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Mahi-mahi (Coryphaena hippurus) are photopic predators that rely on vision for predator avoidance and foraging behavior. Research conducted on Mahi-mahi vision has been primarily focused on adults, with limited knowledge of the visual function and eye development in early life-stages. In this study, larval Mahi-mahi were obtained from spawning wild-caught broodstock and exposed to an optomotor response assay to assess visual function. Following behavioral assessment, histological examination was conducted on the retinal layers to determine changes in eye morphology and visual acuity early in development. There was an age-dependent increase in the ability of Mahi-mahi to exhibit an optomotor response at increasing speeds. Furthermore, this corresponded to an increase in retinal area and lens thickness between 7 and 10 day post-hatch (dph) larvae, where anatomical visual acuity (measured as the minimum separable angle) also improved. These findings help further the knowledge of visual development in early life-stage pelagic fishes. [ABSTRACT FROM AUTHOR]

Chlorpyrifos is an organophosphorus insecticide that elicits acute toxicity through inhibition of acetylcholinesterase (AChE), leading to acetylcholine accumulation and prolonged stimulation of cholinergic receptors throughout the central and peripheral nervous systems. Previous studies have indicated that neurodevelopment may also be impaired through alternative pathways, including reduction of cyclic adenosine monophosphate (cAMP)-catalyzed downstream events. The upstream initiating events that underlie noncholinergic neurological actions of chlorpyrifos and other organophosphorus compounds remain unclear. To investigate the potential role of fatty acid signaling disruption as a mechanism of toxicity, lipid metabolism and fatty acid profiles were examined to identify alterations that may play a critical role in upstream signaling in the central nervous system (CNS). Juvenile rainbow trout were treated for 7 days with nominal chlorpyrifos concentrations previously reported to diminish olfactory responses (10, 20, and 40 μg/l). Although lethality was noted higher in doses, measured chlorpyrifos concentrations of 1.38 μg/l (nominal concentration 10 μg/l) significantly reduced the activity of AChE and two serine lipases, monoacylglycerol lipase, and fatty acid amide hydrolase in the brain. Reductions in lysophosphatidylethanolamines (16:0, 18:0, 18:1, and 22:6) derived from the phosphatidylethanolamines and free fatty acids (palmitic acid 16:0, linolenic acid 18:3, eicosadienoic acid 20:2, arachidonic acid 20:4, and docosahexaenoic acid 22:6) were also noted, suggesting that chlorpyrifos inhibited the metabolism of select phospholipid signaling precursors at sublethal concentrations. These results indicate that in addition to AChE inhibition, environmentally relevant chlorpyrifos exposure alters serine lipase activity and lipid metabolites in the trout brain, which may compromise neuronal signaling and impact neurobehavioral responses in aquatic animals. [ABSTRACT FROM AUTHOR]

Polycyclic aromatic hydrocarbons found in crude oil can impair fish health following sublethal exposure. However, the dysbiosis of microbial communities within the fish host and influence it has on the toxic response of fish following exposure has been less characterized, particularly in marine species. To better understand the effect of dispersed crude oil (DCO) on juvenile Atlantic cod (Gadus morhua) microbiota composition and potential targets of exposure within the gut, fish were exposed to 0.05 ppm DCO for 1, 3, 7, or 28 days and 16 S metagenomic and metatranscriptomic sequencing on the gut and RNA sequencing on intestinal content were conducted. In addition to assessing species composition, richness, and diversity from microbial gut community analysis and transcriptomic profiling, the functional capacity of the microbiome was determined. Mycoplasma and Aliivibrio were the two most abundant genera after DCO exposure and Photobacterium the most abundant genus in controls, after 28 days. Metagenomic profiles were only significantly different between treatments after a 28-day exposure. The top identified pathways were involved in energy and the biosynthesis of carbohydrates, fatty acids, amino acids, and cellular structure. Biological processes following fish transcriptomic profiling shared common pathways with microbial functional annotations such as energy, translation, amide biosynthetic process, and proteolysis. There were 58 differently expressed genes determined from metatranscriptomic profiling after 7 days of exposure. Predicted pathways that were altered included those involved in translation, signal transduction, and Wnt signaling. EIF2 signaling was consistently dysregulated following exposure to DCO, regardless of exposure duration, with impairments in IL-22 signaling and spermine and spermidine biosynthesis in fish after 28 days. Data were consistent with predictions of a potentially reduced immune response related to gastrointestinal disease. Herein, transcriptomic-level responses helped explain the relevance of differences in gut microbial communities in fish following DCO exposure. • Mycoplasma and Aliivibrio were the two most abundant genera following oil exposure. • Photobacterium was the most abundant genus in control groups. • Functional profile of the fish gut microbiota was altered after a 28 d oil exposure. • Similarity in the functional capacity of the microbiome and biological processes. [ABSTRACT FROM AUTHOR]

• Developmental (ELS) norethindrone (NET) exposure alters zebrafish gene expression. • RNAseq data indicates significant effects on phototransduction and eye development. • Mean retinal layer diameter was not affected by NET exposure in ELS zebrafish. • NET exposure may alter transition to adult photoreceptor mosaic pattern in ELS fish. • Glycerolipid/steroid metabolism, protein processing pathways also affected by NET. Synthetic sex steroids, like the synthetic progestin norethindrone (NET), can affect a wide variety of biological processes via highly conserved mechanisms. NET is prevalent in surface waters, yet the sub-lethal effects of NET exposure are not are net yet well characterized in aquatic biota. A few targeted gene expression and behavioral studies have concluded that NET affects the vision of adult fish; however, early life stage (ELS) fish are often more sensitive to contaminants. Furthermore, many species of fish rely heavily on visual perception for survival during development. The goal of the present study was to characterize the effects of developmental exposure to environmentally relevant concentrations of NET on the visual system of ELS zebrafish, using transcriptomics and histological methods. Results indicate that exposure to relatively low levels of NET in aquatic systems may be sufficient to affect the visual function of developing fish. [ABSTRACT FROM AUTHOR]

Abstract: The toxicity of some polycyclic aromatic hydrocarbons (PAHs) increases with ultraviolet (UV) radiation. The intensity of UV radiation varies within aquatic ecosystems, potentially providing reprieves during which tissue repair may occur. Transient/short‐term PAH exposure prior to UV exposure may initiate metabolism/clearance, potentially affecting outcomes. Larval Sciaenops ocellatus were exposed to oil and UV radiation, using either variable photoperiods or pre‐UV oil exposure durations. Shorter PAH exposures exhibited greater toxicity, as did exposure to shorter photoperiods. Environ Toxicol Chem 2018;37:2372–2379. © 2018 SETAC [ABSTRACT FROM AUTHOR]

• miR-34b and miR-203a inhibitor-injected zebrafish exhibit oil-induced responses. • Neurological, cardiovascular and eye toxicity were top predicted pathways impaired. • Reduced eye area in injected zebrafish by 72 h post fertilization. • miR-34b and miR-203a inhibition mediated through AhR and non-AhR pathways. The global sequencing of microRNA (miRNA; miR) and integration to downstream mRNA expression profiles in early life stages (ELS) of fish following exposure to crude oil determined consistently dysregulated miRNAs regardless of the oil source or fish species. The overlay of differentially expressed miRNAs and mRNAs into in silico software determined that the key roles of these miRNAs were predicted to be involved in cardiovascular, neurological and visually-mediated pathways. Of these, altered expression of miRNAs, miR-203a and miR-34b were predicted to be primary targets of crude oil. To better characterize the effect of these miRNAs to downstream transcript changes, zebrafish embryos were microinjected at 1 h post fertilization (hpf) with either a miR-203a inhibitor or miR-34b. Since both miRs have been shown to be associated with aryl hydrocarbon receptor (AhR) function, benzo(a)pyrene (BaP), a potent AhR agonist, was used as a potential positive control. Transcriptomic profiling was conducted on injected and exposed larvae at 7 and 72 hpf, and eye morphology assessed following exposure at 72 hpf. The top predicted physiological system disease and functions between differentially expressed genes (DEGs) shared with miR-203a inhibitor-injected and miR-34b-injected embryos were involved in brain formation, and the development of the central nervous system and neurons. When DEGs of miR-203a inhibitor-injected embryos were compared with BaP-exposed DEGs, alterations in nervous system development and function, and abnormal morphology of the neurosensory retina, eye and nervous tissue were predicted, consistent with both AhR and non-AhR pathways. When assessed morphologically, the eye area of miR-203a inhibitor and miR-34b-injected and BaP-exposed embryos were significantly reduced. These results suggest that miR-203a inhibition and miR-34b overexpression contribute to neurological, cardiovascular and eye toxicity responses that are caused by oil and PAH exposure in ELS fish, and are likely mediated through both AhR and non-AhR pathways. [ABSTRACT FROM AUTHOR]

Estrogenically active compounds (EACs) in surface waters can disrupt the endocrine system of biota, raising concern for aquatic species. Concentrations of EACs are generally higher in effluent-dominated aquatic systems, such as California's Santa Ana River (SAR). Addressing estrogenicity of effluent-dominated waters is increasingly important due to both increasing urbanization and climate change. To this end, water samples were collected from multiple sites downstream of wastewater treatment plants (WWTPs) and intermittent points along the SAR during 2018–2019 and cell-based bioassays were used to determine estrogen receptor activity. During baseflow conditions, the highest estradiol equivalencies (EEQs) from all SAR water between summer (August and September) and fall (November) sampling events in 2018 were from Yorba Linda (EEQ = 1.36 ± 0.38 ng/L) and Prado (1.14 ± 0.13 ng/L), respectively. Water extracts in January 2019 following a major rainfall generally had higher EEQs with the highest EEQ of 10.0 ± 0.69 ng/L observed at Yorba Linda. During low flow conditions in November 2018, male Japanese medaka (Oryzias latipes) fish were exposed to SAR water to compare to cell bioassay responses and targeted analytical chemistry for 5 steroidal estrogens. Chemical-based EEQ correlations with in vitro EEQs were statistically significant. However, vitellogenin (vtg) mRNA expression in the livers of medaka exposed to SAR water was not significantly different compared to controls. These results indicate that seasonal variation and surface water runoff events influence estrogenic activity in the SAR and may induce estrogenic effects to native fish populations in wastewater-dominated streams in general. Unlabelled Image • The highest estradiol equivalencies (EEQs) in the SAR were in samples following major rainfall events. • In vitro bioassays determined that SAR water had estrogenic effects below threshold PNECs. • The in vitro and in vivo bioassays following SAR water exposures were not significantly correlated. [ABSTRACT FROM AUTHOR]

• (1 S ,3 R ,α R)-CP enantiomer induced higher toxicity to HepG2 cells. • Imbalance between cell cycle and apoptosis accounts for the chiral toxicity. • Cell cycle checkpoints and death receptor signaling are key pathways. Cypermethrin (CP) is a frequently used chiral pesticide comprised of different enantiomers that can induce a variable toxic response in biota, dependent on conformational change. However, the potential mechanism accounting for the enantioselective toxicity induced by CP enantiomers remains unknown. Herein, to shed light on the underlying mechanism of enantioselective cytotoxicity on cell cycle and apoptotic function, an MTT assay, flow cytometric (FCM) approach, and qPCR arrays combining bioinformatic analysis were conducted on HepG2 cell lines following exposure to CP enantiomers. Decreased cell viability in keeping with increased cell arrest and apoptosis was observed in cells exposed to (1 S ,3 R ,α R)-CP, relative to the (1 R ,3 S ,α S)-CP treatment group. PCR array also reflected an enantioselective difference in expression of cell cycle and apoptosis-related genes. Ingenuity pathway analysis (IPA) showed that cell cycle checkpoints, arrest in interphase, death receptor signaling, and apoptosis were among the top canonical and disease and functions predicted to be affected between CP enantiomers. Data presented here not only provide potential molecular endpoints for evaluating toxicity by cell cycle and apoptosis but also help to guide the scientific application of chiral pesticides. [ABSTRACT FROM AUTHOR]

• Metabolomic profile altered in the brains of bifenthrin-exposed Chinook salmon. • Metabolites involved in apoptotic responses dysregulated in exposed salmon. • Metabolites involved in inflammatory responses dysregulated in exposed salmon. • Caspase 3 expression significantly increased in the brains of exposed Chinook. An increase in urban and agricultural application of pyrethroid insecticides in the San Francisco Bay Estuary and Sacramento San Joaquin Delta has raised concern for the populations of several salmonids, including Chinook salmon (Oncorhynchus tshawytscha). Bifenthrin, a type I pyrethroid, is among the most frequently detected pyrethroids in the Bay-Delta watershed, with surface water concentrations often exceeding chronic toxicity thresholds for several invertebrate and fish species. To better understand the mechanisms of bifenthrin-induced neurotoxicity, juvenile Chinook salmon were exposed to concentrations of bifenthrin previously measured in the Delta. Non-targeted metabolomic profiles were used to identify transcriptomic changes in the brains of bifenthrin-exposed fish. Pathway analysis software predicted increased apoptotic, inflammatory, and reactive oxygen species (ROS) responses in Chinook following exposure to 0.15 and 1.50 μg/L bifenthrin for 96 h. These responses were largely driven by reduced levels of inosine, hypoxanthine, and guanosine. Subsequently, in the brain, the expression of caspase 3, a predominant effector for apoptosis, was significantly upregulated following exposure to 1.50 μg/L bifenthrin. This data suggests that metabolites involved in inflammatory and apoptotic responses, as well as those involved in maintaining proper neuronal function may be disrupted following sublethal exposure to bifenthrin and further suggests that additional population studies should focus on behavioral responses associated with impaired brain function. [ABSTRACT FROM AUTHOR]

Although concerns about the impacts of antibiotics in aquatic organisms are reported worldwide, the potential adverse effects on fish gut microbial communities and fish health are still not well known. In this study, we investigated the effects of florfenicol (FFC) on the gut microbiome and gastrointestinal (GIT) gene expression in juvenile Atlantic salmon (Salmo salar). Three doses of FFC were used to coat experimental feed at 10, 20 and 30 mg/kg/ fish body weight (bw). The feed was administered for 18 days, followed by a 10-day recovery period. The metatranscriptome analysis revealed that 10 and 30 mg/kg bw of FFC led to the downregulation of genes involved in the transcription of NADH-ubiquinone oxidoreductase chain-1, suggesting that the antibiotic targets bacterial respiratory metabolism. The 30 mg/kg bw FFC treatment upregulated genes that encode glycolytic enzymes, such as phosphoglycerate kinase, indicating a disruption of energy metabolism in the microbiome. Analysis of the fish host transcriptome showed that the FFC treatment affected cellular processes in the GIT system of fish, including pathways related to apoptosis and DNA metabolism. The 30 mg/kg bw FFC treatment specifically activated pathways related to cellular regulation, including LXR/RXR activation, FXR/RXR activation, and protein ubiquitination. At the end of the recovery phase, the 30 mg/kg bw FFC treated group altered pathways related to EIF2 signaling and lysine degradation. This study identified molecular-level effects of FFC treatment on the gut microbiome and the GIT of juvenile Atlantic salmon, although phenotypic changes in growth or condition were not observed. Most of the observed changes were reversible and receded at the end of the recovery period, apart from the highest treatment group. These findings emphasize the importance of understanding the molecular mechanisms that underlie the potential effects of antibiotics in order to optimize antibiotic treatments in aquaculture. • Identification of molecular-level effects of florfenicol exposure in Atlantic salmon. • Metatranscriptome data suggests targeting of bacterial respiratory metabolism. • 30 mg/kg bw of florfenicol altered interactions between gut microbiome and host. • Fish transcriptome showed effects on cellular processes, apoptosis and DNA metabolism. • Phenotypic changes in growth or condition were not observed. [ABSTRACT FROM AUTHOR]

• Whole-mount staining revealed increases in free cholesterol in 72 hpf red drum embryos exposed to crude oil. • Total cholesterol in red drum embryo homogenates was not significantly affected by oil exposure. • Crude oil did not affect red drum survival at concentrations tested. • Crude oil significantly increased pericardial area in red drum embryos. The 2010 Deepwater Horizon oil spill impacted over 2100 km of shoreline along the northern Gulf of Mexico, which coincided with the spawning season of many coastal species, including red drum (Sciaenops ocellatus). Red drum develop rapidly and are sensitive to crude oil exposure during the embryonic and larval periods. This study investigates the predictions from recent transcriptomic studies that cholesterol biosynthetic processes are impacted by oil exposure in fish early life stages. We found that red drum larvae exposed for 72 h to ΣPAH 50 3.55–15.45 µg L−1 exhibited significantly increased pericardial area, a cardiotoxicity metric, but the expression of several genes targeted in the cholesterol synthesis pathway was not affected. However, whole-mount staining revealed significant increases in free cholesterol throughout the larval body (ΣPAH 50 4.71–16.15 µg L−1), and total cholesterol followed an increasing trend (ΣPAH 50 3.55–15.45 µg L−1). Cholesterol plays a critical role in fish embryo development and ion channel function. Therefore, the disruption of cholesterol homeostasis, as observed here, could play a role in the oil toxicity phenotype observed across many fish species. [ABSTRACT FROM AUTHOR]

Perfluorooctane sulfonamide (PFOSA), a typical perfluorooctane sulfonate precursor (PreFOS), has been detected in the aquatic environment globally. However, the effects of PFOSA at levels measured in the environment have not been well characterized in aquatic organisms. In this study, we evaluated the transcriptional, biochemical, histopathological, and morphological effects of PFOSA to characterize the underlying mechanisms of toxicity by using a universal model in aquatic ecotoxicology, zebrafish (Danio rerio). Transcriptional changes in PFOSA-exposed zebrafish predicted hepatic fibrosis and associated immune function. Subsequent, sublethal impacts were observed, which included significant alterations in liver-specific protein levels, increased immune cell numbers, and liver pathological structural damage. In addition, we compared the effects caused by PFOSA and perfluorooctane sulfonate (PFOS) at the same exposure concentration and found a greater hepatotoxic effect of PFOSA relative to PFOS, indicating that the adverse impacts of PFOSA may be more severe. This was the first study to comparatively explore the hepatotoxic response of PFOSA and PFOS in aquatic organisms, which can be used for ecological risk assessments of PreFOS compounds. [Display omitted] • Hepatic fibrosis and associated immune response of zebrafish larvae was induced by PFOSA in RNA-Seq analysis. • PFOSA changed the liver damage specific-protein levels and increased the immune cell numbers in zebrafish larvae. • Hepatotoxicity of PFOSA to fish is greater than that of PFOS. [ABSTRACT FROM AUTHOR]

• Concentrations of antibiotics were detected in F1 eggs after maternal exposure. • Impaired F0 growth was observed after maternal exposure. • Transgenerational changes of antibiotics in F1 offspring survival after maternal exposure. • Pathway analyses profiles from F0 ovaries predicted colorectal disorders. Due to overuse, misuse, and poor absorption during treatment, antibiotics are consistently released into the environment, raising concerns about their impacts on ecological sustainability and health. In this study we performed transcriptome profiling to assess potential reproductive effects of an antibiotic mixture in gravid female zebrafish. Gravid fish (150 dpf) were exposed to a mixture of 15 commonly detected antibiotics at 0, 1, and 100 μg/L for 4 weeks. Concentrations of all the 15 antibiotics, especially chlortetracycline, were detected in the F0 ovary and F1 eggs after treatment, indicating maternal transfer of antibiotics. Impaired F0 growth (average 2.2 % and 24.3 % inductions in body length and ovary weight, respectively), and reduced F1 offspring survival (average 4.2 % reductions in survival at 120 hpf) was observed after maternal exposure to the 100 μg/L treatment. Pathway analyses of whole-transcriptome expression profiles from F0 ovaries predicted colorectal disorders. Similarly, pathways of F1 larval transcriptomes from treated females also predicted colorectal disorders along with intestinal apoptosis and oxidative stress, which may be related to growth impairment. These results show that maternal transfer of antibiotics occurs in zebrafish, resulting in transgenerational changes in F1 offspring survival and transcription that predict adverse gastrointestinal effects in offspring. [ABSTRACT FROM AUTHOR]

• A KEGG analysis in common DEGs of the antibiotics showed the activation of NF-κB. • Low levels of antibiotics induced a NF-κB-mediated immune response. • Induction of cytokines by antibiotics were minor when compared to LPS treatment. • Exposure of fish macrophages to low doses of antibiotics activates the NF-kB pathway. Low doses of antibiotics are ubiquitous in the marine environment and may exert negative effects on non-target aquatic organisms. Using primary macrophages of common carp, we investigated the mechanisms of action following exposure to several common antibiotics; cefotaxime, enrofloxacin, tetracycline, sulfamonomethoxine, and their mixtures, and explored the immunomodulatory effects associated with the nuclear factor-κB (NF-κB) signaling pathway. A KEGG pathway analysis was conducted using the sixty-six differentially expressed genes found in all treatments, and showed that exposure to 100 μg/L of antibiotics could affect regulation of the NF-κB signaling pathway, suggesting that activation of NF-κB is a common response in all four classes of antibiotics. In addition, the four antibiotics induced nf-κb and NF-κB-associated cytokines expression, as verified by qPCR, however, these induction responses by four antibiotics were minor when compared to the same concentration of LPS treatment (100 μg/L). Antagonists of NF-κB blocked many of the immune effects of the antibiotics, providing evidence that NF-κB pathways mediate the actions of all four antibiotics. Moreover, exposure to environmentally relevant, low levels (0.01–100 μg/L) of antibiotics induced a NF-κB-mediated immune response, including endogenous generation of ROS, activity of antioxidant enzymes, as well as expression of cytokine and apoptosis. Moreover, exposure to mixtures of antibiotics presented greater effects on most tested immunological parameters than exposure to a single antibiotic, suggesting additive effects from multiple antibiotics in the environment. This study demonstrates that exposure of fish primary macrophages to low doses of antibiotics activates the NF-kB pathway. [ABSTRACT FROM AUTHOR]

• CaO 2 and sunlight synergistically enhances 75∼ 400% pathogens inactivation. • Roles of sunlight (13∼50%), and HRS (68∼87%, •OH, 1O 2 , OH‒ etc.) to inactivation. • Determine [HRS] SS and second-order reaction rate constants (k H R S , P). • Determine direct photochemical parameter for pathogen inactivation. • Characterize bacterial wall and membrane, viral protein capsid and DNA damage. In the era of the current epidemic, it is urgent to control pathogens in sewage, eliminate the source of infection, and optimize the technology for killing pathogens. Combining calcium peroxide (CaO 2) with sunlight is considered a potentially efficient, economical, and eco-friendly method for pathogen-contaminated water remediation. This paper evaluated the solar activating properties of CaO 2 for inactivating pathogenic indicators and explored the roles of reactive species contributing to pathogen inactivation. Moreover, these reactive species' average steady-state concentrations and second-order reaction rate were tentatively explored, and mechanistic model for photoinactivation were establishment. Pathogen's inactivation was mainly attributed to direct photoinactivation (13∼50%) and exogenous indirect mechanisms with corresponding contributions of reactive species, i.e., OH− (14∼23%), 1O 2 (12∼28%), •OH (20∼32%), O 2 •– (12∼16%), and H 2 O 2 (6∼11%). Furthermore, cell membrane rupture and DNA damage were observed by transmission electron microscopy (TEM) and agarose gel electrophoresis (AGE) experiments. Among experiments on common aqueous constituents influencing photoinactivation, copper and iron ions were found to promote a pathogen-inactivating ability of the system, while fulvic acids (FA) and humic acid (HA) had the opposite effect. This study revealed the potential of CaO 2 /sunlight to inactivate pathogens and laid a foundation for its application in inactivating pathogens in surface water. [Display omitted] [ABSTRACT FROM AUTHOR]

The Sacramento River watershed, California, provides important rearing and migratory habitat for several species of conservation concern. Studies have suggested significant benefits for juvenile fish rearing in floodplain habitats of the watershed compared to the mainstem Sacramento River. However, the potential for contaminant exposure in each of these two habitats is poorly understood. Consequently, the present study aimed to determine the distribution and occurrence of bioavailable pesticides within two known salmon habitats using a suite of approaches including exhaustive chemical extraction, single-point Tenax extraction (SPTE) and ex situ passive sampling. Sediment samples were collected from sites within both habitats twice annually in 2019 and 2020, with inundation of the floodplain and high flows for both areas in 2019 and low flow conditions observed in 2020. Sediment characteristics including total organic carbon, black carbon and particle size distribution were determined to elucidate the influence of physical characteristics on pesticide distribution. Using exhaustive extractions, significantly greater sediment concentrations of organochlorines were observed in the floodplain compared to the Sacramento River in both years, with bioaccessible organochlorine concentrations also significantly greater in the floodplain (ANOVA, p < 0.05). Using both SPTEs and exhaustive extractions, significantly fewer pesticides were detected across both sites under low flow conditions as compared to high flow conditions (Poisson regression, p < 0.05). Sediment characteristics including percent fines and black carbon had significant positive relationships with total and bioaccessible pyrethroid and organochlorine concentrations. Fewer analytes were detected using low-density polyethylene (LDPE) passive samplers as compared to SPTEs, suggesting greater sensitivity of the Tenax technique for bioavailability assessments. These findings suggest that threatened juvenile fish populations rearing on the floodplain may have greater exposure to organochlorines than fish inhabiting adjacent riverine habitats, and that pesticide exposure of resident biota may be exacerbated during high-flow conditions. [Display omitted] • Pesticide presence and bioaccessibility assessed in two important salmon habitats. • Ex situ passive sampling, exhaustive and single-point Tenax extractions used. • Higher organochlorine concentrations in floodplain compared to riverine habitats. • Fewer total and bioaccessible pesticides detected during low flow conditions. • Organochlorine and pyrethroid concentrations related to black carbon and % fines. [ABSTRACT FROM AUTHOR]

• Low levels of CaO 2 effectively inactivated pathogenic bacteria and virus. • HRS (OH−, •OH, H 2 O 2 , and O 2 •−) accounted for pathogens inactivation. • [HRS] SS and their reaction rate constants was determined for micromechanism model. • Environment-level ions and DOM may influence pathogens inactivation. • Bactria and virus underwent morphological and physiological changes. Calcium peroxide (CaO 2), a common solid peroxide, has been increasingly used in contaminated site remediation due to its ability to release oxygen (O 2) and hydrogen peroxide (H 2 O 2) and its environmental friendliness. Our present study is first to explore micromechnisms of CaO 2 to efficaciously inactivate pathogen indicators including gram-negative bacterium of Escherichia coli (E. coli), gram-positive bacterium of Staphylococcus aureus (S. aureus), and virus of Escherichia coli -specific M13 bacteriophage (VCSM13) under low concentration (≤ 4 mmol L−1 (mM)). The inactivation mechanisms of E. coli, S. aureus (1 mmol L−1 CaO 2) and VCSM13 (4 mmol L−1) were mainly attributed to OH− (32∼58%) and •OH (34∼42%), followed by H 2 O 2 (13∼20%) and O 2 •− (10∼12%) generated from CaO 2 , with the observed morphological and physiological-associated damages. Also, average steady-state concentrations of (OH−, •OH, H 2 O 2 , and O 2 •−) and their reaction rate constants with E. coli and VCSM13 were determined. Accordingly, the micro-mechanism model of inactivation was established and validated, and the inactivation efficiency of the same order of magnitude of pathogen was predicted. Furthermore, during the common environmental factors, the copper ions was found to be promote CaO 2 inactivation of pathogens, and dissolved organic matter (DOM) fractions had a negative effect on CaO 2 inactivation. The present study explored the mechanisms of CaO 2 inactivation of pathogens in real surface water, laying the foundation for its potential use in the inactivation of water-borne microbial pathogens. [Display omitted] [ABSTRACT FROM AUTHOR]

Boscalid is a persistent fungicide that is frequently detected in surface waters and may be neurotoxic to aquatic organisms. Herein, we evaluated the effects of environmentally relevant boscalid concentrations to zebrafish to explore its potentially neurotoxic mechanisms of effect. Behavioral responses (swimming, phototaxis, and predation), histopathology, transcriptomics, biochemical parameter analysis and gene expression of larval and adult zebrafish following boscalid treatment were assessed. We found that boscalid significantly inhibited the locomotor ability and phototactic response of larvae after an 8-d exposure, and altered the locomotor activity, predation trajectories and ability in adults after a 21-d exposure. It was noted that predation rates of zebrafish were significantly decreased by 30% and 100% after exposure to 0.1 and 1.0 mg/L boscalid, respectively. Adverse alterations in the cell differentiation of eyes and brain injury were also observed in both larvae and adults following boscalid exposure. The expression of genes related to neurodevelopment, neurotransmission, eye development, and visual function, in conjunction with RNA-Seq results, indicated that boscalid may impair visual phototransduction and nervous system processes in larval zebrafish. Conclusively, boscalid exposure may affect the neurobehavioral response of zebrafish by impairing proper visual and nervous system function. ga1 • Boscalid impaired the motor and visual behaviors of zebrafish. • Boscalid reduced corneal diameter and thickness of photoreceptor layer in retina. • KEGG pathways indicated boscalid significantly affected phototransduction. • Changes in visual and nervous systems may cause abnormal neurobehavior. [ABSTRACT FROM AUTHOR]

• Shopping plastic bag leachates contain complex mixtures of compounds. • Fractions 1 and 2 were primarily responsible for acute toxicity. • Fractions 6 and 9 showed strong estrogenic effects on organisms. • Compounds with acute toxicity distributed among different fractions. • Novel phthalates and phenols were identified in Fractions 6 and 9. In this study, fragments of polyethylene plastic bags were treated with simulated gastric juice of fish for 16 h. Following solid-phase extraction, methanol eluents caused acute toxicity to embryos and larvae of Japanese medaka. Chromatographic fractions (polar to more non-polar with numbers increasing) of the extract were evaluated for toxicity and estrogenic activity using medaka and an estrogen receptor (ER) cell-line. Fractions 6 and 9 had the highest estrogenic effects with relative hydrophobic chemicals. The vtg expression in fraction 6 was 22-fold higher than control, and the ER cellular response in fraction 9 was 8.5-fold higher than controls. Following non-target screening (NTS), several novel phthalates and phenols were identified in the above two fractions. Fractions 1 and 2 appeared to be primarily responsible for the acute toxicity observed with the whole extract. The hatching rate decreased to 36 % in fraction 2, and was not observed following exposure to fraction 1. NTS of these fractions indicated 635 and 808 entities, respectively, most without toxicity information. These results indicate plastic leachates from gastric juices of fish are complex mixtures of many compounds that can have acute reproductive and sublethal endocrine impacts in fish. [ABSTRACT FROM AUTHOR]