Lagoon

A lagoon is a shallow body of water partly separated from the sea or ocean by a natural barrier. The barrier may be made of sand, form a barrier island, or consist of a coral reef. Lagoons are common along low, gently sloping coasts, but their origins vary. Some form when waves and currents accumulate sediment and build a sandy barrier.

Others develop behind coral reefs. One or more openings may connect the lagoon to the sea, allowing tides to move water in and out. Because this exchange is limited, lagoon water can differ from nearby seawater in temperature, salinity, and sediment content. A lagoon is therefore a distinct coastal environment shaped by land, water, waves, currents, and tides.

Lagoons can support diverse ecosystems. Their shallow, sheltered waters may provide feeding or nursery areas for fish, crustaceans, mollusks, birds, and other organisms. These environments change over time: storms may alter channels, sediments may accumulate, and sandy barriers may shift.

Human activities can affect lagoons through pollution, coastal construction, or excessive water extraction. Some lagoons gradually fill with sediment, while others remain for very long periods. Studying them helps scientists understand how coasts evolve and how coastal ecosystems respond to natural changes and human pressure.