ABSTRACT
Population centers, which developed along coastal regions, have placed an enormous demand on estuaries, utilizing this unique environment for food production, transportation, waste disposal, recreation, and other purposes. The growing awareness of the societal importance of estuaries, as well as concern over potential anthropogenic impacts, have prompted an expansion of estuarine research. Estuaries are transition zones or ecotones where freshwater from land drainage mixes with seawater. Most of them are drowned lower reaches of river systems, being highly variable in form and extent. The Atlantic and Gulf coasts of the US are characterized by estuaries that differ structurally from those on the Pacific coast. Drowned river valleys, also known as coastal plain estuaries or rias, are common features of the temperate waters of the Atlantic coast of the US, but can be found throughout the world.
