Counts of dinoflagellate cysts and foraminifera from drifting traps during Maria S. Merian cruise MSM79

During the active upwelling in November 2018 a 7-day drifting trap survey has been performed in an active upwelling cell off Cape Blanc. This survey is performed to extend information about the production, succession and transport of dinoflagellate cysts (dinocysts) and planktonic foraminifera as well as to study the excystment of dinoflagellate cysts in the upper water column. Organic- and calcareous-walled dinoflagellate cysts and planktonic foraminifera have been collected on 7 successive days with drifting traps at 100 m, 200 m, and 400 m water depth. The 7-day survey covered a successive change from active upwelling toward stratified conditions. Highest production of organic dinocysts and planktonic foraminifera were observed under active upwelling conditions and decreased drastically towards the end of the survey. Calcareous dinocysts appeared later during upwelling relaxation. Collected cytoplasm bearing (full) dinocysts and foraminifera were produced in the water column above the traps (<100 m depth). Part of the organic-walled empty dinocysts were resuspended implying that sediments below the survey site are likely to contain both local and allochthonous cyst assemblages. We are the first to show that excystment in the upper water column is species-specific. Brigantedinium excysted in the upper water column before reaching deeper depths whereas no upper water column excystment was observed for the other dinoflagellate species. Both dinoflagellate and planktonic foraminifera associations showed a clear succession from active upwelling conditions towards upwelling relaxation and stratification of the upper water column.