Arctic nekton uncovered by eDNA metabarcoding: diversity, potential range expansions and benthopelagic coupling

The Arctic Ocean is home to a unique fauna that is disproportionately affected by global warming but that remains under-studied. Due to their high mobility and responsiveness to global warming, cephalopods and fishes are good indicators of the reshuffling of Arctic communities. Here, we established a nekton biodiversity baseline for the Fram Strait, the only deep connection between the North Atlantic and Arctic Ocean. Using universal primers for fishes (12S) and cephalopods (18S), we amplified environmental DNA (eDNA) from seawater (50–2700 m) and deep-sea sediment samples collected at the LTER HAUSGARTEN observatory. We detected twelve cephalopod and 31 fish taxa in the seawater and seven cephalopod and 28 fish taxa in the sediment, including the elusive Greenland shark (Somniosus microcephalus). Our data suggest three fish (Mallotus villosus, Thunnus sp. and Micromesistius poutassou) and one squid (Histioteuthis sp.) range expansions. The detection of eDNA of pelagic origin in the sed..., Sample collection, filtration and DNA extraction
Seawater samples for eDNA metabarcoding were collected during the cruises PS121 in August/September 2019, MSM95 in October/November 2020 and PS126 in May/June 2021 in the Fram Strait (Fig. 1C). Samples were taken in triplicate between 50 m and above the bottom (between 2250 and 2705 m deep) at three stations (S3, HG4, N4) in 2020 and four stations (S3, HG4, N4, EG4) in 2019 and 2021, resulting in a total of 282 samples (Fig. 2).
Sampling was conducted using 12-liter Niskin bottles mounted on a CTD rosette. During the cruises PS121 and PS126, six liters were filled from one Niskin bottle into either three 2 L bottles or one 10 L bottle that were previously cleaned with bleach and flushed with MilliQ water. On cruise MSM95, we had the opportunity to directly filter the water from the Niskin bottles by attaching the tubing needed for filtration. In each case, two liters of water were filtered with a peristaltic pump using 0.22 µm Sterivex-GP...,