Summary
Anthropogenic CO2 added to the atmosphere during and since the industrial revolution is entering the global ocean. Addition of extra (anthropogenic) CO2 to the ocean changes the carbonate chemistry and the pH of the surface ocean, decreasing the concentration of carbonate ions and increasing ocean acidity. The ecological effects of changing ocean carbonate chemistry are uncertain, but are believed to include reductions in the calcification rates of marine organisms such as shelled pteropods. The Southern Ocean contains a disproportionate amount of the oceanic inventory of anthropogenic CO2, making it a biogeochemical harbinger for the impacts of ocean acidification, which may spread throughout the global ocean and might be expected to contain some of the first signals of impacts of increasing atmospheric CO2. Through an in situ sustained monitoring sediment trap deployed at 47°S in the deep (2000 m) Southern Ocean we’ve measured a significant drop in shell weight of a common cold-water Southern Ocean pteropod, Limacina helicina antarctica forma antarctica, of 1.17 ± 0.47 µg yr-1 since 1997/98. With increasing levels of CO2 entering the Southern Ocean the potential for further shell weight loss for this, and other, cold-water marine calcifiers could result in the change of distribution or complete removal of keystone species from the Southern Ocean ecosystem.