oa Variations in Pigments, Fatty Acids and Sterols in Arctic Barents Sea Surface Sediments Across Contrasting Sea Ice Extent

Increases in Arctic sea ice extent have been observed over the past decades with warming at the high latitudes especially pronounced, including in the northern Barents Sea. To track variability between years in the timing and extent of ice-out we compared surface sediment pigment, fatty acid and sterol compositions between ice abundant (2017 and 2019) and ice-free (2018) summer sampling seasons across a south to north 30° E gradient. We found total chlorophyll-derived pigments varied predictably across the transect, and were usually markedly higher at station closest to the Polar Front transition. In 2018 which had an unusually low ice-extent and an early ice-out in the northern Barents Sea confirmed by satellite imagery, highest concentrations were present in the northerly station, indicative of increased production from phytoplankton. This trend was mirrored by total fatty acid methyl esters (FAMEs) which in 2018 showed progressive increases from southern to northern stations, with the pattern driven predominantly by short-chain FAMEs which are abundant in phytoplankton. Our findings have consequences for the functioning of the Arctic carbon cycle – if retreat of Arctic sea ice persists and ‘atlantification’ continues, then delivery of phytoplankton bloom-derived carbon to the seafloor could intensify.