Wetlands, Estuaries and Salt Marshes

Doñana National Park occupies a river delta between the cities Sevilla, Huelva and Cadiz in southern Spain. It is an important migration point and agricultural zone. I visited here in July 2022.

If a lake has an outlet -or- the river continues flowing, then generally all water will drain into an ocean. Estuaries may be found where rivers and oceans meet, which is another type of aquatic biome.

Estuary or salt marsh

Estuaries are places where freshwater from rivers mixes with saltwater from the ocean. Organisms that live in estuaries must be adapted to these dynamic environments, where there are variations in water chemistry including salinity, as well as physical changes like the rise and fall of tides.

Sediments transported by water settle at the mouth of the river, where the flow of water slows. These sediments accumulate to provide a growth medium for plants. Estuaries contain important habitats such as wetlands, mudflats, rocky shores, and seagrass beds. The roots, branches and hiding spots produced by the plants in an estuaries serve as nursery and spawning areas.

Almost 80% of the commercial and recreational fish we catch depend on estuaries for part or all of their lives. Agriculture, eco-tourism, fishing, and boating are important revenue sources in the region.

Wetlands, Estuaries and Salt Marshes

Estuary or salt marsh

Nile River Delta

Ganges River Delta

Mekong River Delta