MEPS 598:49-60 (2018)  -  DOI: https://doi.org/10.3354/meps12632

Baltic Sea diazotrophic cyanobacterium is negatively affected by acidification and warming

Allanah J. Paul1,*, Ulrich Sommer1, Carolin Paul1,2, Ulf Riebesell1

1GEOMAR Helmholtz-Centre for Ocean Research Kiel, Düsternbrooker Weg 20, 24105 Kiel, Germany
2Leibniz Institute for Baltic Sea Research Warnemünde, Seestraße 15, 18119 Rostock, Germany
*Corresponding author:

ABSTRACT: Nitrogen fixation is a key source of nitrogen in the Baltic Sea which counteracts nitrogen loss processes in the deep anoxic basins. Laboratory and field studies have indicated that single-strain nitrogen-fixing (diazotrophic) cyanobacteria from the Baltic Sea are sensitive to ocean acidification and warming, 2 drivers of marked future change in the marine environment. Here, we enclosed a natural plankton community in 12 indoor mesocosms (volume ~1400 l) and manipulated partial pressure of carbon dioxide ( pCO2) in seawater to yield 6 CO2 treatments with 2 different temperature treatments (16.6°C and 22.4°C, pCO2 range = 360-2030 µatm). We followed the filamentous, heterocystous diazotrophic cyanobacteria community (Nostocales, primarily Nodularia spumigena) over 4 wk. Our results indicate that heterocystous diazotrophic cyanobacteria may become less competitive in natural plankton communities under ocean acidification. Elevated CO2 had a negative impact on Nodularia sp. biomass, which was exacerbated by warming. Our results imply that Nodularia sp. may contribute less to new nitrogen inputs in the Baltic Sea in the future.


KEY WORDS: Cyanobacteria · Environmental change · Baltic Sea · Nitrogen fixation · Nodularia spumigena


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Cite this article as: Paul AJ, Sommer U, Paul C, Riebesell U (2018) Baltic Sea diazotrophic cyanobacterium is negatively affected by acidification and warming. Mar Ecol Prog Ser 598:49-60. https://doi.org/10.3354/meps12632

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