Climate change impact on primary production and phytoplankton taxonomy in Western Spitsbergen fjords based on pigments in sediments

Arctic climate changes are of global significance. This work investigates the influence of climate change on primary production and phytoplankton taxonomic composition in the western Spitsbergen fjords over the last century, using pigments in sediments. Nine sediment cores were analysed for chloropigment and carotenoid contents, and the five found to be richest in pigments were dated (Pb-210, Cs-137) and analysed for additional parameters (C-org, N-tot, delta C-13, grain size). The three well-dated cores, representing the last 70-130 y, were selected for tracking primary production and phytoplankton taxonomy changes in the past. The sum of chloropigments-a (Sigma Chlns-a) in the undisturbed sediments is a good marker of primary production in the adjacent Spitsbergen fjord waters. The sum of 19'-hexanoyloxyfucoxanthin and 19'-hexanoyloxy-4-ketofucoxanthin to diatoxanthin ratio (Sigma Hexcs/Diato) in sediments is proposed as a proxy of changes in haptophytes to diatom and dinoflagellate proportions, connected with climate variability. Sigma Chlns-a and Sigma Hexcs/Diato ratio sediment profiles have shown that the impact of global warming on primary production and phytoplankton taxonomic composition is observed even in the north of Spitsbergen. In the most northern studied site, Raudfjorden, visible effects of warming started about a decade later than in Kongsfjorden. Recent high primary production in Kongsfjorden and Raudfjorden is related to a high proportion of haptophytes compared to diatoms and dinoflagellates, linked to warm Atlantic Water inflow. In Hornsund, primary production was also observed to have increased, but not as rapidly as at other sites, probably due to a greater influence of cold Arctic Water.