Heterogeneity in the abyssal plains: A case study in the Bering Sea

<p>The abyssal plains are vast areas without large-scale topography that occupy much of the ocean floor. Ecological research in these superficially homogenous regions benefits increasingly from non-destructive visual sampling of epifaunal organisms with imaging technology. We analysed images from ultra high-definition towed camera transects at depths around 3500 m across three stations 100–130 km apart in the Bering Sea to ask whether the density and distribution of visible epifauna indicated any substantial heterogeneity. We identified 71 different megafaunal taxa, of which 24 occurred at only one station. Measurements of the two most abundant faunal elements, the holothurian <em>Elpidia</em> <em>minutissima</em> and xenophyophores, indicated significant differences in local densities and patchy aggregations that were strikingly dissimilar among stations. One station was dominated by xenophyophores, one was relatively depauperate in both target taxa as well as other identified megafauna, and the third station was dominated by <em>Elpidia</em>. This is an unexpected level of variation at relatively small spatial scales (~100 km), within comparable transects in a well-mixed oceanic basin, reinforcing the emerging view that abyssal habitats contain landscape heterogeneity at similar spatial scales to terrestrial continental realms.</p>