Acidification of oceans may contribute to global declines of shellfish

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. … 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. … In their experiments with the Northern quahog, Mercenaria mercenaria, and the Atlantic bay scallop, Argopecten irradians, the scientists introduced different levels of CO2 gas to filtered seawater taken from Shinnecock Bay, NY, USA. Shellfish larvae grown under near preindustrial levels of CO2 (250 ppm) displayed the highest rates of metamorphosis, growth, and survival, they found. Those grown under higher levels developed thinner shells. The high CO2 “severely altered the development of the hinge structure of early stage bivalves. As CO2 levels increased from approximately 250 to 1,500 ppm, there were dramatic declines in the size, integrity, and connectedness of the hinge.” That can impact the ability of the shellfish to feed, they wrote. This research was conducted on the Southampton campus of Stony Brook. “Our findings regarding the effects of future CO2 levels on larval shellfish are consistent with recent investigations of ocean acidification demonstrating that calcifying organisms will experience declines in survival and growth, as well as malformed CaCO3 shells and hard parts,” they wrote. …