Great Barrier Reef acidification predictions get worse

Great Barrier Reef Color Map

Over 3,500 reefs make up the Great Barrier Reef. To get a sense of the current impact of ocean acidification across the reefs and its future fallout, researchers combined local data with models of ocean ciruclation and chemistry. 

Tchami/Flickr (CC BY-SA 2.0

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.

To study carbon mineral levels in the Great Barrier Reef, researchers simulated different factors that contribute to those levels. The map above shows changing phytoplankton blooms (green), deep ocean waters (dark blue) and sediments (browns). The team developed a modeling system that provides data on the state of a reef in close to real time. Mathieu Mongin

Helen Thompson is the multimedia editor. She has undergraduate degrees in biology and English from Trinity University and a master’s degree in science writing from Johns Hopkins University.

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