I believe a leaf of grass is no less than the journey work of the stars,
And the pismire is equally perfect, and a grain of sand, and the egg
of the wren,
And the tree-toad is a chef-d’oeuvre for the highest,
And the running blackberry would adorn the parlors of heaven,
And the narrowest hinge in my hand puts to scorn all machinery,
And the cow crunching with depress’d head surpasses any statue,
And a mouse is miracle enough to stagger sextillions of infidels.
-Walt Whitman, Leaves of Grass (1855)
From its headwaters high in the Canadian Cascades the Skagit River flows south and westward, carrying untold tons of nutrients and sediment from those rugged mountains down to the Salish Sea. A number of smaller rivers contribute their drainage to this westerly outpouring, and hence they are the tributaries of the Skagit: the Sauk, the Suiattle, the Baker, and the Samish, among others. Together these rivers drain an area more than 1.7 million acres across, demarcating the lush watershed known as the Skagit Basin. Wherever this abundant freshwater admixes with the salt of the sea, an estuary is formed—the confluence of two distinct milieux, an ecological mash-up of species and habitats literally teeming with life.
Brackish and intertidal, estuaries act as a sort of staging ground for many marine species, and Padilla Bay in Skagit County is a prime example. The Skagit River empties out here, and the resulting delta is a miles-long expanse of mudflats and finely-ground glacial silt. What makes Padilla Bay special is not merely the mud, though, but what lives in the mud: eelgrass, specifically native Zostera marina, or common eelgrass, and the accidently introduced Zostera japonica. A combination of nutrient-rich substrate, pancake-flat shoreline, and mild winter weather allow the eelgrasses to positively flourish in Padilla Bay. Together the two species cover more than 7,000 acres of mudflat, Z. japonica occurring nearer shore and Z. marina preferring deeper water.
The plants produce both sexually—with flowers and seeds—and by cloning, sprouting repeatedly from their root-like rhizomes to form dense colonies called genets. Because the two species have differing preferences for sunlight, temperature, and water turbidity, they seem to naturally divvy up the shoreline, occupying their respective niches with little overlap. Z. japonica, the invader,is the less robust species and currently constitutes but a fraction of Padilla’s eelgrass bed, but in a changing climate Z. marina’s hold on the mudflats is anything but certain.
It is difficult to overestimate the importance of Z. marina, the common eelgrass. Fast-growing and adaptive, it is the most widespread flowering marine plant in the Northern Hemisphere, and in Padilla Bay forms one of the largest contiguous eelgrass beds on the west coast of North America. A single acre of eelgrass produces almost ten tons of leaves annually—a rate of productivity rivaling that of tropical rainforests—and every aspect of the plant’s lifecycle benefits the estuary. As the grass grows, carbon dioxide is sequestered in the leaves and oxygen released, aerating the turbid shallows. Healthy beds of grass act dually as wavebreak and smokescreen, sheltering larvae of myriad species from surf and predation; organisms as diverse as crabs and clams to nudibranchs and snails to stickleback and salmon find refuge in the tangle. The leaves themselves become habitat to epiphytes like sponges and bryozoans, and the rhizomes—the stems of the plant buried in mud—form a rootwork that is a haven for worms and other benthic invertebrates. When the leaves die off in the winter, a whole suite of detritivorous organisms arise to capitalize on the windfall, recycling the nutrients back into the substrate with their waste.
Of course, all this fecundity in the eelgrass doesn’t escape the notice of other creatures, particularly those with a bird’s-eye view of the land. Ducks, gulls, herons, terns, osprey, eagles, and kingfishers flock to the flats at low tide to feast on the seafood buffet, while Brant geese—who migrate more than 3,000 miles in the fall from their northern nesting grounds—come solely for the grass, which they eat almost exclusively. Larger animals such as raccoons and river otters will sometimes forage in the mud, and harbor seals commonly haul out on the flats to sunbathe. This is a locus for trophic activity, a delicate food-web stretched out for miles. The mudflats and its denizens nourish life from the grassroots on up.
Visit Padilla Bay and gawk at the birds, like I did. Go to the Breazeale Interpretive Center. Sign up for a free beach tour. Witness the rampant proliferation of the Asian mud snail, and then experience their satisfying crunch under your own bare feet. Also, it’s pronounced “Pa-dee-uh”, like “tortilla”—the place was named after a Spaniard, after all.