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 µM, 5.3 µM and 15.9                 µM) under ambient (250 µatm) or acidified (400 µatm) 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 µM to 15.9 µM glucose addition at 250                 µatm pCO2 was eliminated at 400 µatm pCO2. These results suggest that the response                 potential of marine bacteria to DOC input may be altered under acidified                 conditions.