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benthos
benthic system ecosystem at the sea bottom comprising the sediment with its
associated plant and animal life. This includes the upper layer of the sediment where dissolved oxygen is present (aerobic zone) and the deeper anoxic
layer (anaerobic zone) inhabited by anaerobic bacteria and sometimes temporarily by larger macrofauna. The form and functioning of a benthic
system is strongly affected by sediment type and depth. In shallow waters
where sufficient light penetrates to the bottom, the benthic system may
include primary producers (algae), whereas in deeper waters the benthic
system generally receives its food (algae, detritus, fecal pellets) from the overlying water. Sediment type largely determines the species composition of the
benthic system. Schematically, a benthic system could be regarded as a black
box receiving organic matter from the pelagic and oxygen as input (in shallow systems also light, CO 2 and inorganic nutrients), and with inorganic
nutrients and CO 2 as output, together with low amounts of organic matter
in the form of benthic food eaten by fish or birds, or pelagic larvae released
by the benthos. The overall functioning of benthic systems in the whole of the
marine ecosystem is often investigated with bell jars.
benthos all organisms living on or in the sea floor, also called benthic organisms. Their substrate is species-specific and may be either soft sediments
(sand, mud, peat) or hard rock or wood. Benthic organisms live either on the
surface of the sediment (epibenthos) or buried in the sediment (endobenthos).
They may be either plants/algae (phytobenthos) or animals (zoobenthos).
Large benthic organisms belong to the macrobenthos (or even megabenthos),
Benthos