Ästuars

Ästuars are tidal coastal systems located where rivers meet the sea. They form at the mouths of rivers and are shaped by a combination of tides, river discharge, currents, and sediment supply. Typical features include a salinity gradient from freshwater to seawater, extensive intertidal zones, and channels that braid through mud or sand. The landscape can include mudflats, salt marshes or mangroves, barrier beaches, and deltas, with geometry ranging from broad embayments to narrow, funnel-shaped inlets.

Ecology and habitat quality are hallmarks of ästuars. The mix of fresh and saline water creates brackish conditions that support specialized plants and animals. Ästuars often provide rich feeding grounds and nurseries for fish and invertebrates and attract migratory and resident birds. Intertidal zones support a variety of invertebrates, while submerged and emergent vegetation stabilizes sediments and supports biodiversity.

Hydrology in estuaries is dynamic, with tidal exchange driving circulation and seasonal changes in river flow altering salinity and turbidity. Sediment deposition and erosion continually modify channel networks and shoreline forms, while extreme events such as storms can reshape the estuarine landscape.

Humans use and impact ästuars for navigation, fishing, recreation, and coastal development. They are affected by upstream damming, dredging, pollution, and changes in sediment supply. Climate change poses risks through sea-level rise, altered hydrology, and increased flood risk.

Notable examples include the Severn Estuary in the United Kingdom, the Gironde Estuary in France, and the Øresund in the Denmark–Sweden region. The English term is estuary; ästuars is a regional term used in some Nordic contexts.