Department of Environmental and Biological Sciences, University of Eastern Finland, P.O. Box 111, FIN-80101, Joensuu, Finland.
Natural Resource Institute Finland, Yliopistokatu 6, FIN-80100, Joensuu, Finland.
Environ Sci Pollut Res Int. 2024 Oct;31(47):57720-57732. doi: 10.1007/s11356-024-34980-6. Epub 2024 Sep 18.
The Saimaa ringed seal (Pusa hispida saimensis) is a subspecies of ringed seal, landlocked in Lake Saimaa, Finland. The small population of less than 500 seals is facing many human-induced threats, including chemical contaminants. Mercury, in particular, has previously been suggested to be one of the chemicals affecting the viability of this endangered population. We analysed mercury concentrations from placentas and lanugo pup tissues (blubber, brain, kidney, liver, and muscle) to determine current prenatal exposure levels. These pups were found dead in or near birth lairs and were less than 3 months old. Additionally, we used threshold values available in the literature to estimate the potential mercury toxicity to the Saimaa ringed seal. We also determined selenium concentrations for its potential to alleviate the adverse effects of mercury. We further supplemented our study with brain samples collected from various seal age classes. These seals were found dead by either natural causes or by being caught in gillnets. The analysed chemicals were present in all tissues. For lanugo pups, mercury concentrations were the highest in the kidney and liver, whereas the highest selenium to mercury molar ratio was observed in placentas. The toxicity evaluation suggested that, in severe cases, mercury may cause adverse effects in lanugo and older pups. In these cases, the selenium concentrations were low and selenium to mercury ratio was below 1:1 threshold ratio and thus unlikely to provide adequate protection from the adverse effects of mercury. Furthermore, adverse effects are more likely to occur in adult seals, as mercury bioaccumulates, leading to higher concentrations in older individuals. Placental mercury concentrations correlated to those in the livers and muscle tissues of lanugo pups. This, together with the fact that placentas can be collected non-invasively and in good condition, provides a potential novel method for biomonitoring mercury exposure in Saimaa ringed seals.
塞马环斑海豹（Pusa hispida saimensis）是环斑海豹的一个亚种，内陆生活在芬兰的塞马湖。这个不到 500 只海豹的小种群面临着许多人为诱导的威胁，包括化学污染物。特别是汞，此前曾被认为是影响这一濒危种群生存能力的化学物质之一。我们分析了胎盘和胎毛组织（鲸脂、大脑、肾脏、肝脏和肌肉）中的汞浓度，以确定当前的产前暴露水平。这些幼崽在出生洞穴或附近死亡，年龄不到 3 个月。此外，我们使用文献中可用的阈值来估计汞对塞马环斑海豹的潜在毒性。我们还测定了硒浓度，以评估其缓解汞不利影响的潜力。我们还进一步用从不同海豹年龄组收集的脑组织样本补充了我们的研究。这些海豹因自然原因或被刺网捕获而死亡。所有组织中都存在分析的化学物质。对于胎毛幼崽，汞浓度在肾脏和肝脏中最高，而胎盘中的硒与汞摩尔比最高。毒性评估表明，在严重情况下，汞可能会对胎毛和年龄较大的幼崽造成不利影响。在这些情况下，硒浓度较低，硒与汞的比值低于 1:1 的阈值比值，因此不太可能提供足够的保护，以防止汞的不利影响。此外，由于汞生物积累，成年海豹体内的汞浓度更高，因此更有可能出现不利影响。胎盘内的汞浓度与胎毛幼崽的肝脏和肌肉组织中的汞浓度相关。这一点，再加上胎盘可以非侵入性地、在良好的条件下收集，为塞马环斑海豹的汞暴露生物监测提供了一种潜在的新方法。
