V. K. Verma1,
Dinesh Kumar2 and
B. J. Saud3
1 & 3Research
Associate, Central Inland Fisheries Research Institute, Regional
Centre, Guwahati Assam
Research fellow, National Bureau of Fish Genetic Resources, Lucknow
The term benthos is derived from the Greek, meaning 'depths of the
sea' and refers collectively to organisms which live on, in, or near
the bottom of the sea. Benthos is also used in
biology to refer to
organisms at the bottom of freshwater bodies
of water, such as
lakes, rivers, and streams. Many organisms adapted to deep-water
pressure, cannot survive in the upper parts of the water
Light does not penetrate deeper water so;
the energy source for deep benthic ecosystems is often organic
and decaying matter
sustains the benthic food
chain; most organisms
in the benthic zone are scavengers
The depth of water, temperature and salinity, and
type of local substrate all affect the
presence of benthic community. In coastal waters and other places
where light reaches the bottom, benthic photosynthesizing
can proliferate. Filter
feeders, such as
dominate hard, sandy bottoms. Deposit eaters, such as polychaetes,
populate softer bottoms. Fish, sea
are important predators and scavengers.
Benthic organisms, such as sea
stars and sea
anemones, play an
important role as a food source for fish
Benthic organisms can be classified on the
The benthic community includes of a wide range of plants, animals and
bacteria. They are classified into 3 categories
1- Infauna - organisms that live in the sediment
2- Epifauna - organisms which either attach to the bottom or
substrate; move within the sediment; or that live on the sediment
- fish that feed on the benthic infauna and epifauna
Macrobenthos are the larger in size (1 mm), more
visible. For examples: polychaete worms, bivalves, echinoderms, sea
anemones, corals, sponges, sea squirts and larger crustaceans such as
Meiobethos 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 rustaceans such as copepods and ostracodes.
microscopic benthos that are less than 32 μm in size
viz. bacteria, diatoms, ciliates, amoeba, and flagellates
The benthos those are animal origin called
Benthos those are plant origin called
Benthos living on the top of sediment.
live just above the sediment.
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).
Biologists refer to species dwelling on the sea floor at any depth as
benthic organisms or 'the benthos'. They are also known as bottom
dwellers. Fish are common in benthic communities in the mesopelagic
and bathypelagic zones, but there are none on the deeper sea floors
of the abyssopelagic and hadopelagic zones. Energy is in scarce
supply here, deriving mainly from falling food that has made it past
all the waiting mouths above.
Bacteria are probably the base for most benthic food chains, as they
are able to release nutrients that other life forms cannot make use
of directly. For example the armour-like exoskeleton of zooplankton
such as krill contains carbohydrates locked up in the tough chitin or
cellulose that only bacteria can break down. These nutrients can then
be used by slightly larger organisms referred to as the meiofauna,
which live in the fine sediment that covers most of the deep-sea
floor. They in turn concentrate nutrients and make them available to
larger organisms. The occasional bonanza, such as a dead whale, may
provide food for decades.
Echinoderms are the most obvious deep-sea species. They include
starfish (sea stars) and brittle stars, sea urchins and sea
cucumbers. Sea cucumbers may move by swimming or squirting water.
Others walk on the sea floor using tube feet. In 1986 a new group of
echinoderms, the Concentricycloidea, was discovered on wood in deep
water off the New Zealand coast (although some taxonomists no longer
consider them a new class).
of various kinds, polychaete worms and bivalve molluscs are also
reasonably common. Some deep-sea invertebrates — most notably some
isopods and pycnogonids (sea spiders) — are gigantic.
Among the benthic fish species is the strange tripod fish (belonging
to the family Triacanthidae), which has long feelers on its pectoral
and caudal fins. The ventral and caudal fins act like a tripod,
holding the fish on the sea floor, while the pectorals are held
sideways and detect any water movements caused by prey. These fish
are virtually blind. Other bottom-dwelling species are fished
commercially and end up on the table — grenadiers (or rat-tails),
orange roughy, oreos and cusk eels (sold as ling). Less savoury
characters include hagfish, brotulas, toadfish and snailfish.
Encyclopedia Britannica. (Retrieved May 15, 2008, from Encyclopædia
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.