Final answer:
Animals in salt marshes use the marshes for habitat, feeding, and shelter. They have adapted to the rapidly changing salinity and oxygen content due to the mixing of fresh and salt water.
Step-by-step explanation:
The animals in salt marshes use the marshes for a variety of critical functions, including habitat, feeding, and shelter. Salt marshes, which are often inundated by tidal waters, create a unique environment that mixes fresh water and salt water.
This mix poses a physiological challenge for both plants and animals. Halophytic plants, due to their ability to tolerate salty conditions, have adapted to this environment by developing mechanisms to deal with the salinity on their roots or from sea spray.
Similarly, estuarine animals such as mussels and clams have developed behavioral adaptations to cope with the changing salinity; they stop feeding and close their shells when the salinity is low, switching to anaerobic respiration, and then resume feeding and revert to aerobic respiration when the salinity and oxygen levels increase with the return of high tide.
These marshes are important for the life cycle of many marine organisms, providing a protected area for the young of crustaceans, mollusks, and fish.