bottomdwellers

Bottomdwellers are organisms that live on or near the bottom of aquatic environments. The term overlaps with benthic organisms and contrasts with pelagic species that occupy the water column away from the substrate. Bottomdwellers include a broad range of taxa, from demersal fishes that feed along the seabed to invertebrates such as crustaceans, mollusks, echinoderms, and assorted annelids.

Habitat and distribution: They occur in marine, freshwater, and brackish systems, from tides and shallow shoals to deep-sea trenches. They inhabit various substrates—sand, mud, gravel, rock—and may live permanently on the surface, burrow within sediments, or cling to hard substrates. Oxygen availability, organic matter supply, and currents shape community composition.

Ecological roles and adaptations: Bottomdwellers contribute to nutrient cycling, sediment mixing, and energy transfer by consuming detritus, plankton, and other organisms. Adaptations include flattened bodies for tight spaces, burrowing tools, camouflage, reduced eyes in dark environments, and specialized appendages for feeding or locomotion along the substrate.

Examples: Common bottomdwellers include crabs, lobsters, shrimps, clams, mussels, and other bivalves; starfish and sea urchins; polychaete worms; small flatfish, grenadier eels, and other demersal fishes. In freshwaters, crayfish, catfish, and various bottom-dwelling mollusks are typical.

Human interactions and research: Bottomdwellers are affected by dredging, bottom trawling, pollution, sedimentation, and climate-related changes that alter substrates and oxygen levels. They are studied using grabs, cores, and trawls, as well as underwater imagery and remotely operated vehicles to survey habitat structure and community composition.