Evaluation of local- and medium-scale habitat heterogeneity as proxy for biodiversity in deep-sea habitats

Abstract

The deep sea represents the largest biome on earth, and for most of it, no maps of resolutions comparable to terrestrial environments are available. As new species continue to be discovered, it is clear that our knowledge of species spatial patterns is insufficient to properly inform marine spatial planning, and for complex habitats, high-resolution surveys are crucial for understanding species-environment relationships. This thesis examined two deep-sea areas of the NE Atlantic, Rockall Bank and Whittard Canyon. By linking acoustic maps to benthic imagery datasets, environmental variables describing the spatial arrangement of different substratum types and topographic variability were found to be good predictors of species composition and biodiversity. Employing an ensemble of statistical techniques provided a more robust approach for the creation of biological full-coverage predictive maps and allowed for the identification of areas with high biodiversity. With these maps, it was possible to demonstrate that biological spatial patterns in Whittard Canyon required mapping resolutions of 20-50m while the more heterogeneous Rockall Bank area needed to be mapped at <5m. The continued sparse availability of biological datasets in the deep-sea remains a significant limiting factor in informing conservation needs, but the work carried out shows improvements over previous approaches, and can be applied to identify biodiversity hotpots and assess habitat suitability for vulnerable marine ecosystems, such as cold-water corals. Through such hierarchical multi-disciplinary studies, the currently available biological information can be employed to increase our understanding of the relationships between habitat heterogeneity and biodiversity as well as help establish the baseline state of these ecosystems in order to effectively monitor potential impacts.

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ORCID for V.A.I. Huvenne: orcid.org/0000-0001-7135-6360

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