Paper Reviewed

Kerfahi, D., Harvey, B.P., Agostini, S., Kon, K., Huang, R., Adams, J.M. and Hall-Spencer, J.M. 2020. Responses of intertidal bacterial biofilm communities to increasing pCO 2 . Marine Biotechnology https://doi.org/10.1007/s10126-020-09958-3.

Writing as background for their work, Kerfahi et al. (2020) note that "bacteria form a major component of biofilm communities" and that they "cycle nutrients and organic matter and can be a major source of primary productivity in the photic zone, providing an important food resource for higher tropic levels." Consequently, they add, "any changes in biofilm microbial diversity and abundance could have important implications for marine ecosystem structure and function." And thus they set out to examine possible impacts of so-called ocean acidification on coastal biofilm bacterial communities growing in situ along a natural seawater pH gradient in the NW Pacific Ocean.

In all, samples were collected from six sites on the south coast of Shikine Island, East of the Izu peninsula, Japan, covering a pH gradient from 7.2 to 8.3. DNA was extracted and examined from the samples to study bacterial community abundance and diversity.

Results of the study revealed that bacterial biodiversity increased as the pCO 2 concentration increased, with the authors noting that "sites with very low seawater pH had more complex networks and higher diversity, which may suggest that these biofilm communities experienced greater environmental heterogeneity." Kerfahi et al. also report that "differences in pCO 2 were associated with differences in relative abundance of the dominant phyla." However, they add that "both taxonomic and functional analysis showed that the same major groups of bacteria (at family and genus levels) remained abundant at the higher pCO 2 levels, suggesting that the primary productivity and nutrient cycling of the system did not fundamentally change."

In light of the above observations, the scientists conclude "overall, we found that bacterial biofilms had considerable resilience to ocean water acidification, retaining high diversity and functional structure, and attained stronger network complexity," which conclusion they say "is a reassuring indicator of stability of their ecosystem functions."