Water And Oceanography

What Dictates what can Live in the Ocean



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The ocean is filled with a variety of life. People are learning more and more about the Earth's great oceans as they are able to reach depths that were never possible before.  They are finding life where they did not believe life was possible. The ocean offers a variety of different zones where life can exist. There are several factors that can limit where life exists in different ocean zones.

The first limiting factor is the presence of light. Sunlight is essential to aquatic life because plants are necessary for many aquatic food chains.  Plants in the ocean are similar to land plants.  They form the base of food chains.   Sunlight is required for plants to run photosynthesis. As sunlight hits the surface of the ocean it is split into the different colors of the mass spectrum. In more shallow regions of the ocean, green plants are able to absorb a great deal of the mass spectrum and thrive. The deeper down that plants live, the less light they will receive.  Surprisingly, many plants can still survive at great depths.  They have evolved to absorb parts of the spectrum of light that still reaches that far down. An example is red algae. It has a special pigment called phycobillins, that can absorb the portions of light for energy production that other plants cannot.  

Another limiting factor to aquatic life is pressure. A good majority of the deep ocean of the Earth has pressure that ranges from 3,000 to 9,000 per square inch of pressure. This pressure will severely limit the life that can exist at great ocean depths. The body structure and breathing apparatuses of organisms that live at these depths must be well adapted to holding up under extraordinary pressure. Oddly, there are some very unusual creatures and plants that have adapted to life under these pressure conditions.  

Finally, the ocean is quite cold. A large majority of the deep ocean is only a few degrees above freezing.  Plants and animals must be able to survive in an environment that is consistently cold. This means they must have a means for generating heat.  These organisms must also be able to survive on food that is available to them because at that depth and temperature there is not a great abundance of food available.  The majority of the organisms found at this depth are bottom feeders that will live off of the debris that falls to the ocean floor each day.

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