Explain why estuaries, salt marshes, and mangrove forests have more variation in salinity than other marine habitats like the ocean and sea floor.

Answer:

Estuaries, salt marshes, and mangrove forests lie where land-based freshwater meets seawater. River flow and rainfall can dilute the salt, while tides bring in seawater and evaporation can concentrate it. Because these inputs and conditions change, salinity varies more than it does in the open ocean or on the seafloor.