Images of 36-d-old M. mercenaria grown under different levels of CO2, <250, 390, 750, and 1,500 ppm. (Credit: Image courtesy of Stony Brook University)
ScienceDaily (Sep. 29, 2010) — The acidification of the Earth's oceans due to rising levels of carbon dioxide (CO2) may be contributing to a global decline of clams, scallops and other shellfish by interfering with the development of shellfish larvae, according to two Stony Brook University scientists, whose findings are published online and in the current issue of Proceedings of the National Academy of Sciences (PNAS).
Professor Christopher J. Gobler, Ph.D., and Ph.D. candidate Stephanie C. Talmage of the School of Marine and Atmospheric Sciences at Stony Brook conducted experiments to evaluate the impacts of past, present and future ocean acidification on the larvae of two commercially valuable shellfish: the Northern quahog, or hard clam, and the Atlantic bay scallop. The ability of both to produce shells partly depends on ocean water pH. Previous studies have shown that increases in atmospheric CO2 levels can lower the ocean's pH level, causing it to become more acidic.
"In general, the study of ocean acidification on marine animals is a relatively new field. Ocean acidification has been going on since the dawn of the Industrial Revolution but it has been investigated as a process for less than a decade," Dr. Gobler said. "People have known about rising levels of CO2 and have been talking about that for decades but had originally assumed the oceans would be able to maintain their pH while they were absorbing this CO2." The largest contributor to CO2 in the atmosphere and oceans is the burning of fossil fuels, Dr. Gobler said.
EDIT
The researchers reported that larvae grown at approximately pre-industrial CO2 concentrations of 250 ppm had higher survival rates, grew faster and had thicker and more robust shells than those grown at the modern concentration of about 390 ppm. In addition, larvae that were grown at CO2 concentrations projected to occur later this century developed malformed and eroded shells. The findings may provide insight into future evolutionary pressures of ocean acidification on marine species that form calcium carbonate shells, the authors wrote. "CO2 entering the ocean decreases the availability of carbonate ions (CO3−2) and reduces ocean pH, a process known as ocean acidification," the authors wrote. "These changes in ocean chemistry may have dire consequences for ocean animals that produce hard parts made from calcium carbonate (CaCO3)."
EDIT
http://www.sciencedaily.com/releases/2010/09/100928154754.htm