In the Baltic Sea the pelagic biodiversity is low due to factors such as salinity stress and, thus, particularly sensitive to anthropogenic impacts. Yet, the consequences of SOX and NOX emissions for marine primary production, a supportive ecosystem service, have not been studied. We want to assess the consequences of different regulatory regimes for the base of the marine food web as represented by the pelagic microbial ecosystem (nanoflagellates, bacteria, phytoplankton, protozoa). The effects of diluted neutralised seawater scrubbing discharge (SWS) water will be tested on model pelagic microbial communities from the Baltic Proper. The experimental work will mostly be carried out at Askö field station, providing water at salinity representative of the Baltic Proper.

The effects of SWS water will be tested in dilution series corresponding to 3 concentration levels plus control. In the figure below we show an overview of experimental design for the model ecosystem and key variables for each component of the pelagic target community. (1) heterotrophic nanoflagellates, (2) heterotrophic bacteria, (3) autotrophic (mixotrophic) microalgae and cyanobacteria, and (4) protozoa. Effects on higher trophic levels will be tested indirectly through changes in food quality of the microbial community (e.g. fatty acid composition and stoichiometry). Different levels of acidification through SOX and NOX (A, B, C) will be established through dialogue with the reference group.