Vertical export of marine pelagic protists in an ice-free high-Arctic fjord (Adventfjorden, West Spitsbergen) throughout 2011-2012

The ecosystem role of Arctic microbial communities is still largely unknown. Based on a time-series study at the IsA station (West Spitsbergen), the seasonality and contribution of pelagic protists to the vertical flux was investigated at 7 time points during 2011-2012. The hydrography of this high-Arctic fjord was evaluated to identify impacts on the community composition during the different seasons. Protists (10 µm) were sampled at 4 depths from the water column and from short-time sediment traps, and investigated by 454 next-generation sequencing of the V4 region of the 18S ribosomal DNA. An advective event during winter, exchanging the cold and less saline water mass with warmer and saline Atlantic Water, was potentially responsible for an abrupt shift in the protist composition in March. Small cells (