Mud flats (also known as tidal flats) are found next to salt marshes. Twice each day, water flows in and out with the tides, filling or draining the flat. The mud flat receives nutrients from the tidal flow and the nearby marsh, particularly as it decays. This means that mud flats have a rich plant and animal life.
Phytoplankton and zooplankton are abundant. So are mud snails. Animals like oysters and clams that filter-feed live in mud flats because of the availability of plankton. Fish and crabs move through the flats at high tide. Birds and predatory animals visit tidal flats at specific times for their catch.
About one inch below the surface of the mud, burrowing animals such as clams, worms, and crustaceans can be found. Because there is little or no oxygen, they breathe through tubes to get oxygen from the surface.