Biological Adaptaton Due to Pressure and Light Levels in the Sea

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Biological adaptations to high pressure and low light levels found in deep sea

Living in the deep sea can be highly challenging and has high obstacles that need to be overcome, with a large percent of the worlds sea life living at depths greater than 1km. Two of the biggest problems with living in the deep sea is the high pressure and low light levels that the organisms have had to overcome in order to survive.

Organisms that live in such deep depths have to face the simple fact that light dissipates in the waters and the deeper you go the less light is available for the organisms. Light intensity declines by approximately 2.6 log units in the first 100m but less rapidly below that due to the increased clarity of the water with depth. At approximately 1000m there is no visible light left, it is simply pitch black, and it is the blue wave length that penetrates the furthest while reds penetrate the least. As a result to this, organisms have adapted specific features to overcome these testing conditions and have therefore developed good optical systems despite the fact that they live in complete darkness.

The way some organisms have adapted to the extreme light levels is through developing specialised ear structures called the otoliths. The otoliths allows these deep sea species to hear the environment that surrounds them rather than seeing it(H. Hight, 2009). This structure is found in all fish, however, in some deep sea species it has been found to be much larger than others and as a result it is said to play one the most important roles in helping the organisms to survive in the dark. They use this heightened sense of hearing for hunting, much like bats, by pin pointing where the disturbance in the surrounding water is comin...

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...e form of lipids reserve. lipids provide solutions to membrane fluidity regulation at high pressure. A lipids crystal like state which allows the movement of enzymes and transmembrane proteins is key for heathy membrane function (MacDonald, A.G. 1997). Deep-sea species have a higher degree of fluidity, so that under higher hydrostatic pressure and lower temperature, the membrane fluidity is kept within the optimal range for function. This could be an imperative adaptation to the survival of the deep sea organisms.

References
1. The Biology of the Deep Ocean, P. Herring, Oxford Univ. Press, 2001
2. Deep-Sea Fishes, D.J. Randall & A.P. Farrell, Academic Press, 1997
3. Deep Sea Fish See with Sound, H. Hight, 2009
4. MacDonald, A.G. (1997). Hydrostatic pressure as an environmental factor in life processes. Comparative Biochemistry and Physiology, 116A, 291-297.

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