Stanford, CA — Carbon emissions from human activities are not just heating up the globe, they are changing the ocean’s chemistry. This could soon be fatal to coral reefs, which are havens for marine biodiversity and underpin the economies of many coastal communities. Scientists from the Carnegie Institution’s Department of Global Ecology have calculated that if current carbon dioxide emission trends continue, by mid-century 98% of present-day reef habitats will be bathed in water too acidic for reef growth. Among the first victims will be Australia’s Great Barrier Reef, the world’s largest organic structure.
Chemical oceanographers Ken Caldeira and Long Cao are presenting their results in a multi-author paper in the December 14 issue of Science* and at the annual meeting of American Geophysical Union in San Francisco on the same date. The work is based on computer simulations of ocean chemistry under levels of atmospheric CO2 ranging from 280 parts per million (pre-industrial levels) to 5000 ppm. Present levels are 380 ppm and rapidly rising due to accelerating emissions from human activities, primarily the burning of fossil fuels.
“About a third of the carbon dioxide put into the atmosphere is absorbed by the oceans,” says Caldeira, “which helps slow greenhouse warming, but is a major pollutant of the oceans.” The absorbed CO2 produces carbonic acid, the same acid that gives soft drinks their fizz, making certain minerals called carbonate minerals dissolve more readily in seawater. This is especially true for aragonite, the mineral used by corals and many other marine organisms to grow their skeletons.