Biodiversity & ecosystems
Estuary
Definition
An estuary is a coastal body of water, usually found where rivers meet the sea, in which freshwater draining from the land mixes with salty seawater to create brackish conditions. Estuaries support unique plant and animal communities adapted to variable salinity and rank among the most productive ecosystems in the world.
References
definition, productivity, ecosystem services
geological types, salinity dynamics
Overview
What it means
Geologically, estuaries include drowned river valleys, fjords, tectonic and bar-built types; hydrologically they range from salt-wedge to fully mixed systems. They filter runoff, buffer storms and serve as nursery grounds for fish, birds and other wildlife — and are under intense pressure from development, pollution and sea-level rise.
How it is used
Used in coastal management, habitat classification, fisheries science and protected-area systems (e. g. the US National Estuarine Research Reserve System).
Why it matters
Estuaries concentrate biodiversity, fisheries value and human settlement; their condition is a bellwether of coastal sustainability.