Wednesday, October 13, 2010

High concentrations of carbon dioxide lead to decline of shellfish, study says

It is perhaps a well-established fact that the release of carbon dioxide into the atmosphere as a result of man's combustion of fossil fuels has led to negatively affect the environment we live and rely on today. However, not only does this release of excess chemicals affect our lives as humans, it has also been found to affect the world's oceans. The higher concentration of carbon dioxide has led to an increase in the chemical acidity of the water in the oceans, and therefore affects the marine life that inhabits them. A study done by researchers Stephanie Talmage and Christopher Gobler at the School of Marine and Atmospheric Sciences at Stony Brook University in New York has found that the increase of carbon dioxide concentrations in the oceans is affecting the development and lives of marine animals that rely on calcification to produce shells to protect themselves. The study focused on larval shellfish. The shellfish rely on calcium carbonate in order to make strong, protective shells; however, with the higher acidity in the oceans it is more difficult for the shellfish to calcify and make stronger shells. This is because with more carbon dioxide in the ocean, there are less carbonate ions available. The study was published in the Proceedings of the National Academy of Sciences, a well-established and peer-reviewed scientific journal.

The study involved the examination of two bivalve shellfish: the Northern quahog and the bay scallop. These shellfish, which have two shells that are attached by a muscular hinge, are commercially valuable resources on our planet. The United States' mollusk harvests make a profit of about 750 million dollar each year. These shellfish are also ecologically important, as they are a key component of the ecological framework of our oceans. During the experiments in the study, the shellfish were exposed to different concentrations of carbon dioxide. They were exposed to pre-industrial concentrations of about 250 parts per million, modern-day concentrations of about 390 parts per million, and the predicted future concentration in the year 2250 of about 1500 parts per million. The carbon dioxide was delivered using a gas proportionator system. This is a precise system which delivered a mixture of carbon dioxide, low carbon dioxide gas, and pressurized air at multiple rates into identical beakers of seawater treatments that contained the shellfish. The levels of carbon dioxide were closely monitored using this system and the metamorphosis, growth, and survival of the shellfish were observed.

The results of the study found that the Northern quahog shellfish and the bay scallop were affected very similarly by the concentrations of gas in the seawater. Those larvae that were grown under the pre-industrial concentrations of the carbon dioxide had a higher rate of metamorphosis, growth, and survival than those who were exposed to the present-day concentrations. After thirty-six days, forty percent of the pre-industrial concentration exposures survived, while only twenty percent of the modern-day concentration exposures survived. Those that were exposed to the predicted concentration of carbon dioxide in the year 2250 showed weaker, thinner shells than the other shellfish and only six percent survived after thirty-six days.

The study concludes that the carbon dioxide is negatively affecting the survival of these shellfish, and that their work is also consistent with other studies involving marine life that rely on creating shells to protect their soft, vulnerable internal organs and also to protect themselves from predators. Such marine life includes larval oysters, where it was shown that the oysters had larger, stronger shells at lower carbon dioxide concentrations. The study makes it clear that not only is our air affected by our combustion of fossil fuels, but our oceans are affected also. Without reducing the amount of carbon dioxide we release into the atmosphere, it could mean the decline of certain populations of marine life.

A bay scallop.

Works Cited

Gobler, Christopher J. and Talmage, Stephanie C. “Effects of past, present, and future ocean carbon dioxide concentrations on the growth and survival
of larval shellfish.” Proceedings of the National Academy of Sciences (2010): p. 17246-17251. Web. 5 Oct. 2010.

Link to the article:

- Alison Conrad, Student # 0704294

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