The effects of elevated carbon dioxide concentrations on the metamorphosis, size, and survival of larval hard clams (Mercenaria mercenaria), bay scallops (Argopecten irradians), and Eastern oysters (Crassostrea virginica)

We present experiments that examined the metamorphosis, growth, and survivorship of larvae from three species of commercially and ecologically valuable shellfish (Mercenaria mercenaria, Argopecten irradians, and Crassostrea virginica) at the levels of CO2 projected to occur during the 21st century and beyond. Under CO2 concentrations estimated to occur later this century (,66 Pa, 650 ppm), M. mercenaria and A. irradians larvae exhibited dramatic declines (.50%) in survivorship as well as significantly delayed metamorphosis and significantly smaller sizes. Although C. virginica larvae also experienced lowered growth and delayed metamorphosis at ,66 Pa CO2, their survival was only diminished at ,152 Pa CO2. The extreme sensitivity of larval stages of shellfish to enhanced levels of CO2 indicates that current and future increases in pelagic CO2 concentrations may deplete or alter the composition of shellfish populations in coastal ecosystems. The combustion of fossil fuels and the resultant increase in atmospheric CO2 during the past century has had a multitude of effects on this planet, including acidification of the world’s oceans. The oceans have absorbed nearly half of the anthropogenically produced CO2 during the past century (Sabine et al. 2004), altering its inorganic carbon chemistry and pH. Model simulations indicate that combustion of the world’s fossil fuel supply in the coming centuries could result in a fivefold increase in atmospheric CO2 levels to nearly 203 Pa (2000 ppm) and a decrease in surface ocean pH by 0.77 units (Caldeira and Wickett 2003). This decline in the pH of surface waters will concurrently reduce carbonate ion (CO 2{ 3 ) concentrations