To the benthos include all organisms living at the bottom of bodies of water or in the soil column. The term "benthic" suggested by the German naturalist Ernst Haeckel. The Greek word for "benthic" means "depth".
Animals belonging to the benthos, called the zoobenthos, and plants - the phytobenthos.
Some of benthic animals buried in the ground. This part of the benthos called infauna. This includes many polychaetes and bivalves, echiurida, sipunculida, some echinoderms.
Others move along the bottom is infauna (polychaetes and molluscs, most echinoderms, various crustaceans).
Representatives of sessile benthic attached to the bottom. They are the epifauna. It sponges, hydroids, sea anemones, corals, bryozoans, barnacles, some bivalves.
And, finally, there benthic animals that swim near the bottom and only occasionally descend to the ground (shrimp, mysids, some of the sea cucumbers, demersal fish such as flounder).
In the benthos composition also includes bacteria, benthic diatoms, ciliary ciliates, amoebae and flagellates.
By way of foraging on benthic organisms are divided into the following types:
- predators (sea stars, demersal fishes);
- the suspension feeders (plastination shellfish);
- granted (some multiseta and worms, the larvae of Diptera, sipunculida);
- secretely (baetica, nymphs, mayflies);
- filter feeders (sponges, bivalves, Cirripedia).
In the zoobenthos of the seas and oceans is dominated by foraminifera, sponges, corals, polychaetes, molluscs, crustaceans, echinoderms and fish. Zoobenthos of fresh water is the simplest, sponges, worms, leeches, mollusks, insect larvae.
Benthic animals are changing the physical and chemical properties of sediments. In addition, most of the fossil consists of the remnants of benthic organisms. Of great importance in the food chain sea benthic bacteria, although they are a small portion of the total weight, or biomass of the benthic community. Benthic bacteria return nutrients to the ecosystem, and make the detritus and dissolved organic matter in particles that can be used by larger organisms.
Benthic animals in size is divided into:
- the macrobenthos (>1 mm);
- meiobenthos (from 32 μm to 1 mm);
- microbenthos (less than 32 μm).
Benthos serves as food for many fish and other aquatic animals, and human uses (e.g., algae, oysters, crabs, some fish).