An oyster bar' and the many species it supports, is another example of a benthic community. Benthic communities that exist on or in bare, unvegetated substrate are made up of mollusks, worms and crustaceans. As with all aquatic life in the Bay, salinity affects the distribution of bottom-dwellers, but sediment type also plays a role. Neither coarse sand nor soft mud support rich benthic populations. The best sediment for diverse benthic communities consists of a mixture of sand, silt and clay.
Some organisms require specialized substrates.
Oysters need a clean hard surface, preferably another oyster shell, on which the larval spat can attach or set. Oysters form a reef community that is important habitat for other benthic species. The benthic community affects the physical and chemical condition of the water and sediments. Some build tubes or burrows through which they pump water. Infaunal deposit feeders, such as worms, plow through the sediments in search of food.