Tread carefully: Eelgrass is a key to intertidal life

How often have you walked on one of Vashon’s many beaches and seen patches of long slender grass exposed below the high tide line? You might be amazed to learn how incredibly complex and important that seemingly simple patch of grass is.

When I first walked on Vashon’s beaches I had no idea, but through a series of classes and beach training events offered by the Vashon Beach Naturalists, I learned about this so-called eelgrass and the menagerie of critters that rely upon it.

For instance, eelgrass serves as a food source for numerous species. Brant geese eat it before migrating to their arctic nesting grounds. Snails also directly eat the plant, and algae growing on the leaves provide meals for lots of invertebrates and clams. In turn, those invertebrates are the favored food of young salmon and shrimp. Go just one more step along this food chain, and you find that great blue heron prefer to fish in eelgrass beds for their prey. And don’t forget how much we love those salmon and clam dinners!

Yet I’ve only begun to weave this ecological web. Look carefully amongst the eelgrass’s leaf blades and you will find all sizes of crab, seastars, fish, snails, sand dollars, clams and beautifully colored nudibranchs dining and hiding there. A patch of eelgrass makes for a nice place to lay eggs, too. Quartermaster Harbor hosts a large population of spawning Pacific herring, thanks to the eelgrass meadows there. During last year’s Low-Tide Celebration at Point Robinson, we were fortunate enough to find clumped on the leaves numerous egg deposits made by bright orange-red sculpin (yet another type of fish).

The vital link between eelgrass and the multimillion dollar salmon and shellfish industry is well studied; as a result, worldwide conservation efforts are under way to save those eelgrass beds still in existence. We have yet to be successful in restoring beds once they die out, so the best remedy is to minimize negative impacts on their survival. Not surprisingly, human development near shorelines is usually the biggest culprit. Eelgrass can only live as far as the sunlight can penetrate the water, usually to a depth of about 20 feet. But docks, piers and even moored boats have been known to kill eelgrass by shading out the sun, and increased sedimentation in the water suffocates the vegetation. Even the herbicides we use on our properties can wash to the shore and kill these sensitive plants.

So when shoreline management regulations frustrate your beach construction project, keep the humble eelgrass and all its interconnected community in mind. If you value your salmon, herring, crab and clams, then next time you visit our wild neighbors who live in the intertidal zone, please be kind and keep off the grass.

— Adria Pontious is a biologist, teacher and nature photographer, as well as a Vashon Beach Naturalist.

The Vashon Beach Naturalists are beginning a new season of classes for adult and teen volunteers, and Vashon’s Headwaters program helps younger children become Junior Beach Naturalists.

The Beach Naturalist classes begin April 6. For more information, contact Erin Durrett at e.durrett@yahoo.com or 463-4357.  The Headwaters program begins March 18; contact Sarah Wright at starlight@homesteadschool.org or call 463-0822.

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