Study: Man-made ocean acidity threatens sea life

Man-made pollution is acidifying the world’s oceans at unprecedented rates and is threatening sea life, an international team of researchers reports Monday.

Scientists have found that human-caused carbon dioxide emissions, from the burning of fossil fuels in the last 100 to 200 years, have already raised ocean acidity far beyond the range of natural variations. Based on computer modeling and observations, they say these emissions, which increase water acidity by reacting with saltwater, may significantly reduce the calcification rate of marine organisms such as corals and mollusks.

“Our results suggest that severe reductions are likely to occur in coral reef diversity, structural complexity and resilience by the middle of this century,” says co-author Axel Timmermann, a professor at the International Pacific Research Center of the University of Hawaii at Manoa. The study is published in the Jan. 22 online issue of Nature Climate Change.

The team studied the saturation levels of aragonite, a form of calcium carbonate that drops as acidity of seawater rises. It found today’s levels have already dropped five times below the pre-industrial range of natural variability. Given the continued human use of fossil fuels, the scientists say these levels could reduce calcification rates of some marine organisms by more than 40% of their pre-industrial values within 90 years.

“In some regions, the man-made rate of change in ocean acidity since the Industrial Revolution is hundred times greater than the natural rate of change between the Last Glacial Maximum and pre-industrial times,” says co-author Tobias Friedrich, a postdoctoral fellow.

The study says the Hawaiian Islands will be one of the first to feel the impact and that the the Caribbean and the western Equatorial Pacific, both biodiversity hot spots, are also vulnerable. The scientists say some regions, such as the eastern tropical Pacific, will be less stressed, because their greater natural variability in acidity helps to buffer anthropogenic changes.

The study was funded by The Nature Conservancy, the Japan Agency for Marine-Earth Science and Technology and the National Science Foundation.


Wendy Koch, USA today, 23 January 2012. Article.

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