Sponge richness on algae-dominated rocky reefs in the western Antarctic Peninsula and the Magellan Strait

Sponges are important components of high-latitude benthic communities, but their diversity and abundance in algal-dominated rocky reefs has been underestimated because of the difficulty of in situ identification. Further, the influence of canopy-forming algae on sponge richness has been poorly studied in southern high-latitude rocky reefs compared to other latitudes. Here, we quantified taxon richness of sponges in algae-dominated rocky reefs at three sites in the western Antarctic Peninsula (62-64 degrees S) and two sites in the Magellan region (53 degrees S). We found higher sponge richness at sites in Antarctica (15) than in Magallanes (8), with Antarctic sponge richness higher than that reported for Arctic algal beds and similar to that reported for temperate regions. Estimated sponge richness at our Antarctic sites highlights diverse sponge assemblages (16-26 taxa) between 5 and 20 m that are typically dominated by macroalgae. Our results suggest that sponge assemblages associated with canopy-forming macroalgae on southern high-latitude reefs are more diverse than previously thought.