Effects of scrubber washwater discharge on microplankton in the Baltic Sea

Abstract In 2020, the global cap of maximum allowable sulphur content in marine fuel will be reduced from the current 3.5% to 0.5%. Another way to reduce the sulphur emissions is to install a seawater scrubberthat cleans exhausts but instead release acidic water containing nutrients and contaminants back to the marine environment. In the current study, scrubberwashwater was tested on a Baltic Sea microplankton community. A significant increase in chlorophyll a , particulate organic phosphorus (POP), carbon (POC) and nitrogen (PON) were observed when the community was exposed to 10% scrubberwashwater for 13 days as compared to the control. A laboratory experiment with the filamentous cyanobacteria Nodulariaspumigena and the chain-forming diatom Melosira cf. arctica showed negative responses in photosynthetic activity (EC10 = 8.6% for N. spumigena ) and increased primary productivity (EC10 = 5.5% for M. cf. arctica ), implying species-specific responses to scrubberwashwater discharge.