Cold-water coral habitat mapping in submarine canyons

Abstract

Submarine canyons, are geomorphological features of high ecological importance that require detailed faunal distribution maps and an advanced understanding of the processes influencing faunal distribution to ensure effective management. Faunal patterns are influenced by environmental heterogeneity in water mass characteristics, seafloor characteristics and food availability. The high structural complexity of canyon geomorphology, coupled with canyon-modified hydrodynamics (such as internal tides) are important phenomena that generate environmental heterogeneity in these variables. However, few faunal studies in canyons explicitly include physical oceanographic data (water mass characteristics and hydrodynamics) or fine-scale structural complexity as explanatory variables of faunal distribution and assemblage structure. This thesis applies a range of statistical approaches to a novel interdisciplinary dataset to increase our understanding of what drives faunal patterns, including cold-water corals, over a range of spatial scales using Whittard Canyon, North-East Atlantic as a model system. More specifically, this thesis aims to 1) assess the relative importance of physical oceanography in explaining faunal patterns across the canyon by estimating its effect on predictive modelling performance, 2) investigate if spatial patterns in temporal oceanographic variability induced by the internal tide explain variation in spatial patterns of faunal diversity and assemblage structure on canyon walls, and 3) explore the relationship between structural complexity at various spatial scales and faunal diversity/assemblage within mound provinces occurring on canyon interfluves. The research presented shows how structural complexity and internal tides influence faunal patterns by generating environmental heterogeneity at various spatial scales. Predictive distribution modelling demonstrates that including physical oceanographic data improves predictive accuracy and that the omission of these data can lead to an overestimated cold-water coral occurrence. The thesis demonstrates the importance of the internal tide in generating both spatial and temporal gradients in physical oceanography and food supply that influences faunal patterns in diversity, abundance and assemblage composition. The thesis further illustrates how structural complexity at various scales influences faunal patterns by generating environmental heterogeneity in fine-scale substratum characteristics and at broader-scales interacting with internal tides to concentrate food, both of which act to increase faunal diversity. The thesis also demonstrates that even when broad-scale structural complexity of the terrain is reduced, fine-scale structural complexity may still be present and acting to increase faunal diversity.

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Identifiers

ORCID for Tabitha Rosemary Rainbow Pearman: orcid.org/0000-0003-4213-4464

ORCID for Veerle Huvenne: orcid.org/0000-0001-7135-6360

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