Weddell seals and shelf ice-associated cryobenthos

• Main Authors: Bornemann, Horst, Nachtsheim, Dominik A., Owsianowski, Nils, Steinmetz, Richard, Richter, Claudio, Held, Christoph
• Format: Conference Object
• Language: unknown
• Published: 2018
• Subjects: Ice Shelf; Ice Shelves; Larsen Ice Shelf; Polar Science; Riiser Larsen Ice Shelf; Riiser-Larsen Ice Shelf; Weddell Sea; Weddell Seals
• Online Access: https://epic.awi.de/id/eprint/48790/; https://hdl.handle.net/10013/epic.652eb499-e077-4a1d-8692-9e5956a2b63e

Incidences of cryo-benthic communities beneath ice shelves are rare and recent discoveries. Images taken by seal-borne cameras at Drescher Inlet (Riiser-Larsen Ice Shelf, eastern Weddell Sea) in 2004 led to the discovery of a hitherto unknown cryo-benthic community of crustaceans being attached head-down to the underside of the floating ice shelf at depths between 130-150m (Watanabe et al. 2006). Resolution and exposure of these images did not allow distinct identification on species level, being considered as likely isopods or cnidarians, and no information could be gained on the composition, size, dimension and density of the faunal aggregation at that time. Recently, however, a re-assessment and augmentation of the earlier findings (Bornemann et al. 2016) has become feasible due to the use of combined seal- and ROV-borne imagery and novel sampling technologies. The Drescher Inlet is a 25km long and between 2 and 4km wide crack in the Riiser-Larsen Ice Shelf and characterized by perennial fast ice that disintegrates at irregular intervals. The fast ice of the inlet provides habitat for Weddell seals, hauling-out along tidal cracks in numbers of 200 – 300 individuals. In December 2016 German logistics and the research platforms Neumayer Station III and RV Polarstern coordinated a field camp on the ice shelf close to the inlet that had been maintained for four weeks. Weddell seals were instrumented with infrared still picture camera loggers (IR-DSL; Little Leonardo, JP) or CTD-combined satellite relay data loggers (CTD-SRDL; Sea Mammal Research Unit, UK). A Remotely Operated Vehicle (ROV; Ocean Modules, SE) was launched through a hole dug in the fast ice near the shelf ice cliffs. Seal-borne IR-DSLs took close-ups of aggregations of isopods underneath the floating ice shelf at 100m water depth. ROV-borne high resolution video footage showed dense aggregations of a single morphospecies of filter-feeding isopods. Significant size differences and clustering of the isopod aggregations imply a specific association of ...