| Summary: | Sponge grounds are biogenic habitats formed by large structure-forming sponges in the deep-sea. They are biodiversity hotspots because they provide associated fauna a place of refuge, additional substratum, foraging areas, and can act as nursery grounds for many demersal fish. Sponge grounds have a global distribution, though there has been an increased focus in the North Atlantic in recent years due to the Horizon 2020 funded SponGES project. While there are a variety of sponge ground types based on their main sponge composition (monospecific and multispecific) or distribution (temperate, boreal, and arctic), there has been relatively little scientific focus on arctic sponge grounds, in terms of biodiversity, community ecology, and distribution. With potential imposing threats (e.g., climate change, bottom fishing, deep-sea mining) to arctic deep-sea communities such as arctic sponge grounds, there is a clear need to form a baseline understanding of these communities and their spatial ecology. The main aims of this thesis were to fill the current knowledge gaps of arctic sponge ground biodiversity and spatial ecology in the Nordic Seas. More specifically, this project aimed to: 1) describe the megafauna composition and diversity of arctic sponge grounds to improve on their current habitat classification; 2) examine biotic interactions occurring within the sponge grounds to evaluate the ecological services arctic sponge grounds provide; 3) investigate the spatial distribution of arctic sponge grounds and the characterising megafauna to identify how communities are distributed on a seascape and how megafauna are assembled within a habitat; and 4) explore the primary abiotic drivers that influence the distribution and community structure of arctic sponges grounds and their inhabitants in order to understand what conditions sponge grounds need to form and thrive. This thesis provides the first description of the oceanographic setting of Schulz Bank, a seamount on the Arctic Mid-Ocean Ridge used as a case study site ...
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