Deep-sea Ecosystems Affected By Climate Change

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60% of the earth's surface. We understand relatively little about it.

In this cold, dark environment, very little food is available. What food there is takes the form of bits of organic debris drifting down from the sunlit surface waters, thousands of meters above. During its long descent, this organic matter may be eaten, excreted, and decomposed, drastically reducing its nutritive value. It is estimated that less than five percent of the organic matter produced at the surface reaches the abyssal plains.

Research by Smith and his coauthors has shown that the amount of food reaching the deep sea varies dramatically over time. For example, at the Porcupine Abyssal Plain, the amount of organic material sinking from above can vary by almost an order of magnitude from one year to another.

Such variations in food supply have several causes. On a seasonal basis, algal blooms near the sea surface send pulses of organic material to the deep seafloor. Other factors may also come into play, including how much of the algae is eaten by marine animals, and how the material is moved by ocean currents.

The authors point out that global climate change could affect the food supply to the deep sea in many ways. Some relevant ocean processes that may be affected by climate change include wind-driven upwelling, the depth of mixing of the surface waters, and the delivery of nutrients to surface waters via dust storms. Climate-driven changes in these processes are likely to lead to altered year-to-year variation in the amount of organic material reaching the seafloor.

http://www.sciencedaily.com/releases/2009/11/091102171559.htm