Search

Cement used in structures such as bridges, dams, and retaining walls built on the aquatic ecosystem harms different organisms. The current study reveals the effect of pozzolanic cement (PC) on Nile Tilapia (Oreochromis niloticus). The LC50 value for O. niloticus exposed to 6 different PC concentrations for 24 hours was calculated as 306.66 mg L-1. Increasing PC concentration significantly increased the pH of water (<10) at the end of the study (p<0.05). The increase in pH level showed a positive correlation with the increase in fish mortality (p<0.05). In addition, PC negatively affected the hematological parameters of fish. Thus, the current study reveals the negative effects of PC on O. niloticus in the acute period. Future studies should focus on developing cement with environmentally friendly materials that will not affect the pH level of water. [ABSTRACT FROM AUTHOR]

Computational toxicology is a rapidly growing field that utilizes artificial intelligence (AI) and machine learning (ML) to predict the toxicity of chemical compounds. Computational toxicology is an important tool for assessing the risks associated with the exposure of finfish and shellfish to environmental contaminants. By providing insights into the behavior and effects of these compounds, computational models can help to inform management decisions and protect the health of aquatic ecosystems and the humans who depend on them for food and recreation. In aqua-toxicology research, Quantitative Structure-Activity Relationship (QSAR) models are commonly used to establish the relationship between chemical structures and their aquatic toxicity. Various ML algorithms have been developed to construct QSAR models, including Random Forest (RF), Artificial Neural Networks (ANNs), Support Vector Machines (SVMs), Bayesian networks (BNs), k-Nearest Neighbor (kNN), Probabilistic Neural Networks (PNNs), Naïve Bayes, and Decision Trees. Deep learning techniques, such as Convolutional Neural Networks (CNNs) and Recurrent Neural Networks (RNNs), have also been applied in computational toxicology to improve the accuracy of QSAR predictions. Moreover, data mining graphs, networks and graph kernels have been utilized to extract relevant features from chemical structures and improve predictive capabilities. In conclusion, the application of artificial intelligence and machine learning in the field of computational toxicology has immense potential to revolutionize aquatic toxicology research. Through the utilization of advanced algorithms and data analysis techniques, scientists can now better understand and predict the effects of various toxicants on aquatic organisms. [ABSTRACT FROM AUTHOR]

Microplastics are ubiquitous in aquatic systems and break down into submicron particles that can interact with aquatic toxic chemicals. These interactions may affect the detection of toxicants when using bacteria as a biomonitoring tool. This study examined the effects of model polystyrene (PS)-based submicron particles on the detection of aqueous geno- and cytotoxicity by genetically modified bioluminescent (GMB) bacteria. The toxicities were tested in three treated wastewater (TWW) effluents before and after chlorination. The PS plastics included negatively charged sulfate-coated (S-PS) and pristine (P-PS) particles of different sizes (0.1, 0.5, and 1.0 µm) that were present at different concentrations. Chlorinated or not, the S-PS and P-PS particles per se were not toxic to the GMB bacteria. However, exposure of PS particles to TWW effluents can significantly reduce the measured geno- and cytotoxicity. Adsorption of toxic compounds to polymer particles can limit the ability of the bacteria to detect those compounds. This masking effect may be mitigated by TWW chlorination, possibly due to the formation of new toxic material. Due to interactions between toxic TWW constituents and the plastics particles, water samples containing particle-associated contaminants and/or their transformation products may be declared non-toxic, based on bacterial tests as a biomonitoring tool. [ABSTRACT FROM AUTHOR]

William Odling(1829-1921) was a British physician and chemist who carried on important work about chemical nomenclature, classification of the elements, techniques for the toxicological analysis of arsenic, antimony and copper, analysis of river and cesspool waters, etc. Odling showed that the different opinions regarding the composition of hippuric acid were due to the use of different reagents to attack only one of the components of the acid and that the overall picture showed that hippuric acid had to be composed of benzoic acid and glycine. Odling studied in detail the use of the toxicological exams of Reinsch for detecting arsenic, antimony and copper, and of Marsh for arsenic, and determined the appropriate conditions for avoiding false results as well as increase the detection limits. Together with Dupré they showed that copper was naturally present in a large variety of organic matter (i.e. bread, flour, wheat, blood, flesh, human muscle, liver and kidney tissue, etc.). Together with Buckton they used alkyl derivatives of aluminum to prove that the correct formula of aluminum chloride was AlCl3 and not Al2Cl3. Odling used speculative arguments to show that the atomic mass of oxygen was 16 and that the molecular mass and formula of water were 18 and H2O, respectively. [ABSTRACT FROM AUTHOR]

A multigenerational test with Chironomus riparius was performed to assess long‐term effects on life‐traits of exposure to selected perfluoroalkyl compounds: perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA), and perfluorobutane sulfonate (PFBS). These persistent contaminants are widespread in aquatic ecosystems at low concentrations, possibly exerting long‐term toxicity. Larvae of C. riparius of a native population were exposed for 10 generations to 10 μg/L nominal concentrations of PFOS, PFOA, and PFBS, comparable with the maximum values found in European rivers. All treatments showed reduced growth at most/several generations. No effects on survival, development, and reproduction were found. A final tolerance‐induction test was performed exposing the pre‐exposed experimental cohorts to 100 µg/L PFOS and 150 µg/L PFOA for a whole life cycle. Factorial analysis of variance revealed no difference between treatments (i.e., PFOS vs PFOA), indicating no induced tolerance. Instead, organisms pre‐exposed to PFBS were the most stressed, followed by those pre‐exposed to PFOA and PFOS, with earlier emergence and reduced adult weight. The results may be related to general stress and genetic erosion induced by long‐term laboratory culture, but also to long‐term toxicant exposure. However, no effects at the population level (population growth rate) were proved, and thus a toxicity risk in real ecosystems at the tested concentrations seems unlikely. Environ Toxicol Chem 2019;00:1–12. © 2019 SETAC [ABSTRACT FROM AUTHOR]

Flexible, rapid, and predictive approaches that do not require the use of large numbers of vertebrate test animals are needed because the chemical universe remains largely untested for potential hazards. Development of robust new approach methodologies and nontesting approaches requires the use of existing information via curated, integrated data sets. The ecological threshold of toxicological concern (ecoTTC) represents one such new approach methodology that can predict a conservative de minimis toxicity value for chemicals with little or no information available. For the creation of an ecoTTC tool, a large, diverse environmental data set was developed from multiple sources, with harmonization, characterization, and information quality assessment steps to ensure that the information could be effectively organized and mined. The resulting EnviroTox database contains 91 217 aquatic toxicity records representing 1563 species and 4016 unique Chemical Abstracts Service numbers and is a robust, curated database containing high‐quality aquatic toxicity studies that are traceable to the original information source. Chemical‐specific information is also linked to each record and includes physico‐chemical information, chemical descriptors, and mode of action classifications. Toxicity data are associated with the physico‐chemical data, mode of action classifications, and curated taxonomic information for the organisms tested. The EnviroTox platform also includes 3 analysis tools: a predicted‐no‐effect concentration calculator, an ecoTTC distribution tool, and a chemical toxicity distribution tool. Although the EnviroTox database and tools were originally developed to support ecoTTC analysis and development, they have broader applicability to the field of ecological risk assessment. Environ Toxicol Chem 2019;9999:1–12. © 2019 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals, Inc. on behalf of SETAC. [ABSTRACT FROM AUTHOR]

The antidepressant amitriptyline is a widely used selective serotonin reuptake inhibitor that is found in the aquatic environment. The present study investigates alterations in the brain and the liver metabolome of gilt‐head bream (Sparus aurata) after exposure at an environmentally relevant concentration (0.2 µg/L) of amitriptyline for 7 d. Analysis of variance–simultaneous component analysis is used to identify metabolites that distinguish exposed from control animals. Overall, alterations in lipid metabolism suggest the occurrence of oxidative stress in both the brain and the liver—a common adverse effect of xenobiotics. However, alterations in the amino acid arginine are also observed. These are likely related to the nitric oxide system that is known to be associated with the mechanism of action of antidepressants. In addition, changes in asparagine and methionine levels in the brain and pantothenate, uric acid, and formylisoglutamine/N‐formimino‐L‐glutamate levels in the liver could indicate variation of amino acid metabolism in both tissues; and the perturbation of glutamate in the liver implies that the energy metabolism is also affected. These results reveal that environmentally relevant concentrations of amitriptyline perturb a fraction of the metabolome that is not typically associated with antidepressant exposure in fish. Environ Toxicol Chem 2019;00:1–13. © 2019 SETAC [ABSTRACT FROM AUTHOR]

An introduction is presented in which the editor discusses articles in the issue on topics including review of arsenic exposure and lung cancer; chemical aquatic toxicity for marine crustaceans via machine learning; and the effects of lead on the development of somite in chick embryos.

Aquatic toxicity is a crucial endpoint for evaluating chemically adverse effects on ecosystems. Therefore, we developed in silico methods for the prediction of chemical aquatic toxicity in marine environment. At first, a diverse data set including different crustacean species was constructed. We then built local binary models using Mysidae data and global binary models using Mysidae, Palaemonidae, and Penaeidae data. Molecular fingerprints and descriptors were employed to represent chemical structures separately. All the models were built by six machine learning methods. The AUC (area under the receiver operating characteristic curve) values of the better local and global models were around 0.8 and 0.9 for the test sets, respectively. We also identified several chemicals with selective toxicity on different species. The analysis of selective toxicity would promote to design greener chemicals in a specific environment. Finally, to understand and interpret the models, we explored the relationships between chemical aquatic toxicity and the molecular descriptors. Our study would be helpful in gaining further insights into marine organisms, prediction of chemical aquatic toxicity and prioritization of environmental hazard assessment. [ABSTRACT FROM AUTHOR]

Abstract The release of active pharmaceutical ingredients (APIs) into the environment is of great concern for aquatic ecosystem as many of these chemicals are designed to exert biological activity. Hence, their impact on non-target organisms like fish would not be surprising. In this respect, we revisited fish toxicity data of pharmaceuticals to generate linear and non-linear quantitative structure-toxicity relationships (QSTRs). We predicted fish lethality data from the validated QSTR models for 120 APIs with no experimental fish toxicity data. Toxicity of APIs on aquatic organisms is not fully characterized. Therefore, to provide a mechanistic insight for the assessment of API's toxicity to fish, the outcome of the derived QSTR models was integrated with structure-based toxicophore and molecular docking studies, utilizing the biomarker enzyme acetylcholinesterase originating from fish Torpedo californica (Tc AChE). Toxicophore virtual screening of 60 chemicals with p T > 0 identified 23 hits as potential Tc AChE binders with binding free energies ranging from −6.5 to −12.9 kcal/mol. The Tc AChE-ligand interaction analysis revealed a good nesting of all 23 hits within Tc AChE binding site through establishing strong lipophilic and hydrogen bonding interactions with the surrounding key amino acid residues. Among the chemicals passing the criteria of our integrated approach, majority of APIs belong noticeably to the Central Nervous System class. The screened chemicals displayed not only comprehensive toxicophore coverage, but also strong binding affinities according to the docking calculations, mainly due to interactions with Tc AChE's key amino acid residues Tyr121, Tyr130, Tyr334, Trp84, Phe290, Phe330, Phe331, Ser122, and Ser200. Moreover, we propose here that binding of pharmaceuticals to AChE might have a potential in triggering molecular initiating events for adverse outcome pathways (AOPs), which in turn can play an important role for future screening of APIs lacking fish lethality data. Graphical abstract fx1 Highlights • LC 50 values of 120 active pharmaceutical ingredients (APIs) with no data for fish were predicted. • MLR and CP ANN models successfully predict the LC 50 values of APIs. • An integrated approach (IA) was used to understand the potential impact of APIs to fish, which plays an important role in assessing the risk of APIs in the environment. • Potentially toxic APIs mainly belong to the class of central nervous system (CNS) drugs. • The effect of APIs on the CNS in fish may end up with lethality and/or unintended health problems. [ABSTRACT FROM AUTHOR]

Abstract The widespread use of the synthetic estrogen 17 α-ethinylestradiol (EE 2) has resulted in elevated levels in aquatic environments, where it is known to act as an endocrine disrupting chemical affecting fish and other aquatic organisms. Examining changes in the structure of the fish' gonads and liver has proven to be an effective approach for assessing these impacts. While changes have been reported for various fish species, it is not clear whether impacts are equally severe in live-bearing fishes. The present study looked at gonadal and liver development in EE 2 -exposed least killifish (Heterandria formosa), a live-bearing Poeciliid. Exposures to 0, 5, or 25 ng/L EE 2 began within six days of birth and continued until fish became sexually mature 12–23 weeks later. Exposure to 5 ng/L EE 2 resulted in severe intersex in fish with external male characteristics, a slowdown of spermatogenesis in these intersex fish and a slowdown of oogenesis in the female fish. Moreover, these fish had a variety of liver injuries. Fish exposed to 25 ng/L EE 2 exhibited intersex but at a lower frequency than occurred at 5 ng/L. In contrast, liver damage and slowdown of both oogenesis and spermatogenesis exhibited the typical dose-dependence. These findings illustrate the importance of including histological analyses when assessing endocrine disruption in fish, demonstrate that the live-bearing mode of reproduction appears to provide limited protection from the effects of waterborne EE 2 , and provide further evidence that EE 2 has multiple impacts on fish health and reproduction that are severe enough to potentially affect fish populations. Graphical abstract fx1 Highlights • Live-bearing fish are also vulnerable to water-borne endocrine disrupting chemicals. • Exposure from birth to sexual maturity resulted in males with developing eggs. • The production of gametes was also slowed down following exposure, in both sexes. • Exposure not only affected sexual development, it also resulted in liver damage. [ABSTRACT FROM AUTHOR]

Abstract Unionid mussels are considered sensitive to salinity and there is growing concern in arid and semi-arid regions that declining flows coupled with anthropogenic impacts are amplifying natural salinity levels. In this study, we tested the effects of varying salinity concentrations (3.0, 4.0, 5.0, 6.0, 7.0 and 10.0 ppt NaCl) on survival of adult Popenaias popeii , (Texas Hornshell). This species occurs in the Rio Grande basin of Texas and northern Mexico, an arid to semi-arid stream plagued by salinization, and was recently listed as Endangered under the U.S. Endangered Species Act. We performed 2, 4, and 10-day toxicity tests on individuals from two disjunct populations: Laredo, TX, and the Lower Canyons of the Rio Grande near Big Bend National Park. We found no significant differences in LC50 estimates between populations at 96-hrs or 10-days but significant differences in TUD50s at 5 ppt between populations, which indicates that tolerance does not vary but sensitivity may between these populations. Overlaying LC50 estimates at 10-days for both populations on plots of salinity (ppt) measured over time, we show parts of the Rio Grande periodically approach or exceed 4.0 ppt, indicating these reaches are becoming unsuitable for P. popeii and populations within them at risk. Highlights • We assessed salinity tolerance of an endangered mussel from the Rio Grande. • 2, 4, and 10-day toxicity tests were conducted on individuals from two populations. • Salinity tolerance does not vary between populations but sensitivity does. • Springs and groundwater inputs along with local adaptation likely responsible. [ABSTRACT FROM AUTHOR]

Climbazole is an antifungal active ingredient used in personal care products. After application this chemical reaches the aquatic environment and may pose a risk to fish. In the present study, we measured the transcriptional effects of essential genes related to a wide range of signaling pathways on zebrafish eleutheroembryos exposed to climbazole at environmentally relevant and predicted worst‐case environmental concentrations, and explored the potential biomarkers via partial least squares discriminant analysis. Transcription analysis covering up to 73 genes revealed significant down‐regulation of circadian rhythm‐ and steroidogenesis‐related genes in zebrafish embryos and larvae after exposure to environmentally relevant concentrations of climbazole. This topical antifungal agent also modulated the transcripts of genes involved in inflammation, oxidative stress, oocyte maturation, and sexual differentiation at predicted worst‐case environmental concentrations. In addition, mprα, igf3, nr1d1, nr1d2b, cyp19a1a, vtg1, il‐1β, and il‐8 were chosen as potential biomarkers in embryonic zebrafish following exposure to climbazole. These findings can help us understand the remarkable transcriptional response to climbazole in the early life stage of zebrafish. Future research should elucidate whether the transcriptional modulation translates into metabolic phenotypes associated with the corresponding signaling pathways. Environ Toxicol Chem 2019;38:794–805. © 2019 SETAC Regulation of transcriptional response in zebrafish eleutheroembryos exposed to climbazole. [ABSTRACT FROM AUTHOR]

In previous work we intensively studied the acute responses of the cladoceran Ceriodaphnia dubia to major geochemical ions (Na+, K+, Ca2+, Mg2+, Cl–, SO42–, and HCO3–/CO32–), culminating in the development of models to predict acute toxicity from ionic composition. To quantitatively evaluate whether the toxicological behavior of major ions observed for C. dubia extends to chronic toxicity, we conducted 58 chronic toxicity tests with individual major salts and binary mixtures thereof. Chronic responses paralleled those demonstrated previously for acute exposure, specifically 1) similar relative toxicity of individual salts; 2) different Na salts showing similar potency when exposure is expressed as osmolarity; 3) toxicity of Mg, Ca, and K salts related to cation activity; 4) decreased toxicity of Na and Mg salts when Ca activity is increased at less than toxic concentrations; 5) additive behavior for salt mixtures sharing a common cation; and 6) independent behavior for salt mixtures with dissimilar cations, except Mg/Ca mixtures which appeared additive. Acute‐to‐chronic ratios were fairly consistent among salts, with values of approximately 1.8 for acute 50% lethal concentration (LC50) to chronic 50% effect concentration (EC50) and 2.8 for LC50/EC20 when expressed on an activity basis. Adjusting the previous acute toxicity model for acute‐to‐chronic ratios yielded chronic models that predict chronic toxicity within the range of intertest variability. Because these models are informed by a wide range of ion mixtures, they should provide robust assessment tools for natural waters enriched with major ions. Environ Toxicol Chem 2019;38:769–783. © Published 2018 Wiley Periodicals Inc. on behalf of SETAC. This article is a US government work and, as such, is in the public domain in the United States of America [ABSTRACT FROM AUTHOR]

Highlights • The use of individual variation as an endpoint in recent aquatic toxicological literature was evaluated. • The reasons for observed variation were discussed. • The possibility of phenotypic plasticity as a component of environmental responses was introduced. • It was concluded that although variation may change in response to contamination, it is currently not evaluated. Abstract The mean value of any parameter and its changes are usually discussed, when ecotoxicological studies are carried out. However, also the variation of any parameter and its changes can be important components of the responses to environmental contamination. Although the homogeneity of variances is commonly tested, testing is done for the use of correct statistical methods, not because of exploring the possibility that variability and its changes could be important components of environmental responses. We evaluated recent aquatic toxicological literature and found that in the majority of articles indicating that homogeneity of variances was tested and giving the result of testing, the assumption of homogeneity was not fulfilled. Further, it was observed that in some studies experimental treatment clearly affected the variability. In this commentary we discuss the reasons for variability: measurement errors, experimental design, genetic heterogeneity and phenotypic plasticity, and conclude that even after accounting for experimental design and genetic makeup significant variability remains. This plasticity may change in environmental responses as suggested by a hypothetical example, and as confirmed by experimental data. As a consequence, the changes of variability can be significant, even when the means do not differ. Because of this, variability and its changes should always be analysed and reported. This will be easy, since the datasets are exactly the same for comparing the variances and means, and as normally variances are tested for homogeneity. It is likely that much new information about the responses of organisms to environmental contamination will be obtained. However, the present journal practises tend to discourage one from concentrating on anything but the mean. In contrast, we think it is imperative that variability is always included as an endpoint in data analysis in the future. [ABSTRACT FROM AUTHOR]

Highlights • The applicability domain of the fish embryo baseline toxicity QSAR can be extended to ionizables organic compounds. • The use of speciation-corrected liposome-water distribution ratio log D lipw (pH) as descriptor to predict FET baseline toxicity was successfully demonstrated. • Toxic ratio analysis resulted in a generally consistent MoA classification. • Critical aspect for the effect analysis of IOCs is the pH. Abstract The fish embryo toxicity (FET) test with the zebrafish Danio rerio is widely used to assess the acute toxicity of chemicals thereby serving as animal alternative to the acute fish toxicity test. The minimal toxicity of neutral chemicals in the FET can be predicted with a previously published Quantitative Structure-Activity Relationship (QSAR) based on the liposome-water partition coefficient K lipw. Such a QSAR may serve to plan toxicity testing and to evaluate whether an observed effect is caused by a specific mode of action (MoA). The applicability domain of this QSAR was extended to ionizable organic chemicals (IOC) without any modification of slope and intercept simply by replacing the K lipw with the speciation-corrected liposome-water distribution ratio (D lipw (pH)) as descriptor for the uptake into the embryo. FET LC 50 values of IOCs were extracted from an existing FET database and published literature. IOCs were selected that are present concomitantly as neutral and charged, species, i.e., acids with an acidity constant p K a <10 and bases with p K a >5. IOCs were grouped according to their putative MoA of acute aquatic toxicity. The toxic ratios (TR) in the FET were derived by of the experimental FET-LC 50 in comparison with the baseline toxicity QSAR. Baseline toxicants were confirmed to align well with the FET baseline toxicity QSAR (TR < 10). Chemicals identified to act as specific or reactive chemicals with the toxic ratio analysis in the FET test (TR > 10) were generally consistent with MoA classification for acute fish toxicity with a few exceptions that were suspected to have had issues with the stability of the pH during testing. One critical aspect for the effect analysis of ionizable chemicals is the pH, since the difference between pH and p K a determines the speciation and thereby the D lipw (pH). [ABSTRACT FROM AUTHOR]

A database of 1480 chemicals with 47 associated modes of action compiled from the literature encompasses a wide range of chemical classes (alkanes, polycyclic aromatic hydrocarbons, pesticides, and polar compounds) and includes toxicity data for 79 different aquatic genera. The data were split into a calibration group and a validation group (80/20) to apply k‐nearest neighbors (k‐NN) methodology to predict the toxic mode of action for the compound. Other approaches were tested (support vector machines and linear discriminant analysis) as well as variations in the k‐NN technique (distance weighting, feature weighting). Best‐prediction results were found with k = 3, in a voting platform with optimized feature weighting. Using the predicted mode of action, the appropriate polyparameter target site model for that mode of action is applied to calculate the 50% lethal concentration (LC50). Predicted LC50s for the validation database resulted in a root‐mean squared error (RMSE) of 0.752. This can be compared to an RMSE of 0.655 for the same validation set using the reference mode of action labels. The complete database resulted in an RMSE of 0.793 for reference mode of action labels. This confirms that the classification model has sufficient accuracy for predicting the mode of action and for determining toxicity using the target site model. Environ Toxicol Chem 2019;38:375–386. © 2018 SETAC [ABSTRACT FROM AUTHOR]

Abstract The contaminants of emerging concern (CEC) are universally detected in surface water and soil. They can affect the wild life, and their subsequent translocation through the food chain can affect human health, which is an issue of serious concern. Very few amounts of ecotoxicological data are available on the environmental behavior and ecotoxicity of CEC, thus modeling approaches are essential to bridge the existing gap in experimental data. In this present study, we have developed quantitative structure-toxicity relationship (QSTR) models using a data set of 75 compounds for the prediction of aquatic ecotoxicity of CECs on fresh water planarian (Dugesia japonica) by partial least squares (PLS) regression algorithm using simple molecular descriptors selected by genetic algorithm approach. We also explore the correlations between toxicity against D. japonica and those against daphnia (D. magna) and fish (P. promelas), and these were improved on addition of a few molecular descriptors (B08[C-O] and B09[N-O] in case of daphnia and C-006 and H-052 in case of fish) which allowed us to develop predictive interspecies quantitative structure toxicity-toxicity relationship (QSTTR) models, allowing to extrapolate data from one endpoint to another endpoint. The QSTR (Q2 LOO ranging from 0.630 to 0.720 and R2 pred ranging from 0.723 to 0.798) and QSTTR (Q2 LOO = 0.60 and 0.67, R2 pred = 0.88 and 0.84) models have desirable statistical qualities and acceptable internal and external validation measures, meeting rigorous criteria of different validation metrics and showing acceptability for regulatory purposes as proposed by Organization for Economic Cooperation and Development (OECD). Consensus predictions were also performed based on multiple models generated in this study by using the "Intelligent Consensus Predictor" (ICP) tool to enhance the prediction quality for external set compounds. Graphical abstract fx1 Highlights • New QSTR models are developed using computed 2D descriptors for the toxicity of CECs to D. japonica. • We quantitatively show that hydrophobicity and aromaticity increase the aquatic toxicity of CECs. • "Intelligent Consensus Predictor" was used to enhance the prediction quality for external set compounds. • An interspecies model for toxicity between P. promelas and D. japonica was established for the first time. [ABSTRACT FROM AUTHOR]

Abstract Lomefloxacin, an antibacterial agent with known photo-induced toxicity in clinical studies, is frequently detected in aquatic environments. Investigating the photo-induced toxicity of lomefloxacin in aquatic organisms is therefore of importance for assessing its ecological risks. In this study, the effects of lomefloxacin on survival, growth and reproduction of Daphnia magna under simulated sunlight radiation (SSR) were investigated, and the mechanism of action was revealed. Results indicated that SSR containing UV radiation increased the acute toxicity of lomefloxacin to Daphnia magna relative to white fluorescent light irradiation. Under SSR, 100 μM lomefloxacin significantly enhanced reactive oxygen species (ROS) generation and lipid peroxidation, and decreased activities of superoxide dismutase and catalase. The biochemical observations and apparent effects on the organism indicate that oxidative stress plays a central role in the acute photo-induced toxicity. Chronic toxicity results showed that SSR significantly affected growth and reproduction of Daphnia magna , whereas lomefloxacin reduced the damage of UV radiation in SSR through light shielding. This study provides insight into the mechanism of photo-induced toxicity and can support the risk assessment of chemicals in the aquatic environment by including the impacts of sunlight irradiation on toxicity. Graphical abstract fx1 Highlights • Simulated sunlight radiation enhances toxicity of lomefloxacin to Daphnia magna. • Oxidative stress plays a central role in phototoxicity of lomefloxacin to daphnia. • UV and lomefloxacin display an antagonistic joint action on chronic toxicity. [ABSTRACT FROM AUTHOR]

Abstract The recent increase of freshwater eutrophication has favored cyanobacteria blooms and consequently the increase of toxins such as microcystin-LR in aquatic environments, but few is know about the associated effect of toxin and other compounds. Pyriproxyfen is an insecticide indicated by WHO (World Health Organization) to control Aedes aegypti mosquito (vector of Dengue, Chikungunya and Zika diseases), however, the effects are not well described to non-target species, such as fish. The early life stages (ELS) of fish are more sensitive to chemical stress due to higher metabolic rate, immature immune system and high superficial area/volume ratio. In the current study, ELS of R. quelen a Neotropical fish were exposed to environmentally realistic concentrations of microcystin (1, 10 and 100 µg L−1 ; M1, M2 and M3 groups, respectively) from an algal extract, pyriproxyfen (1 and 10 µg L−1, P1 and P2) and their association (co-exposure). The hatching, survival and larvae deformities were analyzed, and applied a mathematical model to evaluate the effects on the population size along further generations. Both compounds were toxic to embryos/larvae of fish , but the effects were more pronounced in M2, P1M2 and P2M1 for hatching and M2, P1M2, P2M1 and P1 for survival. Deformities prevailed in groups exposed to the chemicals at 48 hpf (hours post-fertilization) were suggestions of toxicological interaction in P1M2, P2M1 and P2M2 at 48 and 72 hpf. In 96 hpf, the levels of deformities were lower than in previous times. Model predicted population density over 100 years decreased to lower than 0.5 (50%) in all groups, except for P1M1, indicating risk of extinction. P1M2 had the worse results, followed by M2, P1M3 and P2M1. Cyanobacterial blooms can lead to microcystin-LR levels higher than M2 (10 µg L−1), and the suggestion of toxicological interaction with pyriproxyfen is relevant because both compounds may potentially coexist in aquatic environments. Finally, mathematical models may provide an ecological interpretation of the risk of exposure of fish. Graphical abstract fx1 Highlights • Embryos of R. quelen fish were exposed to the cyanotoxin microcystin and insecticide pyriproxyfen. • Effects on the hatching and survival of embryos and larvae occurred. • Morphological deformities were more frequent at the first 72 h of development. • Mathematical modelling revealed a risk of extinction to the species R. quelen. [ABSTRACT FROM AUTHOR]

Oil spill response requires consideration of several countermeasures including chemical dispersants, but their potential toxicity to aquatic species poses a concern. Considerable in vivo aquatic toxicity data from laboratory exposures have been generated since 2010 for current‐use dispersants. The objective of the present review is to provide a synthesis of these data to improve dispersant hazard assessments. Data from multiple studies were evaluated based on reliability criteria. Although procedures, standards, endpoints, and statistical approaches were usually described, nearly a quarter of sources did not provide sufficient information to judge study quality but were considered on a case‐by‐case basis. Data were used to develop dispersant‐specific species sensitivity distributions and hazard concentrations protective of 95% of the species (HC5). Given data limitations, post‐2010 toxicity data were augmented with pre‐2010 data and model predictions. The HC5s calculated for 54 dispersants fell mostly within the moderate to slightly toxic range and were compared to field dispersant‐only concentrations estimated from operational application rates under conservative assumptions. Based on available evidence, dispersants may not pose a significant risk under field conditions to most aquatic species, if proper application and dilution are taken into account. Recommendations on improved toxicity testing and reporting as well as research needs are also provided. Environ Toxicol Chem 2018;37:2989–3001. © 2018 SETAC SSDs for Corexit 9500 developed from pre‐2010 (red) and post‐2010 (blue) toxicity data. [ABSTRACT FROM AUTHOR]

Abstract Isoprostanes (IsoPs) are a class of oxidation products naturally formed in vivo that are indicative of endogenous oxidative stress. In individuals with chronic and oxidative stress related diseases, IsoPs are increased to pathological levels. Since they are excreted through urine into sewage systems, IsoPs can be detected in wastewater treatment plants' (WWTPs) effluents and thus can be used to evaluate the health status of a given population. The underlying principle is that higher isoprostanes WWTPs' levels correspond to populations undergoing higher levels of oxidative stress, and thus disease. However, IsoPs are not eliminated by WWTPs and will end up being released into the aquatic environment, where they will be available for uptake by aquatic species. Being bioactive molecules, it has been suggested that IsoPs in the environment may elicit oxidative stress in aquatic organisms. In this context, we have critically reviewed the available data on IsoPs as products and effectors of toxicity, and propose the new concept of "circular toxicity". In general, IsoPs excreted by humans as a consequence of oxidative stress are released into the aquatic environment where they may interact with aquatic organisms and induce the production of more IsoPs. These stress markers, in turn, will also be excreted, increasing the already high levels of stressors in the aquatic environment and thus create an escalating cycle of oxidative stress. Graphical abstract Image 1 Highlights • Isoprostanes (IsoPs) are markers of oxidative stress. • IsoPs are released through urine into the sewage system. • IsoPs in influents of WWTPs can be used to monitor population health. • IsoPs are potential emerging contaminants found in the environment. • IsoPs maybe effectors of oxidative stress in aquatic organisms. Isoprostanes as products and effectors of toxicity. [ABSTRACT FROM AUTHOR]

Neonicotinoid insecticides are a group of plant protectants frequently detected in surface waters at low concentrations. Aquatic invertebrates therefore have the potential to be exposed chronically to low concentrations of neonicotinoids. The cladocerans Daphnia magna and Ceriodaphnia dubia are among the most commonly used invertebrate test species in aquatic toxicology. Both species are known to be acutely insensitive to neonicotinoids, and while chronic toxicity has been characterized for D. magna , little research has been conducted with C. dubia. In the present study we conducted 7-d static-renewal life cycle tests for 6 neonicotinoids (acetamiprid, clothianidin, dinotefuran, imidacloprid, thiacloprid, and thiamethoxam) with C. dubia , and a 21-d test with imidacloprid with D. magna . 7-d LC50s for C. dubia ranged from 8.42 mg L −1 for imidacloprid to > 100 mg L −1 for clothianidin; 7-d reproduction EC50s were 2.98 for thiacloprid, to > 67 mg L −1 for dinotefuran. D. magna were less sensitive than C. dubia to imidacloprid, by 4-fold for lethality and 1.5-fold for reproduction; however, acute-to-chronic ratios (ACRs) were similar. ACRs, based on 48-h acute LC50s and 7- or 21-d chronic reproduction EC10s, ranged from 5.4 for acetamiprid to 53.0 for imidacloprid (mean 36.6, CV = 51%). Chronic toxicity values for both species were orders of magnitude greater than concentrations reported in the environment, and thus hazard to these cladocerans is negligible. [ABSTRACT FROM AUTHOR]

Abstract Thiamethoxam is a neonicotinoid insecticide used widely in agriculture to control a broad spectrum of insect pests. To assess potential risks from this compound to non-target aquatic organisms, an outdoor mesocosm study was performed. Mesocosms (1300 L) were treated once with a formulated product with the active substance (a.s.) thiamethoxam at nominal concentrations of 1 (n = 3), 3 (n = 3), 10 (n = 4), 30 (n = 4), and 100 (n = 2) μg a.s./L, plus untreated controls (n = 4). Primary producers (phytoplankton), zooplankton, and macroinvertebrates were monitored for up to 93 days following treatment. Thiamethoxam was observed to have a water column dissipation half-life (DT50) of ≤1.6–5.2 days in the mesocosms. Community-based principal response curve analysis detected no treatment effects for phytoplankton, zooplankton, emergent insects, and macroinvertebrates, indicating a lack of direct and indirect effects. A number of statistically significant differences from controls were detected for individual phytoplankton and zooplankton species abundances, but these were not considered to be treatment-related due to their transient nature and lack of concentration-response. After application of 30 μg a.s./L, slight temporary effects on Asellus aquaticus could not be excluded. At 100 μg a.s./L, there was an effect with no clear recovery of Asellus observed, likely due to their inability to recolonize these isolated test systems. A statistically significant but transient reduction in the emergence of chironomids by day 23 at the 100 μg a.s./L treatment was observed and possibly related to direct toxicity from thiamethoxam on larval stages. Therefore, a conservative study specific No Observed Ecological Adverse Effect Concentration (NOEAEC) is proposed to be 30 μg a.s./L. Overall, based on current concentrations of thiamethoxam detected in North American surface waters (typically <0.4 μg/L), there is low likelihood of direct or indirect effects from a pulsed exposure on primary producers, zooplankton, and macroinvertebrates, including insects, as monitored in this study. Graphical abstract Image 1 Highlights • Thiamethoxam is detected in the surface waters of agroecosystems. • A mesocosm study to understand freshwater aquatic organism responses was performed. • No indications of ecologically significant direct or indirect effects at environmental concentrations. Acute exposures to the neonicotinoid insecticide thiamethoxam at environmentally relevant concentrations do not pose a significant risk to freshwater biota. [ABSTRACT FROM AUTHOR]

Abstract Fluazinam is a pyridinamine fungicide that induces oxidative stress and mitochondrial damage in cells, and it has been reported to be neurotoxic. To characterize the biological effects of fluazinam, we assessed mitochondrial bioenergetics, dopamine system expression, and behavior of early life staged zebrafish (0.01 μM–0.5 μM). Fluazinam at environmentally-relevant levels did not induce sub-lethal effects in larvae, but at the LC 50 (0.5 μM), fluazinam decreased basal and ATP-linked respiration significantly in embryos. As mitochondria are directly related to redox homeostasis and apoptosis, the expression of genes related to oxidative stress and apoptosis were measured. S uperoxide dismutase 2 (sod2), heat stock protein 70 (hsp70), bcl2-associated X protein (bax), and caspase 9 (casp9) mRNA levels were up-regulated by 0.5 μM fluazinam. Taken together, there was evidence for mitochondrial dysfunction and oxidative damage at the highest concentration of fluazinam (0.5 μM) tested. As there are reports for fluazinam-induced neurotoxicity in dopamine synthesizing cells, transcriptional targets in the dopamine system were assessed in the zebrafish. Tyrosine hydroxylase 1 (th1) and dopamine receptor 2a (drd2a) mRNA levels were decreased by 0.5 μM fluazinam, suggesting that this fungicide may affect the dopaminergic system. To further assess the potential for fluazinam-mediated neuromodulation, the dark photokinesis response was assessed in larvae following exposure. Larvae exposed to 0.1 μM fluazinam showed hyperactivity, while larvae exposed to 0.2 and 0.3 μM showed hypo-activity. This study demonstrates that fluazinam disrupts mitochondrial bioenergetics in zebrafish, inducing an oxidative stress response, and aberrant behaviors in larvae that are dose dependent. Highlights • Fluazinam is a pyridinamine fungicide that affects mitochondria and is neurotoxic. • Fluazinam decreased basal and ATP-linked respiration in zebrafish embryos. • Sod2 and hsp7 0 mRNA levels were increased by 0.5 μM fluazinam. • Tyrosine hydroxylase 1 and dopamine receptor 2a mRNA were decreased by fluazinam. • Fluazinam induced hyper- and hypo-activity in larval fish, a response that was dose-specific. [ABSTRACT FROM AUTHOR]

The microbiome plays an essential role in the health and onset of diseases in all animals, including humans. The microbiome has emerged as a central theme in environmental toxicology because microbes interact with the host immune system in addition to its role in chemical detoxification. Pathophysiological changes in the gastrointestinal tissue caused by ingested chemicals and metabolites generated from microbial biodegradation can lead to systemic adverse effects. The present critical review dissects what we know about the impacts of environmental contaminants on the microbiome of aquatic species, with special emphasis on the gut microbiome. We highlight some of the known major gut epithelium proteins in vertebrate hosts that are targets for chemical perturbation, proteins that also directly cross‐talk with the microbiome. These proteins may act as molecular initiators for altered gut function, and we propose a general framework for an adverse outcome pathway that considers gut dysbiosis as a major contributing factor to adverse apical endpoints. We present 2 case studies, nanomaterials and hydrocarbons, with special emphasis on the Deepwater Horizon oil spill, to illustrate how investigations into the microbiome can improve understanding of adverse outcomes. Lastly, we present strategies to functionally relate chemical‐induced gut dysbiosis with adverse outcomes because this is required to demonstrate cause–effect relationships. Further investigations into the toxicant–microbiome relationship may prove to be a major breakthrough for improving animal and human health. Environ Toxicol Chem 2018;37:2758–2775. © 2018 SETAC [ABSTRACT FROM AUTHOR]

The effluent discharged by the textile dyehouses has a seriously detrimental effect on the aquatic environment. Some dyestuffs produce toxic decomposition products and the metal complex dyes release toxic heavy metals to watercourses. Of the dyes used in the textile industry, effluents containing reactive dyes are the most difficult to treat because of their high water-solubility and poor absorption into the fibers. A range of treatments has been investigated for the decolorization of textile effluent and the adsorption seems to be one of the cheapest, effective and convenient treatments. In this review, the adsorbents investigated in the last decade for the treatment of textile effluent containing reactive dyes including modified clays, biomasses, chitin and its derivatives, and magnetic ion-exchanging particles have been critically reviewed and their reactive dye binding capacities have been compiled and compared. Moreover, the dye binding mechanism, dye sorption isotherm models and also the merits/demerits of various adsorbents are discussed. This review also includes the current challenges and the future directions for the development of adsorbents that meet these challenges. The adsorption capacities of adsorbents depend on various factors, such as the chemical structures of dyes, the ionic property, surface area, porosity of the adsorbents, and the operating conditions. It is evident from the literature survey that decolorization by the adsorption shows a great promise for the removal of color from dyehouse effluent. If biomasses want to compete with the established ion-exchange resins and activated carbon, their dye binding capacity will need to be substantially improved. [ABSTRACT FROM AUTHOR]

This study aim to evaluate the potential toxic effects of citrate coated silver nanoparticles (AgNPs) and ionic silver (AgNO 3 ) on marine microalgae Dunaliella salina under three different salinities (35, 70, and 140 g/L). The toxicity was investigated according to modified OECD guideline (No. 201) by 72 h exposure of microalgae to various concentrations of each of the chemicals in Walne's saline media. According to the results, the growth inhibitory effects of AgNPs and AgNO 3 increased significantly coincidence with increasing time and concentration compared to control ( P  < 0.05). The values of median inhibitory concentrations (IC 50 ) of AgNPs and AgNO 3 based on average specific growth rate and yield for D. salina increased significantly with elevation of water salinity from 35 to 140 g/L ( P  < 0.05). Toxicity of AgNO 3 based on IC 50 to D. salina was significantly higher than AgNPs at all salinities ( P  < 0.05). In conclusion, both AgNPs and AgNO 3 inhibited the growth of D. salina at different saltwater medium. [ABSTRACT FROM AUTHOR]

Abstract—This paper considers the bioaccumulation of elements in organs and tissues of whitefish from the Lake Imandra reaches, which were subjected to different anthropogenic impacts, during stabilization of anthropogenic load. It is shown that the element accumulation in the organs and tissues of the whitefish is mainly controlled by the individual resistance to the higher concentrations of toxic elements and physiological state rather than by their concentrations in water. The models of element redistribution in liver and kidney depending on the physiological state of the fish are constructed. Changes in iron and zinc metabolism at different concentrations of hemoglobin in blood and stages of fish disease are shown. [ABSTRACT FROM AUTHOR]

The objective of this study was to assess the effects of municipal wastewater treatment plant effluent on the energetics and stress response of rainbow darter ( Etheostoma caeruleum ). Male and female rainbow darter were collected upstream and downstream of the Waterloo WWTP in the Grand River watershed, ON, Canada. To assess the effects of wastewater treatment plant effluent on whole-body and tissue specific metabolic capacity, closed-chamber respirometry and muscle-enzyme activity analyses were performed. Plasma cortisol was also collected from fish before and after an acute air-exposure stressor to evaluate the cortisol stress response in fish exposed to additional stressors. Male and female rainbow darter collected downstream of the effluent had higher oxygen consumption rates, while differences in enzyme activities were primarily associated with sex rather than collection site. No impairment in the cortisol stress response between downstream and upstream fish was observed, however baseline cortisol levels in female fish from the downstream site were significantly higher compared to other baseline groups. Stress-induced cortisol levels were also higher in female fish from both sites when compared to their male counterparts. Overall, this study demonstrates that chronic exposure to WWTP effluent impacts whole-body metabolic performance. This study was also able to demonstrate that sex-differences are a key determinant of various metabolic changes in response to physiological stress, thereby, providing a novel avenue to be considered and further explored. [ABSTRACT FROM AUTHOR]

While the field of epigenetics is increasingly recognized to contribute to the emergence of phenotypes in mammalian research models across different developmental and generational timescales, the comparative biology of epigenetics in the large and physiologically diverse vertebrate infraclass of teleost fish remains comparatively understudied. The cypriniform zebrafish and the salmoniform rainbow trout and Atlantic salmon represent two especially important teleost orders, because they offer the unique possibility to comparatively investigate the role of epigenetic regulation in 3R and 4R duplicated genomes. In addition to their sequenced genomes, these teleost species are well-characterized model species for development and physiology, and therefore allow for an investigation of the role of epigenetic modifications in the emergence of physiological phenotypes during an organism's lifespan and in subsequent generations. This review aims firstly to describe the evolution of the repertoire of genes involved in key molecular epigenetic pathways including histone modifications, DNA methylation and microRNAs in zebrafish, rainbow trout, and Atlantic salmon, and secondly, to discuss recent advances in research highlighting a role for molecular epigenetics in shaping physiological phenotypes in these and other teleost models. Finally, by discussing themes and current limitations of the emerging field of teleost epigenetics from both theoretical and technical points of view, we will highlight future research needs and discuss how epigenetics will not only help address basic research questions in comparative teleost physiology, but also inform translational research including aquaculture, aquatic toxicology, and human disease. [ABSTRACT FROM AUTHOR]

The EU Commission Ecolabel and the Product and Environmental Footprint (PEF) aim at promoting the development and consumption of greener products. The product aquatic toxicity score from these 2 methods may lead in some circumstances to opposite conclusions. Although this could be interpreted as an inconsistency, the score should not be compared to each other but used in a complementary way. In short, CDV provided a “full” product formula aquatic toxicity score, even if some chemicals may never reach or persist in freshwater ecosystems. The USEtox® score, by integrating fate and exposure, focuses on the potential toxicity of persistent-water-soluble chemicals at steady state. Since no risk or safety assessment can be conducted with USEtox® nor with the CDV, both are a hazard-based scoring system. This short communication clarifies the difference between approaches underpinning the toxicity scores used in Ecolabel and PEF, providing guidance on how to interpret the results. [ABSTRACT FROM AUTHOR]

The Reverse Osmosis desalination has become a technological option to guarantee an adequate drinking water supply in zones with water scarcity. Nevertheless, the process is accompanied by potential adverse impacts on the coastal ecosystem, mainly due to chemical discharges. Taking into account the environmental risk presented by these chemical mixtures, in this work we used a short-term toxicity bioassay with Artemia franciscana nauplii expressed in lethality to exposures individually and their combinations. Results showed that toxicity degree from single exposures was C5H8O2 > NaClO > CuSO4 > KMnO4 > FeCl3, indicated that C5H8O2 was the most toxic biocide. However, all compounds in combination with C5H8O2 exhibited a very strong antagonism. Except, in mixtures, NaClO/FeCl3 and CuSO4/KMnO4 resulted in an additive effect. This environmental assessment will allow reducing risk significantly on the concentrate considering the sensitivity of the marine ecosystem to the application of chemical agents during the desalination process. [ABSTRACT FROM AUTHOR]

Short to long chain alcohols have a range of ecotoxicity to aquatic life driven by hydrophobic interactions with biological membranes. Carbon chain length and octanol:water partitioning coefficients are surrogates for hydrophobicity and strongly relate to aquatic toxicity. In these investigations, the toxicity of ethanol to 1- n -dodecanol to juvenile fish in standard acute toxicity tests is reviewed. Toxicity tests employing fish embryos (zebrafish Danio rerio and fathead minnow Pimephales promelas ) in the Fish Embryo Test (OECD 236) format were conducted from C2 to C10 to compare against standard juvenile fish toxicity. Quantitative structure activity relationships for FET and fish individually and combined demonstrate that embryos are not different in sensitivity to juvenile fish. A combined QSAR was developed of the form Log 96 h LC50 (mM/L) = −0.925*log Kow + 2.060 (R2 10 = 0.954). Alcohols of 11–12 carbons show a deflection in the QSAR as toxicity approaches the solubility limit. Alcohols with longer chain lengths may only be tested at lower exposures relevant for chronic toxicity. Decanol was evaluated in a 33-d fish early life stage test (OECD 210) and survival was the most sensitive endpoint (EC10 = 0.43 mg/L, 0.0027 mM/L). This study suggests a reasonable acute to chronic ratio of 6.5 in line with historical literature for non-polar narcotic compounds. Fish are not uniquely more sensitive than Daphnia magna which suggests estimations of environmental hazard can be confidently made with either taxon. The overall environmental risk assessments for the longer chain alcohols included in this research remain largely unchanged primarily due to previous research demonstrating a very minimal environmental exposure even for highly toxic members of the category. [ABSTRACT FROM AUTHOR]

Amphibians and reptiles are the two most endangered groups of vertebrates. Environmental pollution by pesticides is recognised as one of the major factors threatening populations of these groups. However, the effects of pesticides on amphibians and reptiles have been studied for few substances, which is partly related to the fact that these animals are not included in the mandatory toxicity testing conducted as part of environmental risk assessments of pesticides. Whether risks of pesticides to amphibians and reptiles are addressed by surrogate taxa used in risk assessment is currently under debate. In order to develop a scientifically sound and robust risk assessment scheme, information needs to be gathered to examine whether fish, birds and mammals are valid surrogates for amphibians and reptiles. We updated a systematic review of scientific literature that was recently published compiling toxicity data on amphibians and reptiles. The outcome of this review was analysed with the purposes to (1) compare endpoints from amphibians and reptiles with the available information from fish, birds and mammals, and (2) develop species sensitivity distributions (SSDs) for those substances tested in at least six amphibian species (no substances were found tested in at least six reptile species) to identify a candidate amphibian model species to be used as surrogate in risk assessment. A positive correlation was found between toxicity recorded on fish and amphibians, the former revealing, in general, to be more sensitive than the latter to waterborne pollutants. In the terrestrial environment, although birds and mammals were more sensitive than amphibians and reptiles to at least 60% of tested substances, just a few weak significant correlations were observed. As a general rule, homoeothermic vertebrates are not good surrogates for reptiles and terrestrial amphibians in pesticide risk assessment. However, some chemical-dependent trends were detected, with pyrethroids and organochlorine insecticides being more toxic to amphibians or reptiles than to birds or mammals. These trends could ultimately help in decisions about protection provided by surrogate taxa for specific groups of substances, and also to determine when risk assessment of pesticides needs to pay special consideration to amphibians and reptiles. The outcome of this review reflects that there is still much information needed to reduce uncertainties and extract relevant conclusions on the overall protection of amphibians and reptiles by surrogate vertebrates. [ABSTRACT FROM AUTHOR]

It was hypothesized that interactions between emerging contaminants such as decabromodiphenyl ether (BDE-209) and nanoparticles (NPs) such as nano-SiO 2 (nSiO 2 ), can affect contaminant transport in the aquatic environment and its ecotoxicity. This study assessed the influence of nSiO 2 on the uptake of BDE-209 by zebrafish embryo. The distribution of BDE-209 and nSiO 2 on the external chorion and the internal embryo mass ( i.e. , dechorionated embryo) was measured. For single exposure of nSiO 2 to zebrafish embryo, separately, results showed that nSiO 2 accumulation on the chorion surface was higher than that in the dechorionated embryo. The nSiO 2 accumulation on the chorion surface was 129–200 mg-nSiO 2 /g-chorion at 48 h post fertilization, hpf, of exposure time, whereas the equilibrium adsorption of nSiO 2 on the dechorionated embryo was ca. 0.42–0.54 mg-nSiO 2 /g-embryo at 6 hpf. Results showed that the formation of nSiO 2 -BDE-209 associates promoted both extracellular and intracellular uptake of BDE-209 by zebrafish embryo, thereby increasing the bioconcentration of BDE-209 on the chorion surface and in embryo. The results also revealed that the accumulation of BDE-209 on the chorion was remarkably greater than that on the dechorionated embryo at 48 hpf. The uptake of BDE-209 was 17.2 ± 0.45 mg/g-chorion (or 86 ng-BDE-209/chorionated embryo) and 0.37 ± 0.01 mg/g-embryo (or 18.6 ng-BDE-209/dechorionated embryo), respectively, when co-exposure of zebrafish embryos to BDE-209 and nSiO 2 . Results from the SEM and EDS analysis revealed that nSiO 2 already passed through the chorion and adhered to the embryo surface/mass. [ABSTRACT FROM AUTHOR]

Generation of wastewater is one of the main environmental sustainability issues across food sector industries. The constituents of food process effluents are often complex and require high energy and processing for regulatory compliance. Wastewater streams are the subject of microbiological and chemical criteria, and can have a significant eco-toxicological impact on the aquatic life. Thus, innovative treatment approaches are required to mitigate environmental impact in an energy efficient manner. Here, dielectric barrier discharge atmospheric cold plasma (ACP) was evaluated for control of key microbial indicators encountered in food industry effluent. This study also investigated the eco-toxicological impact of cold plasma treatment of the effluents using a range of aquatic bioassays. Continuous ACP treatment was applied to synthetic dairy and meat effluents. Microbial inactivation showed treatment time dependence with significant reduction in microbial populations within 120 s, and to undetectable levels after 300 s. Post treatment retention time emerged as critical control parameter which promoted ACP bacterial inactivation efficiency. Moreover, ACP treatment for 20 min achieved significant reduction (≥2 Log 10 ) in Bacillus megaterium endospores in wastewater effluent. Acute aquatic toxicity was assessed using two fish cell lines (PLHC-1 and RTG-2) and a crustacean model ( Daphnia magna) . Untreated effluents were toxic to the aquatic models, however, plasma treatment limited the toxic effects. Differing sensitivities were observed to ACP treated effluents across the different test bio-assays in the following order: PLHC-1 > RTG-2 ≥  D. magna ; with greater sensitivity retained to plasma treated meat effluent than dairy effluent. The toxic effects were dependent on concentration and treatment time of the ACP treated effluent; with 30% cytotoxicity in D. magna and fish cells observed after 24 h of exposure to ACP treated effluent for concentrations up to 5%. The findings suggest the need to employ wider variety of aquatic organisms for better understanding and complete toxicity evaluation of long-term effects. The study demonstrates the potential to tailor ACP system parameters to control pertinent microbial targets (mono/poly-microbial, vegetative or spore form) found in complex and nutritious wastewater effluents whilst maintaining a safe eco-toxicity profile for aquatic species. [ABSTRACT FROM AUTHOR]

Saponin-rich plant extracts contain bioactive natural compounds and have many applications, e.g. as biopesticides and biosurfactants. The composition of saponin-rich plant extracts is very diverse, making environmental monitoring difficult. In this study various ecotoxicity data as well as exposure data have been collected to explore which compounds in the plant extract are relevant as plant protection agents and furthermore to clarify which compounds may cause undesired side-effects due to their toxicity. Hence, we quantified the toxicity of different fractions (saponins/non-saponins) in the plant extracts on the aquatic crustacean Daphnia magna and zebrafish ( Danio rerio ) embryos. In addition, we tested the toxicity changes during saponin degradation as well. The results confirm that saponins are responsible for the majority of toxicity (85.1–93.6%) of Quillaja saponaria extract. We, therefore, suggest saponins to be the main target of saponin-rich plant extracts, for instance in the saponin-based biopesticide regulation. Furthermore, we suggest that an abundant saponin fraction, QS-18 from Q. saponaria , can be a key monitoring target to represent the environmental concentration of the saponins, as it contributes with 26% and 61% of the joint toxicity to D. magna and D. rerio , respectively out of the total saponins. The degradation products of saponins are 3–7 times less toxic than the parent compound; therefore the focus should be mainly on the parent compounds. [ABSTRACT FROM AUTHOR]

Citrate esters have been considered as alternatives to phthalate plasticizers. Being considered to have low toxicity in mammals, their toxicological information for aquatic animals remains poorly understood. We examined the developmental toxicity of citrate esters including tributyl O-acetylcitrate (ATBC), triethyl 2-acetylcitrate (ATEC), and trihexyl O-acetylcitrate (ATHC) together with dibutyl phthalate (DBP) based on the frog embryo teratogenesis assay- Xenopus (FETAX). ATBC has the lowest 96 h LC 50 and 96 h EC 50 values. In RT-qPCR, the ratio of bax and bcl-2 mRNA was significantly increased by DBP, but not by ATBC, ATEC and ATHC. DNA fragmentation was obvious in DBP-treated tadpoles, but not in those treated with ATBC and ATEC, whereas ATHC caused necrotic DNA degradation. Lipid hydroperoxide levels in tadpoles were significantly increased by DBP and ATHC, but not by ATBC and ATEC, suggesting that induction of oxidative stress by DBP and ATHC in embryos. In tadpoles with head abnormalities, basihyal bone, ceratohyal bone and Meckel's cartilage were frequently missed together with reduction in branchial gill bones. Col2a1 mRNA in the head of tadpoles was significantly decreased by low concentration of DBP, ATHC, and high concentration of ATEC. In stage 25 embryos FoxN3 mRNA, a master regulator for differentiation of neural crest cells to chondrocytes in head, was significantly decreased by DBP and ATHC, but not by ATBC and ATEC. In conclusion, ATEC was recommended as the alternative to phthalate plasticizer having the lowest developmental toxicity in amphibian embryos. [ABSTRACT FROM AUTHOR]

Uranium mining is an environmental concern because of runoff and the potential for toxic effects on the biota. To investigate uranium toxicity to freshwater invertebrates, we conducted a 96-h acute toxicity test to determine lethal concentrations (testing concentrations up to 262 mg L −1 ) for three stream invertebrates: a shredder caddisfly, Schizopelex festiva Rambur (Trichoptera, Sericostomatidae); a detritivorous isopod, Proasellus sp. (Isopoda, Asellidae); and a scraper gastropod, Theodoxus fluviatilis (Gastropoda, Neritidae). Next, we ran a chronic-toxicity test with the most tolerant species ( S. festiva ) to assess if uranium concentrations found in some local streams (up to 25 μg L −1 ) affect feeding, growth and respiration rates. Finally, we investigated whether S. festiva takes up uranium from the water and/or from ingested food. In the acute test, S. festiva survived in all uranium concentrations tested. LC 50 -96-h for Proasellus sp and T . fluviatilis were 142 mg L −1 and 24 mg L −1 , respectively. Specimens of S. festiva exposed to 25 μg L −1 had 47% reduced growth compared with specimens under control conditions (21.5 ± 2.9 vs. 40.6 ± 4.9 μg of mass increase animal −1 ·day −1 ). Respiration rates (0.40 ± 0.03 μg O 2 ·h −1 ·mg animal −1 ) and consumption rates (0.54 ± 0.05 μg μg animal −1 ·day −1 ; means ± SE) did not differ between treatments. Under laboratory conditions S. festiva accumulated uranium from both the water and the ingested food. Our results indicate that uranium can be less toxic than other metals or metalloids produced by mining activities. However, even at the low concentrations observed in streams affected by abandoned mines, uranium can impair physiological processes, is bioaccumulated, and is potentially transferred through food webs. [ABSTRACT FROM AUTHOR]

Mercury is a globally distributed toxicant to aquatic animals and mammals. However, the potential risks of environmental relevant mercury in terrestrial systems remain largely unclear. The metabolic profiles of the earthworm Eisenia fetida after exposure to soil contaminated with mercury at 0.77 ± 0.09 mg/kg for 2 weeks were investigated using a two-dimensional nuclear magnetic resonance-based ( 1 H- 13 C NMR) metabolomics approach. The results revealed that traditional endpoints (e.g., mortality and weight loss) did not differ significantly after exposure. Although histological examination showed sub-lethal toxicity in the intestine as a result of soil ingestion, the underlying mechanisms were unclear. Metabolite profiles revealed significant decreases in glutamine and 2-hexyl-5-ethyl-3-furansulfonate in the exposed group and remarkable increases in glycine, alanine, glutamate, scyllo-inositol, t-methylhistidine and myo-inositol. More importantly, metabolic network analysis revealed that low mercury in the soil disrupted osmoregulation, amino acid and energy metabolisms in earthworms. A metabolic net link and schematic diagram of mercury-induced responses were proposed to predict earthworm responses after exposure to mercury at environmental relevant concentrations. These results improved the current understanding of the potential toxicity of low mercury in terrestrial systems. [ABSTRACT FROM AUTHOR]

Manufactured titanium dioxide nanoparticles (TiO 2 -NP) have been intensely applied in numerous industrial products and may be a risk for aquatic systems as they are not completely removed from domestic and industrial wastes after water treatment. This study evaluated the osmo- and ionic balance, Na + /K + -ATPase, H + -ATPase and carbonic anhydrase activities and the mitochondria-rich cells (MRC) in the gills and kidney of the Neotropical fish Prochilodus lineatus after 2 (acute) and 14 (subchronic) days of exposure to nominal 0, 1, 5, 10 and 50 mg L −1 TiO 2 -NP. The nominal concentrations corresponded to 0.0, 0.6, 1.6, 2.7 and 18.1 mg L -1 suspended TiO 2 -NP, respectively, in the water column one hour after NP introduction and were maintained for at least 24 h. Acute exposure to TiO 2 -NP decreased plasma osmolality and Ca 2+ levels. Na + /K + -ATPase, H + -ATPase and carbonic anhydrase activities were inhibited in the gills, but not in the kidney. Total MRC density did not change in gills and kidneys. At gill surface, total MRC density decreased in fish exposed to 50 mg L −1 TiO 2 -NP and the total MRC fractional surface area unchanged although, there were some changes in the fractional area of MRC with apical microvilli (MRCm) and MRC with apical sponge-like structure (MRCs). MRCm was more abundant than MRCs. After subchronic exposure, there was no change in plasma osmolality, ionic balance and enzyme activities. Total gill MRC density increased in the filament epithelium and renal tubules. In the gills, MRC contacting water exhibited some adjustments. Total MRC and fractional surface area unchanged, but there was an increase of MRCs contacting water at gill surface after exposure to10 and 50 mg L −1 TiO 2 -NP. MRC proliferation in filament epithelium and in renal tubules as well as the increasing MRCs at gill surface may have contributed to avoid change in plasma osmolality, ionic balance and enzyme activities and suggested a cellular physiological and morphological response to restore and maintain osmotic and ionic homeostasis after subchronic exposure. [ABSTRACT FROM AUTHOR]

Tritium ( 3 H) is a radioactive isotope of hydrogen. In the environment, the most common form of tritium is tritiated water (HTO). The present study aimed to identify early biomarkers of HTO contamination through the use of an aquatic model, the zebrafish ( Danio rerio ). We used the zebrafish embryo-larvae model to investigate the modes of action of HTO exposure at dose rates of 0.4 and 4 mGy/h, dose rates expected to induce deleterious effects on fish. Zebrafish were exposed to HTO from 3 hpf (hours post fertilization) to 96 hpf. The transcriptomic effects were investigated 24 h and 96 h after the beginning of the contamination, using mRNAseq. Results suggested an impact of HTO contamination, regardless of the dose rate, on genes involved in muscle contraction ( tnnt2d , tnni2a.4, slc6a1a or atp2a1l ) and eye opacity ( crygm2d9 , crygmxl1 , mipb or lim2.3 ) after 24 h of contamination. Interestingly, an opposite differential expression was highlighted in genes playing a role in muscle contraction and eye opacity in 24 hpf embryos when comparing dose rates, suggesting an onset of DNA protective mechanisms. The expression of h2afx and ddb2 involved in DNA repair was enhanced in response to HTO exposure. The entrainment of circadian clock and the response to H 2 O 2 signalling pathways were enriched at 96 hpf at 0.4 mGy/h and in both stages after 4 mGy/h. Genes involved in ROS scavenging were differentially expressed only after 24 h of exposure for the lowest dose rate, suggesting the onset of early protective mechanisms against oxidative stress. Effects highlighted on muscle at the molecular scale were confirmed at a higher biological scale, as electron microscopy observations revealed sarcomere impairments in 96 hpf larvae for both dose rates. Together with other studies, the present work provides useful data to better understand modes of action of tritium on zebrafish embryos-larvae. [ABSTRACT FROM AUTHOR]

Pharmaceutical residues and other micro-contaminants may enter aquatic environments through effluent from sewage treatment plants (STPs) and could cause adverse effects in wild fish. One strategy to alleviate this situation is to improve wastewater treatment by ozonation. To test the effectiveness of full-scale wastewater effluent ozonation at a Swedish municipal STP, the added removal efficiency was measured for 105 pharmaceuticals. In addition, gene expression, reproductive and behavioral endpoints were analyzed in zebrafish ( Danio rerio ) exposed on-site over 21 days to ozonated or non-ozonated effluents as well as to tap water. Ozone treatment (7 g O 3 /m 3 ) removed pharmaceuticals by an average efficiency of 77% in addition to the conventional treatment, leaving 11 screened pharmaceuticals above detection limits. Differences in biological responses of the exposure treatments were recorded in gene expression, reproduction and behavior. Hepatic vitellogenin gene expression was higher in male zebrafish exposed to the ozonated effluent compared to the non-ozonated effluent and tap water treatments. The reproductive success was higher in fish exposed to ozonated effluent compared to non-ozonated effluent and to tap water. The behavioral measurements showed that fish exposed to the ozonated STP effluent were less active in swimming the first minute after placed in a novel vessel. Ozonation is a capable method for removing pharmaceuticals in effluents. However, its implementation should be thoroughly evaluated for any potential biological impact. Future research is needed for uncovering the factors which produced the in vivo responses in fish. [ABSTRACT FROM AUTHOR]

Biotic stressors have been demonstrated to change the toxicity of pollutants. While the combined effects of predator cues and pesticides are well documented, the interaction of predator stress with metals is a topic that has remained largely unexplored. In this laboratory experiment, the freshwater isopod Asellus aquaticus is exposed to predator cues and metal mixtures of Cd, Cu and Pb. We examined the effects on growth, respiration and, as behavioral parameters, feeding rate and activity. These were linked to the free ion activities (FIAs) in the water and the metal body concentrations. The findings reveal that Cu accumulation significantly influenced the growth rate, the feeding rate and the activity of isopods exposed to predator stress. Furthermore, we found a concentration-dependent interaction of the Cd + Pb mixtures on the feeding rate and a lower feeding rate for Cd and Pb predator exposed asellids. As several interactions were found between metals and predator stress, it demonstrates the importance of investigating how organisms and whole ecosystems respond to multiple stressors. A better understanding of these interactions will undoubtedly improve risk assessment and management. [ABSTRACT FROM AUTHOR]

Metal nanoparticles from industries contaminate the environment and affect the normal development of fish even human health. However, little is known about their biological effects on fish embryogenesis and the potential mechanisms. In this study, zebrafish embryos exposed to/injected with silver nanopaticles (AgNPs) exhibited shorter body, reduced heartbeats, and dysfunctional movements. Less, loose, and unassembled myofibrils were observed in AgNPs-treated embryos, and genes in myofibrillogenesis and sarcomere formation were found to be down-regulated in treated embryos. Down-regulated calcium (Ca 2+ ) signaling and loci -specific DNA methylation in specific muscle genes, such as bves , shroom1 , and arpc1a , occurred in AgNPs-treated embryos, which might result in the down-regulated expression of myofibrillogenesis genes and muscle dysfunctions in the treated embryos. Our results for the first time reveal that through down-regulating Ca 2+ signaling and myogenic loci -specific DNA methylation in zebrafish embryos, AgNPs might induce defects of myofibril assembly and sarcomere formation via their particles mostly, which may subsequently cause heartbeat reduction and behavior dysfunctions. [ABSTRACT FROM AUTHOR]

Multiple environmental stressors, including nutrient effluents (i.e. nitrates [ N O 3 − ]) and altered pH regimes, influence the persistence of freshwater species in anthropogenically disturbed habitats. Independently, nitrate and low pH affect energy allocation by increasing maintenance costs and disrupting oxygen uptake, which ultimately results in impacts upon whole animal performance. However, the interaction between these two stressors has not been characterised. To address this, the effects of nitrate and pH and their interaction on aerobic scope and physiological performance were investigated in the blueclaw crayfish, Cherax destructor . Crayfish were exposed to a 2 × 3 factorial combination, with two pH levels (pH 5.0 and 7.0) and three nitrate concentrations (0, 50 and 100 mg L −1 N O 3 − ). Crayfish were exposed to experimental conditions for 65 days and growth and survival were monitored. Aerobic scope (i.e. maximal – standard oxygen uptake) was measured at six time points (1, 3, 5, 7, 14, and 21 days) during exposure to experimental treatments. Crayfish performance was assessed after 28 days, by measuring chelae strength and whole animal activity capacity via the righting response. Survival was reduced in crayfish exposed to pH 5.0, but there was no exacerbation of this effect by exposure to high nitrate levels. Aerobic scope was compromised by the interaction between low pH and nitrate and resulted in prolonged elevations of standard oxygen uptake rates. Exposure to nitrate alone affected aerobic scope, causing a 59% reduction in maximum oxygen uptake. Reduced aerobic capacity translated to reduced chelae strength and righting capacity. Together, these data show that low pH and elevated nitrate levels reduce aerobic scope and translate to poorer performance in C. destructor , which may have the potential to affect organismal fitness in disturbed habitats. [ABSTRACT FROM AUTHOR]

Abstract: Ecological risk assessment is commonly based on single‐generation ecotoxicological tests that are usually performed at one standard temperature. We investigated the effects of nickel (Ni) on Daphnia magna reproduction at 15, 20, and 25 °C over 4 generations. Multigenerational Ni effects on D. magna reproduction depended on the magnitude of the effect in the first generation (F0) and showed very different patterns at different temperatures. At low effect level concentrations (<10% effect concentration [EC10] in F0), chronic Ni toxicity at 15 and 20 °C did not increase over 4 generations, and the increase in Ni toxicity at 25 °C observed in F1 and F2 in some Ni treatments did not persist into F3, where complete recovery of reproduction was observed. At higher effect level concentrations, the multigenerational Ni effects depended on the test temperature. In F0, Ni toxicity was 6.5‐fold lower at 25 °C than at 15 °C (based on the median effect concentration), but the temperature effect on Ni toxicity was not explained by differences in Ni accumulation. At a lower temperature, lower internal Ni concentrations in D. magna were necessary to induce the same Ni toxicity as at a higher temperature. Overall, our results indicate that low single‐generation chronic effect concentrations of Ni in D. magna (EC10 in the present study) are also protective in a long‐term, multigenerational context and that temperature should be taken into account in the ecological risk assessment of Ni. Environ Toxicol Chem 2018;37:1877–1888 © 2018 SETAC [ABSTRACT FROM AUTHOR]

The aquatic toxicity of insecticides like the pyrethroids have been discussed intensively over the recent years especially in relation to risk assessment and how seasonality may or may not affect the sensitivity of non-target organisms. To address this issue, the crustacean Gammarus pulex was collected once a month for 16 months and acclimated to 10 °C for four days before being exposed to a 90 min pulse of cypermethrin. In vitro cytochrome P450 activity, total lipid content, total protein content, and dry weight were measured in male and female gammarids from each sampling date and used along with the water temperature as variables for sensitivity prediction by Partial Least Squares (PLS) regression models. The 24 h EC 50 -values varied more than 30 fold across the sampling period from 0.21 ± 0.05 μg L −1 (April 2015) to 6.60 ± 3.46 μg L −1 (October 2015), indicating seasonal variances in the acute sensitivity of G. pulex towards cypermethrin. After 168 h of recovery this difference in EC 50 -values was reduced to seven-fold. In both male and female gammarids seasonal patterns were observed in the total lipid content and in vitro CYP P450 activity, which peaked in spring and fall, respectively. The current study shows the importance of reporting time of organism collection and experimental execution for risk assessment of pyrethroids as season is important for the acute sensitivity of G. pulex . We suggest prolonged acclimation times of sampled macroinvertebrates to constant laboratory conditions in order to even out possible seasonal differences in sensitivity. [ABSTRACT FROM AUTHOR]