Siliceous micro- and nanoplankton fluxes over the Northwind Ridge and their relationship to environmental conditions in the western Arctic Ocean

Abstract

Siliceous planktons are valuable indicators of the environmental conditions in both modern and past marine settings. However, in contrast to diatoms and radiolarians, other siliceous micro- and nanoplankton in the Arctic Ocean have been rarely explored. In this study, silicoflagellates, endoskeletal dinoflagellate Actiniscus pentasterias and chrysophyte cysts were investigated in one-year mooring sediment trap material (from August 2008 to September 2009) collected in the Northwind Ridge, western Arctic Ocean. The silicoflagellate assemblage was dominated by Stephanocha speculum, accounting for > 71% of the total silicoflagellate composition. While S. speculum was overwhelmingly abundant in summer, S. medianoctisol and S. octonaria were more frequent during winter. The export fluxes of endoskeletal dinoflagellate A. pentasterias did not show clear seasonal pattern except for a peak value in September 2009. We suggest that high flux of A. pentasterias reflects nutrient rich environment at sea ice edge rather than cold under sea ice conditions. High fluxes of chrysophyte cysts were recorded in summer 2009 peaking in late July and early August, ~10 times higher than in summer 2008. Peak of chrysophyte cysts and sea ice melting occurred simultaneously. In addition, observed encystment might be triggered by the population density, hence indicating a favorable environment for phytoplankton blooming. These siliceous micro- and nanoplankton provides information on the modern Arctic Ocean environment but requires further investigations to consolidate knowledge for robust use in paleoceanography.