Effect of elevated CO2 on the dynamics of particle-attached and free-living bacterioplankton communities in an Arctic fjord
- 1Alfred-Wegener-Institute, Am Handelshafen 12, 27570 Bremerhaven, Germany
- 2Alfred-Wegener-Institute, Biologische Anstalt Helgoland, Kurpromenade, 27498 Helgoland, Germany
- 3GEOMAR Helmholtz Centre for Ocean Research Kiel, Düsternbrooker Weg 20, 24105 Kiel, Germany
- 4Plymouth Marine Laboratory, Prospect Place, The Hoe, Plymouth, PL1 3DH, UK
- 5Argonne National Laboratory, 9700 South Cass Avenue, Building 202, Argonne, IL 60439, USA
- 6CNRS, UMR7144 & Université Pierre et Marie Curie, Station biologique de Roscoff, Place Georges Tessier, Roscoff, France
Abstract. In the frame of the European Project on Ocean Acidification (EPOCA), the response of an Arctic pelagic community (<3 mm) to a gradient of seawater pCO2 was investigated. For this purpose 9 large-scale in situ mesocosms were deployed in Kongsfjorden, Svalbard (78°56.2´ N, 11°53.6´ E), in 2010. The present study investigates effects on the communities of particle-attached (PA; >3 μm) and free-living (FL; < 3 μm > 0.2 μm) bacteria by Automated Ribosomal Intergenic Spacer Analysis (ARISA) in 6 of the mesocosms, ranging from 185 to 1050 μatm initial pCO2, and the surrounding fjord. ARISA was able to resolve, on average, 27 bacterial band classes per sample and allowed for a detailed investigation of the explicit richness and diversity. Both, the PA and the FL bacterioplankton community exhibited a strong temporal development, which was driven mainly by temperature and phytoplankton development. In response to the breakdown of a picophytoplankton bloom, numbers of ARISA band classes in the PA community were reduced at low and medium CO2 (~ 185–685 μatm) by about 25%, while they were more or less stable at high CO2 (~ 820–1050 μatm). We hypothesise that enhanced viral lysis and enhanced availability of organic substrates at high CO2 resulted in a more diverse PA bacterial community in the post-bloom phase. Despite lower cell numbers and extracellular enzyme activities in the post-bloom phase, bacterial protein production was enhanced in high CO2 mesocosms, suggesting a positive effect of community richness on this function and on carbon cycling by bacteria.