5.6. Food Web in the Estuary Because an estuary produces so much food, many life forms are found there, creating special ecosystems. Estuaries are generally considered prime bird-watching areas and many land animals can also be found there. Food, of course, is the reason. A food web is the story of "who eats who". A food web is how food chains are linked together. Examples of typical estuary food web is shown in the following illustration. Because of biological processes, chemicals become magnified or concentrated as they move up the food chain. A clam, for example, concentrates toxins as it filters the water. As water and plant material in the water (plankton) wash by the clam, it filters the plant material out. The toxins in the plant concentrate in the clam and are passed on to whoever eats the clam, including humans.