October 28, 2008

Earth’s Reefs In Peril Due To High CO2 Levels

New research in Australia has found disturbing new evidence to show that the world's coral reefs may be in more immediate danger than some experts previously considered.

Australian scientists studied the effects of climate change and rising sea temperatures to find that these events may speed the process of coral bleaching, thus leading to the destruction of the world's reefs.

"Previous predictions of coral bleaching have been far too conservative, because they didn't factor in the effect of acidification on the bleaching process and how the two interact," said Professor Ove Hoegh-Guldberg from the ARC Center of Excellence for Coral Reef Studies and Queensland University.

Man-made sources of CO2 are the primary cause, researchers said, adding that previous studies may have failed to factor human-caused change to the atmosphere.

Scientists erected 30 large aquaria in the waters off Heron Island on the Great Barrier Reef to study the combined effects of ocean warming, acidification due to rising CO2, and sunlight on a large range of reef organisms.

Using CO2 and temperatures predicted for the middle and end of the century, the scientists found ocean acidification from CO2, which reduces coral calcification, had the potential to worsen the impact of bleaching and the death of reef-building organisms.

"We found that coralline algae, which glue the reef together and help coral larvae settle successfully, were highly sensitive to increased CO2. These may die on reefs such as those in the southern Great Barrier Reef (GBR) before year 2050," study leader Ken Anthony said in a statement released on Tuesday.

"These may die on reefs such as those in the southern Great Barrier Reef before year 2050," he added.

The study found that some species of coral were more resistant to the effects of ocean acidification, but when a certain CO2 level is reached, "the coral-algal system crashes and the corals die."

"Every time you start your car or turn on the lights, half the CO2you emit ends up in the oceans, turning them just a tiny bit more acidic, as well as causing the climate to warm. What is new is an understanding of how these two effects interact to affect the corals and reef building algae," Anthony said.

"The implications of this finding are massive as it means that our current bleaching models, which are based on temperature only, severely underestimate the amount of coral bleaching we will see in the future."

"These results highlight the urgency of reducing CO2 emissions globally. Without political will and commitment to abatement, entire reef systems such as the Great Barrier Reef will be severely threatened in coming decades," he added.


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