Final answer:
Coastal zones of contact between freshwater from streams and rivers and saltwater from the ocean are called estuaries.
Step-by-step explanation:
Coastal zones of contact between freshwater from streams and rivers and saltwater from the ocean are called estuaries. These are biomes where the river, a source of fresh water, meets the ocean, resulting in a mix of fresh water and salt water known as brackish water.
Estuaries are vital ecological areas as they form protected habitats for the spawning and growth of various marine species such as crustaceans, mollusks, and fish. Salinity is a key factor that affects the life and adaptations of organisms in estuaries. Due to the tidal movements, the salinity levels in these areas fluctuate, which presents a challenge to the plants and animals that inhabit them. Many species have developed specific adaptations to thrive in this ever-changing environment.