Estuaria

An estuary, or estuarine system, is a partially enclosed coastal body of water where freshwater from rivers mixes with seawater. The interaction of tides, river discharge, and coastal geomorphology creates a zone where salinity varies from near-freshwater near the river source to saltwater farther offshore. Estuaries are dynamic and highly productive environments shaped by seasonal flows, sediment supply, weather patterns, and human activity. In Spanish, estuaria is the term used for an estuary.

Estuaries exhibit salinity gradients and are commonly described by their mixing pattern: well-mixed, partially mixed, and highly stratified (salt-wedge) types, though local geometry and tidal range can produce combinations. The circulation, tides, and sedimentation continuously reshape channels, mudflats, salt marshes, mangroves, and shoals that characterize estuarine landscapes.

Ecologically, estuaries function as nurseries and feeding grounds for many species of fish, birds, and invertebrates. Vegetation such as salt marshes (temperate zones), mangroves (tropics), and seagrass beds stabilizes sediments, absorbs nutrients, and supports high biological diversity. They also provide ecosystem services including water filtration, carbon storage, and coastal protection from storms.

Human use includes fisheries, shipping, recreation, and coastal development. Pressures include pollution, overfishing, dredging, sediment starvation due to dams, and habitat loss from development. Climate change and sea level rise threaten estuarine habitats by altering salinity regimes and sediment dynamics. Restoration and conservation efforts aim to safeguard hydrological connectivity, improve water quality, and preserve the ecological services estuaries provide.