Rising Acidity Levels Will Change Ocean Ecosystems

Steadily increasing levels of seawater acidity could re-shape strategic food chains in the polar and sub-Antarctic marine ecosystems earlier than predicted, according to research published in Nature.

 “Within 50 to 100 years, there could be severe consequences for marine calcifying organisms, which build their external skeletal material out of calcium carbonate, the basic building block of limestone,” says Australian scientist, Dr Richard Matear of the Commonwealth Scientific and Industrial Research Organisation (CSIRO). 

“Because these organisms provide essential food and habitat to others, their demise could affect entire ocean ecosystems,” he says. Species most threatened are cold-water calcifying organisms, including sea urchins, cold-water corals, coralline algae, and plankton known as pteropods— winged snails that drift through surface waters. 

Carbon dioxide, considered the primary source of greenhouse warming, promotes acidity and affects the concentration of calcium carbonate. 

The Southern Ocean is recognised as a ‘sink’ – where more carbon dioxide is absorbed into the ocean than anywhere else. The oceans absorb about one third of carbon dioxide, and since about 1800, nearly 50 per cent of this has been absorbed in the Southern Ocean. 

The process of carbon dioxide uptake or absorption at the ocean surface occurs most effectively in high wind and storm conditions, especially in regions between 45S and 65S. The carbon dioxide is carried by currents and eddies into the interior of the ocean and stored away for hundreds or thousands of years. Until now, recent predictions of future change in surface ocean conditions have been averaged across the globe or specifically in tropical oceans where reef-building corals are abundant. 

—Press Release, CSIRO, September 2005

[From WS November/December 2005]

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