Within every habitat, communities of organisms exist in close relationship to each other. Communities may be as small as an oyster bar or as large as the entire Bay. The relationships among species form a complex web.
Some organisms produce food and others serve as prey.
Some communities, such as underwater Bay grasses , provide both food and cover. Many organisms fit into more than one of these categories. The functions within a given community are almost endless, and the Chesapeake Bay supports countless communities both large and small. Change is characteristic of ecological systems, including the Bay. Germination of plant seeds, birth of animals, growth, local movement and migration affect the species composition of each community, as do changes in water quality, loss of habitat or overharvesting.