Current climate change predictions indicate global changes in salinity and temperature, with negative implications for the plankton food web, which plays a crucial role in the functioning of marine ecosystems. Current understanding of how salinity change will impact plankton communities has focused mainly on the salinisation of freshwater environments, with little known about changes in marine systems as well as potential synergistic effects with other stressors, such as warming. We investigate the effect of salinity change coupled with warming on plankton community composition under different climate change scenarios of the Baltic Sea. Projections for future salinity change and warming were used to set-up an indoor mesocosm experiment in the Gulf of Finland. We identified plankton communities combining traditional morphology and environmental DNA (eDNA) metabarcoding of the mitochondrial cytochrome oxidase I (COI) and 18S rRNA genes. Our results suggest shifts in plankton community composition is dependent on both salinity and temperature treatments. Additionally, changes in plankton community assemblage in the different mesocosm treatments were more clearly captured by metabarcoding than by morphology-based methods. Our results asses the sensitivity of planktonic community assemblages to variations in seawater salinity and temperature in the Baltic Sea across all trophic levels of the food web. We also highlight the potential of eDNA metabarcoding to monitor plankton community responses to climate change.

Primary Presenter: Clio Hall, University of Helsinki (clio.hall@helsinki.fi)

Authors:

Clio Hall, University of Helsinki  (clio.hall@helsinki.fi)

Oriol Canales, AZTI Basque Research and Technology Alliance  (ocanals@azti.es)

Nicolas Henry, Station Biologique de Roscoff, CNRS & Sorbonne University  (nicolas.henry@cnrs.fr)

Naiara Rodríguez-Ezpeleta, AZTI Basque Research and Technology Alliance  (nrodriguez@azti.es)

Aleksandra Lewandowska, Tvarminne Zoological Station, University of Helsinki  (aleksandra.lewandowska@helsinki.fi)