FIRST STUDY OF MACROBENTHIC BIODIVERSITY AT CENTRAL ARCTIC SEAMOUNTS

• Main Author: Scheer, Stella Luna
• Format: Thesis
• Language: unknown
• Published: 2018
• Subjects: Arctic; Arctic Ocean; Gakkel Ridge; Stepping Stones; Langseth
• Online Access: https://epic.awi.de/id/eprint/49661/; https://hdl.handle.net/10013/epic.aefed3bb-87eb-4f8a-9c70-fb0296459aad

Seamount systems offer a diverse range of habitats which support the local communities influenced by the hydrographic specifics of the mount area. Efforts to investigate the benthic communities of the Arctic as well as seamounts have risen in the last years, yet the knowledge in these areas remains scarce. For this study the macrofaunal distribution, biodiversity and abundance was studied along a depth gradient based on material collected along the Langseth Ridge for the first time (Gakkel Ridge, Central Arctic Ocean) and in the surrounding area during the R.V. Polarstern expedition PS101. The macrofaunal samples were obtained with a giant box corer (0.25 m²) at seven stations (three replicates each), ranging from a mean depth of 645 m to 3873 m. Common paradigms were tested with additional data from the adjacent basins. The community was strongly structured by depth and featured three distinctive faunal assemblages, the mount, transition and deep assemblage. These varied in species composition, diversity and densities. While biodiversity was found to be highest at intermediate depth levels, i.e. the transition assemblage (~1000-1800m), average species numbers and densities decreased and species evenness increased with increasing depth. A total of 65 putative species, belonging to 14 major taxa, were identified with at least four of these species potentially being new and endemic. Polychaetes contributed the most towards species diversity, while the poriferan Geodia parva exhibited highest overall densities and thus dominated the mount assemblage. The faunal patterns of this study reflect those observed at various other seamounts. While the hypothesis of seamounts as biological hotspots was confirmed for this high Arctic environment, this doesn’t necessarily imply true geographic boundaries. The overall results, with the mount assemblage being very similar on all three mounts, agree with the idea of seamounts serving as stepping stones, enhancing population connectivity. Whether the mounts of the Langseth Ridge can be regarded as island according to the island theory for seamounts will have to be investigated in future studies on larger spatial scales, including genetic analyses on species, in order to gain scientific evidence. However, seamounts, particularly in such extreme environments, are highly vulnerable and valuable marine ecosystems due to their high potential for population connectivity, as well as their potential as a source to maintain populations in surrounding sink habitats.