Faunal communities of Arctic deep-water methane seeps are specialised with links to hydrothermal vents

Cold seeps are common seafloor features on Arctic continental margins, but the cold seep fauna in the region has mainly been characterized from sites on the continental shelf or upper slope (< 800 m). Here, we characterize the fauna of two deep-water cold seeps on the Vestnesa (1300 m) and Svyatogor Ridges (1900 m) based on morphological analyses and DNA barcoding. The Svyatogor Ridge system has been hypothesized to represent a hybrid system with processes resembling both hydrothermal vents and cold seeps, however, until now, it had not been tested whether its fauna shows any similarity to regional hydrothermal vent fauna. The present study documents a clearly specialised fauna at both seeps with seven putatively new and seep-specialised species recorded as well as eight species shared with the sedimented hydrothermal vent Loki’s Castle approximately 540 km further south on the Mohns Ridge. The dataset presented illustrates a close connection between vent and seep faunas in the Arctic, presumably driven by the close geographic proximity of vents and seeps and the presence of intermediate habitats such as sedimented vents. • Fauna from an active cold seep site at Svyatogor Ridge was characterized. • Specialised fauna was documented from both Svyatogor and Vestnesa cold seeps. • Both seep sites share species with Loki’s Castle vent field. • The regional overlap between vents and seeps may be driven by intermediate habitats.