Thus there is constant nutrient input. The grass also serves as an excellent hiding place for all sorts of creatures. This is why a salt marsh is considered a nursery. Most of our commercial marine catches start out their lives in salt marshes. As you move toward the tropics, salt marshes are replaced by mangrove forests along the coast.
Mangroves are a type of tree that can tolerate having it's roots submerged in salt water.
The roots are called prop roots because they prop the tree up out of the water. So much of the root structure is above the sand or mud. Just like salt marshes, these roots tend to trap materials, and so these areas are fairly productive, although not to the extent a salt marsh is. The roots provide nice surfaces for benthic organisms to attach to. They are also important in their role providing shelter and nursery grounds for both marine organisms, and also for animals such as wading birds that feed off those marine organisms.