This research used samples and/or data provided by the Arctic Century Expedition, a joint initiative led by the Swiss Polar Institute (SPI), the Antarctic and Arctic Research Institute (AARI), and GEOMAR Helmholtz Centre for Ocean Research Kiel (GEOMAR), and funded by the Swiss Polar Foundation. GL and ZAK acknowledge that this project has been made possible by a grant from the Swiss Polar Institute, Dr Frederik Paulsen. GPF acknowledges funding from the Academy of Finland (Grant No. 342227). ZAK acknowledges this project has received funding from the Horizon Europe program under Grant Agreement No. 101137680 (Project CERTAINTY), With the institutional support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S), Peer reviewed