Ocean acidification and Antarctic shellfish
Experiments on Antarctic shellfish at NIWA are revealing the potential effects of ocean acidification on fragile marine ecosystems.
Acidification of the world’s oceans from rising carbon dioxide levels in the atmosphere reduces the amount of calcium carbonate in seawater, a compound some marine organisms use to build shells and skeletons. It may even dissolve calcium carbonate structures. Effects on key species have the potential to alter entire ecosystems.
The cold waters of the Antarctic and Arctic naturally contain less calcium carbonate than waters elsewhere and are expected to suffer the effects of acidification decades before the rest of the world. Southern Ocean waters are predicted to reach levels of acidity that would hinder formation of calcium carbonate shells and skeletons as early as 2030.
The repercussions for Antarctic benthic organisms are currently unknown, but could be profound. “It’s already a tough world down there, and it might be difficult for them to adapt to such an environmental change,” says NIWA ecologist Vonda Cummings.
Dr Cummings is leading acidification experiments on key shellfish species as part of a larger project (IceCUBE) investigating the likely impacts of environmental change on coastal ecosystems in the Ross Sea. Her research team collected about 250 live Antarctic shellfish from McMurdo Sound and brought them back to Wellington. They used a purpose-built experimental facility at NIWA’s Mahanga Bay site to test effects of different pH levels on shellfish growth and condition at temperatures typical of McMurdo Sound.
Results so far show that Antarctic geoducs (pronounced ‘gooey ducks’), a key shellfish species in coastal Antarctic ecosystems, are negatively affected by acidity levels predicted to occur in Antarctic waters in the next 30-50 years. Specifically, physiological condition indices indicated more shell dissolution and/or reduced calcification rates, and higher stress levels, than geoducs in water at normal pH. Experiments on Antarctic scallops – another key species in Antarctic seafloor ecosystems – have just been completed.
Final results will be interpreted in the light of the important functional role role that these species play in the Ross Sea coastal ecosystems, as identified in earlier IceCUBE research.
This research was funded by special International Polar Year funding administered by the Foundation for Research, Science & Technology. NIWA will conduct similar experiments on paua and cockles later this year, funded by the Ministry of Fisheries.