Effect of elevated CO2 on the dynamics of particle-attached and free-living bacterioplankton communities in an Arctic fjord

[摘要] In the frame of the European Project on Ocean Acidification (EPOCA), theresponse of an Arctic pelagic community (<3 mm) to a gradient ofseawater pCO₂ was investigated. For this purpose 9 large-scale in situmesocosms were deployed in Kongsfjorden, Svalbard (78°56.2´ N,11°53.6´ E), in 2010. The present study investigates effects onthe communities of particle-attached (PA; >3 μm) and free-living (FL; < 3μm > 0.2 μm) bacteria byAutomated Ribosomal Intergenic Spacer Analysis (ARISA) in 6 of themesocosms, ranging from 185 to 1050 μatm initial pCO₂, and thesurrounding fjord. ARISA was able to resolve, on average, 27 bacterialband classes per sample and allowed for a detailed investigation of theexplicit richness and diversity. Both, the PA and the FL bacterioplanktoncommunity exhibited a strong temporal development, which was driven mainlyby temperature and phytoplankton development. In response to the breakdownof a picophytoplankton bloom, numbers of ARISA band classes in thePA community were reduced at low and medium CO₂ (~ 185–685 μatm) by about 25%, while they were more or less stable athigh CO₂ (~ 820–1050 μatm). We hypothesise thatenhanced viral lysis and enhanced availability of organic substrates at highCO₂ resulted in a more diverse PA bacterial community in the post-bloomphase. Despite lower cell numbers and extracellular enzyme activities in thepost-bloom phase, bacterial protein production was enhanced in highCO₂ mesocosms, suggesting a positive effect of community richness onthis function and on carbon cycling by bacteria.

[学科分类] 地球化学与岩石