Spatial and temporal variations of the Southern Ocean ecosystem: Information from fur seals

Abstract

Marine ecosystems are experiencing important changes worldwide and the Southern Ocean is no exception. Assessing the impact of these changes is difficult when relatively few current, let alone historical data, are available. One source of historical data, however, are samples housed in museums, which can be compared to contemporary samples. We used two widely distributed top predator species within the Southern Ocean as bio-indicators: the Antarctic Arctocephalus gazella (AFS. and Subantarctic A. tropicalis (SAFS. fur seals. Pinnipeds exhibit incremental tooth growth, with each growth layer reflecting the chemical elements deposited during a specific period during the animal’s life. Fine-scale longitudinal sampling can therefore provide information for the 10 to 15 years prior to the animal’s death. Samples collected at three locations (Bouvet Island [AFS], Gough Island [SAFS], Marion Island [AFS and SAFS]. from 1978 to 2016 are compared. Making use of the well-known ?13C isoscapes in the Southern Ocean, bulk carbon stable isotopes of tooth dentine provide information on the geographic locations at which the animal foraged during their lives, while nitrogen stable isotopes indicate the trophic level at which the animal was feeding. Bulk stable isotope analyses are complemented by stable isotope analyses of particular amino-acids to further examine spatial and/or temporal changes in ecosystem stable isotope baselines. Three main questions will be addressed: (1. Do the two fur seal species exhibit differences in trophic ecology depending on their breeding location? (2. Do changes in the fur seal trophic ecology reflect global changes in the marine ecosystem over the last fifty years? (3. If changes are detected, do female and male fur seals react similarly? The answers to these questions will bring new insights for the implementation of management plans in the context of climate change and sustainable exploitation of Antarctic resources. - Abstract as displayed in the - Abstract booklet. The presentation on the day may differ from the - Abstract.