These estuarine marshes are very important to humans and to life in the sea. Plants are the primary producers that collect energy from the sun and convert it so they can grow and reproduce. In an estuary, there are many types of plants, but it is the tiny microscopic floating plants known as phytoplankton that are the starting point for much of the other animal's food. Zooplankton , tiny floating animals, are the next link in the chain, for they graze on these plants. Filter feeders such as clams, oysters, mussels, and sponges also feed on phytoplankton.
Some fish also feed on it.
Zooplankton are eaten by crustaceans, insects, and other zooplankton, which are eaten by something else in the ongoing cycle of life. People in the Philadelphia region feel more connected to the Jersey Shore than to the Delaware Bay. As you may recall, the Delaware Bay receives water draining from Delaware, New Jersey, Pennsylvania, and New York. An even bigger, better known estuary is the Chesapeake Bay. It is nearly 200 miles long.