While sediments may seem removed from biology, they are in fact important. Sediments structure benthic communities because of grain size preference by various organisms. For example, grain size makes a difference in the ability of flatfish to bury themselves in the sediment. Sediments may have biological origins in the skeletal material of corals, macroalgae, phytoplankton, foraminifera, radiolarians, mollusks, etc. Suspended sediments have been shown to cause stress and gill damage in fish, smother coral reefs, and decrease benthic primary production.