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Benthos are the organisms which live on, in, or near the seabed, also known as the benthic zone.[1] They live in or near marine sedimentary environments, from tidal pools along the foreshore, out to the continental shelf, and then down to the abyssal depths. Many organisms adapted to deep-water pressure cannot survive in the upper parts of the water column. The pressure difference can be very significant (approximately one atmosphere for each 10 meters of water depth). Because light does not penetrate very deep ocean-water, the energy source for deep benthic ecosystems is often organic matter from higher up in the water column which drifts down to the depths. This dead and decaying matter sustains the benthic food chain; most organisms in the benthic zone are scavengers or detritivores. The term benthos comes from the Greek for "depths of the sea".[1] 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.[2]
[edit] Food sources 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, sea stars, 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. [edit] By size[edit] MacrobenthosMain article: Macrobenthos 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.
[edit] MeiobenthosMain article: Meiobenthos 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.
[edit] MicrobenthosMicrobenthos are microscopic benthos that are less than 32 µm in size. Some examples are bacteria, diatoms, ciliates, amoeba, flagellates
[edit] By type [edit] ZoobenthosZoobenthos are animals belonging to the benthos. [edit] PhytobenthosPhytobenthos are plants belonging to the benthos. [edit] By location[edit] EpibenthosEpibenthos live on top of the sediment [edit] HyperbenthosHyperbenthos live just above the sediment. [edit] See alsoContrast the terms plankton (the organisms that float or drift within the water), nekton (the organisms that swim (powerfully) in the water), and neuston (the organisms that float on the water). [edit] Notes
[edit] References
[edit] External links
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