Stable isotope composition of Antarctic marine mammals collected at the turn of the 20th century: assessing the baseline for long-term changes in the marine ecosystem
Great Antarctic expeditions, seal hunting and whaling industries left a legacy in natural history collections. To provide the basis for analysing the impact of whaling on marine ecosystem structuring, we conducted the bulk isotope analysis from the specimens of baleen whales (Balaenoptera musculus and B. physalus), and seals (Arctocephalus australis and Hydrurga leptonyx) collected between 1843 to 1951 from the South Atlantic, Patagonian waters, Southern Ocean and Antarctic coastal seas, and preserved in the collection of Natural History Museum, London. Analysis of this material indicates the pre-industrial whaling state of these environments, and changes in the trophic position of whales and seals during the period of extensive human pressure. Having controlled for the Suess effect, {delta}13C values in B. musculus, B. physalus and H. leptonyx were different before and after the onset of industrial-scale whaling (1904). Bone collagen {delta}15N values and corresponding trophic position indicate possible trophic changes in A. australis, and variability of the foraging areas of B. musculus. This study highlights the use of museum specimens for tracing historical trends associated with changes in the population structure and distribution of species and which indicate long- term variability in their foraging ecology.