benthic

Benthic refers to the ecological region at the bottom of a body of water and to the organisms that live there. In oceans, seas, lakes, and rivers, the benthos includes a wide range of life from microbes to large invertebrates and occasional vertebrates that inhabit the substrate or live on its surface.

Benthic habitats are distinguished by their position relative to the substrate. Epibenthic organisms live on the surface of the seabed or lakebed, while infaunal organisms inhabit burrows or tunnels within the sediment. Depth-based zones such as shallow littoral or sublittoral areas, as well as deeper bathyal, abyssal, and hadal zones, influence which communities occur. Substrate type (sand, mud, gravel, rock), oxygen availability, temperature, light, and currents all shape benthic assemblages.

Ecologically, benthic communities play key roles in nutrient recycling, sediment stabilization, and bioturbation, which mixes and oxygenates sediments. They form an essential link in aquatic food webs, serving as prey for demersal fish and other predators. In shallow zones, benthic primary producers such as macroalgae and seagrasses contribute energy to the system.

Organisms commonly found on or in the benthos include microbes, algae, sponges, corals, bivalves, gastropods, crustaceans, echinoderms, and polychaete worms. Many benthic species are sessile or slow-moving, but others are mobile or burrow into the sediment.

Research and management methods include sediment grabs and cores, dredges, and remotely operated or autonomous underwater vehicles for observation, complemented by acoustic surveys. Human activities such as bottom trawling, pollution, and hypoxia pose threats to benthic habitats, prompting conservation measures and sustainable habitat and fisheries management.