Aquatic bacteria withstands predicted acidity changes

Marine bacterial communities are highly resistant to elevated carbon dioxide levels and ocean acidification, a new study has found.

The research, involving the University of Western Australia, the University of Newcastle upon Tyne and the NERC Centre for Hydrology in Wallingford, UK, tested direct bacterial community responses to elevated CO2 in a replicated seawater experiment.

They used six 11,000 litre experimental water enclosures (or mesocosms), three of which were left as ambient controls and three which were enriched with elevated CO2 to replicate projected ocean conditions 100 years from now.

The scientists then sparged the experimental mesocosms with CO2 and established a pH of approximately 7.8, which is 0.3pH lower than present conditions and is the level expected a century from now due to ocean acidification.

Seawater samples were then compared daily over 18 days.

“Specifically, we examined bacterial community turnover, composition, structure and abundance under elevated CO2 and ambient conditions,” UWA Winthrop Professor Andrew Whiteley says.

“It is well established that the release of anthropogenic-derived CO2 into the atmosphere will be mainly absorbed by the oceans, with an associated drop in pH.

“Our results suggest that there are not direct effects on marine bacterial communities and that the bacterial fraction or microbial plankton holds enough flexibility and evolutionary capacity to withstand predicted future changes from elevated CO2 and subsequent ocean acidification.”

Researchers used 16S rRNA terminal restriction fragment length polymorphism (T-RFLP) to infer the richness and relative abundance of the bacteria taxa within each mesocosm.

Distance-decay relationships were also employed to measure bacterial community turnover rates.

Elevated CO2 levels have no effect on bacteria
“We found evidence that species turnover was significantly dampened within the elevated CO2 mesocosms, selecting for a more conserved community composition through time,” W/Prof Whiteley says.

“This gives clear evidence that the bacteria constituted a community resistant to CO2 perturbation, indicating that the elevated CO2 likely had no direct effect upon the mesocosm community.

“The study corroborates the emerging perception that bacteria are able to withstand much environmental change.”

W/Prof Whiteley points out that a century in the future represents millions of bacterial generations, giving bacteria expansive opportunities for evolutionary adaptations.

Researchers say studying marine bacterial communities is vital given their roles in biogeochemical cycles central to the biological chemistry of the earth, and in reprocessing over half of autotrophically fixed oceanic CO2.

They now want to conduct a long-term study in a biological relevant setting and time scale to further confirm their findings.

Rob Payne, Science Network Western Australia, 16 September 2014. Article.

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