Marine Ecosystem

 

Marine Ecosystem

The term marine is for things relating to the bay, sea or ocean etc. Generally the marine environment is characterized by the salty water and tides .The marine ecology is diversified and different from other ecology .Marine environment can be divided into some distinct zones and these is called zonation of marine environment .These zones are determined by a number of factors such as tidal range , individual species range or a combination of the two .The tides are very important which affects turbidity .The number and the abundance of various organisms vary from zone to zone such as in the continental shelf area the biodiversity of aquatic organisms is most comparing to other zones .In the ocean a great diversity of strange and bizarre fishes and organisms can be found. Some zones are economically and environmentally very important while some are unknown or having little knowledge .In the deeper region the water pressure is very high with no light penetration. Amongst the zones of ocean continental shelf is very important because of its higher productivity.

Zonation of marine environment

The sea or ocean of the sea is divided into various divisions which is called zonation of seaThe marine environment can be divided into two zones:

1.     Pelagic zone

2.     Benthic zone

Pelagic zone

The word pelagic is derived from ancient Greek pelagos which means open sea. The pelagic zone occupies 1330 million cubic miles .Fish that live in pelagic area are called pelagic fish. The pelagic environment is divided into the

1.     Neritic zone

2.     Oceanic zone

Neritic zone

This is the part of the ocean extending from the low tide mark to the edge of the continental shelf with a relatively shallow depth extending to about 200 meters. The neritic zone has generally well oxygenated water, low water pressure and stable water temperature. Zooplankton, free-floating creatures ranging from microscopic foraminifera are to small fish and shrimps live in this zone.

Oceanic zone

The oceanic zone begins in the area off shore where the water measures 200 meters deep or deeper .It is the region of open sea beyond the edge of continental shelf and includes 65% of the oceans completely open water shelf break, deep ocean water.

Because of the range in depths, the oceanic zone is subdivided further into the:

1.     Epipelagic (sunlit)

2.     Mesopelagic (twilit)

3.     Bathypelagic (midnight)

4.     Abyssopelagic (lower midnight)

5.     Hadopelagic

Epipelagic (sunlit)

This zone starts from the surface down to around 200 m. This is the illuminated zone at thesurface of the sea where there is enough light for photosynthesis .Nearly all primary productionin the ocean occurs here. With the light heat comes and this heat is responsible for the widerange of temperature .Organisms found in this zone are plankton, seaweeds, jellyfish etc.

Mesopelagic (twilit)

This zone starts from 200 meters down to 1000 m .The name stems from the Greek meson meansmiddle .This mesopelagic zone is sometimes referred to as mid water zone .Although some lights penetrates this second layer, it is insufficient for photosynthesis. Some creatures which live inthis zone are bioluminescent .Organisms that are available here are squid, cuttlefish, wolfish,swordfish etc. A great diversity of strange and bizarre fishes can be found here.

Bathypelagic (midnight)

From 1000 meters down to 4000 m .The name stems from the ancient Greek bathys means deep. At this depth the ocean is pitch black, apart from occasional bioluminescent organisms such as lantern fish .There is no living plant life .Most species depends on prey for food e.g. Giant squid.Most of the animals that live at this depth are black or red in color due to the lack of light.

Abyssopelagic (lower midnight)

The name is derived from the Greek abyssos means bottomless and from 4000 meters down to 6000 m. The water temperature is near freezing and there is no light at all. This zone is mostly unknown and very few species are known to live here .The abyssal plain is covered with soft sludge composed of dead organisms from above.

 Hadopelagic

This zone extends from 6000 m to the ocean bottom. The name is derived from the realm of hades, the underworld in Greek mythology .These areas are mostly found water trenches and canyons. The deepest point in the ocean is located in the Mariana trench off the coast of japan at35797 feet. The temperature of this is zone is above freezing and the pressure is an incredible eight tons per inch .This zone is mostly unknown and very few species are known to live here. However many organisms live in hydrothermal vents in this zone. These deep zone is where some of the most bizarre and fascinating creatures in the sea can be found.

1.     Photic zone

2.     Disphotic zone

3.     Aphotic zone

The oceanic zone can also be divided into different zones based upon depth of light penetration:

Photic zone

The photic zone is the depth of the water of ocean that is exposed to sufficient sunlight for photosynthesis to occur .Typical euphotic depths vary from only a centimeter in highly turbid eutrophic lakes, to around 200 m in the open sea .It also varies with the seasonal changes of turbidity. The number of various kinds of phytoplankton is very higher in this zone.

Disphotic zone

This is the zone start from 200 m to 700 m .In the disphotic zone small amount of sunlight penetrate .The rate of photosynthesis is very low in this layer .Turbidity is an important factor which determine the transparency.

Aphotic zone

This is the zone of ocean where there is no sunlight consequently bioluminescence is essentially the only light found in this zone .Most food comes from dead organisms sinking to the bottom of the ocean from overlaying water. The temperature is very low.

Benthic zone

The zone of the ocean bottom is called benthic zone. The zone can be divided as follows: