Description: To extend information about dinoflagellate cysts (dinocysts) and planktonic foraminifera production, succession, excystment and transport in the upper water column, we investigated their fluxes during a 7-day survey in the active upwelling off Cape Blanc (NW Africa) in November 2018 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. Dinoflagellate and planktonic foraminifera associations showed a clear succession. Echinidinium zonneveldiae, Brigantedinium spp., other peridinioids, Echinidinium spp., cysts of Pentapharsodinium dalei and other photosynthetic organic-walled dinocysts” as well as Neogloboquadrina incompta and Globigerinella calida were collected during active upwelling. Lingulodinium machaerophorum was produced during upwelling relaxation and Gymnodiniaceae cysts (G. microreticulatum, G. catenatum) as well as the foraminifera Globigerina bulloides and Orbulina universa were collected during stratified conditions. Apart from enhancing the biological knowledge of these species, our observations will allow more detailed reconstructions of upwelling history in the Cape Blanc region based on sedimentary archives using fossilised dinoflagellate and planktonic foraminifera assemblages.

Description: 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.