Department of Natural Resource Sciences, McGill University, Ste-Anne-de-Bellevue, QC, Canada.
Faroe Marine Research Institute, Nóatún 1, FO-100, Tórshavn, Faroe Islands.
Neurotoxicology. 2021 May;84:136-145. doi: 10.1016/j.neuro.2021.03.006. Epub 2021 Mar 24.
Mercury is a neurotoxic chemical that represents one of the greatest pollution threats to Arctic ecosystem health. Evaluating the direct neurotoxic effects of mercury in free ranging wildlife is challenging, necessitating the use of neurochemical biomarkers to assess potential sub-clinical neurological changes. The objective of this study was to characterize the distribution and speciation of mercury, as well as exposure-associated changes in neurochemistry, across multiple brain regions (n = 10) and marine mammal species (n = 5) that each occupy a trophic niche in the Arctic ecosystem. We found consistent species differences in mean brain and brain region-specific concentrations of total mercury (THg) and methyl mercury (MeHg), with higher concentrations in toothed whales (narwhal, pilot whales and harbour porpoise) compared to fur-bearing mammals (polar bear and ringed seal). Mean THg (μg/g dw) in decreasing rank order was: pilot whale (11.9) > narwhal (7.7) > harbour porpoise (3.6) > polar bear (0.6) > ringed seal (0.2). The higher THg concentrations in toothed whales was associated with a marked reduction in the percentage of MeHg (<40 %) compared to polar bears (>70 %) that had lower brain THg concentrations. This pattern in mercury concentration and speciation corresponded broadly to an overall higher number of mercury-associated neurochemical biomarker correlations in toothed whales. Of the 226 correlations between mercury and neurochemical biomarkers across brain regions, we found 60 (27 %) meaningful relationships (r>0.60 or p < 0.10). We add to the growing weight of evidence that wildlife accumulate mercury in their brains and demonstrate that there is variance in accumulation across species as well as across distinct brain regions, and that some of these exposures may be associated with sub-clinical changes in neurochemistry.
汞是一种神经毒性化学物质，是对北极生态系统健康构成最大污染威胁之一。评估游离野生动物中汞的直接神经毒性影响具有挑战性，因此需要使用神经化学生物标志物来评估潜在的亚临床神经变化。本研究的目的是描述汞的分布和形态，以及在多个脑区（n = 10）和海洋哺乳动物物种（n = 5）中与暴露相关的神经化学变化，这些物种在北极生态系统中占据不同的营养位。我们发现总汞（THg）和甲基汞（MeHg）在不同物种的脑和脑区特异性浓度上存在一致的差异，齿鲸（独角鲸、领航鲸和港湾海豚）的浓度明显高于有毛哺乳动物（北极熊和环斑海豹）。THg 的平均浓度（μg/g dw）依次降低：领航鲸（11.9）>独角鲸（7.7）>港湾海豚（3.6）>北极熊（0.6）>环斑海豹（0.2）。齿鲸中的 THg 浓度较高，与 MeHg 的比例明显降低（<40%）有关，而北极熊的 THg 浓度较低，MeHg 的比例较高（>70%）。这种汞浓度和形态的模式与齿鲸中与汞相关的神经化学生物标志物的相关性数量总体上更高有关。在所研究的 226 个与脑区中汞和神经化学生物标志物之间的相关性中，我们发现了 60 个（27%）有意义的关系（r>0.60 或 p < 0.10）。我们增加了越来越多的证据表明，野生动物在其大脑中积累汞，并表明在物种之间以及在不同的脑区之间，积累的汞存在差异，并且其中一些暴露可能与亚临床神经化学变化有关。
