Peterson Sarah H, Ackerman Joshua T, Holser Rachel R, McDonald Birgitte I, Costa Daniel P, Crocker Daniel E
U.S. Geological Survey, Western Ecological Research Center, Dixon Field Station, Dixon, California 95620, United States of America.
Institute of Marine Sciences, University of California Santa Cruz, Santa Cruz, California 95064, United States of America.
Environ Sci Technol. 2023 Apr 11;57(14):5678-5692. doi: 10.1021/acs.est.2c08974. Epub 2023 Mar 30.
Mercury bioaccumulation from deep-ocean prey and the extreme life history strategies of adult female northern elephant seals () provide a unique system to assess the interactive effects of mercury and stress on animal health by quantifying blood biomarkers in relation to mercury (skeletal muscle and blood mercury) and cortisol concentrations. The thyroid hormone thyroxine (tT4) and the antibody immunoglobulin E (IgE) were associated with mercury and cortisol concentrations interactively, where the magnitude and direction of the association of each biomarker with mercury or cortisol changed depending on the concentration of the other factor. For example, when cortisol concentrations were lowest, tT4 was positively related to muscle mercury, whereas tT4 had a negative relationship with muscle mercury in seals that had the highest cortisol concentrations. Additionally, we observed that two thyroid hormones, triiodothyronine (tT3) and reverse triiodothyronine (rT3), were negatively (tT3) and positively (rT3) associated with mercury concentrations and cortisol in an additive manner. As an example, tT3 concentrations in late breeding seals at the median cortisol concentration decreased by 14% across the range of observed muscle mercury concentrations. We also observed that immunoglobulin M (IgM), the pro-inflammatory cytokine IL-6 (IL-6), and a reproductive hormone, estradiol, were negatively related to muscle mercury concentrations but were not related to cortisol. Specifically, estradiol concentrations in late molting seals decreased by 50% across the range of muscle mercury concentrations. These results indicate important physiological effects of mercury on free-ranging apex marine predators and interactions between mercury bioaccumulation and extrinsic stressors. Deleterious effects on animals' abilities to maintain homeostasis (thyroid hormones), fight off pathogens and disease (innate and adaptive immune system), and successfully reproduce (endocrine system) can have significant individual- and population-level consequences.
来自深海猎物的汞生物累积以及成年雌性北象海豹独特的生活史策略，提供了一个独特的系统，通过量化与汞（骨骼肌和血液汞）及皮质醇浓度相关的血液生物标志物，来评估汞和应激对动物健康的交互影响。甲状腺激素甲状腺素（tT4）和抗体免疫球蛋白E（IgE）与汞和皮质醇浓度存在交互关联，其中每个生物标志物与汞或皮质醇的关联程度和方向会根据另一个因素的浓度而变化。例如，当皮质醇浓度最低时，tT4与肌肉汞呈正相关，而在皮质醇浓度最高的海豹中，tT4与肌肉汞呈负相关。此外，我们观察到两种甲状腺激素，三碘甲状腺原氨酸（tT3）和反三碘甲状腺原氨酸（rT3），分别以相加的方式与汞浓度呈负相关（tT3）和正相关（rT3），并与皮质醇相关。例如，在繁殖后期、皮质醇浓度处于中位数的海豹中，随着观察到的肌肉汞浓度范围变化，tT3浓度下降了14%。我们还观察到免疫球蛋白M（IgM）、促炎细胞因子白细胞介素-6（IL-6）和一种生殖激素雌二醇与肌肉汞浓度呈负相关，但与皮质醇无关。具体而言，在蜕皮后期的海豹中，随着肌肉汞浓度范围变化，雌二醇浓度下降了50%。这些结果表明汞对野生顶级海洋捕食者具有重要的生理影响，以及汞生物累积与外在应激源之间的相互作用。对动物维持体内平衡（甲状腺激素）、抵御病原体和疾病（先天性和适应性免疫系统）以及成功繁殖（内分泌系统）能力的有害影响，可能会对个体和种群水平产生重大后果。
