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Atlantic Coccolithophores Thrive as the Air's CO2 Content Rises

Paper Reviewed
Rivero-Calle, S., Gnanadesikan, A., Del Castillo, C.E., Balch, W.M. and Guikema, S.D. 2015. Multidecadal increase in North Atlantic coccolithophores and the potential role of rising CO2. Science 350: 1533-1537.

As anthropogenic CO2 emissions continue to rise, Rivero-Calle et al. (2015) note that oceanic calcifiers "generally are expected to be negatively affected." However, they say that "using data from the Continuous Plankton Recorder," they showed that the abundance of coccolithophores (one-celled marine plants that live in large numbers throughout the upper layers of the ocean) in the North Atlantic "increased from ~2% to more than 20% from 1965 through 2010." And being curious about this phenomenon, they report how they used various models to examine more than 20 possible environmental drivers of this change, finding that CO2 and the Atlantic Multidecadal Oscillation were the best predictors."

This finding led them to further think that the rising CO2 content of Earth's atmosphere might have been what had promoted the coccolithophores' accelerating growth rate over the past half century. And in concluding their paper, the five U.S. researchers state that their study does indeed show (1) "a long-term basin-scale increase in coccolithophores" (see figure below) and that this finding does indeed suggest that (2) "increasing CO2 and temperature have accelerated the growth of a phytoplankton group that is important for carbon cycling," while further noting that (3) "a compilation of 41 independent laboratory studies supports our hypothesis."

Top Panel: Annual basin-averaged coccolithophore probability in CPR samples (sum of samples with coccolithophore records per year/total number of samples per year x 100). Bottom Panel: Global atmospheric CO2 measured from Mauna Loa. Adapted from Rivero-Calle et al. (2015).

Posted 22 April 2016