Pyrosequencing reveals effect of increased pCO2 on bacterial assemblage shifts in response to glucose addition in Fram Strait seawater mesocosms

Ocean acidification (OA) may stimulate primary production through
increased availability of inorganic carbon in the photic zone, which may in turn
change the biogenic flux of dissolved organic carbon (DOC) and the growth potential
of heterotrophic bacteria. In order to investigate the effects of OA on marine
bacterial assemblages, a two-by-three factorial mescosom experiment was conducted
using surface seawater from the East Greenland Current in Fram Strait.
Pyrosequencing of the V1-V2 region of bacterial 16S ribosomal RNA genes was used to
investigate differences in the endpoint (Day 9) composition of bacterial assemblages
in mineral nutrient-replete mesocosms amended with glucose (0 M, 5.3 M and 15.9
M) under ambient (250 atm) or acidified (400 atm) partial pressure of CO2 (pCO2).
All mesocosms showed low richness and evenness by Chao1-estimator and Shannon-Wiener
diversity index, respectively, with general dominance by Gammaproteobacteria and
Flavobacteria. Non-metric multidimensional scaling analysis and two-way analysis of
variance of the Jaccard dissimilarity matrix (97% similarity cut-off) demonstrated
that the significant community shift between 0 M to 15.9 M glucose addition at 250
atm pCO2 was eliminated at 400 atm pCO2. These results suggest that the response
potential of marine bacteria to DOC input may be altered under acidified
conditions.