The increase in anthropogenic atmospheric carbon dioxide (CO2) alters the atmosphere-ocean equilibrium, changes seawater carbonate chemistry and lowers ocean pH. Ocean acidification is a predictable consequence of rising atmospheric CO2, and lower seawater pH and calcium carbonate (CaCO3) saturation in surface waters have significant implications for the marine organisms. Also, long-term exposure to increased pCO2 could have complex effects on the growth and reproductive success of calcareous plankton, with implications for the entire food web.
A number of studies have considered ocean acidification in temperate and tropical regions, but less attention has been paid to the polar oceans. In a recent study, Dr. So Kawaguchi and collaborators constructed risk maps for Antarctic krill under projected Southern Ocean acidification by determining the sensitivity of embryonic development to ocean acidification in laboratory experiments. Their results show a rapid decline of hatching success in seawater CO2 concentrations above 1000 ppm and exposure to high CO2 during the first three days of embryonic development significantly reduces development and hatching rates. Circumpolar risk maps of krill hatching success under projected pCO2 levels at the end of the 2100 and 2300 were determined using the Representative Concentration Pathway (RCP) 8.5 — a high emission scenario, with increasing gas emissions over time leading to high greenhouse gas concentration levels. Krill habitats from the Weddell Sea and Haakon VII Sea were identified as the high-risk areas for krill recruitment at the end of this century. They concluded that if CO2 emissions are not mitigated, the populations of Antarctic krill could collapse by 2300, with major consequences for the whole ecosystem.
S. Kawaguchi, A. Ishida, R. King, B. Raymond, N. Waller, A. Constable, S. Nicol, M. Wakita and A. Ishimatsu (2013) Risk maps for Antarctic krill under projected Southern Ocean acidification. Nature Clim. Change, doi:10.1038/nclimate1937