Data from: Foraging and fasting can influence contaminant concentrations in animals: an example with mercury contamination in a free-ranging marine mammal

Large fluctuations in animal body mass in relation to life history events can influence contaminant concentrations and toxicological risk. We quantified mercury concentrations in adult northern elephant seals (Mirounga angustirostris) before and after lengthy at-sea foraging trips (n = 89) or fasting periods on land (n = 27), and showed that mercury concentrations in blood and muscle changed in response to these events. The highest blood mercury concentrations were observed after the breeding fast, whereas the highest muscle mercury concentrations were observed when seals returned to land to moult. Mean female blood mercury concentrations decreased by 30% across each of the two annual foraging trips, demonstrating a foraging-associated dilution of mercury concentrations as seals gained mass. Blood mercury concentrations increased by 103% and 24% across the breeding and moulting fasts, respectively, demonstrating a fasting-associated concentration of mercury as seals lost mass. In contrast to blood, mercury concentrations in female’s muscle increased by 19% during the post-breeding foraging trip and did not change during the post-moulting foraging trip. While fasting, female muscle mercury concentrations increased 26% during breeding but decreased 14% during moulting. Consequently, regardless of exposure, an animal’s contaminant concentrations can be markedly influenced by their annual life history events.

动物体重随生活史事件发生的剧烈波动，会影响其体内污染物浓度与毒理学风险。我们对89次长时间海上觅食之旅以及27次陆地禁食期前后的成年北象海豹（*Mirounga angustirostris*）体内汞浓度进行了定量检测，结果显示其血液与肌肉组织中的汞浓度会随这些事件发生显著变化。血液汞浓度峰值出现在繁殖期禁食结束后，而肌肉汞浓度峰值则出现在海豹返回陆地换毛时。在两次年度觅食之旅中，雌性海豹的平均血液汞浓度均下降了30%，表明随着海豹体重增加，觅食行为会稀释体内汞浓度。在繁殖期和换毛期禁食期间，血液汞浓度分别上升了103%和24%，这表明随着海豹体重下降，禁食会使体内汞浓度被浓缩。与血液组织不同，雌性海豹的肌肉汞浓度在繁殖期后觅食之旅中上升了19%，而在换毛期后觅食之旅中未发生明显变化。在禁食期间，雌性海豹的肌肉汞浓度在繁殖期上升了26%，但在换毛期下降了14%。因此，无论暴露水平如何，动物体内的污染物浓度都会显著受其年度生活史事件的影响。