The mobilization of rare earth elements (REEs) in aquatic ecosystems is expected to rise significantly due to intensified exploitation, erosion, and climate change. As a result, more attention has been brought to study their environmental fate. However, our ability to assess contamination risks in freshwater organisms remains limited due to scarce data on the composition and accumulation of REEs. Understanding how organisms bioaccumulate REEs requires knowledge of their environmental conditions, exposure pathways, and ecological characteristics—areas few studies have explored. In this study, we examined the fate of REEs across abiotic (water, suspended sediments, and sediments) and biotic (invertebrates and fishes) compartments in the St. Lawrence River (Canada), identifying the main drivers of their accumulation and relative composition. The results were consistent with REE biodilution along the food chain, with concentrations greater in suspended (REEs = 76.1–241.4 μg g−1) and bulk sediments (REEs = 4.2–204.2 μg g−1). Higher concentrations were found in fine-grained sediments, with a relative enrichment in middle REEs, likely due to REE adsorption onto Fe- or Mn-bearing minerals. Nonpredatory invertebrates ingesting suspended sediments, such as Ephemeroptera and Diptera larvae, exhibited higher concentrations of REEs than both filter-feeding species (i.e., mussels, polychaetes) and fish. Additionally, some amphipods displayed anomalous concentrations of gadolinium (Gd/Gd∗ = 5.7, 2.6, and 2.0), possibly originating from anthropogenic activities near Montreal Island. While fish bioaccumulated only light REEs in their liver, multiple regression models revealed how their length and the concentration of REEs in surrounding water—in dissolved form or as free ions—influenced their concentrations. Finally, benthivorous species like Moxostoma spp. and Ictalurus punctatus accumulated more REEs compared to piscivorous Sander spp., reflecting differences in feeding behavior and trophic level. Overall, these findings provide insights into how REE concentrations and compositions varied among organisms, likely due to differences in environmental conditions and ecological characteristics.

中文翻译：

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加拿大东部受自然和人为来源影响的大型河流系统非生物和生物隔间中的稀土元素积累和模式


由于开发加剧、侵蚀和气候变化，预计水生生态系统中稀土元素 （REE） 的动员将显着增加。因此，人们更多地关注研究它们的环境命运。然而，由于稀土元素的组成和积累数据稀缺，我们评估淡水生物污染风险的能力仍然有限。了解生物体如何生物积累 REE 需要了解其环境条件、暴露途径和生态特征——很少有研究探索的领域。在这项研究中，我们检查了圣劳伦斯河（加拿大）非生物（水、悬浮沉积物和沉积物）和生物（无脊椎动物和鱼类）隔间的 REE 的命运，确定了其积累和相对组成的主要驱动因素。结果与食物链沿线的 REE 生物稀释一致，悬浮液 （REE = 76.1–241.4 μg g-1） 和大块沉积物 （REE = 4.2-204.2 μg g-1） 中的浓度更高。在细粒沉积物中发现浓度较高，在中 REE 中相对富集，这可能是由于 REE 吸附到含 Fe 或 Mn 的矿物上。摄入悬浮沉积物的非捕食性无脊椎动物，如蜉蝣目和双翅目幼虫，表现出比滤食物种（即贻贝、多毛类）和鱼类更高的稀土元素浓度。此外，一些片足类动物表现出异常浓度的钆 （Gd/Gd∗ = 5.7、2.6 和 2.0），可能来自蒙特利尔岛附近的人为活动。 虽然鱼类在肝脏中仅生物积累了轻质 REE，但多元回归模型揭示了它们的长度和周围水中 REE 的浓度（以溶解形式或自由离子形式）如何影响它们的浓度。最后，与食鱼性 Sander 属相比，Moxostoma spp. 和 Ictalurus punctatus 等底食性物种积累了更多的 REE，反映了摄食行为和营养水平的差异。总体而言，这些发现提供了对 REE 浓度和组成如何因生物体而异的见解，这可能是由于环境条件和生态特征的差异。