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Ocean Environment Facts – Zones and Management

by Sekar Puspa

Many people already know that oceans are very large areas, and most of the earth surface are oceans, but not many people know about ocean environment, such as about water, salinity, temperature, energy and sunrays, etc. Oceans are liaisons between continents, the framer of coastal line and climate by distibuting big quantity of thermal to all of the earth, so the places which has very little light still can be inhabited.

See also: Waves in Ocean – Ocean Phenomena

Definition of Ocean Environment

Ocean environment is an environment consists of saline water or marine water which contains millions of ecosystem and biodiversity mysteries, most of them have not been revealed. Ocean environment covers the beach (coastal environment), estuaries, to the middle of the ocean, from water surface to seabeds, which are varied according to depth and morphology.

With the more developed science and technology about ocean, both the Marine Biology and Oceanography, the mysteries were revealed overtime, especially about ocean environment. Talking about ocean environment, There are 2 essential parts: First, Pelagic Zone, or Water Zone, where we find the water mass. The second, Seabed Zone or Benthic Zone, which is the base or platform of the sea. From those 2 parts, we can divide them into more areas or zones with distinctive characteristics.

See also: Oceans in the World – Ocean Layers

Pelagic Environment

All biota that live in ocean environment but don’t live on seabeds are called pelagic biota. The environment where these biota live is called Pelagic Environment. This environment includes water column from seabeds to water surface. The borderline or zone spreaded from coastal line to marine recesses. Horizontally, pelagic environment is divided into neritic and oceanic zones. Vertically, pelagic environment is divided into epipelagic, mesopelagic, batipelagic, and abysopelagic zones.


1. Neritic Zone

It is the zone from 0-200 m under sea surface. The characteristics are:

  • The sunrays still can reach seabeds
  • The depth is around 200 m
  • The area where we can find many fish and sea plants

Neritic zone is located in continental shelves which is inhabited by different sea biota from oceanic zone because:

  • Nutrient contents are abundant in this zone
  • The chemical properties in neritic water is different from oceanic water because the solutes obtained from mainlands are different.
  • Neritic water is very changeable, both in time and space, when compared with oceanic water. This happens because of the closeness of this zone to mainland, and there arespills of solutes from mainland to the sea.
  • Exposure of sunrays, sediment contents, and physical energy in water column in neritic zone are different from oceanic zone.

2. Oceanic Zone

Oceanic Zone is an area of open water ecosystem which its depth cannot be penetrated by sunrays until the seabeds, so the seabed is very dark. The water from sea surface cannot mix with the water from below, because of difference of temperature. The border of the two water layers is called Termocline Area, where most of the fish are found.

Oceanic zone is a marine water area located outside of continental shelves. This zone is lack of nutrients, has less sediment, so the penetrative power of the sunrays only reaches 200 m.


1. Epipelagic Zone

Epipelagic Zone is the upmost water column. It is also called Photic Zone, with the depth of 200 m. In some area, especially in continental shelves, translucence is so much less than the same layer in oceanic water, because of the high contents of suspended sediment in continental shelves.

The zone is divided into 3 sub-zones:

  • Surface and near-surface zone, where the day time lighting is much more than optimal, even lethal for phytoplanktons and zooplanktons.
  • Under-surface zone, it extends until water almost-recesses, where there are active growth of phytoplanktons
  • Bottom zone, is the water level where zooplanktons usually stay in day time; zooplanktons would migrate to water surface in night time.

2. Mesopelagic Zone

This zone is located under epipelagic zone, with the depth of 200 m – 1000 m. Because it is located under photic zone, there is no activity that generates primary production using detritus that comes down from shallower layer.  In this zone and the rest, oxygen production is lower than the utilized one. Plants can live in this bottom layer, but they will lose more organic substances which they produce than getting it from the environment.

3. Batipelagic Zone

This zone has the depth between 1001 m – 2000 m, we can say that it is the sea bottom. Fish and biota that live here are usually bioluminescence organisms, which can produce their own light. The bioluminescence characteristic is an adaptation to the dark environment, impenetrable by light. The animals that live in this zone are usually giant squids, dumbo octopus, and saltwater fish that has very unique morphology which is so much different from the fish in fotic zone, including lantern fish, and hagfish. Sperm whales also live in this zone, feeding upon giant squids.

With minimum foods and dark environment, most animals here depend on detritus (remaining of organisms that falls from upper zone), which is called Marine Snow. The other animals live as predators.

4. Abysopelagic Zone

This zone is more than 2000 m deep. The zone spreads to the most recess places in the ocean, thus often called “trench zone”. There is no light at all, very cold, and water pressure is very high. This zone is the most simple habitat, with very little plant, if there’s any, because there is no photosyntesis. The lights are produced by bioluminescence.  There is very little change in salinity, mostly no change at all.

Then, the high carbondioxyde here can dillute calcium (CaCO3) easily, so the mollusks and porous animals have soft shells. The very high water pressure makes the animals changed their morphology and phisiology, for example the fish usually have bigger swim bladders to move in water collumns. The foods are usually from carcasses or remaining of drowned biota.

According to Light Intensity

There are several zone of environment depends on light intensity, as follows:

  1. Photic Zone, a zone where the sunrays still can penetrate the sea, maximal depth is 200 m. It is the primary productive zone in the ocean.
  2. Twilight Zone, has little light, not effective for photosyntesis, thus not many plants live here. The depth is 200 – 2000 m.
  3. Aphotic Zone, more than 200 m depth. There is no light at all, so it is dark all the time.

Benthic Zone

Ocean environment is also classified according to seabed environment, or benthic environment. In Pelagic Zone, most of the biota are fish, squids, and other swimmers. In Benthic Zone, the biota are benthos or biota that live on seabeds, like bivalves, arthropodes, echinodermates, corals, coelenterata, and sponges. The dominant biota are the filter feeders, the biota that feed themselves by filtering water or sediment through their feeding organs. As filter feeders, they really depend on conditions of sediment on seabed.

Benthic Zone is classified into 4 sub-zones, according to biota characteristics and different sediments.

See also: Ocean Plants – Ocean Animals

1. Littoral Zone

Littoral zone is the nearest one from coastal line. In coastal environment, littoral zone extends from the highest tidal point to the permanently submerged coastal area. Water height in littoral zone gives many unique characteristic. The erosive power of water current results in unique landform, such as estuaries. Littoral zone also has high variations of plants and animals, because it is the border between land and sea.

In oceanography and marine biology, littoral zone extends to the edge of continental shelf. According to the location, littoral zone is divided into 3 sub-zones:

A. Supralittoral Zone

The area on the border of tides, regularly exposed to saltwater, but not submerged into the water. The water only floods this area during high tides or storms. This zone is dominated by green-blue sea algae, neritidae, and isopod. Some of this are is also covered in mud delivered by the storms.

B. Eulittoral Zone

It is the zone that always exposed to tides regularly, the area is from the highest tide to the lowest tide. In this intertidal zone, there are plenty of edges, inlets, and caves, which are the habitat accomodating sedimentaire organisms. The water is varied from saline water, freshwater from the rain, and dry salts left during low tide. These make the biota in this zone have to adapt well to varied salinity condition.

The temperature is also varied, from very hot during exposed to the sun in summer, to very cold during night time or winter. This zone has very high nutrient contents brought by the waves. The organisms living in this zone are mangroves, kelp, starfish, Littorina snails and other isopods, and mussels.

C. Lower Littoral Zone

This area is located on the lower side of littoral zone, which is almost permanently submerged in water and the environment is not as extreme as eulittoral zone. Brunts of the waves are not big, and there is no extreme temperature changes because this zone rarely get exposed to direct sunrays.

In this zone, we can find various types of biota, such as abalones, anemones,green algae, brown algae, chitons, crabs, hydroids, mussels, sea cucumbers, sea lettuce, sea palms, starfish, sea urchins, prawns, tubeworms, etc. All biota in this area can grow and develop well, because of the stability of the environment and protected from predators (such as fish) because the water is still shallow, and the plants can do photosyntesis effectively due to plenty of sunrays.

D. Sublittoral Zone

The deepest of littoral zone, where the sea bottom is flooded permanently and extended up to the edge of continental shelf, around 200 m depth. According to marine biology, sublittoral zone is an area where sunrays stilll penetrates into seabed, where the water is not too deep and still in photic zone. The benthic area in sublittoral zone is more stable than then eulittoral zone, with constant temperature, water pressure and sun rays. More corals live in this zone than in eulittoral zone.

2. Bathyal Zone

Bathyal Zone is a dim-light water zone, usually around 200-1000 m  depth. The condition of bathyal zone is usually steep slopes which form the wall of deep sea, and also as a part of continental slope. The biota that live in benthic zone are sponges, brachiopods, starfish, echinoids, and other sediment-feeder organisms.

Usually, biota that live in this zone has slow metabolism because they need to preserve energy in an environment with minimal nutrition. Except in very deep sea, bathyal zone can extend into seabed of continental slope, which can vary from 1000 – 4000 m depth.

3. Abyssal Zone

Abyssal Zone extends from the edge of continental shelf up to the deepest seabed in the ocean. Most of abyssal environments are similar to muddy material. The seabed consists of chalk sediment (mostly from foraminifera), silica sediment (mostly from shells of diatoms) and red clay from the deeper seabed with very high pressure that makes other substances can dillute easily. 82% of abyssal zone has the depth of 2000 – 6000 m with stable temperature, between 40C – 1,20C.

4. Hadal Zone

Hadal zone is the deepest zone in the ocean, more than 6000 m deep. This zone is included to aphotic zone, because there is no light at all. The substances are usually calcium carbonate and the remaining of microscopic materials or organisms which have been dead and drown into the seabed. The salinity is similar with abyssal zone. Water pressure is even higher, so the animals that live here need to evolve their morphology, anatomy and physiology to adapt with the harsh condition.

Hadal zone also has natural geothermal resources, called hydrothermal vents. This is why there still are some organisms that can live in such extreme environment, with minimal oxygen, very high pressure  and no light. Organisms that live in this zone are holothurian fish, polychaetes, isopods, actinians, amphipods, and gastropods. Those organisms are predicted to come from abyssal zone. Those organisms mostly get their nutrition with the help of Chemosynthetic bacteria that decompose carcasses of dead biota from upper layer.

Pollution in Ocean Environment

Pollution is the entry process of substances or energy into environment directly by human activities that results in adverse effects which at the end will harm human, ruin natural environment (natural resources) and ecosystem, and reduce proper coziness and utilization of an environmental system.

Human activities that can pollute the ocean environment are:

  1. Pollution from Sailing Activities

The pollution is caused by normal operating activities of the ships; fuel leaks from engines installation, pipes, tanks, other spills, or washing remainings which are mixed with water and become oily waste. Pollution can also happen from shipwreck, because of the spills of oil cargoes, toxic liquid material payloads as a result of shipwreck like collision, stranded, fire, etc.

  1. Ocean Pollution from Off-shore Oil Mining

Pollution from off-shore oil mining is caused by waste and leakage of drilling mud, sediment oil, and leakage during exploitation and during transport operation from pavilion to tanker ship.

  1. Pollution from Dumping Activities into The Sea

There is no special rules regarding dumping into the sea, so there are still many illegal dumping activities in the sea and beach. The more industrial activities, the more industrial waste dumped into the sea.

  1. Pollution from Throwing Garbage into The Sea

Many people still don’t have concern about ocean environment, and sometimes they really do not care at all. They throw garbages like papers, rubbers, and plastics into the sea. These waste, especially plastics, can be dangerous to fish and sea turtles that mistake them from foods. Moreover, plastics can cover corals, preventing them to do photosynthesis properly thus killing the corals.

Pollution of ocean environment will give negative impact to human. A century ago, the oceans were very productive. Fish supply is still abundant, where fish schools made the sea look darker. With more industries, more pollution, and more fishings, fish supply is very much decreasing.

Ocean Environment Conservation

There is an international law which gives the basis of regulating ocean area. The name is UNCLOS (United Nations Convention on the Law of the Sea) 1982. The convention gave consequences to many countries to exercise the rights and obligations of each country to regulate the conservation of the sea/ocean environment. The conservation is very much needed, so there will be no degradation of environment in next generations.

Regulation of the importance of protection and conservation of ocean environment can be found in UNCLOS 1982 Part XII about “Protection and Preservation of the Marine Environment”. However, UNCLOS 1982 does not give any definition of ocean environment; it only gives definition of pollution of ocean environment.

In the convention, it is said that ‘States have the obligation to protect and preserve the marine environment”, which means every country has the obligation of protecting and conservating ocean environment. The convention also said that every country has the rights of exploiting their natural resources according to their own environmental policy, and according to their obligations to protect and conservating ocean environment.

Associated with prevention and control of pollution in ocean environment, every country is asked to take appropriate measures to prevent pollution as a result of management and utilization of ocean area.

Mystery of The Ocean Environment

71 % of the earth surface are oceans, and 97 % of all water in the earth with the total volume more than 1 billion km3 is saltwater.  The biodiversity in the sea is much more diversed than in the lands. Marine organisms with various morphology and sizes, from one cell to the biggest animal in the world (blue whale), live in all part of the sea, in all geographic areas, from equator to the poles. The dispersing of various lives in the sea is influenced by environmental condition.

Most of the ocean areas are still unexplored and unknown. Total of ocean areas which are reachable by diving is less than 1%, and 88% of the oceans have the depth of more than 1000 m. Most of the ocean areas are dark and cold, which hides the biggest mountain range on earth with the summits taller than Mount Everest. The marine scientists who explore the depth of the ocean can be aligned with the astronauts who explorethe moon.

See also: Ocean Pollution

Oceans are the blessings that provide resources with the value of hunderds billions dollars every year, which become the main protein resources for millions of people. Therefore, as younger generation, we should start conservation of the ocean environment, starting from ourselves, by stopping to throw the garbage into the sea.

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