Coral Reef Corrosion Is Worse Than We Thought

The world's coral reefs may be in even worse danger than we thought.

A new study finds that increased ocean acidity caused by heightened levels of carbon dioxide will have a massive effect on coral reefs. This effect is similar to how slightly higher average temperatures are causing a spike in the number of record high temperatures.

"Our study shows organisms residing on shallow coral reefs and in other shallow marine ecosystems will be exposed to far more extreme and variable acidity in the future than deeper ocean organisms," lead author Dr. Emily Shaw, of the University of New South Wales told Phys Org. "This will be caused by a combination of heightened background carbon dioxide levels and the natural cycles found in shallow ecosystems."

The study pulled observational data on offshore reefs around Lady Elliott Island off the coast of Queensland, Australia and the Great Barrier Reef.

Normally, changes in acidity are largely caused by tides and marine organism that live near the reefs. Carbon dioxide levels are low during the day, when algae photosynthesis converts CO2 to oxygen. These levels rise at night when the algae stop photosynthesis, and marine animals' respiration convert all of that oxygen to CO2. Low tides magnify this shift in CO2 levels, and high tides decrease the changes. The chemical properties of seawater tend to smooth out these shifts, but the ocean cannot compensate for the increasing baseline CO2 levels.

"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 affect that will amplify them considerably more," said Shaw.

The researchers predict that we'll begin to see the damage this increased CO2 will cause. By 2100, they estimate that corrosive conditions for reefs in shallow areas will be a daily occurrence.

If these levels continue, it does not bode well for coral reefs, according to Shaw: "We know that if we continue on our current CO2 emissions trajectory that the ocean will take thousands of years to return to chemical conditions resembling those of today."

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