The concentration of dissolved organic matter impacts the metabolic response in Daphnia magna exposed to 17α-ethynylestradiol and perfluorooctane sulfonate

Ecological risks of high-ammonia environment with inhibited growth of Daphnia magna: Disturbed energy metabolism and oxidative stress

High ammonia pollution is a common problem in water bodies. However, research on the mechanisms underlying the toxic effects on organisms at different nutritional levels is still insufficient. Herein, based on the environmental concentration, the toxic effects of high ammonia pollution on Daphnia magna were investigated. Overall, the feeding and filtration rates of D. magna were significantly decreased by ammonia. Growth inhibition of D. magna by ammonia was confirmed by the decreased body length. After ammonia exposure, the metabolic status of D. magna changed, the correlation network weakened, and the correlations between metabolites were disrupted. Changes occurred in metabolites primarily involved in oxidative stress, fatty acid oxidation, tricarboxylic acid cycle, and protein digestion, absorption, and synthesis, which were validated through alterations in multiple biomarkers. In addition, mitochondrial function was evaluated and was found to inhibit mitochondrial activity, which was accompanied by a decreased marker of mitochondrial activity contents and ATPase activity. Thus, the results suggested that energy metabolism and oxidative stress were involved in ammonia-induced growth toxicity. This study provides new insights into the impact of ammonia on aquatic ecological health.

Metabolomic study on ostracods exposed to environmentally relevant concentrations of five pharmaceuticals selected via a novel approach

Pharmaceuticals (PhACs) are increasingly detected in aquatic ecosystems, yet their effects on biota remain largely unknown. The environmentally relevant concentrations of many PhACs may not result in individual-level responses, like mortality or growth inhibition, traditional toxicity endpoints. However, this doesn't imply the absence of negative effects on biota. Metabolomics offers a more sensitive approach, detecting responses at molecular and cellular levels and providing mechanistic understanding of adverse effects. We evaluated bioaccumulation and metabolic alterations in a benthic ostracod, Heterocypris incongruens, exposed to a mixture of five PhACs (carbamazepine, tiapride, tolperisone, propranolol and amlodipine) at environmentally relevant concentrations for 7 days using liquid chromatography coupled with mass spectrometry. The selection of PhACs was based, among other factors, on risk quotient values determined using toxicological data available in the literature and concentrations of PhACs quantified in our previous research in the sediments of the Odra River estuary. This represents a novel approach to PhACs selection for metabolomic studies that considers strictly quantitative data. Amlodipine and tolperisone exhibited the highest bioaccumulation. Significant impacts were observed in Alanine, aspartate and glutamate metabolism, Starch and sucrose metabolism, Arginine biosynthesis, Histidine metabolism, Tryptophan metabolism, Glycerophospholipid metabolism, and Glutathione metabolism pathways. Most of the below-individual-level responses were likely nonspecific and related to dysregulation in energy metabolism and oxidative stress response. Additionally, some pharmaceutical-specific responses were also observed. Therefore, untargeted metabolomics can be used to detect metabolic changes resulting from environmentally relevant concentrations of PhACs in aquatic ecosystems and to understand their underlying mechanism.

The concentration of dissolved organic matter impacts the neurobehavior in female zebrafish exposed to cyclophosphamide

Cyclophosphamide (CP) is a broad-spectrum anticancer drug for various cancers and frequently detected in aquatic environments, reaching concentrations up to 22 μg/L. However, there is limited understanding of the toxicities of CP with the presence of dissolved organic matter, a ubiquitous component in aquatic environments, in fish. In this study, we investigated the behaviors, morphological alterations of retina, and related gene transcripts in zebrafish exposed to CP (0 and 50 μg/L) and Humic acid (HA, a main component of DOM) at concentrations of 0, 3, 10, and 30 mg-C/L for 30 days. The results showed that, relative to the zebrafish in CP treatment, HA at 30 mg-C/L increased the locomotion (12.1 % in the light and 7.2 % in the dark) and startle response (9.7 %), while inhibiting the anxiety (12.5 %) and cognition of female zebrafish (24.6 %). The levels of transcripts of neurotransmitter- (tph1b and ache), neuroinflammation-(il-6 and tnfα) and antioxidant-(gpx) related genes in the brain of female adult were also altered by CP with the presence of HA. In addition, HA promoted the transgenerational effects of CP on the neurobehaviors. Therefore, HA can enhance potential neurotoxicity of CP in female fish through alteration neurotransmission related genes. Our findings provide new insights into the toxicity and underlying mechanisms of CP with the presence of dissolved organic matter, thereby contribute to a deeper understanding of the risks posed by CP in aquatic ecosystems.

Environmental metabolomics uncovers oxidative stress, amino acid dysregulation, and energy impairment in Daphnia magna with exposure to industrial effluents

Anthropogenic activities are regarded as point sources of pollution entering freshwater bodies worldwide. With over 350,000 chemicals used in manufacturing, wastewater treatment and industrial effluents are comprised of complex mixtures of organic and inorganic pollutants of known and unknown origins. Consequently, their combined toxicity and mode of action are not well understood in aquatic organisms such as Daphnia magna. In this study, effluent samples from wastewater treatment and industrial sectors were used to examine molecular-level perturbations to the polar metabolic profile of D. magna. To determine if the industrial sector and/or the effluent chemistries played a role in the observed biochemical responses, Daphnia were acutely (48 h) exposed to undiluted (100%) and diluted (10, 25, and 50%) effluent samples. Endogenous metabolites were extracted from single daphnids and analyzed using targeted mass spectrometry-based metabolomics. The metabolic profile of Daphnia exposed to effluent samples resulted in significant separation compared to the unexposed controls. Linear regression analysis determined that no single pollutant detected in the effluents was significantly correlated with the responses of metabolites. Significant perturbations were uncovered across many classes of metabolites (amino acids, nucleosides, nucleotides, polyamines, and their derivatives) which serve as intermediates in keystone biochemical processes. The combined metabolic responses are consistent with oxidative stress, disruptions to energy metabolism, and protein dysregulation which were identified through biochemical pathway analysis. These results provide insight into the molecular processes driving stress responses in D. magna. Overall, we determined that the metabolic profile of Daphnia could not be predicted by the chemical composition of environmentally relevant mixtures. The findings of this study demonstrate the advantage of metabolomics in conjunction with chemical analyses to assess the interactions of industrial effluents. This work further demonstrates the ability of environmental metabolomics to characterize molecular-level perturbations in aquatic organisms exposed to complex chemical mixtures directly.

Metabolomic analysis of combined exposure to microplastics and methylmercury in the brackish water flea Diaphanosoma celebensis

Owing to their widespread distribution and high bioaccumulation, microplastics (MPs) and mercury (Hg) are considered major threats to the ocean. MP interacts with Hg because of its high adsorption properties. However, their toxicological interactions with marine organisms, especially combined effects at the molecular level, are poorly understood. This study investigated the single and combined effects of MP and Hg on the metabolic profile of the brackish water flea Diaphanosoma celebensis. A total of 238 metabolites were significantly affected by MP, Hg, or MP + Hg. Metabolite perturbation patterns showed that toxicity of Hg and MP + Hg was similar and that of MP was not significant. Among the 223 metabolites affected by Hg, profiles of 32 unannotated metabolites were significantly different from those of MP + Hg, and combined effects of MP + Hg decreased the effect of Hg on 25 of these metabolites. Only 11 annotated metabolites were significantly affected by Hg or MP + Hg and were related to carbohydrate, lipid, vitamin, and ecdysteroid metabolism. Ten metabolites were decreased by Hg and MP + Hg and were not significantly different between the exposure groups. Enrichment analysis showed that galactose, starch, and sucrose metabolism were the most affected pathways. These findings suggest that MP has negligible toxic effect, and Hg can induce energy depletion, membrane damage, and disruption of growth, development, and reproduction. Although the impact of MP was negligible, the combined effects of MP + Hg could be metabolite specific. This study provides better understanding of the combined effects of MP and Hg on marine organisms.

The impact of pharmaceutical pollutants on daphnids - A metabolomic approach

Pharmaceuticals have been classified as emerging contaminants in the aquatic ecosystem, mainly due to their increased use and improper disposal. A significant range of pharmaceutical compounds and their metabolites have been globally detected in surface waters and pose detrimental effects to non-target organisms. Monitoring pharmaceutical water pollution relies on the analytical approaches for their detection, however, such approaches are limited by their sensitivity limit and coverage of the wide range pharmaceutical compounds. This lack of realism in risk assessment is bypassed with effect-based methods, which are complemented by chemical screening and impact modelling, and are able to provide mechanistic insight for pollution. Focusing on the freshwater ecosystem, in this study we evaluated the acute effects on daphnids for three distinct groups of pharmaceuticals; antibiotics, estrogens, and a range of commonly encountered environmentally relevant pharmaceutical pollutants. Combining several endpoints such as mortality, biochemical (enzyme activities) and holistic (metabolomics) we discovered distinct patterns in biological responses. In this study, changes in enzymes of metabolism e.g. phosphatases and lipase, as well as the detoxification enzyme, glutathione-S-transferase, were recorded following acute exposure to the selected pharmaceuticals. A targeted analysis of the hydrophilic profile of daphnids revealed mainly the up-regulation of metabolites following metformin, gabapentin, amoxicillin, trimethoprim and β-estradiol. Whereas gemfibrozil, sulfamethoxazole and oestrone exposure resulted in the down-regulation of majority of metabolites.

Freshwater crustacean exposed to active pharmaceutical ingredients: ecotoxicological effects and mechanisms

Concerns over the ecotoxicological effects of active pharmaceutical ingredients (APIs) on aquatic invertebrates have been raised in the last decade. While numerous studies have reported the toxicity of APIs in invertebrates, no attempt has been made to synthesize and interpret this dataset in terms of different exposure scenarios (acute, chronic, multigenerational), multiple crustacean species, and the toxic mechanisms. In this study, a thorough literature review was performed to summarize the ecotoxicological data of APIs tested on a range of invertebrates. Therapeutic classes including antidepressants, anti-infectives, antineoplastic agents, hormonal contraceptives, immunosuppressants, and neuro-active drugs exhibited higher toxicity to crustaceans than other API groups. The species sensitivity towards APIs exposure is compared in D. magna and other crustacean species. In the case of acute and chronic bioassays, ecotoxicological studies mainly focus on the apical endpoints including growth and reproduction, whereas sex ratio and molting frequency are commonly used for evaluating the substances with endocrine-disrupting properties. The multigenerational and "Omics" studies, primarily transcriptomics and metabolomics, were confined to a few API groups including beta-blocking agents, blood lipid-lowing agents, neuroactive agents, anticancer drugs, and synthetic hormones. We emphasize that in-depth studies on the multigenerational effects and the toxic mechanisms of APIs on the endocrine systems of freshwater crustacean are warranted.

Daphnia magna sub-lethal exposure to phthalate pollutants elicits disruptions in amino acid and energy metabolism

Phthalic acid esters (PAEs) are a class of chemicals that are usually incorporated as additives in the manufacturing of plastics. PAEs are not covalently bound to the material matrix and can, consequently, be leached into the environment. PAEs have been reported to act as endocrine disruptors, neurotoxins, metabolic stressors, and immunotoxins to aquatic organisms but there is a lack of information regarding the impact of sub-lethal concentrations to target organisms. The freshwater crustacean Daphnia magna, a commonly used model organism in aquatic toxicity, was exposed to four phthalate pollutants: dimethyl phthalate (DMP), diethyl phthalate (DEP), monomethyl phthalate (MMP), and monoethyl phthalate (MEP). Liquid chromatography-tandem mass spectrometry (LC-MS/MS) was employed in a targeted metabolomic approach to quantify polar metabolites extracted from a single Daphnia body. Individual metabolite percent changes and hierarchical clustering heatmap analysis showed unique metabolic profiles for each phthalate pollutant. Metabolite percent changes were mostly downregulated or presented opposing responses for the low and high concentrations tested. Meanwhile, pathway analyses suggest the disruption of related and unique pathways, mostly connected with amino acid and energy metabolism. The pathways aminoacyl-tRNA biosynthesis, arginine biosynthesis, and glutathione metabolism were disrupted by most selected PAEs. Overall, this study indicates that although phthalate pollutants can elicit distinct metabolic perturbations to each PAE, they still impacted related biochemical pathways. These chemical-class based responses could be associated with a common toxic mechanism of action. The reported findings show how targeted metabolomic approaches can lead to a better understanding of sub-lethal exposure to pollutants, revealing metabolomic endpoints do not hold a close relationship with traditional acute toxicity endpoints.

Sublethal Exposure of Per- and Polyfluoroalkyl Substances of Varying Chain Length and Polar Functionality Results in Distinct Metabolic Responses in Daphnia magna

Per- and polyfluoroalkyl substances (PFAS) are a class of persistent organic pollutants used in industrial applications because of their physicochemical properties, which results in their ubiquitous presence across environmental matrices. To date, legacy PFAS have been well studied; however, the concentration of alternative PFAS may exceed the concentration of legacy pollutants, and more information is needed regarding the sublethal toxicity at the molecular level of aquatic model organisms, such as Daphnia magna. Perfluorobutanoic acid (PFBA), perfluorohexanoic acid (PFHxA), perfluorohexanesulfonic acid (PFHxS), and perfluorononanoic acid (PFNA) are four widely detected PFAS alternatives of varying chain length and polar functionality that are quantified in aquatic environments. The present study examines the metabolic perturbations of PFAS with varying chemistries to D. magna using targeted mass spectrometry-based metabolomics. Daphnia were acutely exposed to sublethal concentrations of PFBA, PFHxA, PFHxS, and PFNA before the polar metabolite profile was extracted from single organisms. Multivariate analysis demonstrated significant separation between the sublethal concentrations of PFHxA, PFHxS, and PFNA relative to the controls; in sum, longer chain lengths demonstrated greater overall perturbations to the extracted metabolic profiles. Univariate statistics revealed significant perturbations in the concentrations of several amino acids, nucleotides/nucleosides, and neurotransmitters with exposure to PFAS. These metabolic perturbations are consistent with disruptions in energy metabolism (pantothenate and coenzyme A metabolism, histidine metabolism) and protein synthesis (aminoacyl-transfer RNA biosynthesis and amino acid metabolism), which were identified through biochemical pathway analysis. These results provide evidence that although PFAS chemistry (chain length and polar functional group) invokes unique metabolic responses, there is also an underlying toxic mode of action that is common with select PFAS exposure. Overall, the present study highlights the capabilities of environmental metabolomics to elucidate the molecular-level perturbations of pollutants within the same chemical class to model aquatic organisms, which can be used to prioritize risk assessment of substituted PFAS alternatives. Environ Toxicol Chem 2023;42:242-256. © 2022 SETAC.

(Anti)estrogenic activity impacted by complex environmental matrices: A DOM and multiphase distribution approach

The presence of estrogenic endocrine disruptors in aquatic environments has been a concern and bioassays are recommended tools for their monitoring. However, the physicochemical properties of contaminants and the environmental matrix features may influence the resultant response. This study aimed to assess this influence on the Yeast Estrogen Screen (YES) assay. Mixtures of 17β-estradiol (E2) and humic acid (HA) were evaluated through the Schild approach aiming to investigate the interactions between estrogens and dissolved organic matter (DOM). Moreover, environmental samples from municipal landfill leachate and wastewater treatment plant (WWTP) influents and effluents were screened for (anti)estrogenic activity at both dissolved and particulate phases. Finally, results were statistically confronted with physicochemical parameters through principal component analysis (PCA). The HA test concentrations strongly reduced the E2 response, even at low levels. Humic substances may not only reduce estrogen bioavailability, but also interfere with the assay mechanism through enzymatic inhibition thus masking the sample estrogenic potential. Landfill leachate had total E2-Eq in the range 1282-2591 ng L^-1, while WWTP influent and effluent were in the range 12.1-41.4 and <DL-2.3 ng L^-1, so estrogenicity was reduced 92% in average. Particulate phase was responsible for 33-100% of measured E2-Eq between matrices, though cytotoxicity occurred in some extracts. Antiestrogenic activity was observed in both phases and might also have masked the estrogenicity of samples. PCA did not resulted in positive correlations supporting a multiphase distribution pattern of estrogenic compounds. Nevertheless, the solids and organic matter characteristics supported the data interpretation. In conclusion, the in vitro YES assay is subjected to factors intrinsic to the environmental sample that can influence on the measured estrogenic response. Therefore, results interpretation should be performed together with organic matter characterization parameters, cytotoxicity and antiestrogenic activity evaluation.

Comparison of sub-lethal metabolic perturbations of select legacy and novel perfluorinated alkyl substances (PFAS) in Daphnia magna

Per- and polyfluoroalkyl substances (PFAS) are a class of pollutants of concern due to their ubiquitous presence, persistence, and toxicity in aquatic environments. Legacy PFAS pollutants such as perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) have been more widely studied in aquatic environments. However, replacement PFAS, such as ammonium perfluoro (2-methyl-3-oxahexanoate; GenX) are increasingly being detected with little known information surrounding their toxicity. Here, Daphnia magna, a model organism for freshwater ecotoxicology was used to compare the acute sub-lethal toxicity of PFOS, PFOA, GenX, and PFAS mixtures. Using liquid chromatography with tandem mass spectrometry (LC-MS/MS), the targeted polar metabolic profile extracted from single Daphnia was quantified to investigate perturbations in the exposure groups versus the unexposed organisms. Multivariate statistical analyses demonstrated significant non-monotonic separation in PFOA, GenX, and PFAS mixture exposures. Sub-lethal exposure to concentrations of PFOS did not lead to significant separation in multivariate analyses. Univariate statistics and pathway analyses were used to elucidate the mode of action of PFAS exposure. Exposure to all individual PFAS led to significant perturbations in many amino acids including cysteine, histidine, tryptophan, glycine, and serine. These perturbations are consistent with biochemical pathway disruptions in the pantothenate and Coenzyme A (CoA) biosynthesis, thiamine metabolism, histidine metabolism, and aminoacyl-tRNA biosynthesis pathways. Overall, the collected metabolomic data is consistent with disruptions in energy metabolism and protein synthesis as the primary mode of action of sub-lethal PFAS exposure. Secondary modes of action among individual pollutant exposures demonstrated that the structural properties (carboxylic acid vs. sulfonic acid group) may play a role in the metabolic perturbations observed. Sub-lethal exposure to PFAS mixtures highlighted a mixed response when compared to the individual pollutants (PFOS, PFOA, and GenX). Overall, this study emphasizes the niche capability of environmental metabolomics to differentiate secondary modes of action from metabolic perturbations in both single pollutant and pollutant mixtures within the same chemical class.

Metabolomic analysis predicted changes in growth rate in Daphnia magna exposed to acetaminophen

As urbanization and the global population increases, pollutants associated with municipal wastewater such as pharmaceuticals are becoming more prevalent in aquatic environments. Acetaminophen (paracetamol) is a widely used drug worldwide and one of the most frequently detected pharmaceuticals in freshwater ecosystems. This study investigated the impact of acetaminophen on the metabolite profile of Daphnia magna at two life stages; and used these metabolomic findings to hypothesize a potential impact at a higher organismal level which was subsequently tested experimentally. Targeted polar metabolite analysis by liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used to measure changes in the concentration of 51 metabolites in the neonate (> 24 h old) and adult (8 day-old) daphnids following a 48-h exposure to sub-lethal concentrations of acetaminophen. The impact of acetaminophen on the metabolic profile of neonates was widely different from adults. Also, acetaminophen exposure perturbed the abundance of nucleotides more extensively than other metabolites. The acute metabolomic experimental results led to the hypotheses that exposure to sub-lethal concentrations of acetaminophen upregulates protein synthesis in D. magna and subsequently increases growth during early life stages and has an opposite impact on adults. Accordingly, a 10 day growth rate experiment indicated that exposure to acetaminophen elevated biomass production in neonates but not in adults. These novel findings demonstrate that a targeted analysis and interpretation of the changes in the polar metabolic profile of organisms in response to environmental stressors could be used as a tool to predict changes at higher biological levels. As such, this study further emphasizes the incorporation of molecular-level platforms as critical and robust tools in environmental assessment frameworks and biomonitoring of aquatic ecosystems.

Fate, occurrence, and removal of estrogens in livestock wastewaters

During the last decades, livestock and animal feeding operations have been expanded. In parallel, these activities are among the major sources of estrogens in the environment. Thus, considering the environmental and health risks associated with estrogenic compounds, this work reviews the fate, occurrence, and removal of free and conjugated E1, E2, and E3 in livestock wastewaters. A systematic literature review was carried out, and after applying the eligibility criteria, 66 peer-reviewed papers were selected. Results suggest high estrogen concentrations and, consequently, high estrogenic activity, especially in samples from swine farming. E1 and E2 are frequently found in wastewaters from bovine, swine, and other livestock effluents. Aerobic treatment processes were more efficient for estrogen removal, whereas anaerobic systems seem poorly effective. Removal efficiencies of estrogens and estrogenic activity of up to 90% were reported for constructed wetlands, advanced pond systems, trickling filters, membrane bioreactors, aerated and nitrifying reactors, combined air flotation, and vegetable oil capture processes. High concentrations found in wastewaters from livestock allied to the removal efficiencies reported for anaerobic processes (usually used to treat livestock wastewaters) evidence the importance of monitoring these compounds in environmental matrices.

Assessing the Ecological Risks of Per- and Polyfluoroalkyl Substances: Current State-of-the Science and a Proposed Path Forward

Per- and poly-fluoroalkyl substances (PFAS) encompass a large, heterogenous group of chemicals of potential concern to human health and the environment. Based on information for a few relatively well-understood PFAS such as perfluorooctane sulfonate and perfluorooctanoate, there is ample basis to suspect that at least a subset can be considered persistent, bioaccumulative, and/or toxic. However, data suitable for determining risks in either prospective or retrospective assessments are lacking for the majority of PFAS. In August 2019, the Society of Environmental Toxicology and Chemistry sponsored a workshop that focused on the state-of-the-science supporting risk assessment of PFAS. The present review summarizes discussions concerning the ecotoxicology and ecological risks of PFAS. First, we summarize currently available information relevant to problem formulation/prioritization, exposure, and hazard/effects of PFAS in the context of regulatory and ecological risk assessment activities from around the world. We then describe critical gaps and uncertainties relative to ecological risk assessments for PFAS and propose approaches to address these needs. Recommendations include the development of more comprehensive monitoring programs to support exposure assessment, an emphasis on research to support the formulation of predictive models for bioaccumulation, and the development of in silico, in vitro, and in vivo methods to efficiently assess biological effects for potentially sensitive species/endpoints. Addressing needs associated with assessing the ecological risk of PFAS will require cross-disciplinary approaches that employ both conventional and new methods in an integrated, resource-effective manner. Environ Toxicol Chem 2021;40:564-605. © 2020 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. This article has been contributed to by US Government employees and their work is in the public domain in the USA.

Insights into total estrogenic activity in a sewage-impacted urban stream assessed via ER transcriptional activation assay: Distribution between particulate and dissolved phases

Endocrine disrupting chemicals (EDC) are exogenous substances that can potentially mimic hormonal substances and cause adverse effects on the endocrine system of living beings. The behavior and fate of these compounds in the environment is directly related to their physical-chemical properties, which indicate great affinity for solid and organic particles and suggest an inherent mechanism of fractionation between dissolved and particulate phases of aqueous matrices. However, few studies have been considering this fact when quantifying these pollutants and their effects through bioassays. In this study, the fractionation of estrogenic substances between dissolved and particulate phases in an urban stream was investigated via estrogenic activity evaluation by the YES assay. Two fractions of suspended solids (< 0.7 µm and between 0.45 and 0.7 µm) and the dissolved phase were considered and two approaches of SPE percolations were applied. Total estradiol equivalent (E2-Eq) values were observed in the 29-65 ng L^-1 range, of which 35-62% were associated with the particulate phase. Most of the estrogenicity was associated with particles between 0.45 and 0.7 µm, whereas cytotoxicity was induced by extracts of particles greater than 0.7 µm. Results demonstrated the importance of solid fractions analysis towards the quantification of total estrogenic activity from aqueous environmental matrices and highlights the relevance of controlling fine suspended solids in sewage treatment plant effluents, regarding the control of endocrine disrupters in the environment.

Influence of dissolved organic matter on the accumulation, metabolite production and multi-biological effects of environmentally relevant fluoxetine in crucian carp (Carassius auratus)

Fluoxetine is a widely prescribed antidepressant that has been frequently detected in aquatic environments and is associated with a series of neurological, behavioural and neuroendocrine disruptions in nontarget organisms. However, studies on its effects in fish under realistic environmental conditions are still limited. In this study, we determined the influences of an environmentally relevant concentration of fluoxetine (100 ng/L) on crucian carp (Carassius auratus) in the presence of dissolved organic matter (DOM). Endpoints that were assessed included accumulation of fluoxetine and metabolite formation as well as related biological responses involving neurotransmission and metabolic processes. Fluoxetine was significantly bioconcentrated in the fish brain and liver and largely transformed to the active metabolite norfluoxetine. Brain neurotransmission processes related to serotonin and choline and liver metabolic status were simultaneously altered. DOM added at 1 mg/L had no effect on the accumulation of fluoxetine or its metabolites in different tissues of the fish. However, at 10 mg/L DOM facilitated fluoxetine and norfluoxetine accumulation in the liver, brain, kidney, gill and bile tissues of the fish. The neuroendocrine-disrupting effects on fish caused by fluoxetine were also enhanced by the co-addition of DOM at 10 mg/L. Binding with fluoxetine and the inhibition of metabolic functions caused by DOM may be responsible for this increase in effects. These findings imply that at high concentrations DOM can increase the toxicity of environmentally relevant concentrations of fluoxetine to fish.

Transcriptome alterations in female Daphnia (Daphnia magna) exposed to 17β-estradiol

The molecular mechanism of evaluating 17β-estradiol (E₂)-induced toxicity in female Daphnia magna has not been determined. In this study, the transcriptome of D. magna was analyzed after exposure to three different concentrations (0, 10, and 100 ng L^-1) of E₂ at 3, 6, and 12 h. The results showed 351-17,221 significantly up-regulated and 505-10,282 significantly down-regulated genes (P < 0.05). Overall, the selected largest 10,282 (10 ng L^-1vs control at 12 h) down-regulated and 17,221 (100 vs 10 ng L^-1) up-regulated genes were identified; following annotation, pathways in cancer and RNA transport were found to be enriched according to the interaction network. Among all completed comparisons, KEGG pathways related to the immune system, cancer, disease infection, and active compound metabolism were identified by short time series expression miner analysis. A different set of genes fluctuated in a "U"-shaped pattern over time and at different concentrations of E₂, whereas some genes associated with disintoxication showed a reverse "U"-shaped response as E₂ administration was increased. These results suggest that E₂ exposure caused transcriptional changes in the immune system, disintoxication, disease prevention, and the protein degradation pathway.

Invertebrates facing environmental contamination by endocrine disruptors: Novel evidences and recent insights

The crisis of biodiversity we currently experience raises the question of the impact of anthropogenic chemicals on wild life health. Endocrine disruptors are notably incriminated because of their possible effects on development and reproduction, including at very low doses. As commonly recorded in the field, the burden they impose on wild species also concerns invertebrates, with possible specificities linked with the specific physiology of these animals. A better understanding of chemically-mediated endocrine disruption in these species has clearly gained from knowledge accumulated on vertebrate models. But the molecular pathways specific to invertebrates also need to be reckoned, which implies dedicated research efforts to decipher their basic functioning in order to be able to assess its possible disruption. The recent rising of omics technologies opens the way to an intensification of these efforts on both aspects, even in species almost uninvestigated so far.

Metabolomic profiles associated with exposure to per- and polyfluoroalkyl substances (PFASs) in aquatic environments

Per- and polyfluoroalkyl substances (PFASs) are frequently detected in aquatic environments. Longer chained perfluoroalkyl acids (PFAAs), in particular, have been found to bioaccumulate in a broad range of aquatic biota. PFAAs have a physiochemical similarity to naturally occurring fatty acids and could potentially disrupt metabolic processes, however, there has been limited study in this area, especially in aquatic species. In this study, the associations between PFAAs and metabolite profiles were investigated in crustaceans. Eastern School Prawn (Metapenaeus macleayi) were obtained from three different locations (n = 15 per location) with similar environmental conditions but different levels of PFAA contamination. The concentrations of PFAAs, fatty acids and amino acids were analysed and differences in PFAA and metabolite profiles were evaluated. Different PFAA profiles were mirrored by significant differences in the composition of both fatty acid and amino acid profiles, indicating a potential association between PFAA concentration and the composition of metabolites in prawns. These results highlight a need for further research investigating the impacts of PFAA exposure, with the current study providing a foundation for further investigation of the relationship between PFAA bioaccumulation and organism metabolism.

Metabolic profiling of Daphnia magna exposure to a mixture of hydrophobic organic contaminants in the presence of dissolved organic matter

The hydrophobic organic contaminants triclosan, triphenyl phosphate (TPhP) and diazinon sorb to dissolved organic matter (DOM) and this may alter their bioavailability and toxicity. ¹H nuclear magnetic resonance (NMR)-based metabolomics was used to investigate how DOM at 1 and 5 mg organic carbon/L may alter the metabolome of Daphnia magna from exposure to equitoxic mixtures of triclosan, TPhP and diazinon. These contaminants have different modes of action toward D. magna. The contaminant concentrations in each mixture were an equal percentage of their lethal concentration to 50% of the population (LC₅₀) values, which equates to 1250 μg/L TPhP, 330 μg/L triclosan and 0.9 μg/L diazinon. The ternary mixture exposure at 1% LC₅₀ values did not alter the D. magna metabolome. Contaminant mixture exposures at 5%, 10%, and 15% LC₅₀ values decreased glucose, serine and glycine concentrations and increased asparagine and threonine concentrations, suggesting disruptions in energy metabolism. The contaminant mixture had a unique mode of action in D. magna and DOM at 1 and 5 mg organic carbon/L did not change this mode of action. The estimated sorption of triclosan, TPhP or diazinon to DOM at 1 or 5 mg organic carbon/L in this experimental design was calculated to be <50% for each contaminant. This suggests that the mode of action of the contaminant mixture was not altered by DOM because the two environmentally relevant concentrations of DOM may have not substantially altered contaminant bioavailability. Our results indicate that DOM may not inevitably mitigate or alter the sub-lethal toxicity of a mixture of hydrophobic organic contaminants. This indicates the complexity of predicting the molecular-level toxicity of environmental mixtures. For adequate risk assessment of freshwater ecosystems, it is vital to account for the combined sub-lethal toxicity of an environmental mixture of contaminants.

Effect of corn straw biochar application to sediments on the adsorption of 17α-ethinyl estradiol and perfluorooctane sulfonate at sediment-water interface

The immobilization of organic contaminants in sediment-water systems is of growing concern. Using biochar as sorbent amendment to reduce the mobility of pollutants in the sediment-water interface is becoming increasingly popular as a low-cost and environmentally friendly option. In this study, we mixed sediment from the Weishan Lake with biochar (0%, 2%, and 5% (w/w)) derived from corn straw to investigate the adsorption of perfluorooctane sulfonate (PFOS) and 17α-ethinyl estradiol (EE2). Biochar addition significantly improved the adsorption rates and capacities of EE2 and PFOS on sediments by the factors 1.7-3.5; the organic carbon concentration in the sediment was the main factor influencing this process. The sorption of EE2 and PFOS to sediment was near-linear (Freundlich exponent 1/n of 0.799-0.805), but non-linear for biochar (0.430-0.476) and sediment+biochar (0.370-0.421). The mobility of PFOS in the water-sediment system after biochar addition was significantly reduced, with a considerable increase (about three times) in the sediment-water distribution coefficient K_d. Compared to EE2, PFOS is anionic compound and contains hydrophobic C-F chains and hydrophilic S-O groups, making it more susceptible pH influences and resulting in interactions with-OH, -C=O, Si-O-Si, -O-Si, and -Al-O-Al groups via hydrogen bonding, ligand exchange, and surface complexation. We suggest that biochar amendment at ～5% is a viable approach to immobilize EE2 and PFOS at the sediment-water interface.

Metabolomic responses to pre-chlorinated and final effluent wastewater with the addition of a sub-lethal persistent contaminant in Daphnia magna

Consumer products such as perfluorooctanesulfonic acid (PFOS) and pharmaceuticals (PCPPs) enter aquatic ecosystems through inefficient removal during wastewater treatment. Often, the sterilization process of wastewater includes the addition of sodium hypochlorite that can react with PCPPs and other organic matter (i.e., dissolve organic matter) to generate disinfection by-products and can cause the final effluent to be more harmful to aquatic organisms. Here, we exposed Daphnia magna to two stages of wastewater, the pre-chlorinated wastewater (PreCl) and the final effluent. In addition, we exposed D. magna, to the final effluent with a concentration gradient of added PFOS, to investigate if this persistent contaminant altered the toxicity of the final effluent. After 48 h of contaminant exposure, we measured the daphnids metabolic responses to the different stages of wastewater treatment, and with the addition of PFOS, utilizing proton nuclear magnetic resonance spectroscopy and liquid chromatography tandem mass spectrometry. We found few significant changes to the metabolic profile of animals exposed to the PreCl wastewater; however, animals exposed to the final effluent displayed increases in many amino acids and decreases in some sugar metabolites. With the addition of PFOS to the final effluent, the metabolic profile shifted from increased amino acids and decreased sugar metabolites and energy molecules especially at the low and high concentrations of PFOS. Overall, our results demonstrate the metabolome is sensitive to changes in the final effluent that are caused by sterilization, and with the addition of a persistent contaminant, the metabolic profile is further altered.