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Assessing the environmental risks of contaminated groundwater presents significant challenges due to its often-complex chemical composition and to dynamic processes affecting exposure of organisms in receiving surface waters. The objective of this study was to characterize the effects of groundwater collected from a legacy contaminated industrial site, in fish under environmentally relevant conditions. A 21-day fish short-term reproduction assay was conducted in outdoor wetland mesocosms by exposing adult fathead minnows (Pimephales promelas) to graded concentrations of groundwater (1 %, 3 %, and 6 %). Offspring were held in mesocosms up to four days post-hatch to apply a new approach method (NAM), the EcoToxChip™, to explore whether traditional apical endpoints could be predicted using an alternative mechanistic approach. None of the groundwater concentrations used in this study were lethal to fish. There was greater cumulative number of eggs produced at the highest concentration of exposure. However, no abnormal histological appearance was observed in the liver and gonads of fish and no significant effect was observed in the relative expression of genes, tubercle counts, and erythrocyte micronuclei counts compared to the negative control. Food availability in the mesocosms was also assessed and the abundance of zooplankton increased in all groundwater-treated mesocosms. Fathead minnow findings are in contrast to those obtained from previous controlled laboratory studies that revealed significant genotoxicity, hepatotoxicity, and reprotoxicity of the same mixtures. Several factors could explain these observations, including the aging of groundwater in mesocosms before fish addition resulting in photo- and biodegradation and binding to sediments of toxic components. Our static exposure scenario likely underestimated realistic exposure scenarios where groundwater inflow to surface water is generally semi-continuous. Nevertheless, focused transcriptome analysis using EcoToxChips also observed greater toxicity during previous laboratory tests compared to mesocosm scenarios, and thus, our results support the use of this NAM in the ecological risk assessment of contaminated groundwater., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Laura Gasque-Belz reports financial support was provided by Natural Sciences and Engineering Research Council of Canada and the industry partner. The author (s) acknowledge the potential conflict of interest due to funding received from the industry partner and owner of the study site for this research project. However, for the present study they had no role in study design, in the collection, analysis and interpretation of data and in the writing of the report., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

Traditional risk assessment methods face challenges in the determination of drivers of toxicity for complex mixtures such as those present at legacy-contaminated sites. Bioassay-driven analysis across several levels of biological organization represents an approach to address these obstacles. This study aimed to apply a novel transcriptomics tool, the EcoToxChip, to characterize the effects of complex mixtures of contaminants in adult fathead minnows (FHMs) and to compare molecular response patterns to higher-level biological responses. Adult FHMs were exposed for 4 and 21 days to groundwater mixtures collected from a legacy-contaminated site. Adult FHM showed significant induction of micronuclei in erythrocytes, decrease in reproductive capacities, and some abnormal appearance of liver histology. Parallel EcoToxChip analyses showed a high proportion of upregulated genes and a few downregulated genes characteristic of compensatory responses. The three most enriched pathways included thyroid endocrine processes, transcription and translation cellular processes, and xenobiotics and reactive oxygen species metabolism. Several of the most differentially regulated genes involved in these biological pathways could be linked to the apical outcomes observed in FHMs. We concluded that molecular responses as determined by EcoToxChip analysis show promise for informing of apical outcomes and could support risk assessments of complex contaminated sites., Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests. Laura Gasque-Belz reports financial support was provided by Natural Sciences and Engineering Research Council of Canada. The author (s) acknowledge the potential conflict of interest due to funding received from the industry partner and owner of the study site for this research project. However, for the present study they had no role in study design, in the collection, analysis and interpretation of data and in the writing of the report., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Current ecotoxicity testing programs are impeded as they predominantly rely on slow and expensive animal tests measuring adverse outcomes. Therefore, new approach methodologies (NAMs) increasingly involve short-term mechanistic assays that employ molecular endpoints to predict adverse outcomes of regulatory relevance. This study aimed to elucidate the application of NAMs in adult fathead minnows using fluoxetine (FLX) as a model compound. Fish were exposed to three FLX concentrations (measured: 2.42, 10.7, and 56.7 μgL -1 ) and a control. After 96 h, molecular toxicity signatures were characterized using proteomics and transcriptomics analyses in livers and brains of a sub-set of fish. The remaining fish were sampled at 21 days and assessed for liver histopathology and morphometric measurements. Fecundity was monitored throughout the study. In the livers, 56.7 μgL -1 FLX caused enrichment of PPAR signaling in the proteome and fatty acid-related pathways in the transcriptome, potential upstream responses that led to lipid-type vacuolation of hepatocytes, observed via histopathology. Upregulated genes in the brain suggested alterations in serotonin-related signaling processes and reproductive behaviour, which may explain the observed significant decrease in fecundity. While the relationships between molecular responses and adverse outcomes remain complex, this research provided important insights into the mechanistic toxicity of FLX., 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 © 2022 Elsevier B.V. All rights reserved.)

This study investigated the influence of habitat quality (HQ) on the reproduction and bioenergetics (energy reserve and metabolic enzyme activities) of the oribatid mite, Oppia nitens, in response to cadmium (Cd). In the baseline toxicity test, Cd elevated the carbohydrate reserve of adult mites at intermediate Cd concentrations (88 and 175 mg Cd kg -1 ) but without a change in lipid and protein reserve across 0-700 mg Cd kg -1 . The activities of glucose metabolism enzymes, glucose-6-phosphate dehydrogenase (G6PDH) and pyruvate kinase (PK) were inhibited in the mites at 700 mg Cd kg -1 . Adult mites reared in high HQ soils had higher reproduction relative to mites from low HQ soils when exposed to Cd in OECD soil, but there was no difference in bioenergetics between mites from low and high HQ soils. Hence, HQ significantly (p = 0.024) influenced the reproduction of mites (i.e., juvenile production) irrespective of the Cd concentration in the OECD soil but did not significantly affect the bioenergetics of the mites. We suggest that habitat quality's effect could be more significant than metal concentration on the biological fitness (juvenile production) of O. nitens in metal-contaminated soils., (Copyright © 2020 The Authors. Published by Elsevier B.V. All rights reserved.)

Sediment toxicity studies and ecological risk assessments on organic contaminants routinely apply organic carbon normalization to toxicity data; however, no studies examine its potential for use in soils with petroleum hydrocarbon (PHC) contamination. Limited studies in soil ecotoxicology assess the influence of species assemblages used in species sensitivity distribution construction on the resulting guideline designated to of soil dwelling organisms. Canadian regulations utilize more conservative approaches to deriving guidelines with soil ecotoxicology data compared to the rest of the world, so we investigated the impact of these on soil invertebrates in a variety of field soils. In addition to toxicity, the persistence of a medium PHC mixture was also assessed in the field soils to determine the duration of toxic effects. We found organic matter influenced PHC toxicity to soil invertebrates, but persistence was influenced more by soil cation exchange capacity. Incorporating organic carbon normalization into species sensitivity distribution curves provided a higher level of protection to soil dwelling receptors in low organic matter soils as well as reduce the variability of PHC soil toxicity data. Soil remediation guidelines derived for protection of soil dwelling organisms using a diverse species assemblage provided similar levels of protection as guidelines developed with test species specific for remote, forested land uses in Canada. We conclude that: (i) Canadian hazard concentration values for PHC contamination of soils should be revisited as they may not be protective and (ii) that soil PHC guidelines for protection of soil dwelling organisms should be expressed as carbon normalized values., (Copyright © 2019 Elsevier B.V. All rights reserved.)

In recent years, laboratory soil toxicity testing has advanced with the introduction of ecologically relevant boreal forest soil invertebrate and plant species, as well as increased adoption of avoidance toxicity tests. In this study, we investigated the toxicity of a binary petroleum hydrocarbon (PHC) mixture to six agronomic and boreal forest plant species (Elymus lanceolatus, Lactuca sativa, Medicago sativa, Raphanus sativus, Pinus banksiana and Picea glauca) and the avoidance response of five soil invertebrate species (Eisenia fetida, Enchytraeus crypticus, Folsomia candida, Oppia nitens and Hypoaspis aculeifer). We assessed concentration addition and independent action mixture toxicity reference models, with potential interactions, using observed responses from the mixture and individual component toxicity endpoints from literature. Our key finding was soil invertebrate avoidance of PHC-contaminated soil was in the similar range of growth measurements for plant species sensitive to PHC-contaminated soils. This study further supports the inclusion of avoidance tests in toxicity test batteries for assessing PHC toxicity as invertebrate avoidance response appears to be linked to plant growth and informative of plant habitat quality., (Copyright © 2018 Elsevier B.V. All rights reserved.)

The objective of this study was to investigate the effects of naturally contaminated Fusarium wheat containing deoxynivalenol (DON) on growth and performance of broiler chickens from 0 to 35 d. The BoMill TriQ individual kernel sorting technology uses near infrared transmittance (NIT) spectra to separate Fusarium-damaged kernels (FDK) from healthy kernels based on individual kernel CP. Three Fusarium-contaminated wheat sources were individually sorted into 3 test fractions: outlier (10% of the source), high mycotoxin (20% of the source), and low mycotoxin (70% of the source). These fractions were reconstituted into 4 ratios-M0, M20, M40, and M60-relating to the proportion of the high mycotoxin fraction in the reconstituted diets. These 12 reconstituted wheat sources with varying levels of DON were incorporated at ∼70% (starter) or ∼75% (grower/finisher) into diets. The fractions of wheat used had FDK ranging from 0.1 to 25.8% and DON from 0.0 to 14.3 ppm. A total of 480 newly hatched Ross 308 male broilers were randomly divided into 96 cages. Each test diet was assigned to 8 replicates with 5 birds per replicate cage. At 21 d, 180 birds were transferred to 36 cages, allowing 3 replicates of 5 birds per diet until 35 d. A factorial arrangement analysis compared the 3 wheat sources and 4 ratios produced from each sorted wheat. Growth and performance were evaluated as BW (g), feed intake (FI; g/bird/day), feed conversion ratio (FCR; g:g), AME (kcal ME/kg diet), nitrogen retention (NR; %), and mortality (%) for 0 to 21 d and 21 to 35 d. Results indicate no significant difference in BW, FI, and FCR (P > 0.05). Significant differences were seen in AME and NR (P < 0.01). This study demonstrates the potential of this novel sorting technology to produce naturally contaminated diets with a large range of mycotoxin concentrations from a single wheat source to enable future investigations of mycotoxin exposure in any species., (© 2015 Poultry Science Association Inc.)

Rainbow trout were exposed in situ to oil sands-affected waters for 21 d, either with or without an immune stimulation using inactivated Aeromonas salmonicida. Three aquatic systems were utilized for the experiment: a pond containing oil sands tailings capped with approximately 3 m of natural surface water, a second pond where unextracted oil sands materials were deposited in the watershed, and a reservoir receiving Athabasca River water as a reference caging location. The three systems showed a gradient of oil sands-related compounds, most notably, total naphthenic acids were highest in the system containing tailings (13 mg/L), followed by the system influenced by unextracted oil sands (4 mg/L), followed by the reference cage location (1 mg/L). Biochemical and chemical measures of exposure in rainbow trout showed the same trend, with the tailings-influenced system having the highest hepatic EROD activity and elevated bile fluorescence measured at phenanthrene wavelengths. Trout caged in the tailings-influenced location had significantly fewer leukocytes and smaller spleens as compared to the reference fish, though liver size and condition factor were unaffected. Fish in the tailings-influenced waters also demonstrated increased fin erosion, indicative of opportunistic infection. The trout exposed to tailing-influenced waters also showed a significantly decreased ability to produce antibodies to the inactivated A. salmonicida. Given the complexity of the exposure conditions, exact causative agents could not be determined, however, naphthenic acids, polycyclic aromatic hydrocarbons and pH correlate with the immunotoxic effects while elevated salinity or metals seem unlikely causes., (Copyright © 2012 Elsevier Inc. All rights reserved.)