Life does not stop at the seafloor. Organisms that live on, in, or immediately above the bottom are collectively called the benthos. They range from microbes and tiny crustaceans living between sand grains to large crabs, sea stars, and demersal fish.

Soft sediments host infauna that burrow; hard substrates support epifauna that attach or crawl. Food arrives as sinking particles from the surface or is produced locally by chemosynthesis at vents and seeps. Depth, temperature, oxygen, and substrate type strongly influence which species occur.

Benthic communities process organic matter, recycle nutrients, and form the base of many food webs that ultimately support commercial fisheries. They are also sensitive indicators of pollution, trawling damage, and climate-driven changes in oxygen and temperature. Sampling the benthos requires grabs, cores, trawls, or remotely operated vehicles, each suited to different habitats and questions.

Even the deepest trenches support specialized benthic animals adapted to extreme pressure and scarce food.