The Mud Flat

The leading edge of the salt marsh, lowest in elevation and nearest the water when the tide is out, is a seemingly barren expanse of mud. But this mud flat is by no means a sterile wasteland. Algae proliferate on its surface, and clams, worms, shrimp, and other invertebrates burrow in the mud below.
American Oyster
American Oyster
Scientific Name: Crassostrea virginica
Young “spat” oysters need a firm surface to grow on. Hard bottoms of sand or mud will do, as will rocks, pilings, and especially other oyster shells. Oysters growing on oysters form beds or “bars,” frequently extensive and usually home to a host of guest species, including sponges, worms, crabs, snails, and fish.
Size: 10” (25 cm)
Mud Snail
Mud Snail
Scientific Name: Nassarius obsoletus
Found in the tidal flats, this common snail grazes on golden-brown diatoms that carpet the mud in fair weather. The spire of the snail’s shell is usually eroded and whitish, in contrast with the brown of the shell body.
Size: 1.25 in. (3.2 cm) 
Bay Barnacle
Bay Barnacle
Scientific Name: Balanus improvisu
Despite its shell, the barnacle is not a mollusk like clams and mussels, but a relative of crabs and shrimp. Barnacles attach to rocks, pilings, shells, or other hard surfaces, opening and closing the plates of their shells at will. When the tide is in, the barnacle combs food particles from the water with waving appendages. When the tide departs, the plate valves close to prevent drying.
Size: ½ in. (1.2 cm) width
Soft-Shelled Clam
Soft-Shelled Clam
Scientific Name: Mya arenaria
This well-known clam harvested extensively throughout the Chesapeake Bay, burrows into the bottom and uses a long siphon to reach the water for oxygen and food. When disturbed, the siphon is retracted, at the same time squirting water from the hole in the mud, thus revealing its location to clam diggers.
Size: 5.5 in. (14 cm)
Clamworm
Clamworm
Scientific Name: Nereis succinea
Clamworms are abundant and widespread in the Chesapeake Bay, inhabiting mud bottoms where they build tubular burrows of sand particles held together by a mucous glue. These voracious predators roam the bottom in search of any soft-bodied prey. In late spring and summer nights during the last quarter of the moon they change form slightly and swim to the surface in great numbers to breed.
Size: 6 in. (15 cm)
Great Blue Heron
Great Blue Heron
Scientific Name: Ardea herodias
This stately bird, the largest native heron, stalks through the shallows, its head drawn back on its shoulders. When a fish, frog, or small mammal come within striking range, the heron snatches it in the pincers of its beak. Like most herons, the great blue nests in colonies, sometimes with birds of other species.
Size: 38 to 52 in. (97 to 130 cm) 
Raccoon
Raccoon
Scientific Name: Procyon lotor
The familiar raccoon thrives near marshes and other wetland habitats where it searches the shallows with its sensitive hands for such prey as clams, crabs, crayfish, and frogs. An omnivore and opportunist, the raccoon also feeds on insects, eggs, young birds, small rodents, and fruit. Raccoons living in the salt marsh keep dry by pulling cordgrass together and perching atop this platform.
Size: 3 ft. (92 cm)
Mud Crab
Mud Crab
Scientific Name: Panopeus herbstii
These little crabs can be identified by their claws, one larger than the other, and both tipped in black. Mud crabs frequently live in shells of large oysters, from which they prey on smaller crabs and other shellfish.
Size: 1.5 in. (3.8 cm)
Ribbed Mussel
Ribbed Mussel (Atlantic ribbed mussel)
Scientific Name: Geukensia demissa
Ribbed mussels are found in clusters partially buried in tidal muds. A filter-feeder, the ribbed mussel ejects inedible particles and binds them with mucus. Where not washed away by tidal currents, these leavings form low mounds that dot the marsh surface.
Size: 2 to 4 in. (5 to 10 cm)