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Response of marine bacterioplankton pH homeostasis gene expression to elevated CO2


Bunse, Carina
Lundin, DanielKarlsson, Christofer M. G.Akram, NeelamVila-Costa, MariaPalovaara, J.Svensson, LovisaHolmfeldt, KarinGonzález, José M.Calvo, Eva MaríaPelejero, CarlesMarrasé, CèliaDopson, MarkGasol, Josep M.Pinhassi, Jarone.  Nature Climate Change 6: DOI: 10.1038/NCLIMATE2914 (2016)  DIGITAL.CSIC

Human-induced ocean acidification impacts marine life. Marine bacteria are major drivers of biogeochemical nutrient cycles and energy fluxes1; hence, understanding their performance under projected climate change scenarios is crucial for assessing ecosystem functioning. Whereas genetic and physiological responses of phytoplankton to ocean acidification are being disentangled2–4, corresponding functional responses of bacterioplankton to pH reduction from elevated CO2 are essentially unknown. Here we show, from metatranscriptome analyses of a phytoplankton bloom mesocosmexperiment, that marine bacteria responded to lowered pH by enhancing the expression of genes encoding proton pumps, such as respiration complexes, proteorhodopsin and membrane transporters. Moreover, taxonomic transcript analysis showed that distinct bacterial groups expressed di erent pH homeostasis genes in response to elevated CO2. These responses were substantial for numerous pH homeostasis genes under low-chlorophyll conditions (chlorophyll a<2.5 g l1); however, the changes in gene expression under high-chlorophyll conditions (chlorophyll a>20 g l1) were low. Given that proton expulsion through pH homeostasis mechanisms is energetically costly, these findings suggest that bacterioplankton adaptation to ocean acidification could have long-term e ects on the economy of ocean ecosystems.