University of Cambridge > > British Antarctic Survey > Antarctic krill: Life is all about balance in a high CO2 world

Antarctic krill: Life is all about balance in a high CO2 world

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Ocean acidification is caused by sequestration of atmospheric CO2 into ocean surface waters, a process that increases ocean pCO2 and decreases ocean pH. Present day levels of atmospheric CO2 have reached 400 ppm, and are predicted to rise as high as 2000 ppm by the year 2300, equating to a decrease in ocean pH of up to 0.7 pH units. Organisms from Polar regions are particularly vulnerable to ocean acidification, due to the increased rate of CO2 sequestration in colder seawater. Antarctic krill were reared for 11 months in a flow-through seawater system at the Australian Antarctic Division’s Krill Aquarium in Tasmania, under five pCO2 levels (400, 1000, 1500, 2000 and 4000 ppm). We examined the effects of increased seawater pCO2 on the lipid and fatty acid composition, respiration rate, growth, mortality, intermoult period, haemolymph pH and maturity of adult Antarctic krill. Haemolymph pH decreased with increasing seawater pCO2 but it appears that krill were compensating for this decrease, possibly through the transport of bicarbonate ions into their extracellular space. Maturation was delayed in krill exposed to CO2 levels of 1500 ppm and above. Seawater pCO2 had no effect on the lipid and fatty acid composition, respiration rate and intermoult period of krill. Our research suggests that the adult life stages of Antarctic krill have the capacity to tolerate levels of near-future acidification, when elevated pCO2 is assessed as a single stressor. However, the energetic costs of maintaining physiological acid-base balance over the long term are unknown, and previous studies have shown that krill eggs and embryos may be vulnerable to pCO2 levels predicted for the year 2100 and beyond.

This talk is part of the British Antarctic Survey series.

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