Multidisciplinary field campaigns were carried out in the Fram Strait region during late summer 2019 (JR18007, 04/08/2019 to 28/08/2019) aboard RRS James Clark Ross. A motion-compensated Bongo net fitted with 200 um mesh was deployed at all locations to a maximum depth of 200 m or to within 10 m of the seabed.In the Arctic and sub-Arctic sectors adjacent to the Atlantic, three species of Calanus co-occur. However, their respective core distributions align with different water masses, with Calanus hyperboreus being a high-Arctic oceanic species, C. glacialis being associated with Arctic shelf waters, and C. finmarchicus dominating inflowing Atlantic Water.The proportions of these three species in each deployment was established through molecular analysis of the paired ethanol preserved sample. Subsamples of the ethanol sample were analysed using a 16S ribosomal RNA gene barcode (16SAR, 16SB2R primers) following an adapted protocol. Amplified DNA was sequenced using llumina high-throughput sequencing (HTS) platform. Resultant sequences processed through the Qiime pipeline, clustered into Operational Taxonomic Units at 97% homology and taxonomy was assigned using BLASTn (NCBI).

Funded by UKRI Natural Environment Research Council (NERC; NE/P006213/1, NE/P006353/1, NE/P006302/1, NE/ P005985/1 amongst others).