Presenter: Véronique Merten (GEOMAR Helmholtz Centre for Ocean Research Kiel)

Description:
Nekton biodiversity and contribution to the carbon cycle in the Arctic Ocean is widely understudied and may be subject to rapid change due to climate change and anthropogenic impacts. Such changes can only be detected if baseline knowledge is available. In the Arctic, boreal nekton groups are introduced due to increased inflow of warm Atlantic water. Such influx of boreal species might displace native Arctic species. Here, we test the hypothesis that nekton range expansions occur in the Arctic by establishing a cephalopod and fish diversity baseline from eDNA analysis and existent knowledge on nekton diversity and distribution. We also test if eDNA of pelagic origin can be detected in sediment to predict potential foodfall species that contribute to the carbon cycle. We sampled in the Fram Strait, which is influenced by warm Atlantic water, rendering it a modelsite to study community change. We collected seawater at four stations (50 – 2700 m) and sediment at 12 stations. eDNA metabarcoding targeting cephalopods (nuclear 18S rRNA) and fish (mitochondrial 12S rRNA) resulted in the detection of six cephalopod and 27 fish taxa in the seawater. The most often detected cephalopods were Gonatus sp./Gonatidae, the most abundant squid in the North Atlantic. No cephalopod eDNA was detected in the sediment. Detected fish included Mallotus villosus (capelin), Zoarcidae, Sebastes sp. and Liparidae and Somniosus microcephalus, the Greenland shark. We detected 18 fish taxa including capelin in the sediment. We show that eDNA successfully detected species range expansions of capelin, which is a key species in the foodweb and a potential foodfall species due to its semelparous life history. Low diversity of cephalopods was encountered in the water column which is in line with current knowledge on Arctic diversity. Ongoing efforts are focused on methodology of eDNA extractions from sediment and increase of arctic reference sequence databases via barcoding of Arctic species.