Department of Biology, University of Southern Denmark, Campusvej 55, DK-5230, Odense, Denmark.
Department of Biology, University of Southern Denmark, Campusvej 55, DK-5230, Odense, Denmark.
Environ Pollut. 2021 Sep 15;285:117401. doi: 10.1016/j.envpol.2021.117401. Epub 2021 May 19.
Methylmercury accumulated at the top of aquatic food chains constitutes a toxicological risk to humans and other top predators. Biomagnification of methylmercury takes place among vertebrates at the higher trophic levels, but this process is less elucidated in benthic invertebrates at the lower trophic levels. Therefore, we investigated the accumulation from food and elimination of methylmercury and inorganic mercury in the benthic sea star Asterias rubens (L.) - a representative of trophic level ~3 - in laboratory experiments. Sea stars fed over 49 days with contaminated mussels (Mytilus edulis) accumulate methylmercury and inorganic mercury to the highest concentrations in the digestive glands, the pyloric caeca, less in stomach, gonad, tube feet, aboral body wall and not to detectable levels in the coelomic fluid. Concerning whole body contents, steady states were reached for both methylmercury and inorganic mercury during the 7-week feeding period and the sea stars reached approximately ½ and ¼ of the concentrations in the mussel food for the two mercury forms, respectively. Half-lives for the elimination of the two mercury forms varied between 45 and 173 days in a 140-d elimination period following the feeding period; inorganic mercury was eliminated faster than methylmercury. Examination of total mercury concentrations in field-collected sea stars confirmed this lack of trophic magnification in relation to the major food items, soft parts of molluscs. We suggest that mercury is not trophically magnified in sea stars 1) because they eliminate methylmercury faster than larger fish and decapod crustaceans and 2) maybe more importantly, because inorganic mercury with its faster elimination constitutes a larger fraction of the total mercury in the food at the lower trophic levels - as opposed to methylmercury which dominates at the higher trophic levels.
甲基汞在水生食物链的顶端积累，对人类和其他顶级捕食者构成了毒理学风险。在较高营养级别的脊椎动物中，甲基汞发生生物放大作用，但在较低营养级别的底栖无脊椎动物中，这一过程的了解较少。因此，我们在实验室实验中研究了底栖海星 Asterias rubens（L.）——代表营养级~3——从食物中积累和消除甲基汞和无机汞的情况。海星在被污染的贻贝（Mytilus edulis）中喂食 49 天后，甲基汞和无机汞在消化腺、幽门盲囊中积累到最高浓度，在胃、性腺、管足、体壁背面的浓度较低，在体腔液中未检测到。就整个身体的含量而言，在 7 周的喂养期内，甲基汞和无机汞达到了稳定状态，海星对这两种汞形态的浓度分别达到贻贝食物浓度的约 1/2 和 1/4。在喂养期结束后的 140 天消除期内，两种汞形态的消除半衰期在 45 至 173 天之间变化；无机汞的消除速度快于甲基汞。对从野外采集的海星进行的总汞浓度检测证实，与主要食物（软体动物）相比，这种汞在营养级上没有放大。我们认为，汞在海星中没有营养放大作用，1）是因为它们消除甲基汞的速度比大型鱼类和十足目甲壳类动物快，2）更重要的是，因为在较低营养级别的食物中，消除速度较快的无机汞构成了总汞的更大部分——而不是在较高营养级别的食物中占主导地位的甲基汞。
