The discovery of Borealis mud volcano: a natural sanctuary for threatened Arctic species

Abstract This paper presents the recent discovery of Borealis, a submerged mud volcano systemlocated in the Polar North Atlantic, distinct from the numerous methane seepages previously identified in the region. In situ observations using a remotely operated vehicle (ROV) have captured the expulsion of warm (11.5°C) Neogene sediments and the eruption of methane-dominated fluids from a localised site within a ~500 m diameter crater. The seafloor around Borealis comprises laterally extensive carbonate deposits, suggesting long-lasting diffuse methane migration. Sampling and seafloor images reveal that Borealis hosts unique habitats thriving in the low-oxygen environments around methane seeps. Additionally, the irregualry shaped carbonate structures serve as a natural refuge from bottom trawling as well as a substratum for sessile fauna and function as nursing grounds for threatened fish species. This discovery in the Polar North Atlantic highlights the ecological value of cold seep ecosystems, which play a critical role in biodiversity by acting as sanctuaries for marine species, hence emphasising the importance of their conservation.