Mercury accumulation in planktonic food webs from Atlantic and Arctic water masses around Spitsbergen.

Sammendrag

As the global climate change is becoming more evident it is increasingly important to understand more about how these changes might affect the uptake and tropic transfer of contaminants in Arctic food webs. We have studied the accumulation of mercury in planktonic food webs from different water masses around Svalbard, and the goal was to investigate how the trophic transfer of mercury varies between Arctic and Atlantic water. Plankton samples were collected around Spitsbergen in July 2008 at four different localities, two stations in Kongsfjorden, one in Liefdefjorden and onein the Hinlopen strait. To collect only meso- and macro plankton species we used 1000 μm nets (MIK and WP3), and all samples were sorted by species using a stereomicroscope. The dominating plankton groups from which we collected samples are calanoid copepods (Calanus hyperboreus and Calanus glacialis), amphipods (Themisto libellula, Themisto abyssorum and Gammarus wilkitzkii),chaetognats (Sagitta elegans), gastropods (Limacina helicina and Clione limacine) and euphausiids (Thysanoessa inermis). The samples were lyophilized and analyzed for trace elements including totalmercury using a double focusing magnetic sector field high resolution ICP-MS (Element 2, Thermo Scientific). To assess tropic level of the respective species stable carbon and nitrogen isotopes (δ13C and δ15N) were analyzed in subsamples from each station. Preliminary results show large interspecies variation which seems to correlate with the trophic level of the species. We also see some spatial variations regarding the levels of mercury.