Summary
Antarctic krill (hereafter krill) is the key species of the Antarctic marine ecosystem as well as a target of commercial fishery in the Southern Ocean, which compels careful predictions about potential impacts of Ocean Acidification (OA) and warming on this species and the associated ecosystem ramifications. Krill lay eggs at the surface that sink 1000 m before hatching; their larvae then actively swim to the surface to feed on phytoplankton thus exposing them to varying levels of CO2. We have modelled future CO2 concentrations in the Southern ocean and have experimentally examined the effects of the predicted CO2 levels on krill early development. Our model projections demonstrate some parts of Southern Ocean pCO2 could rise up to 1400 µatm within krill’s depth range under the IPCC IS92a scenario by the year 2100 (atmospheric pCO2 788 µatm). Our laboratory study reveals krill embryonic development is negatively affected, with its hatch rate rapidly decreasing beyond 1000 µatm and total inhibition at 2000 µatm pCO2. This effect was milder at a higher temperature (at 3.0 degrees C vs 0.5 degrees C). The first 3 days of embryonic development) were more susceptible compared to later embryonic stages. These results indicate a high susceptibility of krill embryos to OA compared to other pelagic crustaceans such as copepods. We are also currently analysing these effects at molecular levels through investigating CO2-related changes in gene expression. We will present a circumpolar potential risk map for krill early development to further understand how the OA might impact future distribution of krill.
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