lagoon

lagoon, a shallow area of water separated from the open sea by a coral reef or sandbank. Lagoons are a regular inshore feature of fringing coral reefs and support a rich variety of marine plants and animals, and are important nursery grounds for the young fry of many fishes. The coastal lagoons of Baja California in Mexico are important calving areas for Gray whales (Eschrichtius robustus). Along coastlines exposed to the open sea, the lagoons perform a key role in absorbing much of the wave energy that hits the shore during tropical storms. In tropical lagoons, where exchanges of water with the open sea are limited, the water heats up rapidly and the high evaporation results in the water becoming very salty, so lagoons are often exploited as a source of sea salt. Their productive waters, high in salinity, attract large numbers of seabirds, particularly flamingos (Phoenicopterus spp.), whose bills are especially adapted for filtering the abundant fine algae from the water. Around Britain, lagoons are uncommon coastal features, and almost without exception they are considered important conservation sites because of the rarity of the animals and plants that inhabit them; they are threatened by eutrophication, an important environmental issue, and coastal developments. For illus. see atoll.

M. V. Angel