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.
Many benthic animals bind sediments together as fecal pellets that remain at the bottom.
Predators, such as adult blue crabs, scurry across bottom searching for food. These activities stir the sediments, increasing the rate of exchange of materials into the water column. This mixing also increases diffusion of oxygen into the sediments. Filter feeders, like oysters and clams, pump large volumes of water through their bodies and extract food from it. As they filter water for food, they also remove sediments and organic matter, cleaning the water.