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Report on the Health of the World's Oceans (6) - Page 2

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Well-known oscillations and current changes that occur are El Nino, and La Nina. El Nino is characterized by a warming of waters around the equator, while the alternate current, La Nina, is typified by a cooling of waters around the equator. The PDO shift may lead to an increase in La Nina years over El Nino years (22). The effects these oceans currents have on the climate of the land areas is easily observed, but the effects within the ocean itself can be just as dramatic.

El Nino events can lead to ideal conditions for marine disease spread (1), and cause stress that increases the susceptibility of marine animals to disease. In addition to this, widespread coral bleaching (a response to high water temperatures, ending in coral death) is associated with El Nino conditions (4). Without El Nino conditions, but with increasing water temperatures due to climate change, corals are expected to suffer bleaching throughout the tropics (4). The observation of bleaching events can even be a warning that temperatures are rising (4).

A general warming trend of ocean waters (25) and air temperatures has been observed and recorded. There is some controversy and disagreement as to the extent that CO2 and other "greenhouse gasses" have played in the warming trend. There are too many factors involved to make a simple cause and effect relationship between the two. The possibility remains that the increase in CO2 has played a significant role. The ocean acts as a buffer and absorbs CO2 from the atmosphere. The very reactions that occur to absorb the CO2 may cause an increase in the water temperature.

If excess CO2 is causing global warming, it can also cause chemical damage to coral reefs. Coral reefs form through calcification, and this process depends on the concentration of aragonite (35). Increased CO2 has the effect of reducing the concentration of aragonite, and thus reducing the rate at which the corals can calcify (35).

continued next month. . .

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