Summary
Laboratory experiments suggest that decreased ocean carbonate-ion concentrations due to anthropogenic CO2 will result in reduced calcification rates in marine calcareous organisms. Here we use sediment trap and Holocene sediment evidence to show reduced calcification in Southern Ocean planktonic foraminifera since the industrial revolution. Our sediment trap results provide the first field observations for reduced calcification (inferred from planktonic foraminiferal shell weights) in Southern Ocean carbonate organisms and indicate there has been a 38% reduction in calcification, consistent with the impact due to altered ocean chemistry resulting from anthropogenic CO2 storage. Down-core shell weight variations show reduced calcification during glacial-interglacial CO2 increases that are similar to the post-industrial increase. Planktonic foraminifera contribute ~23 – 50 % of the total open-marine carbonate flux in the modern ocean, thus a reduction in the calcification of planktonic foraminifera may imply a corresponding decrease in calcium carbonate export from the surface ocean.