Is sea ice ridge formation sustaining ice-associated ecosystem activity during Arctic winter?
To investigate the role of sea ice ridging in providing organic matter that can sustain microbial winter activity several DNA samples were taken for the HAVOC project as part of the Multidisciplinary drifting Observatory for the Study of the Arctic Climate (MOSAiC) expedition. This study was done in the Arctic Ocean during leg 2 of MOSAiC, when RV Polarstern was drifting with an ice floe from 86.6 °N, 118.4°E on Dec 13, 2019 to 88.6°N, 61.3°E on Feb 23, 2020 in the eastern Amundsen Basin (Krumpen et al. 2020, Nicolaus et al. 2022). The sampling for the study was performed in the Central Observatory (CO) close to Polarstern, including the on ice oceanography site Ocean City and the MOSAiC sea ice coring site (MCS). A Sea Ice Ridge Observatory (SIRO) was established during leg 2 at a ridge in the CO named Fort Ridge. The ridge keel studied was approximately 100 m long and 20 m wide. DNA was extracted from water samples (250 – 500 mL) from 20 and 1000 m depth (10.02.2020), from a water- filled void inside the ridge (at 204-224 cm below the ice surface; 24.01.2020), a gypsum net tow (08.02.2020) and melted sea ice samples from FYI (ice interior; 03.02.2020), SYI (60-70 cm, 70-80 cm, 80-93 cm; 13.01.2020) and ridge ice above and below the water-filled void (157- 204 cm; 224 -  260 cm; 24.01.2020). The DNA was extracted and prepared for paired-end MiSeq sequencing (Illumina, CA, USA) using a two-step PCR method to amplify the V1 to V3 region of the eukaryotic 18S rRNA  genes and the V4 region of the bacterial and archaeal 16SrRNA genes before attaching MiSeq adapter and barcode sequences.