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Eelgrass—Habitat of the Month

Underwater grasses, also called submerged aquatic vegetation—or seagrasses if they grow in the ocean—are flowering plants that live in shallow waters. Different species of underwater grasses prefer different water temperatures and salinity, but they all require sunlight to grow and reproduce.

This month we’re focusing on one type of underwater grass in particular: eelgrass.

Making the Beds

Eelgrass comes in both freshwater and marine varieties. Eelgrass forms beds and meadows that grow in bays and coves, tidal creeks, and estuaries. These beds are a haven for crabs, scallops, numerous species of important fish, and other wildlife. The long blades of grass are often covered with tiny marine plants and animals. Here, these creatures find habitat, protection from predators, nursery grounds, food, and oxygen.

Did you know?

Eelgrass provides benefits to humans as well as marine life. It improves our water clarity by filtering polluted runoff and by absorbing nutrients such as nitrogen and phosphorus. It also protects our shorelines from erosion by absorbing wave energy.

            Five more facts about eelgrass:

  • Eelgrass is not a seaweed; it is a blooming, underwater grass
  • Eelgrass blades can grow up to 3 feet long
  • Eelgrass was once harvested, dried, and used for insulation in houses
  • Eelgrass has been used as packing material and stuffing for mattresses and cushions
  • Eelgrass was even used to stuff seats in early models of Volkswagens!

Threats to Eelgrass

Since the 1850s, 90 percent of the California’s eelgrass acreage has been destroyed, and the remaining 10 percent is continuously exposed to increasing sedimentation from eroding watersheds, raw sewage spills, and urban run-off pollutants. On the Atlantic Coast, declines in eelgrass have been caused by outbreaks of disease. Eelgrass wasting disease destroyed approximately 90 percent of all eelgrass along the Atlantic in the 1930s. When eelgrass is destroyed, whole populations of fish—including threatened salmon, rockfish, and shellfish—are affected. Our shorelines are also left vulnerable to erosion.
The threats to eelgrass are both natural and man-made:

  • Excessive nutrients from urban runoff cause algal blooms that block the sunlight from reaching the eelgrass, limiting its growth and reproduction
  • Structures, such as docks, can prevent eelgrass from getting enough sunlight
  • Scarring from boat propeller and chain anchors uproots plants
  • Invasive species—such as sea squirts and nuisance algae—compete with eelgrass for habitat, light, and nutrients, often overtaking the beds and meadows
  • Some shellfish harvesting practices, such as hydraulic clamming that involve dredging, can damage eelgrass blades and roots
  • Rising temperatures and sea level could also cause eelgrass diebacks

NOAA’s Recent Eelgrass Conservation Efforts

Since 2001, NOAA has helped fund underwater grass restoration for Virginia’s Eastern Shore, from the mouth of the Chesapeake to Wachapreague inlet. Since 2005, 250 acres of eelgrass have spread to 5,000 acres.

On Martha’s Vineyard, NOAA partnered with the Town of Tisbury, Massachusetts Division of Marine Fisheries, Environmental Protection Agency, and The Nature Conservancy to protect important eelgrass habitat in two harbors by replacing traditional boat moorings with new conservation moorings. The old moorings had chains that dragged, scouring the bottom clear of marine vegetation. The new moorings replace chains with flexible, floatable lines that never touch bottom, leaving eelgrass to flourish.

On the West Coast, NOAA just awarded funds to Northwest Straits Foundation in Port Townsend, Washington to continue their long-running voluntary, no anchor, eelgrass protection efforts. The program has dramatically changed the behavior of the boaters anchoring along the Port Townsend shoreline and has nearly eliminated negative impacts to the sensitive eelgrass habitat from anchoring.

NOAA’s Southwest Region has drafted the California Eelgrass Mitigation Policy with recommendations concerning eelgrass impacts and management through Essential Fish Habitat consultations throughout California.

For more on NOAA’s eelgrass conservation projects, please see our Useful Links box.


Posted on 10/22/2012