Studying marine life along and underneath Antarctic ice shelves
Weddell seals allow novel insights into their fast ice covered coastal habitat. Images taken by seal-mounted cameras at about 150 m depth showed unexpected aggregations of isopods and other invertebrates attached to the underside of the floating Riiser-Larsen Ice Shelf that is more than a hundred metres thick. These "hanging gardens" of cryo-benthic communities may represent an attractive food horizon where seals may benefit from the availability of fish and other prey. About half of the Antarctic coastline has floating ice shelves attached. Are our findings from the Riiser Larsen Ice Shelf representative for Antarctic ice shelves in general? What is the species composition of the under ice shelf fauna, to what horizontal extent do invertebrates inhabit this icy substrate, what are the immediate hydrographic properties, and how are these organisms supplied with nutrients? These questions are challenging joint seal-shelf ice studies using both the seals as autonomous samplers and remotely operated vehicles to further our understanding of bentho-pelagic coupling processes in coastal shelf ecosystems of the high Antarctic sea ice zone.
Drescher Camp. Photo: J. Plötz, AWI, Germany
Weddell seal mother and pup during lactation. Photo: J. Plötz, AWI, Germany
Weddell seal. Photo: J. Plötz, AWI, Germany
Weddell seal at breathing hole. Photo: J. Plötz, AWI, Germany
Weddell seal coming out of the water. Photo: J. Plötz, AWI, Germany
Weddell seal mother and pup. Photo: J. Plötz, AWI, Germany
Scientists instrumenting a Weddell seal. Photo: N. Liebsch, University of Wales, UK
Data logger on a Weddell seals back. Photo: Y. Watanabe, NIPR, Japan
Crustaceans below shelf ice seen from the seal's perspektive. Photo: DSL-camera, Y. Watanabe et al., NIPR, Japan and AWI, Germany
Weddell seal under the ice, seen from the seals' perspective. Photo: DSL-camera, Y.Naito et al., NIPR, Japan and AWI, Germany
Methods
Weddell seals are instrumented with miniaturized biologging units such as camera loggers, dive depth and acceleration loggers, and satellite transmitters combined with oceanographic probes (CTDs) which are temporarily glued to the animals' fur.
Ongoing Research
Our recent field studies are part of the international project Marine Mammals Exploring the Oceans Pole to Pole (MEOP) and were conducted on the sea ice at Atka Bay from mid November to mid December 2008. Satellite-relayed dive loggers combined with CTD's (called CTD-SRDL) were deployed on Weddell seals. The CTD-SRDL measures temperature, pressure and salinity and transmits data along with geographic positions to satellites when the seals surface. Some seals were instrumented with Digital Still Image Loggers (DSL) and Jaw Accelerometers (JAM) which had to be retrieved some days after deployment to download data. From each of the CTD-SRDL tagged seals we obtained daily temperature, salinity and depth profiles almost in real time allowing us to study how changes in the under-ice environment alter prey distribution as being indicated by the seals' diving and foraging behaviour. We expect that these key physical oceanographic variables collected from hitherto inaccessible and thus undersampled coastal shelf regions may help scientists to refine their computer models of the Southern Ocean circulation.
Research Platforms
Recent results
Public outreach
- The Weddell seal - living on the icy edge
- Studies at the Drescher Inlet pp 78 - 79 in: "Effects of ocean warming and acidification on marine ecosystems - AWI Report 2008/2009"
- Illuminating a hidden world - Weddell seals
- Warmblüter im Eis: Weddellrobben
Previous work
- Mouthing off about fish capture: Jaw movement in pinnipeds reveals the real secrets of ingestion
- Under-ice foraging of Weddell seals
- Seal-mounted cameras detect invertebrate fauna on the underside of an Antarctic ice shelf
- Foraging behaviour of Weddell seals and its ecological implications
- Effect of sea ice break-up on the foraging behaviour of Weddell seals
- The tide as zeitgeber for Weddell seals
