Ocean acidification shows negligible impacts on high-latitude bacterial community structure in coastal pelagic mesocosms

[摘要] The impact of ocean acidification and carbonation on microbial communitystructure was assessed during a large-scale in situ costal pelagic mesocosmstudy, included as part of the EPOCA 2010 Arctic campaign. The mesocosmexperiment included ambient conditions (fjord) and nine mesocosms withpCO₂ levels ranging from ~145 to ~1420 μatm.Samples for the present study were collected at ten time points (t–1, t1,t5, t7, t12, t14, t18, t22, t26 to t28) in seven treatments(ambient fjord (~145), 2 × ~185, ~270,~685, ~820, ~1050 μatm) and were analysed for"small" and "large" size fraction microbial community composition using16S RNA (ribosomal ribonucleic acid) amplicon sequencing. Thishigh-throughput sequencing analysis produced ~20 000 000 16S rRNA V4reads, which comprised 7000 OTUs. The main variables structuring thesecommunities were sample origins (fjord or mesocosms) and the community sizefraction (small or large size fraction). The community was significantlydifferent between the unenclosed fjord water and enclosed mesocosms (bothcontrol and elevated CO₂ treatments) after nutrients were added to themesocosms, suggesting that the addition of nutrients is the primary driver ofthe change in mesocosm community structure. The relative importance of eachstructuring variable depended greatly on the time at which the community wassampled in relation to the phytoplankton bloom. The sampling strategy ofseparating the small and large size fraction was the second most importantfactor for community structure. When the small and large size fractionbacteria were analysed separately at different time points, the only taxonpCO₂ was found to significantly affect were the Gammaproteobacteriaafter nutrient addition. Finally, pCO₂ treatment was found to besignificantly correlated (non-linear) with 15 rare taxa, most of whichincreased in abundance with higher CO₂.

[学科分类] 地球化学与岩石