A few years ago thousands of icebergs calved from the Larsen A/B area. The fauna inhabiting the seafloor in this region was probably not disturbed on a large scale, but further north, where the icebergs ran aground with a higher frequency, iceberg scouring is now apparent.



We reported earlier that the seafloor in the region where the collapse of the Larsen A and B ice shelves happened shows very little damage. However, in order to evaluate the specific conditions beneath the ice shelf we had to investigate an area without the influence of an ice shelf cover for comparison. At the end of our station work we were fortunate enough to successfully sample two reference stations around Paulet and Seymour Island, approximately 150 nautical miles north of the Larsen area. Drawing from my experience with bottom-dwelling animals in the eastern Weddell Sea, it was obvious that these communities are almost entirely and constantly impacted by grounding icebergs. At depths below 200m we predominantly found animals, which are known to be fast growing and are among the first colonizers of iceberg scours. These include bushy sponges and the by now very familiar sea squirts. In between there are tracks that demonstrate how icebergs rework the sediment. Mobile animals such as brittle stars and starfish initially re-colonize these recently scoured areas. At greater water depths the fauna is able to develop a more balanced species diversity. However, very slow-growing glass sponges indicating undisturbed growth for centuries, which we have even found beneath the former Larsen A ice shelf, were almost entirely absent.



Even though this area is rather distant from the Larsen A/B region, there is a connection. The icebergs that cause large-scale damage to the seafloor derive from this area, as well as from the larger, still intact ice shelves further south.

Further analyses will reveal whether these disturbances contribute to enhanced biodiversity. This is usually brought about by patchworks of different recolonization stages which are known from other areas in Antarctica.

Text and Photographs: Julian Gutt