Carbon Dioxide (CO2) Increase Killing Corals
Rising CO2 Levels in the Oceans Cause Corals to Struggle and Die
Nov 23, 2008
A major new investigation by Australian scientists has revealed that acidification of the oceans from CO2 emissions will worsen the impact of the bleaching and death of reef-building organisms expected to occur under global warming.
Professor Ove Hoegh-Guldberg, Director of the University of Queensland’s Centre for Marine Studies and Deputy Director, ARC Centre for Excellence in Coral Reef Studies, said the results of the group’s simulations of global warming and CO2 emissions “were alarming”.
“They clearly suggest that 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.”
Simulating CO2 Emissions And Acidity
The scientists, led by Dr Ken Anthony of the ARC Centre of Excellence for Coral Reef Studies, set up experiments on Heron Island on the Great Barrier Reef in Southeast Queensland, simulating the effects of human-caused CO2 emissions and the resultant warming and acidity of the waters around the reef.
The experiments measured the combined effects of warming, high CO2 and sunlight on reef organisms placed in large aquariums for two to six months.
“We found that the branching corals were very susceptible to the influence of ocean acidification and warming,” Professor Hoegh-Guldberg said.
Both rising temperatures and rising acidity levels had serious effects on the corals.
“While other corals like Porites appeared to be less susceptible, all the corals showed a strong impact of a warm and acidified conditions,” he said.
Acidity, Warming Seas Threaten Coral Reefs’ Survival
Dr Anthony said the group’s analyses of the bleaching, growth and survival of a number of organisms. including corals, indicated that “a number of very important reef builders may be completely lost in the near future.
“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 before year 2050.”
“If CO2 rises above 450 ppm, it will destroy coral dominated reef systems,” Professor Hoegh-Guldberg warned.
“This [level] is one of the lower scenarios predicted by the Intergovernmental Panel on Climate Change. The significance of our most recent paper is that the two factors do not operate on their own, and combined have a much greater impact.
“Basically, corals become much more susceptible to the effects of temperature (bleaching, disease and mortality) when daily experience acidified conditions.”
Loss of Corals Means Loss of Other Reef Dwellers
“Corals are like the trees of rainforest, and provide habitat for as many as a million species of animals, plants and protists,” Professor Hoegh-Guldberg said.
“If you remove the corals from a coral reef, you lose the habitats and homes of these organisms. What happens to the fish that live on coral reefs when coral has been removed, by either mass coral bleaching or predators such as the crown of thorns starfish, is that 50% of the species of fish on coral reefs disappear.
“These fishes require corals for their reproduction, food and shelter. If this is multiplied for all of the other creatures that live on coral reefs, the losses of species from coral reefs is likely to be catastrophic if we go into a warmer and more acidified world.”
"Ocean acidification causes bleaching and productivity loss in coral reef builders" was published in November 11, 2008 Proceedings of the National Academy of Sciences
See also: New Hope for Coral Reefs from Map
Reef Sharks at Risk from Climate Change
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