Risk maps for Antarctic krill under projected Southern Ocean acidification

The embryonic development of Antarctic krill (Euphausia superba) is sensitive to elevated seawater CO₂ levels and successful hatching is impaired at CO₂ levels greater than 1000 μatm. Exposure to elevated CO₂ during the first 3 days of embryonic development significantly retards subsequent development even if the embryos are transferred to seawater with current levels of CO₂. Krill embryos appear more vulnerable to ocean acidification than other pelagic crustaceans such as copepods. pCO₂ in the Southern Ocean are predicted by models to rise to above 1500 μatm in some parts of krill’s depth range by the year 2100 unless emissions are mitigated.  Risk maps, combining modelled hatch rates and the 3-dimensional circumpolar projection of future pCO₂, predict that by 2100 the Weddell Sea and the waters to the east (the Haakon VII Sea) are the highest risk areas for krill embryos.  The entire Southern Ocean south of the Polar Front is predicted to be unsuitable for hatching by the year 2300, which would lead to collapse of the krill population. This is the first report that explores the circumpolar impacts of ocean acidification on krill.