Fate and Trophic Transfer of Rare Earth Elements in Temperate Lake Food Webs

Many mining projectS targeting rare earth 4 elements (REE) are in development in North America, but the background concentrations and trophic transfer of these elements in natural environments have not been well characterized. We sampled abiotic and food web components, in 14 Canadian temperate lakes unaffected :by mines to assess 1; the natural ecosystem fate of REE. Individual REE and total REE concentrations, (suit of individual element concentrations FREE) were strongly related with each other throughout different components of lake food webs. Dissolved organic carbon and dissolved oxygen in the water column, as well as Sigma REE in sediments, were identified as potential drivers of aqueous Sigma REE. Log(10) of median bioaccumulation factors ranged from 1.3, 3.7, 4.0, and 4.4 L/kg (wet weight) for fish muscle, zooplankton, predatory invertebrates, and nonpredatory invertebrates, respectively. [Sigma REE] in fish, benthic macroirivertebrates,,and zooplankton declined as a function of their trophic position, as determined by functional feeding groups and isotopic signatures of nitrogen (delta N-15), indicating that REE were subject to trophic dilution. Low concentrations of REE in freshwater fish muscle,compared to, their potential invertebrate prey suggest that fish fillet consumption is unlikely to be a significant source of REE to humans in areas unperturbed by mining activities. However, other fish predators (e.g., piscivorous birds and mammals) may accumulate REE from whole fish as they are more concentrated than muscle. Overall, this study provides key information on the baseline concentrations and trophic patterns for REE in freshwater temperate lakes in Quebec, Canada. .