benthos: see marine biology.

Benthos are the organisms which live on, in, or near the seabed, also known as the benthic zone. They live in or near marine sedimentary environments, from the littoral to the deep-sea.

The term benthos comes from the Greek for "depths of the sea". Benthos is also used in freshwater biology to refer to organisms at the bottom of freshwater bodies of water, such as lakes, rivers, and streams.

The main food sources for benthos are plankton and organic runoff from land. The depth of water, temperature and salinity, and type of local substrate all affect what benthos is present. In coastal waters and other places where light reaches the bottom, benthic photosynthesizing diatoms can proliferate. Filter feeders, such as sponges and pelecypods, dominate hard, sandy bottoms. Deposit eaters, such as polychaetes, populate softer bottoms. Fish, starfish, snails, cephalopods, and crustaceans are important predators and scavengers.

Benthic organisms, such as sea stars, oysters, clams, sea cucumbers, brittle stars and sea anemones, play an important role as a food source for fish and humans.

By size


Macrobenthos are the larger, more visible, benthos that are greater than 1 mm in size. Some examples are polychaete worms, bivalves, echinoderms, sea anemones, corals, sponges, sea squirts, turbellarians and larger crustaceans such as crabs, lobsters and cumaceans.


Meiobenthos are tiny benthos that are less than 1 mm but greater than 32 µm in size. Some examples are nematodes, foraminiferans, water bears, gastrotriches and smaller crustaceans such as copepods and ostracodes.


Microbenthos are microscopic benthos that are less than 32 µm in size. Some examples are bacteria, diatoms, ciliates, amoeba, flagellates

By type


Zoobenthos are animals belonging to the benthos.


Phytobenthos are plants belonging to the benthos.

By location


Epibenthos live on top of the sediment


Hyperbenthos live just above the sediment

See also



  • Benthos. (2008) Encyclopædia Britannica. (Retrieved May 15, 2008, from Encyclopædia Britannica Online.)
  • Ryan, Paddy (2007) Benthic communities Te Ara - the Encyclopædia of New Zealand, updated 21 September 2007.
  • Yip, Maricela and Madl, Pierre (1999) Benthos University of Salzburg.

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