Trace element concentrations in Australian fur seals.

Trace elements (TE) in living organisms can have detrimental health impacts depending on their concentration. As TE are obtained through diet, trophic niche changes associated with the impacts of anthropogenic activities and climate-change may influence their uptake in top predators. The Australian fur seal (Arctocephalus pusillus doriferus; AUFS) represents the largest resident, marine-predator biomass in south-eastern Australia. With adult female foraging ranges limited to the continental-shelf, their source of TEs is geographically restricted. Plasma, red blood cell and milk samples collected from individuals between 1998- 2022 at Kanowna Island, were analysed for TEs. Plasma fatty acid profiles and ocean-climate variables were used to investigate trophic and environmental influences, respectively, on TE concentrations. Elements, including Se and Hg, showed concentrations considered to be toxic in humans while estimated milk-transferred TE represented harmful doses for pre-weaning pups. Relationships with fatty acid profiles suggest diet influenced TE concentrations in adult female plasma. In addition, inter-annual variation in TE concentrations were influenced by broad-scale environmental indices, such as the Southern Annular Mode and the Southern Oscillation Index, and local conditions associated with the seasonally-active Bonney Upwelling. These findings suggest the TE concentrations in blood and milk of AUFS will be affected by anticipated oceanographic changes, mediated by alterations in prey type availability, with potential impacts on the population’s health.