Chronic Radiation Exposure at Chernobyl Shows No Effect on Genetic Diversity in the Freshwater Crustacean, Asellus aquaticus Thirty Years On

International audienceAnalysis of genetic diversity represents a fundamental component of ecological risk assessments in contaminated environments. Many studies have assessed the genetic implications of chronic radiation exposure at Chernobyl, generally recording an elevated genetic diversity and mutation rate in rodents, plants and birds inhabiting contaminated areas. Only limited studies have considered genetic diversity in aquatic biota at Chernobyl, despite the large number of freshwater systems where elevated dose rates will persist for many years. Consequently the present study aimed to assess the effects of chronic radiation exposure on genetic diversity in the freshwater crustacean, Asellus aquaticus, using a genome-wide SNP approach (Genotyping-by-sequencing). It was hypothesised that genetic diversity in A. aquaticus would be positively correlated with dose rate. A. aquaticus was collected from six lakes in Belarus and the Ukraine ranging in dose rate from 0.064 to 27.1 µGy/hr. Genotyping-by-sequencing analysis was performed on 74 individuals. A significant relationship between geographical distance and genetic differentiation confirmed the Isolation-by-Distance model. Conversely, no significant relationship between dose rate and genetic differentiation suggested no effect of the contamination gradient on genetic differentiation between populations. No significant relationship between five measures of genetic diversity and dose rate were recorded, suggesting that radiation exposure has not significantly influenced genetic diversity in A. aquaticus at Chernobyl. This is the first study to adopt a genome-wide SNP approach to assess the impacts of environmental radiation exposure on biota. These findings are fundamental to understanding the long-term success of aquatic populations in contaminated environments at Chernobyl and Fukushima

Genetic alterations and cancer formation in a European flatfish at sites of different contamination burdens

Fish diseases are an indicator for marine ecosystem health since they provide a biological end-point of historical exposure to stressors. Liver cancer has been used to monitor the effects of exposure to anthropogenic pollution in flatfish for many years. The prevalence of liver cancer can exceed 20%. Despite the high prevalence and the opportunity of using flatfish to study environmentally induced cancer, the genetic and environmental factors driving tumor prevalence across sites are poorly understood. This study aims to define the link between genetic deterioration, liver disease progression, and anthropogenic contaminant exposures in the flatfish dab (Limanda limanda). We assessed genetic changes in a conserved cancer gene, Retinoblastoma (Rb), in association with histological diagnosis of normal, pretumor, and tumor pathologies in the livers of 165 fish from six sites in the North Sea and English Channel. The highest concentrations of metals (especially cadmium) and organic chemicals correlated with the presence of tumor pathology and with defined genetic profiles of the Rb gene, from these sites. Different Rb genetic profiles were found in liver tissue near each tumor phenotype, giving insight into the mechanistic molecular-level cause of the liver pathologies. Different Rb profiles were also found at sampling sites of differing contaminant burdens. Additionally, profiles indicated that histological “normal” fish from Dogger sampling locations possessed Rb profiles associated with pretumor disease. This study highlights an association between Rb and specific contaminants (especially cadmium) in the molecular etiology of dab liver tumorigenesis

Hepatocellular adenoma in a European flatfish (Limanda limanda) : genetic alterations in laser-capture microdissected tissue and global transcriptomic approach

Liver tumours in flatfish have been diagnosed using histopathology for decades to monitor the impacts of marine pollution. Here we describe the application of specific gene (retinoblastoma, Rb) profiling in laser capture micro-dissected samples, and a suppression subtractive hybridization (SSH) approach to isolate differentially expressed genes in hepatocellular adenoma (HCA) samples from dab, Limanda limanda. The Rb profiles from apparently normal and HCA micro-dissected samples of fish from the North Sea showed no significant difference, and genotypic heterogeneity within defined histological phenotypes was observed. In the SSH, sequences associated with cell signalling, cell cycle, gene expression regulation, protein transport and protein degradation were isolated. These included up-regulation of arrestin domain containing 3 (arrdc3), Rac-1 and tribbles, and down-regulation of ankyrin repeat/sterile alpha-motif domain-containing protein 1B-like (ANKS1B-like), c-fos, CDKN1B and RhoA-like sequences, previously implicated in mammalian HCA. This study offers new candidates involved in fish liver tumour development

Impact of environmental radiation on the health and reproductive status of fish from Chernobyl

Aquatic organisms at Chernobyl have now been chronically exposed to environmental radiation for three decades. The biological effects of acute exposure to radiation are relatively well documented, but much less is known about the long - term effects of chronic exposure of organisms in their natural environment. Highly exposed fish in freshwater systems at Chernobyl showed morphological changes in their reproductive system in the years after the accident. However, the relatively limited scope of past studies did not allow robust conclusions to be drawn. Moreover, the level of the radiation dose at which significant effects on wildlife occur is still under debate. In the most comprehensive evaluation of the effects of chronic radiation on wild fish populations to date, the present study measures specific activities of 137Cs, 90Sr and transuranium elements (238Pu, 239,240Pu and 241Am), index conditions, distribution and size of oocytes, as well as environmental and biological confounding factors in two fish species perch (Perca fluviatilis) and roach (Rutilus rutilus) from seven lakes. In addition, relative species abundance was examined. The results showed that both fish species are, perhaps surprisingly, in good general physiological and reproductive health. Perch, however, appeared to be more sensitive to radiation than roach: in the most contaminated lakes, a delay of the maturation of the gonads and the presence of several undeveloped phenotypes were evident only for perch and not for roach

Evaluation of cataract formation in fish exposed to environmental radiation at Chernobyl and Fukushima

Recent studies apparently finding deleterious effects of radiation exposure on cataract formation in birds and voles living near Chernobyl represent a major challenge to current radiation protection regulations. This study conducted an integrated assessment of radiation exposure on cataractogenesis using the most advanced technologies available to assess the cataract status of lenses extracted from fish caught at both Chernobyl in Ukraine and Fukushima in Japan. It was hypothesised that these novel data would reveal positive correlations between radiation dose and early indicators of cataract formation.The structure, function and optical properties of lenses were analysed from atomic to millimetre length scales. We measured the short-range order of the lens crystallin proteins using Small Angle X-Ray Scattering (SAXS) at both the SPring-8 and DIAMOND synchrotrons, the profile of the graded refractive index generated by these proteins, the epithelial cell density and organisation and finally the focal length of each lens.The results showed no evidence of a difference between the focal length, the epithelial cell densities, the refractive indices, the interference functions and the short-range order of crystallin proteins (X-ray diffraction patterns) in lens from fish exposed to different radiation doses. It could be argued that animals in the natural environment which developed cataract would be more likely, for example, to suffer predation leading to survivor bias. But the cross-length scale study presented here, by evaluating small scale molecular and cellular changes in the lens (pre-cataract formation) significantly mitigates against this issue

Impact of environmental radiation on the health and reproductive status of fish from Chernobyl

© 2018 American Chemical Society. Aquatic organisms at Chernobyl have now been chronically exposed to environmental radiation for three decades. The biological effects of acute exposure to radiation are relatively well documented, but much less is known about the long-term effects of chronic exposure of organisms in their natural environment. Highly exposed fish in freshwater systems at Chernobyl showed morphological changes in their reproductive system in the years after the accident. However, the relatively limited scope of past studies did not allow robust conclusions to be drawn. Moreover, the level of the radiation dose at which significant effects on wildlife occur is still under debate. In the most comprehensive evaluation of the effects of chronic radiation on wild fish populations to date, the present study measures specific activities of 137Cs, 90Sr, and transuranium elements (238Pu, 239,240Pu, and 241Am), index conditions, distribution and size of oocytes, as well as environmental and biological confounding factors in two fish species perch (Perca fluviatilis) and roach (Rutilus rutilus) from seven lakes. In addition, relative species abundance was examined. The results showed that both fish species are, perhaps surprisingly, in good general physiological and reproductive health. Perch, however, appeared to be more sensitive to radiation than roach: in the most contaminated lakes, a delay of the maturation of the gonads and the presence of several undeveloped phenotypes were evident only for perch and not for roach

Spatio-temporal contamination of microplastics in shellfish farming regions: A case study

International audienceThe seasonal pattern of microplastics (MPs) contamination of the French littoral area of the Pertuis Charentais, one of the main French shellfish production regions, was assessed for the first time, between May 2019 and May 2020 at four different sites. The reference site was located at “Ile de Ré” and the other sites were located in the estuaries of the Sèvre Niortaise, Charente and Seudre rivers. Both blue mussels (Mytilus edulis) and Pacific oysters (Magallana gigas), that are considered sentinel species for the quality of the marine environment were analysed, along with sediment and seawater samples. MPs were extracted from each sample, counted, measured and sorted by colour and type. Micro-Raman spectroscopy was used to determine the proportion of confirmed MPs and the polymer types. The results showed that the contamination of mussels by fibres and fragments (1.9 ± 2.1 MPs/g ww) was significantly higher than for oysters (0.4 ± 0.4 MPs/g ww). Specifically, the contamination by fibres in both species was significantly greater than the contamination by fragments. Significant variations of MPs contamination were observed across the seasons and sites in bivalves, and depended on the species and the type of MPs (fibres or fragments). Mean concentrations of MPs measured in water and sediment were 0.007 MPs/L and 210 MPs/kg dw, respectively. Finally, blue was the dominant colour for fibres (79%) and fragments (81%). Blue fragments were mainly made of PS (70%) followed by PC (18%) and PP, PA or PLA (3%) whereas blue fibres were mainly made of PA (80%) followed by PET (13%) or PP (7%). This rare environmental case study of long-term chronic exposure of farming areas to MPs provides new knowledge on in situ variations of plastic fibres and fragments contamination throughout the seasons

Development and validation according to the SANTE guidelines of a QuECh-ERS-UHPLC-QTOF-MS method for the screening of 204 pesticides in bivalves

International audienceA qualitative screening high resolution mass spectrometry method was developed and validated according to the EU SANTE/12682/2019 guidelines for the analysis of 204 pesticides in seven commercial bivalve species spiked at three concentrations (0.01, 0.05 and, 0.1 mg.kg−1). Samples were extracted using QuEChERS and analysed using ultra-high-performance liquid chromatography coupled to quadrupole time-of-flight mass spectrometry. The QuEChERS method was optimised by the Taguchi Orthogonal Array approach. The best conditions were obtained with pure ACN, MgSO4/NaCl as extraction salts, MgSO4/PSA/C18 as clean-up, and the non-dilution of extracts. The impact of different HRMS acquisition modes on detection and identification rates were also evaluated. The screening detection limits were determined to be 0.01 mg.kg−1 and 0.1 for 66% and 87% of pesticides, respectively. These screening procedure was finally applied to different bivalve samples using target and suspect analysis. This allowed the identification of diuron and its metabolite 1-(3,4-dichlorophenyl)-3-methylurea in the investigated sample