CONICET | Buscador de Institutos y Recursos Humanos

Bone apatite grows at a constant temperature in mammals and, hence, variations in the 18O of apatite carbonate reflect changes in the 18O of ingested water. As in marine mammals food is the only relevant source of water, the 18O of their apatite bone is expected to reflect that of their food, which in turn reflects that of the surrounding water mass. Thus, the 18O of apatite in marine mammal bone is a potentially useful habitat tracer for marine ecosystems and we used it to investigate dispersal patterns of South American sea lions in the south-west Atlantic. Samples were collected from the skulls of individuals that were found dead stranded in Brazil (32 males), northern Patagonia (39 males and 39 females) and Tierra del Fuego (19 males). Bone samples were grinded and soaked into a hydrogen peroxide solution to oxidize organic matter, the original structural carbonate was isolated from potential contaminants using a solution of acetic acid buffered with calcium acetate, and its O isotopic signal analysed using a mass spectrometer. A statistically significant correlation was found between the latitude of the stranding point and the 18O value of mature males (n=58, rp= -0.285, p < 0.030), which agrees with the latitudinal gradient of 18O in the ocean. This correlation suggests limited dispersal of adult males along the coast of South America. On the other hand, variability in the 18O values of young and immature sea lions of both sexes from northern Patagonia is much wider than that of adults from the same region, which suggests that young and immature sea lions disperse more widely than adults. Nevertheless, the dispersal period of females was much shorter (

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