High Levels of Carbon Dioxide Threaten Oyster Survival

http://www.sciencedaily.com/releases/2010/08/100805143051.htm

ScienceDaily (Aug. 6, 2010) — It has been widely reported that the build up of carbon dioxide (CO2) in the air, which is caused by human behavior, will likely lead to climate change and have major implications for life on earth. But less focus has been given to global warming's evil twin, ocean acidification, which occurs when CO2 lowers the pH of water bodies, thus making them more acidic. This lesser known phenomenon may have catastrophic effects on all sea life.

Inna Sokolova, associate professor of biology at the University of North Carolina at Charlotte, studies the affect of high carbon dioxide on oyster survival, growth and shell hardness. The results of her research suggest that creatures once thought to be fairly adaptable to changes in the environment, may be in serious trouble.

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The research group monitored oysters that were kept in high CO2 conditions. Juvenile oysters were affected the most by high CO2 conditions. These young oysters grow at a faster rate than the adults and need to use more energy for survival. There was a higher chance that juvenile oysters would die if kept in high CO2. They also had reduced growth of their shells and their soft bodies. The young oysters' shells were also more fragile and prone to breaking, potentially making them more susceptible to predators.

"Living in the high CO2 world may increase the cost of living which cuts into other energy expending pathways," says Sokolova. "Everyday maintenance becomes harder making it harder to live."

The effects on growth were less pronounced in the adult oysters since they don't grow as fast and have slower metabolisms than the juveniles.

The fact that the early life stages are more affected by high CO2, suggests that this may serve as a bottleneck for oyster decline. Sokolova says, "Expect to see huge effects on populations in the future."

The researchers found evidence that the oysters are sensing and trying to offset the affects of a high CO2 environment. The oyster's soft body covering called the mantle had increased expression of carbonic anhydrase, an enzyme that regulates pH and helps make bicarbonate, which is used to make the shell. Sokolova believes that the increased levels of this enzyme show that the oysters are at least trying to compensate for the acidic conditions in response to CO2, but it doesn't seem to be enough.

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