Bergen, B., Endres, Sonja , Engel, Anja , Sommer, Ulrich and Jürgens, K. (2015) Effect of acidification and warming on planktonic bacterial communities during two seasonal phytoplankton bloom mesocosms. [Talk] In: ASLO Aquatic Sciences Meeting 2015. , 22.-27.02.2015, Granada, Spain .

Abstract

The effects of temperature and pCO2 on the development of bacterial communities were investigated in mesocosm experiments with Baltic Sea water, during a diatom bloom in autumn and during a cyanobacterial bloom in summer. We measured prokaryotic cell numbers and activity and used 454 pyrosequencing to compare the development of the bacterial community composition (BCC) and to identify the major bacterial taxa. Organic matter dynamics were assessed to differentiate between direct effects and indirect phytoplankton induced effects. The development of BCC followed well-known bloom dynamics. A principle coordinate analysis (PCoA) of bacterial OTUs (operational taxonomic units) revealed that phytoplankton succession and temperature were the major bacterial community structuring variables whereas only a very weak impact of pCO2 was found. This was corroborate by the trends in bacterial bulk parameters. However, significant effects of pCO2 on the relative abundance of individual dominant OTUs occurred. Our results suggest that increasing pCO2 only slightly affects the development of overall bacterial community composition but impacts specific bacterial groups which might influence also particular organic matter degradation processes.

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