epifauna

Epifauna are animals that live on the surface of a substrate in aquatic environments. They occupy the outermost layer of the benthos, as opposed to infauna, which dwell within the sediment, and meiofauna, which inhabit the spaces between sediment grains. Epifauna include both sessile organisms that attach to a surface and mobile ones that move across the substrate.

Habitat and distribution vary widely. Epifaunal communities occur from shallow intertidal zones to the deep sea and can be found on rocky shores, coral reefs, seagrass beds, and man-made structures. Common sessile epifauna include barnacles, mussels, oysters, sponges, bryozoans, and tunicates, while mobile forms include crabs, sea stars, sea urchins, and various snails. Attachments are achieved through cementation, byssal threads, or other adhesive mechanisms; some species are free-living and actively forage on the surface.

Ecological role and significance. Epifauna contribute to habitat structure, filter feeding, grazing, and nutrient cycling. They provide shelter and food for other organisms and can influence the physical stability of substrates. The composition of epifaunal communities often reflects substrate type, wave exposure, and environmental conditions.

Taxa and examples. Notable groups include Cirripedia (barnacles), Bivalvia (mussels, oysters), Porifera (sponges), Cnidaria (sea anemones), Bryozoa, Tunicata (ascidians), along with echinoderms and various crustaceans such as crabs and amphipods.

Study and threats. Epifauna are studied via dredges, grabs, scuba-based surveys, and transects. They are sensitive to habitat disturbance, including trawling, pollution, and climate-driven changes, and protection of reefs, seagrass beds, and other substrates helps conserve epifaunal communities.