Eelgrass (Zostera marina)
One of several species of seagrass in Puget Sound, eelgrass is the largest, with perennial blades that are more than three-sixteenths of an inch wide and several feet or more long. Eelgrass grows in sheltered intertidal and shallow subtidal areas in clear water that allows photosynthesis to depths of about 20 feet.
Eelgrass, like other seagrasses, are flowering plants that have invaded the sea. They sink their roots in muddy sand, producing flowers and seeds. Beds also expand through the growth of rhizomes. This species occurs in marine water throughout the northern hemisphere.
Eelgrass occurs in small to large beds that change the ecology of the setting. The roots stabilize the sediments, while the blades not only trap sediment but offer shelter for a range of animals and other plants. Animals commonly found in the beds are hydroids, nudibranchs, anemones, jellyfish, starfish and urchins, various crab including Dungeness along with a wide variety of smaller crustaceans, sculpins, pipefish, tubesnouts and several kinds of perch and juvenile salmon. Eelgrass also is an important spawning substrate for herring.
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An eelgrass bed produces a considerable amount of vegetable matter per year, making it important as a food source for a variety of large and small animals, including the Brandt sea goose and the American wigeon duck.
Until recently, eelgrass beds have been found only as far south in Puget Sound as the Nisqually River Delta. However, there have been recent reports of isolated small clumps in parts of Dana Passage. The state Department of Natural Resources, Aquatic Resources Division, monitors eelgrass as a part of its Nearshore Habitat Program (go to www.dnr.wa.gov/htdocs/aqr).
David W. Jamison is a Boston Harbor resident and marine biologist.