Cyanobacteria of the Subtropical North Atlantic Ocean
Lomas, M.W., Hopkinson, B.M., Losh, J.L., Ryan, D.E., Shi, D.L., Xu, Y. and Morel, F.M.M. 2012. Effect of ocean acidification on cyanobacteria in the subtropical North Atlantic. Aquatic Microbial Ecology 66: 211-222.
Against this backdrop and working on board the RV Atlantic Explorer between July 2009 and April 2010 at the Bermuda Atlantic Time-series Study (BATS) site in the subtropical North Atlantic Ocean about 86 km southeast of Bermuda, Lomas et al. examined the C-fixation responses of natural assemblages of cyanobacteria dominated by Synechococcus and Prochlorococcus and the N2- and C-fixation responses of isolated Trichodesmium colonies to changes in pH/pCO2 conditions between the time of the last glacial minimum (8.4/150 ppm) and projected year 2100 values (7.8/800 ppm). So what did they find?
The seven scientists report that "whole community assemblages dominated by Prochlorococcus and Synechococcus, whether nutrient-replete or P-limited, did not show a clear response of C-fixation rates to changes in pH/pCO2." However, they found that "Fe- and P-replete colonies of Trichodesmium increased N2-fixation rates at pH 7.8 by 54% over ambient pH/pCO2 conditions, while N2-fixation at pH 8.4 was 21% lower than at ambient pH/pCO2." Likewise, they say that C-fixation rates of Trichodesmium "were on average 13% greater at low pH than at ambient pH and 37% greater than at high pH." And they make a point of noting that "these results for natural populations of all three cyanobacteria concur with previous research and suggest that one important response to changes in ocean pH and pCO2 might be an increase in N2 and C fixation by Trichodesmium under nutrient-replete conditions."
Quoting the team of researchers that conducted the study, their results for Trichodesmium, along with the similar results of several other marine scientists, suggest that "ocean acidification would likely result in a positive feedback on the growth and physiology of natural populations, resulting in a positive change in their role in ocean carbon and nitrogen cycles," which is, of course, great news for the biosphere!
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