Climate change effects on plankton communities in the Baltic Sea: A Mesocosm Experiment

Abstract

The study focussed on analysing potential impacts of climate change on plankton communities in the Baltic Sea. Phytoplankton being the primary producers in the marine trophic system, and zooplankton being the trophic link to higher levels of the food web, have critical functional roles. Shifts in their communities could potentially have significant impacts in the ecosystem and even ecosystem services. For this study, a five-week indoor mesocosm experiment was set up to simulate projected warming and changing salinities in the Baltic Sea. Freshwater and seawater were collected and mixed in 600 L containers and were subjected to two temperature scenarios (18˚C and 21˚C) at different salinity levels to represent climate change effects. My results show that temperature had a significant relationship with fluorescence (proxy for phytoplankton biomass) and with zooplankton species richness. Specifically, diatom groups such as Navicula sp. and Thalassiosira sp. as well as cyanobacteria Anabaena sp. (now known as Dolichospermum sp.), and Merismopedia sp. were found to have significant relationship with salinity. In addition, the presence of Vorticella sp. was observed in all warm treatments. Overall, the experiment concludes that plankton community shifts are driven by abiotic factors such as temperature and salinity in line with climate change effects. For the Baltic Sea, results showed that Keratella sp. have high adaptability and can thrive wider range of salinity and temperature scenarios while Anabaena sp. can benefit from the slow freshening of the Baltic Sea.