Whiskers provide time-series of toxic and essential trace elements, Se:Hg molar ratios, and stable isotope values of an apex Antarctic predator, the leopard seal

In an era of rapid environmental change and increasing human presence, researchers need efficient tools for tracking contaminants to monitor the health of Antarctic flora and fauna. Here, we examined the utility of leopard seal whiskers as a biomonitoring tool that reconstructs time-series of significant ecological and physiological biomarkers. Leopard seals (Hydrurga leptonyx) are a sentinel species in the Western Antarctic Peninsula due to their apex predator status and top-down effects on several Antarctic species. However, there are few data on their contaminant loads. We analyzed leopard seal whiskers (n = 18 individuals, n = 981 segments) collected during 2018-2019 field seasons to acquire longitudinal profiles of non-essential (Hg, Pb, and Cd) and essential (Se, Cu, and Zn) trace elements, stable isotope (delta N-15 and delta O-13) values and to assess Hg risk with Se:Hg molar ratios. Whiskers provided between 46 and 286 cumulative days of growth with a mean similar to 125 days per whisker = 18). Adult whiskers showed variability in non -essential trace elements over time that could partly be explained by changes indict. Whisker Hg levels were insufficient (<20 ppm) to consider most seals being at high risk for Hg toxicity. Nevertheless, maximum Hg concentrations observed in this study were greater than that of leopard seal hair measured two decades ago. However, variation in the Se:Hg molar ratios over time suggest that Se may detoxify Hg burden in leopard seals. Overall, we provide evidence that the analysis of leopard seal whiskers allows for the reconstruction of time-series ecological and physiological data and can be valuable for opportunistically monitoring the health of the leopard seal population and their Antarctic ecosystem during climate change.

Automated summary

In this study, the utility of leopard seal whiskers as a biomonitoring tool for tracking contaminants and monitoring the health of Antarctic flora and fauna was examined. The analysis of leopard seal whiskers revealed variability in non-essential trace elements over time that could be partly explained by changes indict. The levels of mercury (Hg) in the whiskers were not high enough to indicate high risk of Hg toxicity, but the maximum Hg concentrations observed were higher than those measured two decades ago. The study also suggested that selenium (Se) may detoxify the Hg burden in leopard seals.