Transcript benthic zone - Lectures For UG-5

Zones of marine Environment
Tahir
Intertidal,
Ocean ecosystem
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Marine ecosystems are among the largest of Earth's aquatic ecosystems. They
include oceans, salt marshes, intertidal zones, estuaries, lagoons, mangroves, coral
reefs, the deep sea, and the sea floor. They can be contrasted with freshwater
ecosystems, which have a lower salt content. Marine waters cover two-thirds of the
surface of the Earth. Such places are considered ecosystems because the plant life
supports the animal life and vice-versa.
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Nearly three-quarters of the earth’s surface is covered by ocean with an average depth
of 3,750m and with salinity averaging 35ppt, about 90 per cent of which is sodium
chloride.
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Oceans into zones. The divisions are based on things such as water depth, the amount
of sunlight, and water temperature.
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The major zones in marine ecosystem are littoral, neurotic, pelagic and benthic. The
littoral zone is the
The intertidal zone
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The intertidal zone, also known as the foreshore and seashore and
sometimes referred to as the littoral zone, is the area that is above
water at low tide and under water at high tide.
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This area can include many different types of habitats, with many
types of animals like starfish, sea urchins, and some species of coral.
The well known area also includes steep rocky cliffs, sandy beaches,
or wetlands (e.g., vast mudflats).
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The area can be a narrow strip, as in Pacific islands that have only a
narrow tidal range, or can include many meters of shoreline where
shallow beach slopes interact with high tidal excursion.
The intertidal zone
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Organisms in the intertidal zone are adapted to an environment of harsh
extremes. Water is available regularly with the tides but varies from
fresh with rain to highly saline and dry salt with drying between tidal
inundations.
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The action of waves can dislodge residents in the littoral zone. With the
intertidal zone's high exposure to the sun the temperature range can be
anything from very hot with full sun to near freezing in colder climates.
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Some microclimates in the littoral zone are ameliorated by local features
and larger plants such as mangroves.
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Adaptation in the littoral zone allows the use of nutrients supplied in
high volume on a regular basis from the sea which is actively moved to
the zone by tides.
The intertidal zone
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A typical rocky shore can be divided into a spray zone or splash zone
(also known as the supratidal zone), which is above the spring high-tide
line and is covered by water only during storms and the intertidal zone,
which lies between the high and low tidal extremes.
Along most shores, the intertidal zone can be clearly separated into the
following subzones: high tide zone, middle tide zone, and low tide
zone.
The intertidal zone is one of a number of marine biomes or habitats,
including estuaries, neritic, surface and deep zones.
The Intertidal Zone Sea grasses, periwinkle snails, and herons are
common in an intertidal mudflat.
Sea stars and anemones often live on rocky
shores, while clams, crabs, snails, and
conchs are common on sandy beaches
The intertidal is also home to marine vertebrates,
some of whom prey on intertidal animals,
such as fish, gulls and seals..
Challenges in the Intertidal Zone:
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Moisture: There are usually two high tides and two low tides each day.
Depending on the time of day, different areas of the intertidal zone may
be wet or dry. Organisms in this habitat must be able to adapt if they are
left “high and dry” when the tide goes out. Sea snails such as
periwinkles have a “trap door” called an operculum that they can close
when they are out of water to keep moisture in.
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Waves: In some areas, waves hit the intertidal zone
with force, and marine animals and plants must be
able to protect themselves. Kelp, a type of algae,
has a root-like structure called a “holdfast” that it
uses to attach to rocks or mussels, thus keeping it in place.
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Salinity: Depending on rainfall, the water in the intertidal may be more or
less salty, and tide pool organisms must adapt to increases or decreases in
salt throughout the day.
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Temperature: As the tide goes out, tide pools and shallow areas in the
intertidal will become more vulnerable to temperature changes that could
occur from increased sunlight or colder weather. Some tide pool animals
hide under plants in the tide pool to find shelter from the sun.
The pelagic zone
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Any water in a sea or lake that is neither close to the bottom nor near
the shore can be said to be in the pelagic zone. The word "pelagic" is
derived from Greek πέλαγος (pélagos), meaning "open sea". The pelagic
zone occupies 1,330 million km3 (320 million mi3) with a mean depth of
3.68 km (2.29 mi) and maximum depth of 11 km (6.8 mi). The pelagic
zone can be divided into sections making several sub-zones based on
the different ecological characteristics. They are mostly divided by
depth.
Epipelagic (sunlight)
The epipelagic zone is located from the surface of the water down to
around 200 meters. This zone is known for many varieties of
photosynthetic life because of the abundant sunlight. This zone is
where there are a large concentration of fish including tuna, sharks, and
dolphin . Jellies are also very abundant in this location because of the
large amount of other fish in the area.
Mesopelagic (twilight)
The mesopelagic zone is located from about 200meters to around 1,000
meters. Some light does make it down this far but it is not sufficient
enough for photosynthetic animals to thrive. Animals that are located
here include swordfish, squid, and a few species of cuttlefish. Some
other creatures can also be found here.
Bathypelagic (midnight)
 The Bathypelagic zone is located from 1,000 meters to about 4,000 meters. This
zone of the ocean is almost entirely in the dark because the light cannot penetrate
this deep. Many of the animals that live in this zone have adapted to the
enviroment by having bioluminescent structures on their body. An example of
such a creature is a lanternfish.
 Most of the animals that are located here are carnivores or feed on the dead
material that falls down from the other parts of the pelagic zone. Giant squid are
also known to live in this zone as well as the dumbo octpus.
 Abyssopelagic (lower midnight)
 The abyssopelagic zone is located from about 4,000 meters to just above the
ocean floor. This zone is completely dark because no light is able to penetrate to
this depth.
 Most creatures in this zone are blind and colorless or shades of red. The
organisms are red because no red light is able to
penetrate down making them well camouflaged
in the dark.
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Hadopelagic
The hadopelagic zone is located in deep water
in ocean trenches. Little is known about this
zone and very few species are known to live
there. Many of the organisms that do live here
are located near hydrothermal vents. Some
organisms that live here include Giant tube
worms
The benthic zone
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The benthic zone is the ecological region at the lowest level of a body of water such as an ocean or a lake,
including the sediment surface and some sub-surface layers. Organisms living in this zone are
called benthos, e.g. the benthic invertebrate community, including crustaceans and polycheates. The
organisms generally live in close relationship with the substrate bottom and many are permanently attached
to the bottom. The superficial layer of the soil lining the given body of water, the benthic boundary layer, is
an integral part of the benthic zone, as it greatly influences the biological activity which takes place there.
Examples of contact soil layers include sand bottoms, rocky outcrops, coral, and bay mud.
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The benthic zone of the ocean is varied. There are mountains, trenches, volcanoes, flat muddy areas,
sandy areas and rocky areas.
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There is a wide variety of life that makes its home on the ocean floor. Some organisms live in the mud,
some crawl or swim along the bottom and some anchor themselves to the ocean floor.
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Life in the benthos region is organized by size. Macrobenthos are organisms that are larger than one
millimeter like oysters, starfish, lobsters, sea urchins, shrimp, crabs and coral. Meiobenthos are between
one tenth and one millimeter in size. Organisms in this group include diatoms and sea worms.
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Microbenthos are very tiny organisms like diatoms, ciliates and bacteria. They are smaller than one tenth
of a millimeter.
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A lot of the marine fish we eat come from pelagic fisheries. Some
commercially important species of fish that are fished are Pacific mackerel,
jack mackerel, Pacific sardine and Blue-fin tuna. Unfortunately toady,
many fish stocks have been over-exploited and some species, such as many
shark species, even face extinction due to over fishing. On top of this many
pelagic animals that are not targeted by the fishing boats, such as dolphins
and turtles, sometimes also get affected by negative fishing methods.
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jack mackerel
Sardine
Few favorite commercial fishes from pelagic zone
Red snapper
Tuna
salmon
Cobia