Massive icebergs, alteration in primary food resources and change in benthic communities at Cape Evans, Antarctica

The presence of massive icebergs in the Southwestern Ross Sea (Antarctica) in the early-to-mid-2000s changed the regional sea ice regime and phytoplankton productivity. We exploit data on benthic macro- and megafaunal communities collected on six occasions between 2001 and 2009 in the shallow waters adjacent to Cape Evans to link these oceanographic shifts to changes in benthic ecology. Changes in the abundance of individual species and community composition were generally strongest, and mostly negative, in 2002 and 2003, which exhibited the largest decrease in water column productivity and thick and persistent sea ice. This pattern of decreasing numbers from the start of sampling in 2001 to the lowest values in 2003 is consistent with the impact of the icebergs and a lagged response on the part of the benthic populations in response to food shortage. The patterns of stronger effects on macrofauna than on megafauna, and on abundance rather than species richness, are consistent with a change in food supply and/or recruitment for short-lived species, rather than a physical disturbance effect. Nevertheless, recovery patterns are likely to reflect changes in benthic communities associated with larval supply and changes in top-down control after the years of predicted lowest food supply. There are many potential manifestations of climate change in Antarctica, and many of the ecological responses to environmental change are likely to be mediated through the foodweb. Long-term studies in different locations are essential if we are to understand and forecast changes in sea-floor ecosystems.