Naturally occurring radioactive substances in freshwater ecosystems pose potential radiological risks to both aquatic organisms and humans through dietary exposure. This study quantified the activity concentrations of [228]Ra, [210]Pb, [226]Ra, [210]Po and [40]K in ten commonly consumed fish species from the Red River, Vietnam. The results showed significant inter-isotope variability, with [40]K dominating all samples. Mean activity concentrations were 1.22 ± 0.2 (LOD-7.61) for [228]Ra, 9.1 ± 1.7 (LOD-37.1) for [210]Pb, 7.69 ± 1.04 (0.70-24.7) for [226]Ra, 11.8 ± 0.9 (5.16-18.7) for [210]Po, and 101 ± 8.6 (65-169) Bq.kg[-1] for [40]K. These variations reflect the different behaviors of the isotopes in aquatic environments. Negative correlation was observed between [226]Ra and body weight, suggesting morphological influences on radioactivity absorption in fish. Radiation risk assessments revealed average annual effective doses of 0.105 mSv.y[-1] (0.030-0.247 mSv.y[-1]), significantly lower than the safety threshold, with lifetime cancer risks ranging from 1.4 × 10[-7] to 7.7 × 10[-7], within acceptable limits. Ecological risk assessment using the ERICA Tool revealed total dose rates ranging from 0.2 to 10.4 µGy.h[-1] (mean: 3.0 µGy.h[-1]), with the Zig-zag eel exceeding the screening threshold of 10 µGy·h[-1], indicating a potential radiological risk for this species, while risks remained negligible for the remaining species. These findings enhance understanding of radionuclide dynamics in freshwater food webs and inform public health risk assessments for fish consumption in the Red River basin. The study establishes essential baseline data for regional radiation monitoring programs while contributing to biodiversity protection and food safety.

The presence of microplastics (MPs) in freshwater environments represents a growing environmental concern due to their persistence and ability to interact with contaminants such as pesticides. This study evaluated the influence of photodegradation on the toxicity of polyethylene microplastics (PE-MPs), alone and combined with the pesticide Imidacloprid (IMI), on the cladoceran Daphnia similis. Microparticles of polyethylene were aged under UV-C radiation for 94 days and subsequently characterized by Scanning Electron Microscopy (SEM) and Fourier-Transform Infrared Spectroscopy (FTIR). Surface analysis indicated polymer degradation through cracks and cavities, and increased surface roughness, while FTIR analyses showed polymer oxidation. Ecotoxicological results revealed that pristine MPs significantly reduced survival by 90% at 80 mg L[-1], while photodegraded MPs caused more pronounced sublethal effects, particularly on reproduction, with a 69.8% reduction in neonates at 140 mg L[-1]. When associated with IMI, significant reductions in reproduction were observed, with a decrease of up to 75.7% in the number of neonates. However, the presence of IMI attenuated the toxicity of PE-MPs, evidencing an antagonistic interaction between the contaminants, particularly at concentrations of 80 and 140 mg L[-1] of pristine PE-MPs. Taken together, these results demonstrate that the interactions between MPs and pesticides, as well as the state of particle degradation, significantly modulate ecotoxicological effects, posing a potential risk to the ecological integrity of aquatic ecosystems.

The present study investigates how host-parasite interactions influence mercury (Hg) distribution in the common toad (Bufo bufo) under contrasting environmental conditions. Using road-killed specimens as an ethical sampling source, Hg concentrations were quantified in multiple host tissues (muscle, liver, kidneys, lungs, and skin) and associated parasitic nematodes from two sites in eastern Slovakia with different contamination levels. In both populations, Hg accumulation followed a tissue-specific pattern, with the highest concentrations occurring in detoxification organs, particularly the kidneys and liver. Bayesian regression models revealed that habitat was the primary driver of Hg burdens, whereas biological factors, including sex and body condition factor, had no significant effect on host Hg concentrations. Parasitological analyses showed markedly higher infection levels at the contaminated site, with nematode prevalence reaching 100%, and females harbouring significantly higher parasite abundances than males. Morphometric analysis based on 14 measured traits revealed no differences between populations, suggesting that chronic Hg exposure did not induce detectable morphological divergence. Although parasite abundance was not a strong predictor of host Hg levels, bioconcentration factors indicated a concentration-dependent host-parasite interaction: under high environmental exposure, host detoxification organs accumulated more Hg than parasites, whereas at lower contamination levels, nematodes sequestered Hg more efficiently than host tissues. These findings emphasize that integrating host-parasite dynamics into ecotoxicological frameworks is essential for a comprehensive assessment of the biological fate of Hg in amphibian populations.

Pesticide contamination in tropical agricultural soils represents a growing concern due to its impacts on environmental integrity and human health, particularly in transition zones where intensive agricultural converges with coastal wetlands. This study aimed to identify and quantify pesticide residues in soils from northwestern Mexico. Forty-eight composite soil samples were collected within a ≈ 30,000 ha polygon surrounding the study area in the municipality of Santiago Ixcuintla, one of the most agriculturally productive regions of the country. Sampling sites were preselected using remote sensing and geographic information systems. Pesticide extraction was performed using a modified QuEChERS method, and compounds were analyzed by UPLC-MS/MS and GC-TQ-MS/IT-MS. Of the 73 validated pesticides, 26 active ingredients (31.5%) were detected, including 19 insecticides, six fungicides, and one herbicide. Organochlorine compounds were the most frequently detected, with p,p'-DDE present in 97.9% of samples and chlorpyrifos in 87.0%. Total pesticide concentrations (ΣPesticides) ranged from 10.3 to 1491 ng/g. The highest concentrations were observed at sites 27, 36, and 43, exceeding the European Union's soil limit (0.1 mg/kg). Spatial analysis revealed a heterogeneous distribution, with elevated concentrations associated with active agricultural areas and runoff pathways toward coastal wetlands. The predominance of chlorinated and aromatic pesticides indicates environmental persistence and bioaccumulation potential. These findings highlight the vulnerability of habitats adjacent to intensive agriculture and suggest that soils may function as contaminant reservoirs and secondary sources through dust resuspension or water transport. Improved understanding of pesticide degradation is essential for soil management strategies globally.

Wild boar (Sus scrofa) have been used as sentinel species for monitoring environmental metal contamination; however, developmental variation in internal metal distribution remains poorly understood in free-ranging wildlife. Here, we investigated organ-specific distribution patterns of copper (Cu), zinc (Zn), cadmium (Cd), and lead (Pb) by explicitly comparing fetal and non-fetal wild boar collected in western Japan. A total of 13 individuals, including eight fetuses from two pregnant females, the two pregnant females, one adult male, and two juveniles, were analyzed. Metal concentrations were determined in muscle, heart, liver, kidney, and femur using ICP-MS, and relative organ distributions were evaluated using non-metric multidimensional scaling and permutational multivariate analysis of variance. Developmental differences were apparent for Cu, Cd, and Pb, whereas Zn exhibited stable distribution patterns across stages, suggesting maintained physiological regulation. Fetal individuals showed pronounced hepatic enrichment of Cu, reflecting active placental transport and developmental hepatic storage. In contrast, Cd displayed renal dominance exclusively in non-fetal individuals, indicating postnatal accumulation, while Pb showed relatively greater femoral contributions in non-fetal individuals despite low absolute concentrations. Together, these results suggest that multi-organ distribution patterns provide useful insight into developmental metal partitioning beyond absolute concentration data and highlight the importance of incorporating developmental context into ecotoxicological assessments of free-ranging wildlife under natural exposure conditions.

The presence of potential toxic elements (PTEs) in water, soil, and plant resources poses a significant risk to human health. A field investigation on the content of PTEs and macronutrients in soils and 11 dominant plants (roots and shoots) from Ahangaran, a Pb-Zn mine in western Iran was carried out. The bioconcentration factors (BCF) for roots and shoots (BCF root, BCF shoot) based on both total and available PTEs and macronutrients in soils and translocation factors (TF) of 11 plant species were calculated. The average contents of total soil Cd, Cu, Ni, Pb, and Zn were 198, 124, 86, 38, and 5 times higher than their corresponding background values, respectively. The high and variable contents of P, K, Ca, and Mg, with lower Na, were observed across the plant species. Potential toxic elements like Pb, and Zn have high mobility indices in the soils, meaning these PTEs are more likely to be taken up by plants, potentially causing toxicity. Simultaneous presence of elevated levels of Pb, Fe, and Cd characterizes the contamination profile of the plants at the study locations. When various BCF values based on available PTEs in soils were taken into account, Stachys inflata and Senecio gallicus consistently function as effective phytostabilizers, exhibiting higher root accumulation than shoot accumulation and TF below 1 for all PTEs except Stachys inflata for Zn, making them the most reliable candidates for PTEs retention in roots. Conversely, Phlomis olivieri, Euphorbia szovitsii, and particularly Achillea millefolium consistently perform as phytoextractors across all six PTEs, displaying TF above 1 and high shoot bioconcentration factors, with Achillea millefolium showing exceptional TF (up to 3.03 for Fe). The native plant species identified in this study offer practical applicability for large-scale phytoremediation in similar semi-arid mining environments, enabling evidence-based selection of stabilizers for long-term PTEs containment and accumulators for active PTEs removal.

The habitats of the pearl oyster (Pinctada maxima Jameson, 1901) are facing competition from anthropogenic activities, particularly tourism, which is prevalent in the Southeast Asian region. This situation poses a threat to P. maxima, as such activities can lead to the emission of microplastics, a subject that has been little studied. This study aimed to investigate microplastic contamination in the tissues of P. maxima found in popular tourist destinations around Lombok Island, Indonesia. The tissues evaluated included the gills, mantle, digestive tract, muscle, and gonads. The result confirms that the tourist areas have smaller P. maxima individuals in terms of tissue weight and shell size and higher levels of microplastics compared to those from pristine areas. In both tourist and pristine areas, the microplastic concentrations in tissues followed this order: gills > digestive tract > gonads > mantle > muscle. Specifically, the gills of P. maxima in tourism areas had an average concentration of 12.09 particles/g ww, whereas those from pristine sites had 5.23 particles/g ww. The presence of microplastic in the mantle tissue in spite of the quantity indicates the reduced ability of oysters to remove inorganic particles due to the accumulation of microplastics. The predominant shapes of microplastics were granules/pellets, followed by films and fibers, while the most common colors were black and green. This study highlights the negative impact of marine tourism on marine resources. Additionally, it provides guidance on which tissues should be avoided and removed to ensure the safe consumption of oysters.

Global pollution by MPs has become an emerging concern, and recent studies have focused on analyzing their presence in wastewater treatment systems. One of the main challenges in this field is the absence of standardized methods, reference materials, and comparative data. This study aimed to develop, optimize, and validate a methodological framework for the extraction and identification of MPs in wastewater matrices. Reference MPs were produced from the polymers such as polyethylene terephthalate (PET), high-density polyethylene (HDPE), low-density polyethylene (LDPE), polyvinyl chloride (PVC), polypropylene (PP), and polystyrene (PS). To evaluate the integrity of these MPs after digestion, five Fenton reagent protocols were tested, and the carbonyl index was applied. For density-based separation, sodium chloride (NaCl) and zinc chloride (ZnCl2) solutions at different concentrations were used in a density separation device. The MPs obtained presented irregular fragments ranging from 0.1 to 3.0 mm. FTIR analysis performed before and after Fenton digestion showed no significant spectral deviations. The optimal Fenton conditions involved temperatures between 40 and 60 °C and 2 h of reaction time. ZnCl2 provided the best performance for particle recovery, ensuring high separation efficiency. The optimized methodology was subsequently validated using raw wastewater and dewatered sewage sludge collected from a full-scale WWTP. The validation demonstrated effective organic matter removal, successful recovery of spiked MPs, and reliable identification of native MPs present in the environmental samples. Overall, the proposed methodology proved to be a robust and reliable approach for the extraction and characterization of MPs in complex wastewater matrices, providing methodological support for future monitoring programs and contributing to the development of standardized protocols for MPs analysis.

Copper (Cu) and hypoxia are two environmentally relevant stressors that are increasing globally due to natural and anthropogenic influences. While the effects of each stressor have been looked at individually in previous work, the present study aimed to understand their combined effect on the behaviour of adult zebrafish (Danio rerio). As a model species, the behavioural ethogram of zebrafish is well-described, allowing for a suite of behaviours to be quantified, utilizing analysis software and by visual observation. In this study, we assessed behaviours associated with movement (velocity and distance metrics), resting, oxygen-seeking, and sociality following a mechanical stimulus. We compared the behaviour of fish after a 96-h exposure to sublethal Cu (45 µg/L) to those not exposed to Cu, with both groups being tested under normoxic (> 90% oxygen saturation [> 7.44 mg/L O2]) and hypoxic (< 30% oxygen saturation [< 2.48 mg/L O2]) conditions. Hypoxia influenced behaviours associated with movement (average velocity, darting, total distance travelled, maximum velocity). Exposure to Cu affected bottom-resting and air-seeking behaviours. Cu and hypoxia independently impacted two indices of sociality (shoal area and proximity) in a similar fashion. Many of the effects of hypoxia were dampened by Cu, whereas effects of hypoxia on responses to Cu were variable. This study highlights the value of using both high-throughput automated software and visual observation to reveal subtle interactive effects of Cu and hypoxia on key behaviours.

Pesticide poisoning poses a continuing threat to wildlife, particularly avian species such as the Indian Peafowl Pavo cristatus, which holds ecological and cultural significance in India. Despite increasing reports of mass mortalities of the National bird across the country, confirmed and reported, cases of pesticide poisoning remain limited. In this study, eight mass mortality incidents involving death of 121 Indian Peafowls were investigated in Tamil Nadu between 2019 and 2021. Five separate tissue samples from each of 41 individuals were analysed for the presence of 45 pesticides using Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS). In all cases, monocrotophos a highly toxic organophosphate pesticide was consistently detected in both tissue and bait samples at concentrations far exceeding known avian toxicity thresholds, indicating it as the cause of mortality. Concentration pattern was in the order; crop content (339.0 mg/Kg) > gut content (83.5 mg/Kg) > liver (1.59 mg/Kg) > kidney (1.00 mg/Kg) > muscle (0.45 mg/Kg). High concentration of monocrotophos were highest in crop and gut contents, suggesting oral ingestion through baited food grains recently. Additionally, flubendiamide, profenophos and carbendazim were also detected in one incident each, representing the first report of these pesticide residues in wild birds globally. These findings provide definitive toxicological evidence of pesticide-induced mortality in Indian Peafowls, reinforcing earlier suspicions from news and field reports. The study highlights the widespread possible misuse of the regulated pesticide and the urgent need for coordinated monitoring, stricter regulation, and community-level awareness to mitigate poisoning risks to non-target wildlife species in the country.

In this study we provide a comprehensive assessment of metal contamination in the Amazon River and its main tributaries, with a focus on urban contamination hotspots. A monitoring campaign was conducted across 40 sampling sites, analysing water concentrations of As, Cd, Cu, Cr, Fe, Mn, Pb, Ni, and Zn. Metal concentrations were evaluated against national and international water quality standards and compared between urbanized and less impacted regions to delineate pollution patterns. Additionally, an ecological risk assessment was conducted for individual metals and for metal mixtures using Species Sensitivity Distributions (SSDs). The results of this study show that Fe levels in the Amazon River were exceptionally high, with potential implications for aquatic species distribution across the basin. Exceedances of water quality standards were identified for four metals (Fe, Pb, Mn, Cu), with metal enrichment observed particularly in Manaus, Macapá, and Belém. Acute multi-substance potentially affected fraction (msPAF) of species in the Amazon River and its tributaries indicated insignificant risks, while chronic values ranged from 3% to 33%. In urban areas, acute msPAF values were generally low, with the exception of two samples taken in Manaus that exhibited values of 11% and 16%. Chronic riskvalues, however, were consistently high in these urban locations, reaching up to 72% of species potentially affected and reflecting sustained ecotoxicological stress. Cu, Zn and Mn were identified as the primary contributors to chronic toxicity, with Cu and Zn dominating in Manaus, and Mn in Macapá. These findings underscore the need for stricter industrial discharge regulations and improved wastewater treatment systems to preserve Amazonian freshwater ecosystems.

Small streams are important ecosystems in many areas globally, playing a crucial role in conserving biodiversity and providing ecosystem functions. However, owing to their high connectivity with surrounding landscapes, small streams are particularly susceptible to drivers of biodiversity decline. We report here the results of a monitoring program conducted between 2018 and 2021 at 18 sites in two stream catchments in southwest Germany, characterized by near-natural to highly anthropogenic land use. The monitoring program included 26 environmental, biological, and anthropogenic stressor variables describing the landscape context, aquatic ecosystem compartments, and riparian areas. We used ordination analysis and factor analysis of mixed data (FAMD) to analyse the relationship between variables and the effects of anthropogenic stressors on ecosystem structure and functioning. Results showed that near-natural upstream sites are substantially less impacted by anthropogenic stressors (e.g., pesticide pollution, morphological alterations) compared with agricultural and urban downstream sites. Biotic parameters, such as abundances and taxa richness of aquatic macroinvertebrates, fish, and carabid beetles, as well as leaf litter decomposition, exhibited overall high variations between sites. FAMD assigned the stream sites into four groups (i.e., forest, grassland, agriculture, viticulture), primarily based on land use and anthropogenic stressor influences and found anthropogenic stressors to often co-occur. Lower aquatic macroinvertebrate abundances and diversity, as well as reduced leaf litter decomposition, were observed at sites with higher anthropogenic disturbances. Overall, our findings suggest that small streams are subjected to multiple anthropogenic stressors, resulting in negative effects on both aquatic and riparian ecosystem health.

Estrone (E1) is one of the major natural estrogens influencing the reproductive system of vertebrates. However, it contaminates aquatic environments due to runoff from livestock waste and the discharge of domestic sewage. The aim of this study was to investigate the impact of exposure to environmentally relevant concentrations of E1 on oogenesis and spawning in zebrafish (Danio rerio). Fish were exposed, in duplicate, to 20, 200, and 2000 ng/L of E1 for 49 days for oogenesis analysis evaluating histology, sex steroids, morphometry, cell proliferation, apoptosis, immunohistochemistry for insulin-like growth factor (IGF) and inducible nitric oxide synthetase (iNOS). 17β-estradiol (E2) and 11-ketotestosterone (11-KT) were assessed by ELISA assay. Nitric oxide production was evaluated indirectly by quantifying nitrite. Results revealed that E1 exposure altered the proportions of ovarian follicles and somatic components, with significant increase of oogonia, follicular atresia and inflammatory infiltrate, and decrease of follicular cells. Levels of E2, and immunoreaction for IGF1 increased in E120 and 200 ng/L groups, but 11-KT, IGF2 and IGF1R were not altered. Nitrite concentrations in ovaries were significantly elevated in E1 200 and 2000 ng/L groups, but iNOS immunoreaction was not altered. These changes led to reduced egg production in all groups exposed to E1 and significatively decreased fertilization rates at 200 and 2000 ng/L. Overall, the findings demonstrate that E1, even at concentrations commonly found in surface waters, has detrimental effects on ovarian development, gametogenesis and reproductive success in zebrafish. Monitoring environmental estrogens levels in aquatic environments is therefore essential for fish conservation.

The use of artificial sediment in toxicity testing is required in studies assessing the impact of chemicals on benthic communities and testing chemicals for registration, as it offers increased repeatability and enhances consistency across bioassays and laboratories. While peat is conventionally incorporated into artificial sediment formulations for toxicological testing as the source of organic matter (OM), it is not a sustainable resource due to the long time it takes to form and the environmental impact of its extraction (carbon loss equivalent to 2.1 megatons of carbon dioxide emissions annually and potential release of other elements into the environment). In a preliminary effort, the usability of coconut husk as an alternative to peat in formulating artificial sediments for toxicity testing was assessed. Post-larval American lobsters (Homarus americanus) were exposed for 15 days to test sediment prepared with either peat or coconut husk as a source of OM. Three OM levels were tested: 0.5, 2.3, and 5% of sediment. Dry sediment was mixed with an antiparasitic drug, ivermectin, to achieve 4 desired concentrations (nominal 0, 40, 100, 400 ng/g DW). Immobility and mortality were assessed every day to calculate EC50s and LC50s, as well as incipient EC50 and LC50. The test was replicated twice over two years. Although the test is preliminary and warrants further investigation, the control performances (within validity criteria in all cases) and the EC-LC50 results indicate that the presence of coconut husk does not introduce toxicity effects of the tested chemical, suggesting its suitability as a viable alternative for toxicity testing.

The Indian Bay of Bengal coast represents an important marine fishing area and serves as a significant source of dietary protein for consumers. These highlights growing concerns regarding the bioaccumulation of potentially toxic elements (PTEs) in fish and the associated environmental and human health risks linked to their consumption. Thus, this study aims to assess the accumulation of PTEs (As (arsenic), Sr (strontium), Ti (titanium), Be (beryllium), Cd (cadmium), Sb (antimony), Pb (lead), Hg (mercury), and Li (lithium)) in the muscles of three groupers. The highest value (29.88 ± 0.17 µg/g dry wt.) was observed in Epinephelus areolatus for As, and the lowest in E. bleekeri for Be (0.59 ± 0.20 µg/kg dry wt.). Multivariate analyses (PCA and HCA) confirmed a very close relationship among the As, Cd, Sb, Ti, and Be, while Pb, Hg, Th, and Li had their own specific habitats of bioaccumulation, implying distinct inputs of PTE. Health risk evaluations reveal that As was the most hazardous PTE, with the incidence of toxic effects and cancer risk, especially for habitual consumers. However, Ti is the most hazardous PTE, posing the highest non-carcinogenic risk of the studied species. Metal-protein docking further showed the strong binding of Pb[2+] and Sr[2+] to Nrf2, p53, and DNMT1, indicating potential disruption of redox regulation, genomic stability, and epigenetic control. The findings indicate that the intake of the specified grouper species poses a significant arsenic-related health risk to people, underscoring the necessity for ongoing monitoring and management of PTE contaminants in fisheries.