Bathyal infaunal communities from a deep seamount (Galicia Bank, northeast Atlantic)

Seamounts are isolated topographic elevations rising steeply from the ocean floor that are characterized by high spatial heterogeneity and topographic complexity. They offer a large number of microhabitats that favour faunal diversity as well as fish feeding and spawning grounds. Though there is increasing research interest in seamounts, it is most often focused on studying large suspension feeders or fish populations, while the infauna is usually neglected. In this paper, we studied the infaunal macrobenthic diversity and distribution of sedimentary habitats on the Galicia Bank (northwest Iberian peninsula), as well as their links with the environment. We sampled 28 sites (683–2274 m depth) and identified more than 1300 specimens from 182 taxa, mostly polychaetes (67% of the total). Sediments were mainly sandy (medium, fine and very fine sands) with low levels of organic matter. We found three major macrobenthic assemblages through multivariate analyses: A, with medium depths and the lowest abundances; B, the shallowest, with medium sands and intermediate abundances; and C, the deepest and most diverse with the finest sediments. Depth, mud content and median grain size were best related to macrofauna distribution patterns, separating shallow environments with medium sands from deeper ones with finer sediments.