An estuary is a region where a river meets the sea, forming a transition zone between freshwater and saltwater.

Estuaries are characterized by the mixing of freshwater and saltwater, tidal influence, and high biological productivity.

Estuaries provide habitat for a variety of organisms, serve as important nursery grounds for fish and shellfish, and help to filter pollutants from water.

Estuaries are threatened by pollution, habitat loss, and climate change.

Estuaries can be protected by reducing pollution, restoring and protecting habitats, and mitigating the effects of climate change.

Chesapeake Bay, Mississippi River Delta, and San Francisco Bay are all examples of estuaries.

Estuarine expansion is the term for the gradual widening of an estuary as it approaches the sea.

Spartina marsh is a type of salt marsh found in estuaries.

Accretion is the name of the process by which sediment is deposited in an estuary.

Flounder is a type of fish that is commonly found in estuaries.

Salinity gradient is the term for the mixing of freshwater and saltwater in an estuary.

Osprey is a type of bird that is commonly found in estuaries.

Tidal exchange is the term for the movement of water in and out of an estuary.

Mangrove, seagrass, and saltwort are all types of plants that are commonly found in estuaries.

Estuarine mouth is the term for the area where an estuary meets the open sea.