Marine Park, whose 798 acres are mostly saltwater wetland, is tucked into the westernmost inlet of Jamaica Bay. The bay was formed over the last 5,000 years, when ocean currents deposited sand in a series of long strips off the south shore of Long Island. The strips formed barriers against the pounding surf and allowed saltwater wetlands to grow on their protected bay side. Rockaway is the barrier beach that protects Jamaica Bay’s wetland. (Other Long Island barrier beaches are Atlantic Beach and Fire Island.) Grasses, sedges, and reeds, including Phragmites and spartinas, dominate the vegetation. Although Phragmites was once thought to be an unwanted weed, naturalists have found that it has some value: it purifies the air and soil it occupies, provides dense cover for animals, and drops from its feathery flowers seeds that sustain wildlife when all other food sources are depleted.
Other park plants that do similar duty include blackberry, bullthistle, burdock, pokeweed, and evening primrose. Those who feed on and take refuge among the wetland plants include the fish and shellfish that breed there and many varieties of migratory birds, especially waterfowl. Birds sighted in Marine Park include myrtle warblers, ring necked pheasants, purple martins, terns, cormorants, marsh hawks, peregrine falcons, egrets, kestrels, ospreys, and gulls. The park is also home to cottontail rabbits, horseshoe crabs, and oyster toad fish, just to name a few of the animals that live on the bay or around Gerritsen Creek. This freshwater stream once extended about twice as far inland as it does now. Around 1910, the creek north of Avenue U was turned into an underground storm drain. But because it still supplies the saltmarsh south of Avenue U with fresh water, Gerritsen Creek allows the area to support a much wider variety of organisms than would live in ordinary salt water.