Rising ocean acidity threatens coral diversity

By John von Radowitz

Monday, January 23, 2012

Man-made carbon emissions since the industrial revolution have acidified the oceans far beyond natural levels, research suggests.

Ocean acidity makes it harder for organisms such as molluscs and coral to construct the shells they need to survive.

In some regions, acidity rose faster in the last two centuries than it did in the previous 21,000 years.

Measuring changes in ocean acidity is difficult because it varies naturally between seasons, years and regions.

Direct observations only date back 30 years — not long enough to reveal a meaningful trend.

The new research used simulations of ocean and climate conditions going back 21,000 years to the last glacial maximum and forward in time to the end of the 21st century.

Scientists looked at changes in the saturation level of aragonite, a form of calcium carbonate used to measure acidification.

In many coral reef regions, aragonite saturation is already five times below its lowest pre-industrial range, translating to a decrease in overall calcification rates of shell-forming organisms of 15%, scientists believe.

They fear calcification rates of some organisms could drop by over 40% of pre-industrial levels within the next 90 years.

Prof Axel Timmermann said: "Our results suggest that severe reductions are likely to occur in coral reef diversity, structural complexity and resilience by the middle of this century."

This appeared in the printed version of the Irish Examiner Monday, January 23, 2012