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Marine Ecology Progress Series

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MEPS 453:37-48 (2012)  -  DOI:

Effects of stratification depth and dissolved organic matter on brackish bacterioplankton communities

Lorena M. Grubisic1, Andreas Brutemark2,5, Gesa A. Weyhenmeyer1,3, Johan Wikner4, Ulf Båmstedt4, Stefan Bertilsson1,*

1Department of Ecology and Genetics, Limnology, Uppsala University, 75236 Uppsala, Sweden
2Marine Science Centre, University of Kalmar, 39182 Kalmar, Sweden
3Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences (SLU), 75007 Uppsala, Sweden
4Department of Ecology and Environmental Science, Umeå Marine Sciences Centre, Umeå University, 90187 Umeå, Sweden
5Present address: ARONIA Coastal Zone Research Team, Novia University of Applied Sciences & Åbo Akademi University, 10600 Ekenäs, Finland

ABSTRACT: Bacterioplankton growth is often directly or indirectly controlled by external energy subsidies via organic matter inputs or solar radiation. We carried out a mesocosm experiment to assess how bacterioplankton communities responded to elevated levels of dissolved organic matter (DOM) and experimentally controlled stratification depth. The month-long experiment consisted of 2500 l mesocosms subjected to 4 experimental manipulations in triplicate: the stratification depth was set to either 1.5 or 3.5 m, with or without experimental addition of ambient levels of chromophoric DOM. DOM addition had a significant effect on bacterial community composition as assessed by terminal restriction fragment length polymorphism of amplified 16S rRNA genes. In contrast, there were no effects of the DOM amendment on bacterial biomass or production. Mixing depth and the coupled effective light climate in the photic zone also had a significant effect on bacterial community composition. Furthermore, shallow mixing depth was associated with enhanced primary production, whereas DOM addition had a negative effect on phytoplankton biomass and productivity. Our results suggest that bacterial community composition is coupled to primary production under the studied coastal nutrient regime, and point to a key role of DOM quality in controlling bacterioplankton communities.

KEY WORDS: Bacterial community composition · Dissolved organic matter · Stratification depth · Mesocosm · Brackish · Phytoplankton

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Cite this article as: Grubisic LM, Brutemark A, Weyhenmeyer GA, Wikner J, Båmstedt U, Bertilsson S (2012) Effects of stratification depth and dissolved organic matter on brackish bacterioplankton communities. Mar Ecol Prog Ser 453:37-48.

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