Role of prey subcellular distribution on the bioaccumulation of yttrium (Y) in the rainbow trout

Trophic dilution of rare earth elements along the food chain of the Seine estuary (France)

Society's interest in rare earth elements (REEs) and their increasing use in many fields is leading to enrichments in aquatic environments, such as estuaries. This study of the Seine estuary assessed the distribution of REEs along the food web, including different species from 5 phyla representing different trophic levels. Total REE concentrations, which were higher in algae, mollusks, crustaceans and annelids (4.85-156; 1.59-4.08; 2.48 ± 1.80 and 0.14 ± 0.11 μg/g dw, respectively) than in vertebrates (0.03-0.15 μg/g dw), correlated with δ15N indicated a trophic dilution. REE contributions in the studied species were higher for light REEs than for heavy and medium REEs. Positives anomalies for Eu, Gd, Tb and Lu were highlighted particularly in vertebrates, possibly due to species-dependent bioaccumulation/detoxification or related to anthropogenic inputs. The calculated BAF and BSAF indicated an important partitioning of REEs in organisms compared to the dissolved phase and a limited transfer from sediment to organisms.

Global natural concentrations of Rare Earth Elements in aquatic organisms: Progress and lessons from fifty years of studies

Rare Earth Elements (REEs) consist of a coherent group of elements with similar physicochemical properties and exhibit comparable geochemical behaviors in the environment, making them excellent tracers of environmental processes. For the past 50 years, scientific communities investigated the REE concentrations in biota through various types of research (e.g. exploratory studies, environmental proxies). The extensive development of new technologies over the past two decades has led to the increased exploitation and use of REEs, resulting in their release into aquatic ecosystems. The bioaccumulation of these emerging contaminants has prompted scientific communities to explore the fate of anthropogenic REEs within aquatic ecosystems. To achieve this, it is necessary to determine the natural concentration levels of REEs in aquatic organisms and the factors controlling REE dynamics. However, knowledge gaps still exist, and no comprehensive approach currently exists to assess the REE concentrations at the ecosystem scale or the factors controlling these concentrations in aquatic organisms. Based on a database comprising 102 articles, this study aimed to: i) provide a retrospective analysis of research topics over a 50-year period; ii) establish reference REE concentrations in several representative phyla of aquatic ecosystems; and iii) examine the global-scale influences of habitat and trophic position as controlling factors of REE concentrations in organisms. This study provides reference concentrations for 16 phyla of freshwater or marine organisms. An influence of habitat REE concentrations on organisms has been observed on a global scale. A trophic dilution of REE concentrations was highlighted, indicating the absence of biomagnification. Lastly, the retrospective approach of this study revealed several research gaps and proposed corresponding perspectives to address them. Embracing these perspectives in the coming years will lead to a better understanding of the risks of anthropogenic REE exposure for aquatic organisms.

Trophic transfer of rare earth elements in the food web of the Loire estuary (France)

The increasing use of rare earth elements (REEs) in many industrial sectors and in medecine, causes discharges into the environment and particularly in estuarine areas subjected to strong anthropogenic pressures. Here, we assessed the distribution of REEs along the food web of the Loire estuary. Several species representative of different trophic levels were sampled: 8 vertebrates, 3 crustaceans, 2 mollusks, 3 annelids and 4 algae, as well as Haploops sp. tubes rather related to sediment. The total REE concentrations measured by ICP-MS were the highest in Haploops sp. tubes (141.1 ± 4.7 μg/g dw), algae (1.5 to 34.5 μg/g dw), mollusks (9.9 to 12.0 μg/g dw), annelids (0.7 to 19.9 μg/g dw) and crustaceans (1.4 to 6.3 μg/g dw) and the lowest in vetebrates (0.1 to 1.6 μg/g dw). The individual contribution of REEs was, however, similar between most studied species with a higher contribution of light REEs (76.7 ± 7.6 %) compared to heavy REEs (14.1 ± 3.7 %) or medium REEs (9.2 ± 5.8 %). Trophic relations were estimated by stable isotope analysis of C and N and the linear regression of δ15N with total REE concentrations highlighted a trophic dilution with a corresponding TMS of -2.0. The tissue-specific bioaccumulation investigated for vertebrates demonstrated a slightly higher REE accumulation in gonads than in the muscle. Finally, positive Eu, Gd, Tb and Lu anomalies were highlighted in the normalized REE patterns of most studied species (especially in fish and crustaceans), which is consistent with results in the dissolved phase for Eu and Gd. These anomalies could either be due to anthropogenic inputs or to various bioaccumulation/elimination processes according to the specific species physiology. This study, including most of the trophic levels of the Loire estuary food web provides new insights on the bioaccumulation and trophic transfer of REEs in natural ecosystems.

Rare earth element bioaccumulation and cerium anomalies in biota from the Eastern Canadian subarctic (Nunavik)

Recent increases in the demand for rare earth elements (REE) have contributed to various countries' interest in exploration of their REE deposits, including within Canada. Current limited knowledge of REE distribution in undisturbed subarctic environments and their bioaccumulation within northern species is addressed through a collaborative community-based environmental monitoring program in Nunavik (Quebec, Canada). This study provides background REE values (lanthanides + yttrium) and investigates REE anomalies (i.e., deviations from standard pattern) across terrestrial, freshwater, and marine ecosystems in an area where a REE mining project is in development. Results are characteristic of a biodilution of REE, with the highest mean total REE concentrations (ΣREE) reported in sediments (10² nmol/g) and low trophic level organisms (i.e., biofilm, macroalgae, macroinvertebrates, common mussels, and reindeer lichens; 10¹-10² nmol/g), and the lowest mean concentrations in higher-level consumers (i.e., goose, ptarmigan, char, whitefish, cod, sculpin and seal; 10^-2 - 10¹ nmol/g). The animal tissues are of importance to northern villages and analyses demonstrate a species-specific bioaccumulation of REE, with mean concentrations up to 40 times greater in liver compared to muscle, with bones and kidneys presenting intermediate concentrations and the lowest in blubber. Further, a tissue-specific fractionation was presented, with significant light REE (LREE) enrichment compared to heavy REE (HREE) in consumer livers (LREE/HREE ≅ 10¹) and the most pronounced negative cerium (Ce) anomalies (<0.80) in liver and bones of fish species. These fractionation patterns, along with novel negative relationships presented between fish size (length, mass) and Ce anomalies suggest metabolic, ecological, and/or environmental influences on REE bioaccumulation and distribution within biota. Background concentration data will be useful in the establishment of REE guidelines; and the trends discussed support the use of Ce anomalies as biomarkers for REE processing in animal species, which requires further investigation to better understand their controlling factors.

From geochemistry to ecotoxicology of rare earth elements in aquatic environments: Diversity and uses of normalization reference materials and anomaly calculation methods

The geochemistry of rare earth elements (REEs) has been studied for a long time and has allowed us to highlight enrichments or depletions of REEs in aquatic ecosystems and to estimate anthropogenic inputs through normalization of data to different reference materials. This review of current literature on REE normalization highlighted the large number of different reference materials (a total of 12), as well as different anomaly calculation methods. This statement showed a real need for method harmonization to simplify the comparison between studies, which is currently very difficult. Normalization to Post-Archean Australian Shale (PAAS) emerged as being the most used (33 % of reported studies) regardless of the location and the nature of the studied samples and seem to be of higher quality. The interest of other reference materials was nevertheless underlined, as they could better represent the geographical situation or the nature of samples. Two main anomaly calculation methods have been highlighted: the linear interpolation/extrapolation and the geometric extrapolation using logarithmic modeling. However, due to variations in the estimation of neighbors' values, these two methods produce many different equations for the anomaly calculation of a single element. Current normalization practices based on shales and chondrites are suitable for abiotic samples but are questionable for biota. Indeed, normalization is increasingly used in studies addressing ecotoxicological issues which focus on biota and often aim to estimate the anthropogenic origin of bioaccumulated REEs. Due to the interspecific variability, as well as the complexity of mechanisms occurring in organisms when exposed to contaminants, new reference materials need to be established to consider the bioaccumulation/metabolization processes and the anthropogenic inputs of REEs based on the results of biotic samples.

Lanthanides Toxicity in Zebrafish Embryos Are Correlated to Their Atomic Number

Rare earth elements (REEs) are critical metallic materials with a broad application in industry and biomedicine. The exponential increase in REEs utilization might elevate the toxicity to aquatic animals if they are released into the water due to uncareful handling. The specific objective of our study is to explore comprehensively the critical factor of a model Lanthanide complex electronic structures for the acute toxicity of REEs based on utilizing zebrafish as a model animal. Based on the 96 h LC₅₀ test, we found that the majority of light REEs display lower LC₅₀ values (4.19–25.17 ppm) than heavy REEs (10.30–41.83 ppm); indicating that they are atomic number dependent. Later, linear regression analyses further show that the average carbon charge on the aromatic ring (aromatic C_avg charge) can be the most significant electronic structural factor responsible for the Lanthanides’ toxicity in zebrafish embryos. Our results confirm a very strong correlation of LC₅₀ to Lanthanide’s atomic numbers (r = 0.72), Milliken charge (r = 0.70), and aromatic C_avg charge (r = −0.85). This most significant correlation suggests a possible toxicity mechanism that the Lanthanide cation’s capability to stably bind to the aromatic ring on the residue of targeted proteins via a covalent chelating bond. Instead, the increasing ionic bond character can reduce REEs’ toxicity. In addition, Lanthanide toxicity was also evaluated by observing the disruption of photo motor response (PMR) activity in zebrafish embryos. Our study provides the first in vivo evidence to demonstrate the correlation between an atomic number of Lanthanide ions and the Lanthanide toxicity to zebrafish embryos.

Rare earth element organotropism in European eel (Anguilla anguilla)

Rare earth elements (REEs) are metallic elements with electronic, magnetic, optical and catalytic properties which make them essential in many industrial and medical fields. REEs are therefore becoming emerging pollutants and it is important to understand their implications for ecosystem health. However, little knowledge of REE bioaccumulation in aquatic organisms is available and especially on their internal distribution in fish. In the present study, REE organotropism was determined in Anguilla anguilla from the Loire estuary (France) by determining burdens in a wide set of tissues, organs and biological fluids. Differences have been observed between life stages and genders. For yellow eels, the most accumulating organ was the gills (126.90 ± 50.78 μg/kg dw) and for silver eels, it was the liver (181.78 ± 62.04 μg/kg dw for males; 203.79 ± 111.86 μg/kg dw for females). The comparison between female silver and yellow eels shown that female silver individuals accumulated significantly more REEs in the urinary system (US), muscles, gonads, spleen and liver, while yellow individuals accumulated more in gills. The comparison between male and female silver eels also highlighted differences, indeed the females accumulated significantly more REEs in the US, gonads, skin and spleen, compared to males which accumulated significantly more in muscles and gills. REEs abundances are also different between organs, life stages and genders. The gonads of female silver eels exhibited a particular profile with the dominance of gadolinium (Gd) (up to 74.2% of ∑REEs). Moreover, the presence of Anguillicola crassus in the swim bladder of organisms seemed to have an impact on REE bioaccumulation: parasitized yellow eels present higher concentrations of REEs in muscles, gills, gonads and liver than non-parasitized individuals. Regarding glass eels, REE contribution profiles in the whole body were close to those of yellow and silver eel skin.