Past and present dinoflagellate cysts from large northern inland seas (Hudson Bay and the Baltic Sea) – implications for primary productivity

Primary producers form the foundation of the food web, transferring energy to higher trophic levels, and serve as key players in carbon and nutrient cycling. Projected changes in climate, ice cover and nutrient input will undoubtedly have an influence on the quantity, quality and seasonal pattern of future primary productivity in northern seas. The overarching objective of the research proposed here is to provide insight into long-term changes in primary productivity in Hudson Bay and the Baltic Sea.

Dinoflagellates are unicellular eukaryotic organisms, a focal group of primary producers of the ocean. During their life cycle ca. 10-20% of dinoflagellate species produce highly resistant resting cysts that deposit in the sediment. The distribution of modern dinoflagellate cysts in marine environments is known to be controlled by water temperature, salinity and the availability of nutrients, and hence fossil cysts can be used to shed light on past environmental conditions. This project will provide systematically collected and documented data on the distribution of dinoflagellate cysts with respect to environmental variables in Hudson Bay and the Baltic Sea, in collaboration with a team of international experts. Dinoflagellate cyst assemblages will be used to reconstruct past trends in productivity in the recent past (ca. 100 years) and during the postglacial time (ca. 10,000 years).

The results of this work will provide sought-after information on the controls of primary productivity in cold-water seas. In particular, the use of multiple time-scales allows untangling the roles of nutrient status and human influence. Moreover, as dinoflagellate cysts have not been systematically studied in Hudson Bay nor in the Baltic Sea, the proposed study will produce important new data. The choice of the study regions allows examining the ecology of dinoflagellate cysts in a large range of salinities and nutrient levels.