Final answer:
An estuary is where a river meets the ocean, leading to the mixture of fresh and salt water. The salinity in an estuary varies due to tidal movements and the organisms living there must adapt to these changes.
Step-by-step explanation:
What is an Estuary?
An estuary is a biome where a river (fresh water) meets the ocean (salt water). The mixture of these two water types creates brackish water with varied salinity. Estuaries are known for their biological productivity and biodiversity, serving as protected nurseries for the young of various aquatic species like crustaceans, mollusks, and fish. The salinity of an estuary changes with the tides and freshwater input, creating a unique challenge for the plants and animals living there.
Movement and Interaction of Water in Estuaries
The daily cycle of high and low tides causes ocean water to move in and out of estuaries, altering the salinity. Organisms in estuaries, such as halophytic plants and molluscs, have developed adaptations to survive these fluctuations in salinity.