52
, with the completion of a turn , the fish that were swimming at the sides
of the school find themselves at the head of the cluster . The size and
number of fish in a school vary enormously with the species : a school
can range from a few individuals to millions of fish that stretch out for
tens of kilometers.
Sublittoral zone :
The bottom energy on continental shelves is a function of the wave
energy and tidal currents. Bottom energy varies inversely with water
depth . the sea bed of the shelf can be subdivided into energy bands :
high-energy bottom conditions prevail nearshore , in shallow water ,
and low-energy conditions prevail offshore , in deep water.
Bottom energy affects the benthos in at least two ways. First, bottom
turbulence continually moves sediment about . This creates an unstable
substrate and makes it difficult for an epifaunal community (one living
on the sea bed) of any size to become established.
Second , bottom energy directly controls the grain size of sediment that
is deposited . Mud , a low-energy sediment deposit, consists of small
clay and silt particles
and accumulates in wave-protected shore
environment or far offshore in quiet water that is below the wave base.
Deposits of sand and gravel , high-energy deposits , are common along
the inner and middle parts of the shelf , where the shallow bottom is
regularly swept clean of mud
by wave activity and tidal actions ,
leaving clean sand and gravel to accumulate.
The feeding habits of the benthos clearly correlate with grain size of the
sediment cover . Gravel and coarse-sand
bottoms are populated
overwhelmingly by filter feeders.
Substrates of fine sand and coarse silt support a mixed faunal
assemblage , composed predominantly of detritus and deposit feeders ,
some infaunal (living in the substrate)
filter feeders, and few
epifaunal(living on the substrate) filter feeders. Muddy substrate are
almost exclusively inhabited by deposit and detritus feeders , because
such substrate tend to have a high content of organic matter.
Two major benthic communities are defined according to the character
of the substrate :hard bottom and soft-bottom communities.
, with the completion of a turn , the fish that were swimming at the sides
of the school find themselves at the head of the cluster . The size and
number of fish in a school vary enormously with the species : a school
can range from a few individuals to millions of fish that stretch out for
tens of kilometers.
Sublittoral zone :
The bottom energy on continental shelves is a function of the wave
energy and tidal currents. Bottom energy varies inversely with water
depth . the sea bed of the shelf can be subdivided into energy bands :
high-energy bottom conditions prevail nearshore , in shallow water ,
and low-energy conditions prevail offshore , in deep water.
Bottom energy affects the benthos in at least two ways. First, bottom
turbulence continually moves sediment about . This creates an unstable
substrate and makes it difficult for an epifaunal community (one living
on the sea bed) of any size to become established.
Second , bottom energy directly controls the grain size of sediment that
is deposited . Mud , a low-energy sediment deposit, consists of small
clay and silt particles
and accumulates in wave-protected shore
environment or far offshore in quiet water that is below the wave base.
Deposits of sand and gravel , high-energy deposits , are common along
the inner and middle parts of the shelf , where the shallow bottom is
regularly swept clean of mud
by wave activity and tidal actions ,
leaving clean sand and gravel to accumulate.
The feeding habits of the benthos clearly correlate with grain size of the
sediment cover . Gravel and coarse-sand
bottoms are populated
overwhelmingly by filter feeders.
Substrates of fine sand and coarse silt support a mixed faunal
assemblage , composed predominantly of detritus and deposit feeders ,
some infaunal (living in the substrate)
filter feeders, and few
epifaunal(living on the substrate) filter feeders. Muddy substrate are
almost exclusively inhabited by deposit and detritus feeders , because
such substrate tend to have a high content of organic matter.
Two major benthic communities are defined according to the character
of the substrate :hard bottom and soft-bottom communities.
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