On the rocks: recruitment and distribution patterns on deep-sea hard substrata in the Labrador Sea and Baffin Bay (Canada)

The study of larval recruitment and colonization patterns in hard-bottom benthic communities is crucial to the understanding of species distributions, community assembly, and the potential effects of anthropogenic activity and climate change on the maintenance of biodiversity. Expanding our knowledge of early and established communities is an important first step. To explore this need, I first examined recruitment patterns on four substratum types (mesh, plastic, stone, wood) deployed for ~1 y at four sites in bathyal Labrador Sea (Canada). I determined that colonial hydrozoan recruits dominated all substratum types and sites; arthropods, octocorals, and other anthozoans were sparser. The features of each substratum type facilitated differential recruitment patterns: the complex, three-dimensional structure of mesh had higher morphospecies richness and diversity, while the sheltered, larger surface area of plastic had higher abundance and density by recruits. Wood, as a single elongated panel, had the most surface and canopy coverage. Secondly, I examined regional diversity and zonation patterns of morphospecies colonizing terrigenous ice-rafted dropstones at bathyal depths in the Labrador Sea (LAB) and Baffin Bay (BAF). Based on in-situ images, dropstones exhibited more epibenthic megafaunal richness than surrounding finer-grained substrata and, following analysis of collected dropstones, a total of 101 taxa spanning 10 phyla were recorded with bryozoans dominating numerically at all depths. The richness of dropstone communities was higher in LAB than BAF overall, though 19 morphospecies spanned both locations. Zonation patterns were consistent, with a majority of morphospecies positioned above the stone-sediment boundary or at the boundary, and one morphospecies of polychaete below. Ecological interactions appeared to influence both positioning and regional distributions. By combining early and established community studies, my thesis provides data on how deep-sea hard-bottom epibenthic assemblages form and develop.