The Great Barrier Reef is in worse shape than suspected thanks to ocean acidification, Mathieu Mongin of Australia’s CSIRO and colleagues estimate February 23 in Nature Communications.
Driven by rising atmospheric carbon dioxide, acidification lowers seawater levels of the mineral aragonite, which corals use to build their exoskeletons. The Great Barrier Reef actually contains 3,581 individual reefs, and a clear picture of aragonite levels across the reefs doesn't exist. Mongin’s team used a combination of carbon, salinity and temperature data at 22 coastal sites from 2010 to 2012 and models of ocean circulation and chemistry from 2010 to 2014 to determine the current state of aragonite levels across the reefs and to predict which reefs might be most at risk.
By their analysis, aragonite levels drop by an estimated 50 percent around individual reefs compared with the open ocean. Those saturation levels are also much more variable across the Great Barrier Reef than previous estimates projected. Northern reef corals probably drive this variability by using up all carbon resources, leaving reefs to the south at greater risk.
More variability doesn’t bode well when they factored in models of climate change over the next century. Even the best possible future carbon emissions scenario may produce significant losses on the Great Barrier Reef, the researchers write.