Eelgrass: nursery of the sea

Meadows of grass growing below the surface of Puget Sound? It may not be the same as the grass on your local playfield—but it’s there, and it serves a vital purpose.

You’ve probably seen eelgrass on the beach at low tide. Many people mistake it for seaweed, but it’s a perennial, underwater grass, and it spreads the same way grass does on land—with rhizomes.

Eelgrass is found in subtidal and intertidal estuaries, bays and coves in temperate climates throughout the world. Like perennial plants on land, eelgrass grows in the spring and summer, then decays in the fall and winter. Eelgrass blades can grow to be up to three feet long.

What makes eelgrass so extraordinary—and unique—is that it provides an important, irreplaceable home for young marine creatures including crabs, salmon, scallops, herring and more. That’s because eelgrass blades provide food for an array of invertebrates, which in turn become a rich food source themselves.

At low tide, eelgrass shelters small animals, protecting them from warm temperatures and predators. And, similar to grass on land, eelgrass helps prevent erosion—by cushioning the impact of waves. Eelgrass also benefits humans by filtering polluted runoff.

Juvenile salmon, or fry

No other underwater plant duplicates what eelgrass does.  But, as shoreline development has increased around the world, eelgrass has declined. Dredging ravages eelgrass beds. Docks can block the light that eelgrass needs to grow. Rising temperatures may also cause eelgrass diebacks. And, when eelgrass is destroyed, entire populations of fish and invertebrates are affected.

Eelgrass restoration efforts are underway, locally and worldwide. In 2010, the Washington state Department of Natural Resources recommended a 20 percent restoration of eelgrass by 2020. Whether or not the goal is attainable remains to be seen—but work continues, with “gardeners” cultivating eelgrass in tubs, and divers planting the specimens below the surface.

Sculpin eggs on eelgrass

You can help preserve eelgrass simply by not walking on it when you visit the beach. Instead, kneel at the edge of the eelgrass bed and gently explore below the blades. Interested in learning more about eelgrass? Join the Seattle Aquarium beach naturalists this summer!

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