AME - Vol. 66 No. 3 - Feature article

At sea ocean acidification experiments show contrasting responses between dominant unicellular and colonial natural cyanobacteria populations. Insets (top to bottom): Synechococcus (epifluorescence microscopy), Prochlorococcus (bright-field microscopy) and Trichodesmium (bright-field microscopy).
Photos: S. Jaeger and M. Lomas.

Lomas MW, Hopkinson BM, Losh JL, Ryan DE, Shi DL, Xu Y, Morel FMM

 

Effect of ocean acidification on cyanobacteria in the subtropical North Atlantic

 

Cyanobacteria contribute significantly to global carbon and nitrogen cycling, particularly in the oligotrophic subtropical and tropical ocean gyres. Colonies of Trichodesmium increased both N2 and carbon fixation rates under projected pH/pCO2 conditions, relative to current conditions. In contrast, whole communities dominated by the single-cell cyanobacteria Prochlorococcus and Synechococcus did not show a response of carbon fixation rates to future pH/pCO2. Time course of carbon fixation responses across pH/pCO2 treatments suggests a rapid acclimation of cellular physiology in Prochlorococcus and Synechococcus that does not happen in Trichodesmium. These results for natural populations of all three cyanobacteria suggest that while Trichodesmium may display a direct response to changes in ocean pH and pCO2, the response of single-cell cyanobacteria will likely be indirect and controlled by the response to other variables such as nutrients.

 

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