Effects of seawater scrubbing on a microplanktonic community during a summer-bloom in the Baltic Sea
Journal article, 2021

The International Maritime Organization (IMO) has gradually applied stricter regulations on the maximum sulphur content permitted in marine fuels and from January 1, 2020, the global fuel sulphur limit was reduced from 3.5% to 0.5%. An attractive option for shipowners is to install exhaust gas cleaning systems, also known as scrubbers, and continue to use high sulphur fuel oil. In the scrubber, the exhausts are led through a fine spray of water, in which sulphur oxides are easily dissolved. The process results in large volumes of acidic discharge water, but while regulations are focused on sulphur oxides removal and acidification, other pollutants e.g. polycyclic aromatic hydrocarbons, metals and nitrogen oxides can be transferred from the exhausts to the washwater and discharged to the marine environment. The aim of the current study was to investigate how different treatments of scrubber discharge water (1, 3 and 10%) affect a natural Baltic Sea summer microplanktonic community. To resolve potential contribution of acidification from the total effect of the scrubber discharge water, “pH controls” were included where the pH of natural sea water was reduced to match the scrubber treatments. Biological effects (e.g. microplankton species composition, biovolume and primary productivity) and chemical parameters (e.g. pH and alkalinity) were monitored and analysed during 14 days of exposure. Significant effects were observed in the 3% scrubber treatment, with more than 20% increase in total biovolume of microplankton compared to the control group, and an even greater effect in the 10% scrubber treatment. Group-specific impacts were recorded where diatoms, flagellates incertae sedis, chlorophytes and ciliates increased in biovolume with increasing concentrations of scrubber water while no effect was recorded for cyanobacteria. In contrast, these effects was not observed in the “pH controls”, a suggestion that other parameters/stressors in the scrubber water were responsible for the observed effects.



Baltic sea

Sulphur oxides



Erik Ytreberg

Chalmers, Mechanics and Maritime Sciences (M2), Maritime Studies

Maria Karlberg

University of Gothenburg

Ida-Maja Hassellöv

Chalmers, Mechanics and Maritime Sciences (M2), Maritime Studies

Mikael Hedblom

University of Gothenburg

Amanda Nylund

Chalmers, Mechanics and Maritime Sciences (M2), Maritime Studies

University of Gothenburg

Kent Salo

Chalmers, Mechanics and Maritime Sciences (M2), Maritime Studies

Henrik Imberg

Chalmers, Mathematical Sciences, Applied Mathematics and Statistics

David R. Turner

University of Gothenburg

Lucy Tripp

University of Gothenburg

Joanne Yong

University of Gothenburg

Angela Wulff

University of Gothenburg

Environmental Pollution

0269-7491 (ISSN) 1873-6424 (eISSN)

Vol. 291 118251

Ecotoxicological effects of seawater scrubbing and its relation to ocean acidification

Formas (210-2012-1298), 2013-01-01 -- 2016-12-31.

Subject Categories

Water Engineering

Oceanography, Hydrology, Water Resources

Environmental Sciences





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