Ocean Acidification

Scientists used to think that the oceans’ absorption of carbon dioxide was a good thing for the environment as it lessens the effects of global warming. However, it has now been shown that by taking up one-third of the carbon dioxide from the atmosphere, the pH level of the oceans is changing and becoming more acidic. In the past 200 years, the oceans have absorbed about 175 billion tons of carbon dioxide. This significant change in the chemistry of the ocean threatens corals and other marine organisms that secrete skeletal structures. This means, that by the end of the century, coral reefs could be totally destroyed.

PH is the measure of a liquids acidity or alkalinity. The lower the pH, the higher its acidity and the higher the number, the more alkaline it is. The pH of the planet’s oceans was stable at between 1000 and 1800 but has dropped since the Industrial Revolution by one-tenth of a unit. By 2100, the ocean’s pH level is expected to drop by another 0.3 units. When carbon dioxide is absorbed by seawater, it forms carbonic acid, which lowers the ocean’s pH. This makes it harder for corals, plankton and tiny marine snails (pteropds) to make their shells and skeletons.

It is easy for scientists to prove ocean acidification using basic chemistry. Global-warming predictions are based on computer models but ocean acidification can be proved in an aquarium. Experiments show that adding carbon dioxide to sea water slows corals’ growth rates and dissolves pteropods’ shells. When corals in aquariums are exposed to the level of carbon dioxide expected by 2050, they grew half as fast as they do now. If you add to acidification the rise in sea temperatures caused by climate change, it is unlikely that corals will survive to the end of the century.

Acid levels in the world’s oceans are increasing due to the increasing amounts of carbon dioxide produced by the burning of fossil fuels by industry and car exhaust fumes. It was originally predicted that acidification would take place over centuries but it is now apparent that it is taking place over decades.

Ecological Impact

Corals and plankton with chalky shells make up about a third of all marine life and are the basis of the marine food change. The loss of these would mean widespread ecological problems. When Carbon Dioxide levels in the atmosphere reach about 500 parts per million these organisms will no longer be able to use calcium to make their skeletons. At the moment Carbon Dioxide levels are 385 ppm, having risen from 305 ppm in 1960.

, 4 October 2009. Full article.

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