Altered oceans: Growing seawater acidity creating a chemical imbalance

By | August 3, 2006

Altered oceans Growing seawater acidity creating a chemical imbalance

As she stared down into a wide-mouthed plastic jar aboard the R/V Discoverer, Victoria Fabry peered into the future. The marine snails she was studying — graceful creatures with wing-like feet that help them glide through the water — had started to dissolve. … The greenhouse gas, [carbon dioxide] best known for accumulating in the atmosphere and heating the planet, is entering the ocean at a rate of nearly 1 million tons per hour — 10 times the natural rate. Scientists report that the seas are more acidic today than they have been in at least 650,000 years. At the current rate of increase, ocean acidity is expected, by the end of this century, to be 2 1/2 times what it was before the Industrial Revolution began 200 years ago. Such a change would devastate many species of fish and other animals that have thrived in chemically stable seawater for millions of years. … Some marine biologists predict that altered acid levels will disrupt fisheries by melting away the bottom rungs of the food chain — tiny planktonic plants and animals that provide the basic nutrition for all living things in the sea. … The oceans have been a natural sponge for carbon dioxide from time immemorial. Especially after calamities such as asteroid strikes, they have acted as a global safety valve, soaking up excess CO2 and preventing catastrophic overheating of the planet. …

When carbon dioxide is added to the ocean gradually, it does little harm. Some of it is taken up during photosynthesis by microscopic plants called phytoplankton. Some of it is used by microorganisms to build shells. After their inhabitants die, the empty shells rain down on the seafloor in a kind of biological snow. The famed white cliffs of Dover are made of this material. Today, however, the addition of carbon dioxide to the seas is anything but gradual. Scientists estimate that nearly 500 billion tons of the gas have been absorbed by the oceans since the start of the Industrial Revolution. That is more than a fourth of all the CO2 that humanity has emitted into the atmosphere. Eventually, 80% of all human-generated carbon dioxide is expected to find its way into the sea. – more

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