Islands of biodiversity created by remote Arctic kelp forests of the central Kitikmeot Sea

Large brown algae known as kelp cover extensive areas of Arctic coastlines and can form underwater forests that support diverse faunal communities. In many ice-scoured environments, where shallow subtidal habitats are structurally simplified, kelp may act as the primary foundation species, yet their ecological role across Arctic seascapes remains poorly resolved. Using baited cameras, diver surveys, habitat mapping, and satellite remote sensing, we assessed kelp distribution and associated biodiversity in the central Kitikmeot Sea, a near-estuarine, nutrient-poor system of the Northwest Passage. Across our study area ~80% of the seascape was bare, with kelp restricted to ~9 discrete, low-canopy forests (max ~0.6 km2) located in hydrodynamically exposed areas with earlier spring ice opening. Epifaunal communities differed among habitat types, with kelp and understorey algae supporting disproportionately higher invertebrate richness and densities than bare and kelp-adjacent habitats (up to 900 ind. m-2). Faunal assemblages also differed among individual kelp forests, amplifying biodiversity at the seascape scale. Distribution of larger motile fauna (mainly fish and crabs) was driven primarily by temperature rather than habitat: Gadus ogac sightings and foraging increased above water temperatures of 2.5 °C, whereas Hyas alutaceus occurred mainly below 0 °C; fish sightings in kelp forests increased with temperature. Together, these results identify kelp forests of the Kitikmeot Sea as spatially isolated yet functionally important “islands of diversity,” highlighting the role of habitat-forming macrophytes in polar coastal seascapes with limited benthic productivity and providing a baseline for anticipating change as ice and circulation regimes evolve.