Question

What are estuaries, how are they suitable for both marine and river fish to live?

Answer 1

Hint: An estuary is a semi-enclosed and semi-salt coastal area into which one or more rivers or streams flow and connect freely to the open sea. The estuary forms a transition zone between the river environment and the marine environment (called ecotone)

Complete answer:
The estuary is affected not only by the ocean such as tides, waves and salt water influx, but also by rivers, such as the inflow of fresh water and sediment.

Suitable to live: The combination of seawater and freshwater provides high levels of nutrients in the water column and sediments, making the estuary one of the most productive natural habitats in the world.

Most of the estuaries formed during the Holocene occurred when the sea level began to rise about 10,000-12,000 years ago, and valleys washed by river water or glaciers flooded. Estuary is usually classified according to its geomorphological characteristics or water circulation pattern.

They can have many different names, such as bays, ports, lagoons, entrances or sounds, although some of them do not strictly conform to the above definition of estuaries and may be completely salty. Many estuaries suffer damage from multiple factors, including soil erosion, deforestation, overgrazing, overfishing and wetland filling.

Note: Brackish water, sometimes called brack water, is water that has a higher salinity than freshwater in the natural environment, but not as much as seawater. The estuary is an incredibly dynamic system in which temperature, salinity, turbidity, depth and flow change daily according to tides.