Marine bacterial communities are resistant to elevated carbon dioxide levels.

It is well established that the release of anthropogenic-derived CO2 into the atmosphere will be mainly absorbed by the oceans, with a concomitant drop in pH, a process termed ocean acidification. As such, there is considerable interest in how changes in increased CO2 and lower pH will affect marine biota, such as bacteria, which play central roles in oceanic biogeochemical processes. Set within an ecological framework, we investigated the direct effects of elevated CO2, contrasted with ambient conditions on the resistance and resilience of marine bacterial communities in a replicated temporal seawater mesocosm experiment. The results of the study strongly indicate that marine bacterial communities are highly resistant to the elevated CO2 and lower pH conditions imposed, as demonstrated from measures of turnover using taxa–time relationships and distance–decay relationships. In addition, no significant differences in community abundance, structure or composition were observed. Our results suggest that there are no direct effects on marine bacterial communities and that the bacterial fraction of microbial plankton holds enough flexibility and evolutionary capacity to withstand predicted future changes from elevated CO2 and subsequent ocean acidification.