The Benthic Zone: the Sea Floor
alexander hamp
deepest ocean trenches. Learn about this varied habitat and the
organisms that live there.
The benthic zone begins at the edge of the sea at the intertidal zone,
extends out along the continental shelf, and continues down the
continental slope to the abyssal plain, thousands of meters below sea
level. It includes the entire seabed, rising along the mid-ocean
ridges where new sea floor is continually being made, and dives down
into the deep ocean trenches.
The habitats of the benthic zone vary widely depending on how far
below the surface the bottom lies. Just beyond the intertidal zone,
the shallow water receives ample sunlight and oxygen. Continuing down
along the continental slope, the environment becomes increasingly dark
and cold, and the pressure increases. A remarkable variety of
organisms live in these different habitats, each with specialized
adaptations reflecting the conditions of their environment.
Benthos: Inhabitants of the Benthic Zone
The organisms that live in the benthic zone are collectively called
"benthos." They include crustaceans, mollusks, worms, fish, and any
other type of organism that makes its home on or in the seabed.
The majority of benthos are scavengers or detritus feeders that eat
decomposing organic matter. Much of the food supply in the benthic
zone is in the form of "marine snow," small particles of decaying
organic matter that slowly descend through the water column and
accumulate on the ocean floor.
Benthos in the intertidal zone include sea stars, barnacles, mussels,
sea anemones, sea urchins, snails, and other creatures that attach
themselves to the rocky substrate or burrow in the sand. Benthos in
deeper zones include fish, crustaceans and tube worms.
Benthic Fish
Benthic fish, also known as groundfish, are those that stay on or very
near the sea bottom, whether in shallow or deep water. Unlike fish
that spend their time swimming, benthic fish are very dense and have
negative buoyancy, allowing them to effortlessly lie on the bottom or
bury themselves. Other adaptations commonly seen in benthic fish
include the lack of a swim bladder and a flattened body shape. They
are predominantly bottom feeders that eat detritus, or ambush
predators that lie in wait for their prey to come within striking
distance.
There are many different types of benthic fish. Flatfish, including
flounder, halibut, plaice, sole and turbot, lie on the the sea floor
or bury themselves in the sand. Asymmetrical physical adaptations
include having both eyes on one side of their head, and different
pigmentation on each side of their bodies; the side facing down is
usually pale, while the side facing up is camouflaged. Some species of
flatfish are predators, feeding on smaller fish, while others eat
mainly invertebrates.
Rays and skates are also flat, but are bilaterally symmetrical, with
their eyes on top of their head. These cartilaginous fish are
predators that bury themselves and wait for prey, feeding largely on
crustaceans, clams, oysters and snails.
Rattails are benthic fish that have a large head and mouth, and a body
that rapidly tapers down to a long, narrow tail. They live in the deep
sea, and are scavengers, feeding chiefly on invertebrates. Some
species of rattails are brotulas, chimaeras and grenadiers.
Source: http://www.thegreeno.com/articles/environment-articles/the-benthic-zone-the-sea-floor.html