A classification of estuarine ecosystems is proposed that is based on energy flow as the common denominator among the biological, geological, chemical, and physical features that give estuaries their character. Estuarine ecosystems consist of organisms, populations, water flows, invisible pathways of cycling chemical elements, and various organizational mechanisms that cause the parts to be interrelated. Because conditions are never exactly the same, the estuarine systems that develop are all unique, but there are similarities that may form the basis for grouping and classification.
A discussion is provided of the relation between the principal animals and plants; the vertical and horizontal zonation of species and energy; the pathways for processing food, minerals, and work; and the time variation of these in estuaries. The kinds of energy that usually dominate coastal systems are light energy, organic fuels, and mechanical fluid energy. Stress is considered an energy drain. Organisms are considered to adapt to particular combinations of energy flow and stress and their timing to provide programming of the biological and chemical processes that are characteristic of different types of estuarine systems. Organisms reflect differences between estuaries in their adaptations and diversities.
New ecological systems are evolving in response to the unique energy flows provided by man’s civilization. These have their characteristic complexes of organisms, chemical properties, and physical and geological parameters.
A system of 48 estuarine ecosystem types based on their characteristic energy sources is given.