Antarctic Krill Embryos Severely Affected by Ocean Acidification

Antarctic krill, the key link in the food chain of the Southern Ocean, could face a grave threat should ocean acidification reach high levels in the future, according to a study by the Australian Antarctic Division. Scientists discovered that krill embryos failed to hatch when concentrations of CO2 in seawater reached 2,000 parts per million (ppm), about five times current levels. The world’s oceans are becoming increasingly acidic as human activity pours CO2 into the atmosphere, which is then absorbed by seawater. The Southern Ocean, which surrounds Antarctica, is expected to be severely affected by acidification because cold water more readily takes up CO2. Acidic seawater inhibits the formation of shells of the shrimp-like krill, and Australian scientists discovered that while acidification at current levels (380 ppm) and moderate levels (1,000 ppm) did not adversely affect krill embryos, none of the embryos in an experimental tank survived when concentrations reached 2,000 ppm. CO2 concentrations increase in deeper waters, and carbon dioxide levels at depth could rise to 1,400 ppm by 2100. Antarctic krill are the most important food for the hundreds of millions of penguins, seabirds, seals, and whales in Antarctica and the Southern Ocean.