Estuaries provide vital environmental functions and values.
For example, they:
- provide many different habitats, including seagrass meadows, mangroves, saltmarshes, mudflats, sandflats, rocky shorelines, rocky reefs, oyster reefs, sandy shorelines and beaches and deep open water areas
- support incredible biodiversity including fish, shore birds, prawns, crabs, shellfish, marine mammals, reptiles, algae and specialised plant species
- act as breeding places and nurseries for many estuary and marine species
- provide essential ecosystem services such as food provision, carbon storage, filtering nutrients and sediment in runoff from the surrounding catchment area and storm protection.
Estuaries act as natural filters. Water from rivers and streams can carry sediments, nutrients and pollutants into estuaries in runoff from the land, some of which can be retained in estuaries by a natural filtration process. Excessive amounts of sediment, nutrients and pollutants in runoff from the land puts estuaries and their biodiversity at risk.
This natural filtration can occur in riparian areas – the vegetated area adjacent to the edge of a waterway – where the vegetation and soils act to intercept sediment and nutrients in runoff from the land.
As rivers, creeks and streams flow into estuaries the speed of currents reduces, resulting in material being deposited into different parts of estuaries. This means water that flows to the downstream parts of estuaries and out to the ocean can be much clearer and cleaner. Clear, clean water benefits marine life and people interacting with waterways and the coast.