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Biogeosciences An interactive open-access journal of the European Geosciences Union
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https://doi.org/10.5194/bg-2016-383
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
https://doi.org/10.5194/bg-2016-383
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Submitted as: research article 04 Oct 2016

Submitted as: research article | 04 Oct 2016

Review status
This discussion paper is a preprint. It has been under review for the journal Biogeosciences (BG). The manuscript was not accepted for further review after discussion.

Climate-driven change in a Baltic Sea summer microplanktonic community – desalination play a more important role than ocean acidification

Angela Wulff1, Maria Karlberg1, Malin Olofsson2, Anders Torstensson1,a, Lasse Riemann3, Franciska Steinhoff1, Malin Mohlin4, Nina Ekstrand2, and Melissa Chierici2 Angela Wulff et al.
  • 1Department of Biological and Environmental Sciences, University of Gothenburg, Box 461, SE 405 30 Göteborg, Sweden
  • 2Department of Marine Sciences, University of Gothenburg, Box 46 0 , SE 405 30 Göteborg, Sweden
  • 3Department of Biology, Marine Biological Section, University of Copenhagen, Strandpromenaden 5, DK - 3000 Helsingør, Denmark
  • 4Swedish Meteorological and Hydrological Institute, Sven Källfelts gata 15, SE 426 71 Västra Frölunda, Sweden
  • anow at: School of Oceanography, University of Washington, Box 357940, Seattle, WA 98195, USA

Abstract. Scenario modeling suggests that the Baltic Sea, one of the largest brackish-water bodies in the world, could expect increased precipitation (decreased salinity) and increased concentration of atmospheric CO2 over the next 100 years. These changes are expected to affect the microplanktonic food web, and thereby nutrient and carbon cycling, in a complex and possibly synergistic manner. In the Baltic Proper, the extensive summer blooms dominated by the filamentous cyanobacteria Aphanizomenon sp., Dolichospermum sp. and the toxic Nodularia spumigena, contribute up to 30 % of the yearly new nitrogen and carbon exported to the sediment. In a 12 days outdoor microcosm experiment, we tested the combined effects of decreased salinity (from 6 to 3) and increased CO2 concentrations (380 and 960 µatm) on a natural summer microplanktonic community, focusing on diazotrophic filamentous cyanobacteria. Based on our results, the most important factor was salinity, and pCO2 showed only minor effects on total biovolumes of phytoplankton and abundances of heterotrophic bacteria. No interaction effects of salinity and pCO2 were found on any of the measured parameters. The biovolume of the toxic N. spumigena was negatively affected by salinity 3, and the treatment with salinity 3 and 960 µatm CO2 resulted in increased biomass of the presumably non-toxic Dolichospermum sp. Biovolumes of ciliates, diatoms and dinoflagellates were lower in salinity 3. Thus, the lower salinity seemed more important than increased pCO2, and considering the Baltic Proper, we do not expect any dramatic effects of increased pCO2 in combination with decreased salinity on the microplanktonic food web. We believe that our study can add one piece to the complicated puzzle to reveal the combined effects of increased pCO2 and reduced salinity levels on the Baltic microplanktonic community.

Angela Wulff et al.
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AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
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Interactive discussion
Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version Supplement - Supplement
Angela Wulff et al.
Angela Wulff et al.
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Short summary
The Baltic Sea could expect increased precipitation (lower salinity) and increased concentration of atmospheric CO2 over the next 100 years. In a 12-day outdoor experiment, we tested the combined effects of lower salinity and increased CO2 concentrations on a natural summer microplanktonic community. Lower salinity seemed more important than increased pCO2. Thus, we do not expect any dramatic effects of increased pCO2 in combination with decreased salinity on the Baltic microplanktonic food web.
The Baltic Sea could expect increased precipitation (lower salinity) and increased concentration...
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