Know Your Estuary
By Henry S. Parker
The best way to know an estuary is to get in it. Not on it, over it, or safely by its side. Don a bathing suit, T-shirt and stout, well-tied sneakers that the sucking mud won’t pull off. Then wade in. Bring a face mask and be ready to dunk your head. Much of what you see will lie below the surface. And what you see, if you are patient and observant, will amaze and delight you.
But before you go, learn a bit about what you’re getting into.
Estuaries are bodies of water that are partly landlocked and where entering fresh water mixes with the sea. Like people and puppies, no two estuaries are alike. They differ in size, geology, salt content, circulation and the nature of their inhabitants. The smallest may be a place where a tiny stream trickles into a coastal pond with a narrow opening to the ocean. The largest are outlets for major rivers and spread over thousands of square miles.
But regardless of characteristics, all estuaries are vitally important. Because they are shallow, rich in nutrients and full of hiding places, they nourish and protect large numbers and varieties of life forms, including juvenile fish and shellfish. They serve as spawning grounds and nurseries for many marine species. They stabilize and help protect shorelines. They make good harbors and support large human populations. Two -thirds of the world’s major cities are located on estuaries. They are focal points for tourism and recreation.
The same characteristics that make estuaries so valuable also make them vulnerable. It is distressingly easy for humans to abuse these special places.
Chesapeake Bay is the crown jewel of estuaries. The largest in the U.S., it covers 64,000 square miles, holds over 64 trillion gallons of water, and has nearly 12,000 miles of shoreline. Even in its degraded state, it annually produces close to 500 million pounds of seafood. The Bay’s value, including fisheries, recreation and real estate, may approach a trillion dollars. It receives fresh water from 50 major tributaries of which three—the Susquehanna, Potomac and James rivers—make up 80 percent. And it’s beautiful.
Ready to go wading? Let’s pick a crisp, calm, early fall day when the crowds are off the Bay, the sea nettles are gone for the season, and the water is still warm. We’ll immerse ourselves at the mouth of a cove with a small beach rimmed by a ribbon of waving grasses. Let’s check the grasses first—a species of Spartina called salt marsh cord grass. These are critical to the Bay’s health. They stabilize the shoreline, provide habitat and food sources, trap sediments and filter wastes. But erosion has severely reduced their acreage.
Tucked among the grasses, thick clusters of black bivalves thrust out of the mud. Their corrugated shells identify them as Atlantic ridged mussels. You could eat them, but, unlike the smooth-shelled blue mussels, they wouldn’t taste very good. Yet they’re important filter-feeders and food sources for other animals. Half-buried, with tightly closed shells, they look safe and secure. But life is not easy in an estuary, even for a clammed-up mussel. How would you like to be alternately covered in salt water and drenched by torrential rains in a single tidal cycle? Freezing at night and baked by the sun in the day? Exposed to any foraging predator and unable to run and hide? Good thing ribbed mussels, like most mollusks, reproduce prolifically.
We wade out to thigh-high depth. Time to dunk our heads and view what lies beneath. A minimountain range of barnacles covers a half-buried rock. Look closely. Tiny feathery appendages fan out from trap-door-like openings and rhythmically sweep the water, drawing in suspended bits of food. Diaphanous, inch-long grass shrimp flit in search of prey. A periwinkle scurries across the bottom. Wait—periwinkles don’t scurry. At best, they creep. Closer examination reveals tiny claws protruding from the shell’s opening. A squatter—a hermit crab—has taken up residence in a snail’s former home.
Tiny fish with sharp spines—sticklebacks most likely—flash through the water. Larger fish lurk deeper. And you’ll want to spend time with oysters and blue crabs, ospreys and terns, and a host of other Bay denizens, some common, some obscure. But it’s getting late. It’s time to head home. The Bay’s remaining secrets will have to wait for another day—and another article.
Henry can be reached at firstname.lastname@example.org