residential development that replaces wetlands and by urban runoff that pollutes the wetlands.
Historical uses for eelgrass include food, roofing material, basket weaving, medicine, fuel and mulch. Eelgrass has also been used in paper making, as packaging material, and as a gelling agent.