Advection of zooplankton in an Arctic fjord (Kongsfjorden, Svalbard)

The aim of this study was to qualify the impact advection has on local populations of planktonic organisms. The study area was Kongsfjorden, an open glacial fjord on the West Coast of Spitsbergen, divided into two basins. On a cruise in May 2001 water masses with different salinity and temperature characteristics were identified from CTD data and sampled for mesozooplankton. Water velocity was measured with a ship-mounted broad band ADCP. Flux of the calanoid copepods Calanus finmarchicus and Calanus glacialis was calculated and based on this advection of zooplankton into the fjord was determined by simulation. The younger copepodite stages were concentrated in surface and subsurface waters and subject to high water velocities. Thus the advective impact on these copepodites was high. Older stages were located deeper in the water column and could maintain their position for a longer time. An eddy was observed in the outer basin and retained zooplankton in the fjord in simulations. The inner basin is likely to be more isolated from the shelf and residence time in this basin is thus probably longer. Calanus finmarchicus was most abundant in the outer basin at the periphery of the eddy and the population in May in Kongsfjorden consisted presumably mainly of individuals advected into the fjord from the surrounding shelf. Calanus glacialis was most abundant in the inner basin and local production there is assumed to exceed advection. Net inflow of zooplankton exceeded outflow during the study period. This impact of zooplankton is probably of high importance for higher trophic levels.