Increased acidity strangling shallow reefs
Sydney: Increasing acidity in oceans, caused by heightened levels of atmospheric carbon dioxide (CO2), may be strangling shallow coral reefs, says a new study.
Just as small increases in global temperature can lead to more extremely hot, record-breaking days, similarly small hikes in overall ocean acidity can cause extreme localised changes in ocean pH (acidity) around shallow coastal reefs and eco-systems.
"Our study shows organisms residing on shallow coral reefs and in other shallow marine eco-systems will be exposed to far more extreme and variable acidity in the future than deeper ocean organisms," said Emily Shaw, from the University of New South Wales (UNSW) Climate Change Research Centre.
"This will be caused by a combination of heightened background carbon dioxide levels and the natural cycles found in shallow eco-systems," said Shaw, according to an UNSW statement.
"If we continue to add carbon dioxide at our current rate the increased background CO2 will not simply add a little to these extreme events but will have a multiplying effect that will amplify them considerably more," added Shaw.
The scientists used observational data from coral communities on the shallow offshore reef around Lady Elliott Island, Great Barrier Reef, as their baseline.
There they looked closely at how certain conditions in concert have a powerful amplifying or diluting impact on CO2 levels at local levels in shallow reefs.
The prime causes of changes in acidity on the reef are through respiration by marine organisms and tides. CO2 levels are lower during the day when photosynthesis of the symbiotic algae in coral takes place and higher at night when respiration occurs.