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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., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Marie-Christine Lafreniere reports financial support was provided by Quebec Research Fund Nature and Technology. Marc Amyot reports financial support was provided by Natural Sciences and Engineering Research Council of Canada. Jean-Francois Lapierre reports financial support was provided by Natural Sciences and Engineering Research Council of Canada. Marc Amyot reports financial support was provided by Canada Research Chairs Program. Gilbert Cabana reports financial support was provided by Réseau Québec Maritime. Gesche Winkler reports financial support was provided by Réseau Québec Maritime. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

A mining tailing dam rupture in Brazil in November 2015 released millions of tons of mining waste into the Rio Doce ecosystem, leading to long-term aquatic ecosystem impacts. Although multiple lines of evidence indicate tailings associations with potentially toxic elements in estuarine sediments and biological impact and bioaccumulation pathways in fishes, the extent of contamination in base benthic species is still largely unknown. Moreover, Rare Earth Elements (REE) have not received any attention in this regard. This study assessed REE in fiddler crabs (Minuca rapax) sampled from the Rio Doce estuary in 2017, nearly 2 years after the disaster. The ΣREE in crab hepatopancreas and muscle were high (327.83 mg kg -1 w.w. and 33.84 mg kg -1 w.w., respectively, compared to other assessments in crabs, indicating a preference for REE bioaccumulation in the hepatopancreas compared to muscle. Neodimium, La, and Ce were detected at the highest concentrations. The REE from the Rio Doce Basin were, thus, transported and deposited in the estuary with the mine tailings slurry, leading to bioaccumulation in crabs. This may lead to trophic effects and other ecological impacts not readily measured by typical impact assessment studies, revealing an invisible and not typically acknowledged damage to the Rio Doce estuary., Competing Interests: Declarations. Competing interests: The authors declare no competing interests., (© 2024. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

The presence of rare earth elements (REE) in the southern hemisphere, particularly marine ecosystems of Patagonia, have received little attention. The Magellanic penguin, which is also known as the Patagonian penguin, inhabits only in austral regions of South America. Although seabird feathers have been used extensively as a bio-monitoring tool, no studies have addressed the effect of age on REE accumulation in Magellanic penguins. In this study, the concentrations of REE were determined by ICP-MS to detect La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Sc, Lu and Y in the feathers of Magellanic penguins from Magdalena Island, an important rookery in the Strait of Magallan. Age-related differences were studied to investigate the different patterns of REE bioaccumulation between adults and juveniles. The data showed that juvenile penguins exhibit higher REE-levels than adult individuals (p < 0.05). Mean REE-values (μg g -1 d.w) differed several orders of magnitude, ranging from 0.002 for Lu in adults to 1.15 for Ce in juvenile individuals. The results are useful to understand the bioaccumulation of REE in fauna from remote and cold regions of the southern hemisphere., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

The importance of rare earth elements is increasingly recognized due to the increased demand for their mining and separation. This demand is driving research on the biology of rare earth elements. Biomolecules associated with rare earth elements include rare earth element-dependent enzymes (methanol dehydrogenase XoxF, ethanol dehydrogenase ExaF/PedH), rare earth element-binding proteins, and the relevant metallophores. Traditional (chemical) separation methods for rare earth elements harvesting and separation are typically inefficient, while causing environmental problems, whereas bioharvesting, potentially, offers more efficient, more green platforms. Here, we review the current state of research on the biological functions of rare earth element-dependent biomolecules, and the characteristics of the relevant proteins, including the specific amino acids involved in rare earth metal binding. We also provide an outlook at strategies for further understanding of biological processes and the potential applications of rare earth element-dependent enzymes and other biomolecules., (© The Author(s) 2024. Published by Oxford University Press on behalf of the International Society for Microbial Ecology.)

Rare Earth Elements and Yttrium (REY) are widely used as proxies for environmental conditions and biogeochemical processes, but have also become (micro)contaminants of surface waters worldwide. Soft tissues and shells of mussels are increasingly used in environmental science and geology as bioarchives for REY, but REY fractionation by and in these organisms is still not well understood. We report on the distribution of REY in different compartments of marine M. edulis mussels from Norway, and in their ambient water and food (plankton). The shale-normalised REY patterns of all compartments studied decrease from light to heavy REY (LREY and HREY, respectively), while the LREY depletion occasionally reported in the literature cannot be observed. The bivalves show REY concentrations up to five orders of magnitude higher than those in ambient water (with preferential uptake of Ce and of LREY over HREY) but lower than those in their potential plankton food (with minor REY fractionation, except for preferential uptake of La and Y). While metabolic REY fractionation within the bivalves is minor, vital effects affect the REY distribution in the shells of M. edulis mussels. Rejection and decoupling of Ce during shell formation occurs due to Ce oxidation and formation of Ce(IV) solution-complexes in the extrapallial fluid (EPF). While discrimination against HREY incorporation results from strong solution-complexation of the HREY, preferential uptake of La, Gd and Y during shell formation is due to the less stable solution-complexes of these ions. These observations are compatible with the presence of siderophores in the EPF, suggesting that in contrast to freshwater mussel A. anatina, vital effects can to some extent affect the size of anomalies in the REY patterns of marine M. edulis shells. This implies that these anomalies are (partially) of biological origin, which limits their use as paleo-redox proxies., Competing Interests: Declaration of competing interest We, the authors, declare that we have no conflicts of interest to this work. There are no commercial or associative interests that could pose a conflict of interest in connection with the submitted research., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

The ontogenetic bioaccumulation of trace elements in marine species is influenced by both biotic and abiotic factors, including parasitic infestation. The Mackerel icefish (Champsocephalus gunnari) plays a significant role in the Antarctic ecosystem. Yet the impact of parasites on trace element accumulation in this species remains unclear. This study aims to gain insight into the ontogenetic accumulation patterns of trace elements in C. gunnari and how parasitic infestations affect these patterns. Two ectoparasites (Eubrachiella antarctica and Notobdella nototheniae) were found on C. gunnari, but no endoparasites were detected. Concentrations of 34 elements in C. gunnari were analyzed, including essential elements (e.g., Ca, Mg, P), trace elements (e.g., As, Co, Cr, Cu, Fe, Mn, Mo, Ni, V, Zn, Li, Ti, Ba, Cd, Pb, Sr, Zr, Ga, Rb, Cs), and rare earth elements (e.g., Sc, Ce, Eu, Gd, La, Nd, Pr, Sm, Dy, Er, Yb). Major essential elements, such as magnesium (Mg, 1420-2380 μg g -1 ) and calcium (Ca, 436-1850 μg g -1 ), were significantly higher than minor elements like zinc (Zn, 19.5-29.3 μg g -1 ) and iron (Fe, 6.59-19.4 μg g -1 ) in both infested and non-infested fish. Strontium (Sr), though a non-essential element exhibited concentrations comparable to Fe of ranging from 2.45 to 13.6 μg g -1 . Although the rare earth elements were detected, their concentrations were significantly lower, several orders of magnitude below those of the major and trace elements. Scandium (Sc, 0.06-0.27 μg g -1 ) was the only rare earth element comparable in magnitude to certain trace elements. Parasitic infestation altered the relationships between certain elements (e.g., P, Zn, and Dy) and fish length, as well as (e.g., Li, Co, Cu, and Sr) with fish weight. Nevertheless, all elements displayed consistent relationships with the condition factor, regardless of parasitic infestation, indicating that it remains a reliable indicator of trace element bioaccumulation in C. gunnari, even in the presence of ectoparasites., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)