Spatial variability in the distribution of dominant shallow-water benthos at Adelaide Island, Antarctica

Studies from temperate and tropical regions have shown that variability in the distribution of benthos exists at different spatial scales. There are very few similar studies from polar systems, the shallows of which represent some of the most intensely disturbed habitats on the planet. Variability in the abundances of the five most common macrofauna was examined at three spatial scales, metres, tens of metres and hundreds of metres, in the shallows (5-25 m depth) of Adelaide Island, West Antarctic Peninsula. Whilst significant community change occurs along a depth gradient at the study sites, not all of the common species studied showed clear depth-related patterns of distribution. Furthermore, although abundance patterns varied between the organisms, consistent depth-related trends in the spatial scale contributing most to the variability were observed for four of the five species. For four species the relative importance of large-scale variability (between sites) decreased from 5 to 25 m depth, whilst small-scale variability (between replicates) increased along the depth gradient. Variation between sites is probably largely driven by ice disturbance, which becomes less frequent with depth. Conversely, small-scale patchiness is promoted by biological interactions, which become relatively more influential as community complexity and species richness increase along the depth gradient.