Study: Reefs may help in fight against ocean acidity

While many scientists have been warning about potentially dire consequences of the ocean’s increasing acidity, a recent scientific paper suggested that coral reefs — such as those around Bermuda — might actually help offset ocean acidification.

They point out the ocean is the largest natural sink for carbon dioxide (CO2), absorbing one quarter to one third of the CO2 produced by humans. However, as the amount of CO2 in the atmosphere increases, fundamental properties of seawater chemistry are also impacted.

Scientists have projected that waters in the open ocean will experience a decreased pH (the water becomes more acidic), as well as a reduced “aragonite saturation state,” meaning it will be more difficult for corals and other calcifying marine organisms to build their skeletons and shells.

In a recent paper published in Nature Climate Change, a group of researchers from Scripps Institution of Oceanography and the Bermuda Institute of Ocean Sciences (BIOS) present compelling evidence that coral reef ecosystems may, in fact, modify seawater chemistry and help balance — or even counteract — the local impacts of ocean acidification.

Lead author Dr. Andreas Andersson, a chemical oceanographer at Scripps Institution of Oceanography and adjunct faculty at BIOS, said: “Other researchers have shown that different benthic communities can alter the chemistry on the reef, but we’re the first to show it on this scale, the whole ecosystem scale, over five years of observations.”

Using a combination of seawater samples taken from across the Bermuda coral reef platform, time series measurements from the Bermuda Atlantic Time-series Study (BATS) programme, and computer models, the paper’s authors found that naturally occurring reef biogeochemical processes act to modify the seawater pH and aragonite saturation state. The longer the water remains within the reef system (known as ‘residence time’), the more pronounced the offset on pH and aragonite saturation state.

While it’s not known how these results translate to other reefs around the world, Andersson points out that: “Some marine organisms may have ‘tipping points,’ or certain pH thresholds below which they aren’t able to survive. This reef feedback that we observed may buy them some more time.”

Professor Nick Bates, Senior Scientist at BIOS and co-author of the paper, said: “The study also highlights the critically needed value of sustaining observations over time for vulnerable marine ecosystems so that scientists and governments can better prepare strategies and mitigation approaches to cope with serious environmental challenges that are impacting both local and global communities.”

The Royal Gazette, 29 November 2013. Article.

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