Estuarine Classification and Responses to Disturbances

There are many similarities among estuaries of a given type, whether the estuary is located on the east, west or Gulf coast of the United States. Based upon these similarities, the estuarine systems of the United States have been classified into types. The general types, based on broad similarities, include five main categories: 1) naturally stressed systems of wide latitudinal range; 2) natural tropical systems of high diversity; 3) natural temperate systems with strong seasonal programming; 4) natural arctic systems with ice stress; and 5) emerging new systems associated with man. The response to disturbances is related to the system type. Those systems already subjected to energy‐requiring stresses are more likely to resist changes than those (such as tropical systems) adapted to relatively constant environments. There is differential response to various disturbances, which is related to the dominant structure of the system. For example, a system supported by a grass bottom will be more affected by a “bottom‐covering” waste than one relying upon mid‐water plankton for primary support. New coastal systems are arising from the dominance of old systems by man‐made wastes. Where waste inputs are large and constant, the emerging new system is one that can be described and is as much an ecological system as those evolved through many years of adaptation and evolutionary history. Because of the absence of long periods for adaptation and evolution, these new emerging systems are erratic and unstable.