The study, recently published in the journal PLOS one, examined the carbon chemistry of waters around the Great Barrier Reef. Led Dr. Sven Uthicke, a senior research scientist at the Australian Institute of Marine Science, researchers discovered that the rate of CO2 absorption has increased in the last 30 years – particularly in inshore waters.
Carbon dioxide and other atmospheric gases are absorbed by the ocean in a process called gas exchange. Today, over 25 percent of the planet’s carbon dioxide is absorbed by the ocean, which has led to the formation of carbonic acid – a weak acid that can nevertheless dissolve calcium carbonate and limestone, the main ingredients in building shells and coral. Present-day emission levels have increased the concentration of carbon dioxide in seawater by 30 percent on average.
In its annual Greenhouse Gas Bulletin, the World Meteorological Organization (WMO) recently announced that the rate of acidification taking place in the world’s oceans is unprecedented in modern history.
“The Greenhouse Gas Bulletin shows that, far from falling, the concentration of carbon dioxide in the atmosphere actually increased last year at the fastest rate for nearly 30 years,” said Michel Jarraud, secretary general of the WMO.
In the GBR study, Uthicke and his team compared waters around the GBR to samples taken thirty years ago and found that, while offshore waters were consistent with average increases in acidification, inshore waters have acidified at two to three times that rate.
This suggests that human activities near the shore are behind the discrepancy and that, lacking the buffering capacity of offshore reefs, inshore reefs are a bellwether for the extremes of pollution and climate change.
“These samples indicated that 30 years ago this trend of inshore waters being more acidic than offshore did not occur,” said Uthicke. “Something has really changed in these 30 years.”