ABSTRACT
As Rachel Carson has described so well in her book The Edge of the Sea, the margins of the oceans are transition zones between land and sea, and are therefore places that demand every shred of adaptability that living things can muster. Humans have increased those demands, sometimes to intolerable levels, by adding toxic chemicals or excesses of nutrient chemicals to inshore waters. We have, for instance, added pesticides and other synthetic industrial chemicals that can, even in low concentrations, drastically affect the physiology of fish and shellfish (and even aquatic plants), and with which the species may have had no previous evolutionary experience. Heavy organic loads, in the form of sewage sludge and effluents, have been superimposed on some aquatic habitats, and they can produce anaerobic or low-oxygen environments. Effluents often contain contaminants such as heavy metals and chlorinated hydrocarbons that interfere with the physiology and biochemistry of the fish and the food organisms that they consume.
