Lagoons

There is an array of enclosed coastal water bodies around the world, with little clear division between definitions for these bodies. A lagoon is often described as a shallow sound, pond or lake generally near but separated from the open ocean. A coral reef lagoon is described as the central, shallow body of an atoll or the water separating a barrier reef from the shore. Despite the variance in definitions, lagoons have the universal characteristics of limited exchange with ocean waters and limited flushing by rivers (as is often the case with estuaries). Three interlinked properties greatly influence the physical and biotic diversity of lagoons: salinity, amount of ocean flushing, and the degree of enclosure. As an example of this interaction, an atoll's central lagoon connects to the deep water outside through a series of channels or grooves, but coral does not usually thrive in the lagoon because the water may become either too fresh during rains or too hot, and because feeding opportunities for corals are limited. With greater flushing from the sea, salinity would be more stable, temperature more conducive to coral growth, and in feeding opportunities increased. Because of these unique characteristics of a lagoon habitat, the biological diversity that they possess is likewise unique.

The limitations on circulation and flushing make coastal lagoons particularly sensitive to adverse impacts (most notably various forms of pollution) from all types of development activity both on their shorelines and in their watersheds. In almost all coastal nations, conflicts among the development activities that compete for the occupation of use of coastal environments and resources are most intense around enclosed bays and coastal lagoons. The natural protection afforded by lagoons and enclosed bays stimulate the development of ports for shipping, fishing and recreational boating.