Environmental Relevant Concentrations Research Articles

Organophosphorus flame retardant induced hepatotoxicity and brain AChE inhibition on zebrafish (Danio rerio)

Organophosphorus flame retardants (OPFRs) are high production volume (HPV) chemicals. Recent reports reveal that OPFRs are ubiquitous in the environment. Unfortunately, the toxicity profiles for OPFRs on organisms remain limited. Hence, to illustrate the potential toxic effects of OPFRs at environmental relevant concentrations on aquatic biota, in the present study, we investigated biochemical, enzymological, antioxidants, and histological (at long-term study) changes of zebrafish tissues under short- (96 h) and long- (21 days) -term triphenyl phosphate (TPhP) exposure. The hepatic glucose production (except short-term TPhP treatment up to 48 h), aspartate transaminase, alanine transaminase, lactate dehydrogenase, reactive oxygen species generation, lipid peroxide, and catalase activities were found to be increased in TPhP exposed groups when compared to control groups (normal and solvent control groups). The hepatic protein content and sodium dismutase activity were declined in TPhP exposed groups. Likewise, brain tissue acetylcholinesterase activity was declined in TPhP exposed groups. The hepatic glutathione S-transferase activity increased after 24 h under short-term TPhP exposure (96 h), while under long-term exposure period (21 days) the enzyme activity was accelerated when compared to control groups. Long-term TPhP exposure resulted in a series of morphological anomalies in the hepatic tissues of zebrafish. Our study reveals that TPhP can potentially cause antioxidants imbalance, alterations in enzymological and biochemical profiles, and morphological anomalies in hepatic tissues of zebrafish. Moreover, TPhP could cause neurotoxic effects on zebrafish at studied concentrations. Our findings expand the available toxicity profiles for TPhP on aquatic biota and propose that zebrafish are a good indicator, and studied parameters are valid biomarkers in assessing the eco-toxicological effects of OPFRs.

Developmental neurotoxicity fingerprint of silica nanoparticles at environmentally relevant level on larval zebrafish using a neurobehavioral-phenomics-based biological warning method

BackgroundLarval zebrafish (Danio rerio) is not only an ideal vertebrate applied in Fish Embryos Toxicity (FET) test but also a well-accepted model in behavioral neurotoxicity research. By applying the commercial standard behavioral tracking system (Zebrabox), the locomotion profiles (neurobehavioral-phenomics) of larval zebrafish can be comprehensively monitored and systematically analyzed to probe ecotoxicological neurotoxicity of nano-pollutants at environmental relevant concentration level. ResultsHerein, the potential toxicity of at environment relevant concentration level on embryonic zebrafish was evaluated by FET and neurobehavioral-phenomics (NBP). The embryos were exposed to the environmental relevant concentration (0.05, 0.1,1, 5, 10, 100 μg/L). The FET criteria were utilized to evaluate the ecotoxicological effect induced by silica NPs. Subsequently, behavioral neurotoxicity of silica NPs was further quantified via locomotion response (LMR). Specifically, the alteration of Light/Dark challenge (LDC) evoked by light/dark stimulation was detected and analyzed by commercially standard behavioral protocols using zebrabox. We revealed that the exposures of silica NPs at environmental relevant concentration (0.05, 0.1, 1, 5, 10,100 μg/L) significantly disturbed locomotion profiles of larval zebrafish. Additionally, it was obviously noted that low, environmentally relevant silica concentrations might result in altering the total behavioral profiles in developing zebrafish. ConclusionsIn sum, neurobehavior phenomics profiling based on LMR and LDC is a potent methodology for the evaluation of sub-lethal or sub-teratogenic toxicity. Compared with the FET tests characterized by the detection of embryonic teratogenicity, the neurobehavior phenomics based method can be more sensitive to determine sub-teratogenic toxicity of silica NPs at environmental concentrations. With the combination of multivariate data analysis, this approach would offer effective technical reference for environmental nano-toxicology research.

Acute exposure to environmentally relevant lead levels induces oxidative stress and neurobehavioral alterations in larval zebrafish (Danio rerio)

The ubiquitous contamination of environmental lead (Pb) remains a worldwide threat. Improper Pb mine waste disposal from an abandoned lead-zinc mine has recently unearthed widespread Pb poisoning in children in Kabwe Zambia. Although the adverse effects of Pb on human health have begun to receive attention, the ecotoxicological effects on aquatic vertebrates still need further investigation. In addition, there is paucity in the knowledge on the behavioural and molecular subcellular responses in larval zebrafish exposed to Pb within the range of environmental relevant concentration (average 3 μg/L with maximum of 94 μg/L) on aquatic organisms such as zebrafish. The adverse effects of environmentally relevant levels of Pb on larval zebrafish was evaluated by measuring swimming behaviour under alternating dark and light conditions. Larval zebrafish acutely exposed to environmentally relevant Pb exhibited neuro-behavioural alteration including enhanced hyperactivity under light conditions evidenced by increased distanced covered and speed compared to the control. The alteration of entire behavioral profiles was further associated with the disturbed expression patterns of mRNA level of key genes associated with antioxidant (HO-1, Ucp-2 and CoxI), proapoptotic gene (TP53), and antiapoptotic gene (Bcl-2). To our knowledge, this is the first report on the effects of environmentally relevant Pb levels from Kabwe, Zambia and their adverse neurobehavioural effects and subcellular molecular oxidative responses in larval zebrafish acutely exposed within a 30 min period. The current results would be beneficial in our understanding of the effects of low Pb levels acutely discharged into an aquatic environment and the life of aquatic organisms.

Toxic mechanism of three azole fungicides and their mixture to green alga Chlorella pyrenoidosa

Currently, few studies have investigated the joint toxicity mechanism of azole fungicides at different exposure times and mixed at the relevant environmental concentrations. In this study, three common azole fungicides, namely, myclobutanil (MYC), propiconazole (PRO), and tebuconazole (TCZ), were used in studying the toxic mechanisms of a single substance and its ternary mixture exposed to ambient concentrations of Chlorella pyrenoidosa. Superoxide dismutase (SOD), catalase (CAT), chlorophyll a (Chla), and total protein (TP), were used as physiological indexes. Results showed that three azole fungicides and ternary mixture presented obvious time-dependent toxicities at high concentrations. MYC induced a hormetic effect on algal growth, whereas PRO and TCZ inhibit algal growth in the entire range of the tested concentrations. The toxicities of the three azole fungicides at 7 days followed the order PRO > TCZ > MYC. Three azole fungicides and their ternary mixture induced different levels of SOD and CAT activities in algae at high concentrations. The ternary mixture showed additive effects after 4 and 7 days exposure, but no effect was observed at actual environmental concentrations. The toxic mechanisms may be related to the continuous accumulation of reactive oxygen species, which not only affected protein structures and compositions but also damaged thylakoid membranes, hindered the synthesis of proteins and chlorophyll a, and eventually inhibited algal growth. These findings increase the understanding of the ecotoxicity of azole fungicides and use of azole fungicides in agricultural production.

Transcriptomic analysis of bisphenol AF on early growth and development of zebrafish (Danio rerio) larvae

Bisphenol AF (BPAF), an alternative to bisphenol A, is widely detected in aquatic environments. Owing to health concerns, the toxic effects of BPAF on organisms are drawing attention. The present study aims to evaluate the toxicity of BPAF, combining the results of omics techniques and experiment. Employing transcriptome sequencing (RNA-seq), we obtained 391, 648, 512, and 545 differentially expressed genes (DEGs) in 0.1, 1, 10, and 100 μg/L BPAF-exposed zebrafish larvae, respectively. Gene ontology (GO) analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment revealed the early development, stimulus-response, and MAPK signaling pathway were significantly affected by BPAF. In addition, five hub genes (fgf3, fgf4, map2k1, myca, and casp3b) were highlighted as the key genes in MAPK signaling pathway using the protein-protein interaction network. Therefore, the RNA-seq results showed that early development and stimulus-response were the main processes affected by BPAF, which was consistent with our morphological and pathological results. The hatching rate of zebrafish embryos in 1 and 10 μg/L BPAF groups was significantly inhibited, and the oxidative stress indexes, including the level of total antioxidant capacity (T-AOC), superoxide dismutase (SOD), and lipid peroxidation (LPO), were significantly increased by the 100 μg/L BPAF treatment. Moreover, the activity of alkaline phosphatase (AKP) was significantly decreased in all BPAF exposure groups. In conclusion, exposure to BPAF at environmental relevant concentrations affected the early development and immune system of zebrafish larvae by modulating MAPK signaling pathway, and our results provide solid evidence for the future studies on the toxicity of bisphenols.

Comparison of Sensitivity of Tropical Freshwater Microalgae to Environmentally Relevant Concentrations of Cadmium and Hexavalent Chromium in Three Types of Growth Media.

Sensitivity of tropical freshwater microalgae (Mesotaenium sp., Chlorococcum sp. and Scenedesmus sp.) to environmentally relevant concentrations of hexavalent chromium (Cr6+) and cadmium (Cd2+) was compared individually in three growth media viz. Bold's Basal Medium (BBM), Test Medium 1 (TM1) and Test Medium 2 (TM2) based on fluorescence reduction. Free metal content of growth media was determined by Visual MINTEQ (version 3.1). After 24h, relative fluorescence of microalgae in the three media decreased with increased metal concentration showing a concentration dependent graded toxicity response. All microalgae were more sensitive to the metals when grown in TM1, when compared, more sensitive to Cr6+ than Cd2+. Metal speciation indicated that TM1 and TM2 media have higher percentage of bioavailable Cd2+ than BBM, and chromium was present mainly as CrO42- and HCrO4-. The results suggest that the TM1 medium is more suitable under short term exposure of microalgae to metals in environmental monitoring.

Cytotoxic responses of the anticancer drug cyclophosphamide in the mussel Mytilus galloprovincialis and comparative sensitivity with human cells lines

The rise of cancer cases worldwide led to an increase in production and consumption of anticancer drugs, that ultimately end up in the marine environment and are accumulated in aquatic organisms. Cyclophosphamide (CP) is a cytotoxic alkylating agent frequently prescribed in cancer treatments. This study assess ecotoxicological effects of CP on mussels Mytilus galloprovincialis, through in vivo and ex vivo approaches and compares the sensitivity of mussel haemocytes with well-established human cell lines (RPE and HeLa). Mussels were exposed in vivo to CP (1000 ng L−1) and several biomarkers analysed in gills and digestive glands namely neurotoxicity (AChE activity), oxidative stress (GPx activity), biotransformation (GST activity), lipid peroxidation (LPO) and apoptosis (caspase activity), whereas genotoxicity was determined in mussels’ haemocytes. Cytotoxicity was also assessed in haemocytes (in vivo and ex vivo) and human cell lines (in vitro) exposed to a range of CP concentrations (50, 100, 250, 500 and 1000 ng L−1) over 24 h, via neutral red assay.In in vivo exposure, detoxification of CP did not efficiently occur in the gills while in digestive glands GPx and GST activities were induced, jointly with a decrease in lipid peroxidation, indicating a potential outcome of the protective antioxidant mechanisms, whereas no apoptosis was noted. Moreover, cytotoxicity and DNA damage were detected in haemocytes. The ex vivo exposure haemocytes to CP caused cytotoxicity (from 100 ng L−1), whereas no effects occurred in human cell lines. This suggests that, at relevant environmental concentrations, CP cause subtle and irreversible impacts on M. galloprovincialis.

Cadmium exacerbates dextran sulfate sodium-induced chronic colitis and impairs intestinal barrier

The potential health risk of environmental pollutant, cadmium, has become a public concern due to its widespread existence and long biological half-life. High-dose cadmium can induce various adverse outcomes, however, the chronic biological influences of cadmium at an environmental dosage and its mechanism remain largely unclear. Here, we investigated the effect of long-term exposure of cadmium at the environmental-relevant concentration on intestinal function. A chronic colitis mouse model was established through multiple cycles of dextran sulfate sodium (DSS) challenge and recovery. 200 nM cadmium in drinking water intensified colonic inflammation induced by DSS (histological score, DSS vs. DSS + Cd: 7.4 ± 1.21 vs. 10.67 ± 0.67, P < 0.05), including fecal occult bleeding and fecal consistency loss. Multiple inflammatory cytokines were significantly up-regulated by cadmium both in colon and plasma (P < 0.05). In addition, intestinal integrity was compromised by cadmium. Goblet cells were markedly reduced (ctrl vs. Cd: 48.33 ± 3.07 vs. 37.5 ± 2.14, P < 0.05) and plasma D-lactate (ctrl vs. Cd: 1.88 ± 0.20 vs. 2.80 ± 0.15, P < 0.01) and diamine oxidase (ctrl vs. Cd: 5.00 ± 0.87 vs. 11.21 ± 2.17, P < 0.05) were increased in cadmium-treated mice, indicating an elevated intestinal permeability. In vitro results showed that long-term exposure of cadmium down-regulated the expression and membrane localization of adherent and tight junction proteins in a time-dependent manner. In conclusion, long-term exposure of environmental dose of cadmium aggravated DSS-induced chronic colitis and disrupted intestinal barrier and impaired the adherent and tight junction proteins. These findings provide a better understanding about the health risk of cadmium in the environment.

Exposure to environmentally-relevant concentrations of hexavalent chromium does not induce ovarian toxicity in mice

Exposure to high concentrations of hexavalent chromium [Cr(VI)] in drinking water (≥250 ppm) is reported to decrease ovarian follicle counts and increase follicular atresia in mice. To assess effects at lower concentrations, herein we exposed B6C3F1 mice to 0.1–150 ppm Cr(VI) in drinking water for 90 days in a GLP-compliant study. Ovarian follicular counts, differentiation, and degeneration were assessed from every 10th serial section (up to 14 sections per ovary). Ovarian follicular counts, differentiation, and rate of atresia were not altered in any exposure group. Gross and microscopic changes were not apparent in any of the evaluated reproductive or glandular organs. The no observable adverse effect level (NOAEL) for follicular effects was 150 ppm. In addition to these findings, published Cr(VI) studies examining follicles were scored using two methods for assessing study quality for use in risk assessment—including the Toxic Substance Control Act (TSCA) scoring method. Both methods revealed that studies reporting adverse effects on follicles generally received low scores. Overall, the current study indicates no/low potential for Cr(VI) to induce follicular toxicity in mice below 150 ppm Cr(VI) in drinking water (17.7 mg/kg bodyweight).

Waterborne Exposure of Paclobutrazol at Environmental Relevant Concentration Induce Locomotion Hyperactivity in Larvae and Anxiolytic Exploratory Behavior in Adult Zebrafish.

The available arable land is unable to fulfill the food production need of rapidly the exponentially growing human population in the world. Pesticides are one of those different measures taken to meet this demand. As a plant growth regulator to block gibberellin, paclobutrazol (PBZ) is used excessively throughout the world to promote early fruit setting, and to increase seed setting which might be harmful because PBZ is a very stable compound; therefore, it can bioaccumulate into the food chain of an ecosystem. In the present study, we discovered unexpected effects of PBZ on zebrafish larvae and adult behaviors by challenging them with low dose exposure. Zebrafish larvae aged 4 days post-fertilization (dpf) were exposed for 24 h at 10 µg/L (0.01 ppm) and 100 µg/L (0.1 ppm) of PBZ, respectively, and adults were incubated at 100 µg/L (0.1 ppm) and 1000 µg/L (1 ppm) concentrations of PBZ, respectively, for fourteen days. After incubation, the locomotor activity, burst, and rotation movement for the larvae; and multiple behavioral tests such as novel tank exploration, mirror biting, shoaling, predator avoidance, and social interaction for adult zebrafish were evaluated. Brain tissues of the adult fish were dissected and subjected to biochemical analyses of the antioxidant response, oxidative stress, superoxide dismutase (SOD), and neurotransmitter levels. Zebrafish larvae exposed to PBZ exhibited locomotion hyperactivity with a high burst movement and swimming pattern. In adult zebrafish, PBZ resulted in anxiolytic exploratory behavior, while no significant results were found in social interaction, shoal making, and predator avoidance behaviors. Interestingly, high dose PBZ exposure significantly compromised the innate aggressive behavior of the adult fish. Biochemical assays for oxidative stress, antioxidant response, and superoxide dismutase (SOD) showed significant reductions in their relative contents. In conclusion, for the first time, our behavior assays revealed that chronic PBZ exposure induced behavioral alterations in both larvae and the adult zebrafish. Because PBZ is a widely-used plant growth regulator, we suggest that it is necessary to conduct more thorough tests for its biosafety and bioaccumulation.

Environmental relevant concentration of λ-cyhalothrin and 3-phenoxybenzoic acid caused endocrine-disrupting effects on male lizards (Eremias argus)

In the present study, the endocrine toxicity of LCT and PBA was investigated through exposure to Eremias argus for two weeks under environmental relevant concentration. RNA-sequencing identified 4442 and 4653 differentially expressed genes in lizard liver after LCT and PBA exposure. Four differentially expressed genes (hsd17β, ar, sult, ugt) related with hypothalamic-pituitary-gonadal axis were quantified by qPCR. The expression of genes associated with HPG axis in different tissues differed significantly. In LCT treatment group, ar, cyp17 and hsd3β genes involved in testosterone synthesis and transportation were significantly decreased in lizard testes, and the spermatogensis was inhibited in the testes, which indicated the anti-androgenic activity of LCT. After PBA exposure, the genes related with estradiol synthesis, transportation and metabolism, such as hsd17β, erα, ugt in lizard liver were important biomarkers and the significant decrease of estradiol level was highly correlated with hsd17β, erα, ugt gene expressions. The relative high binding affinity of PBA with ERα further demonstrated the anti-estrogenic activity of PBA. Our results elucidate the different toxic mechanism of LCT and PBA on lizard endocrine system at environmental relevant concentration. Pyrethroids metabolism may cause more seriously toxicity rather than detoxification.

Quantitation and localization of beta-blockers and SSRIs accumulation in fathead minnows by complementary mass spectrometry analyses

Beta-blockers and selective serotonin reuptake inhibitors (SSRIs) enter the environment through the improper disposal of drugs in garbage, sinks, or toilets as well as via excretion after their intended use. Beta-blockers and SSRIs are resistant to biodegradation and highly water soluble, leading to limited removal capabilities by wastewater treatment plants. As a result, these compounds can easily enter the aquatic environment in a biologically active state, posing risks to the behavior, anatomy, and physiology of aquatic organisms through exposure. However, there is insufficient research on the effects of beta-blockers on aquatic vertebrates to have a complete understanding of the impact of beta-blocker pollution on aquatic organisms. Exposing fathead minnows at environmentally-relevant concentrations allows for an accurate representation of how beta-blockers and SSRIs affect and accumulate in aquatic vertebrates. Singular exposures to two beta-blockers and two selective serotonin reuptake inhibitors (SSRIs) at seven days modeled how pollution affects aquatic wildlife during acute exposure events. After exposure, the entire organism was analyzed quantitatively by liquid chromatography mass spectrometry and qualitatively by matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI). Imaging allowed for the determination of the part of the organism in which the drugs were accumulating. Results showed that after seven days of exposure there was accumulation of both the beta-blockers and SSRIs in the fathead minnows. This data represents the first application of LC-MS quantitation guided by MALDI-MSI in aquatic toxicology-type research in environmental analytical chemistry.

Competitive co-adsorption of bacteriophage MS2 and natural organic matter onto multiwalled carbon nanotubes

A leading challenge in drinking water treatment is to remove small-sized viruses from the water in a simple and efficient manner. Multi-walled carbon nanotubes (MWCNT) are new generation adsorbents with previously demonstrated potential as filter media to improve virus removal. This study therefore aimed to evaluate the field applicability of MWCNT-filters for virus removal in water containing natural organic matter (NOM) as co-solute to viruses, using batch equilibrium experiments. Contrary to previous studies, our results showed with MS2 bacteriophages single-solute systems that the affinity of MWCNT for MS2 was low, since after 3 h of equilibration only 4 log10 reduction value (LRV) of MS2 (20 mL at an initial concentration of 106 PFU MS2/mL) were reached. Single solute experiments with Suwannee river NOM (SRNOM) performed with environmentally-relevant concentrations showed MWCNT surface saturation at initial SRNOM concentrations between 10 and 15 mgC/L, for water pH between 5.2 and 8.7. These results suggested that at NOM:virus ratios found in natural waters, the NOM would competitively suppress virus adsorption onto MWCNT, even at low NOM concentrations. We confirmed this expectation with SRNOM-MS2 co-solute experiments, which showed an exponential decrease of the MS2 LRV by MWCNT with an increase in the initial SRNOM concentration. More interestingly, we showed that pre-equilibrating MWCNT with a SRNOM solution at a concentration as low as 0.4 mgC/L resulted in a LRV decrease of 3 for MS2, due to the formation of a negatively charged SRNOM adlayer on the MWCNT surface. Complementary batch experiments with natural NOM-containing waters and competition experiments with SRNOM in the presence of CaCl2 confirmed that the presence of NOM in waters challenges virus removal by MWCNT-filters, irrespective of the concentration and type of NOM and also in the presence of Ca2+. We therefore conclude that MWCNT-filters produced with commercially available pristine MWCNT cannot be considered as a viable technology for drinking water virus removal.

Single and combined effects of carbamazepine and copper on nervous and antioxidant systems of zebrafish (Danio rerio).

Various pollutants co-exist in the aquatic environment such as carbamazepine (CBZ) and copper (Cu), which can cause complex effects on inhabiting organisms. The toxic impacts of the single substance have been studied extensively. However, the studies about their combined adverse impacts are not enough. In the present study, zebrafish were exposed to environmental relevant concentrations of CBZ (1, 10, and 100 μg/L), Cu (0.5, 5, and 10 μg/L) and the mixtures (1 μg/L CBZ + 0.5 μg/L Cu, 10 μg/L CBZ + 5 μg/L Cu, 100 μg/L CBZ + 10 μg/L Cu) for 45 days, the effects on nervous and antioxidant systems of zebrafish were investigated. The results demonstrated that, in comparison with single exposure group, the combined presence of CBZ and Cu exacerbated the effect of antioxidant system (the ability of inhibition of hydroxyl radicals (IHR), superoxide dismutase (SOD), catalase (CAT) and glutathione S-transferase (GST)) but not nervous system (Acetylcholinesterase [AChE]). The qPCR results supported the changes of corresponding enzymes activities. Hepatic histopathological analysis verified the results of biomarkers. Our work illustrated that the toxicity of mixed pollutants is very complicated, which cannot simply be inferred from the toxicity of single pollutant, and calls for more co-exposure experiments to better understanding of the co-effects of pollutants on aquatic organisms.

Toxicity of tris(2-chloroethyl) phosphate in Daphnia magna after lifetime exposure: Changes in growth, reproduction, survival and gene transcription.

In recent years, with the elimination of brominated flame retardants (BFRs), the product volume of tris(2-chloroethyl) phosphate (TCEP), as a main substitute of BFRs, was increasing and frequently detected in natural waters. However, the current toxicological studies on TCEP were mainly focused on the partial life stage assessment of model animals, and thus it might underestimate the impact of TCEP on environmental risks. Therefore, the whole-life-stage effects of TCEP on growth, reproduction, survival and gene transcription in Daphnia magna (D. magna) were studied in this study after exposure to environmentally relevant or greater concentrations (500 or 5000ng/L). It was found that chronic exposure to TCEP at environmental relevant or greater concentrations promoted growth of D. magna and the expressions of genes involved in the pathways associated with growth were significantly up-regulated. TCEP did not affect reproduction of D. magna, but the expressions of some genes screened in reproduction stage were significantly changed. Furthermore, the expressions of genes involved in two heart disease-related pathways were down-regulated at the death stage of D. magna after TCEP exposure for 62 days, suggesting that TCEP delayed the death of D. magna by retarding their heart senility.

Effects of Combined Ag and ZnO Nanoparticles on Microbial Communities from Crab Orchard Creek, Illinois, USA

The widespread use of Ag and ZnO nanoparticles (NPs) in commercial products has raised concern of their potential adverse impact on humans and the environment. These NPs most commonly enter the environment from the effluents of wastewater treatment plants (WWTPs). To understand the impact of these NPs on microbial communities, this study focused on adding environment-relevant concentrations of Ag (1 μg/L), ZnO (0.1 μg/L), and Ag+ZnO (1 μg/L+0.1 μg/L) to water collected from where the Carbondale Southeast WWTP effluent mixes with Crab Orchard Creek in IL, USA. Nanoparticles-spiked samples were withdrawn immediately and after 72 h for dynamic light scattering analysis. Optical density analysis by ultraviolet–visible spectroscopy, quantitative PCR analysis, and deoxyribonucleic acid sequencing were also conducted after 72 h. The results showed that ZnO NPs, at the studied concentration, were toxic, as a decrease in microbial biomass at Day 3 compared to the Control was reached, with an increase in mass fraction of nanoscale particles over time. However, when ZnO NPs were added in combination with Ag NPs, the adverse impact of ZnO NPs was mitigated, as an increase in microbial biomass was reached compared to the Control at Day 3, with a decrease in mass fraction of nanoscale particles over time. Ag NPs alone, at the studied concentration, did not bring significant impact on the microbial biomass. The relative abundance of the bacterial population affected the most by the addition of NPs was Firmicutes, with an increase in 13.74% compared to the Control when Ag+ZnO NPs were added. This study demonstrated the response of microbial communities to increased environment-relevant concentrations of NPs in a short period of time. The result will provide information that may aid in the preparation of guidance or regulations related to discharge of mixtures of NPs to surface water.

Effects of chronic exposure to a pharmaceutical mixture on the three-spined stickleback (gasterosteus aculeatus) population dynamics in lotic mesocosms

Pharmaceutical substances are ubiquitous in the aquatic environment and their concentration levels typically range from ng/L up to several μg/L. Furthermore, as those compounds are designed to be highly biologically active, assessing their impacts on non-target organisms is important. Here, we conducted a mesocosm experiment testing a mixture of five pharmaceuticals (diclofenac, carbamazepine, irbesartan, acetaminophen and naproxen) on fish, three-spined stickleback (Gasterosteus aculeatus). The mixture concentration levels were chosen on the basis of the contamination of the Meuse river in Belgium which had been measured previously during a monitoring campaign undertaken in 2015 and 2016. Three nominal mixture concentration levels were tested: the lowest concentration level mixture was composed by environmentally-relevant concentrations that approximate average realistic values for each pharmaceuticals (Mx1); the two other levels were 10 and 100 times these concentrations. Although no impact on stickleback prey was observed, the mixture significantly impaired the survival of female fish introduced in the mesocosms at the highest treatment level without causing other major differences on fish population structure. Impacts on condition factors of adults and juveniles were also observed at both individual and population levels. Using a modelling approach with an individual-based model coupled to a bioenergetic model (DEB-IBM), we concluded that chronic exposure to environmentally-relevant concentrations of five pharmaceuticals often detected in the rivers did not appear to strongly affect the three-spined stickleback populations. Mechanisms of population regulation may have counteracted the mixture impacts in the mesocosms.

Changes in lipid profiles in Daphnia magna individuals exposed to low environmental levels of neuroactive pharmaceuticals

Disruptive effects of chemicals on lipids in aquatic species are mostly limited to obesogens and vertebrates. Recent studies reported that antidepressants, anxiolytic, antiepileptic and β-adrenergic pharmaceuticals, with putative distinct mechanisms of action at low environmental relevant concentrations, up-regulated common neurological and lipid metabolic pathways and enhanced similarly reproduction in the crustacean Daphnia magna. Conversely CRISPR mutants for the tryptophan hydrolase enzyme gene (TRH) that lack serotonin had the opposed phenotype: the lipid metabolism down-regulated and impaired reproduction. Lipid metabolism is strongly linked to reproduction in D. magna. The aim of this study is to test if the above mentioned neuro-active chemicals disrupted common lipid groups and showed also the opposed lipidomic effects as those individuals lacking serotonin. This study used ultra-high performance liquid chromatography/time-of-flight mass spectrometry (UHPLC/TOFMS) to study how neuro-active chemicals (carbamazepine, diazepam, fluoxetine and propranolol) at low (0.1 μg/L) and higher concentrations (1 μg/L) and three CRISPR TRH mutant clones disrupt the dynamics of glycerophospholipids and glycerolipids in Daphnia adults. Lipidomic analysis identified 267 individual lipids corresponding to three classes of glycerolipids, eleven of glycerophospholipids, one of sterols and one of sphingolipids, of which 132 and 125 changed according to the chemical treatments or across clones, respectively. Most pharmaceutical treatments enhanced reproduction whereas mutated clones lacking serotonin reproduced to a lesser extent. Except for carbamazepine, most of the tested pharmaceuticals increased some triacylglycerol species and decreased monoacylglycerols, lysophospholipids, sphingomyelins and cholesterol esters in exposed females. Opposed lipidomic pattern was observed in mutated clones lacking serotonin. Lipidomic data, thus, indicate a close link between reported transcriptomic and lipidomic changes, which are likely related to serotonin and other neurological signalling pathways.

Effects of short-term exposure to environmentally-relevant concentrations of benzo(a)pyrene-sorbed polystyrene to White seabass (Atractoscion nobilis)☆

Plastic marine debris hyper-concentrates hydrophobic contaminants such as polycyclic aromatic hydrocarbons (PAHs) and can transfer these sorbed contaminants to biota following ingestion. PAHs are known to induce cardiotoxicity and visual toxicity at sublethal doses. Juvenile White seabass (Atractoscion nobilis) fish were fed environmentally relevant concentrations of either virgin polystyrene or benzo(a)pyrene (BaP)-sorbed polystyrene for 5 days and were monitored for changes in phototactic response, swimming behavior, and hepatic cytochrome p450 1A (CYP1A) enzyme activity. No significant differences in the monitored endpoints were recorded in fish that ingested either polystyrene or BaP-sorbed polystyrene relative to control fish following the short-term exposure. However, fish exposed to 252 μg/L BaP alone as a positive control had significantly elevated CYP1A enzyme activity (p = 0.046) and impaired phototactic response (p = 0.020), though no altered swimming behavior was observed (p = 0.843) relative to control fish. These results demonstrate that pelagic fish ingesting environmentally relevant concentrations of BaP-sorbed polystyrene for a short, 5-day duration do not demonstrate measurable changes in vision, swimming activity, nor CYP1A activity. High variability within enzyme activity and behavioral responses suggest that lack of significant effects may be due to low sample size.

Effects of florfenicol on growth, photosynthesis and antioxidant system of the non-target organism Isochrysis galbana

Florfenicol (FFC) is one of the most universally used antibiotics in aquaculture, which is substitute for chloramphenicol extensively, while the massive residues in aquatic environment were assumed to threaten the non-target organisms. Present research investigated the effects of florfenicol on growth, chlorophyll content, photosynthesis, and antioxidant ability of Isochrysis galbana. The results showed that FFC at 0.001–1 mg/L stimulated the growth of I. galbana and increased the content of chlorophyll. In addition, photosynthesis of I. galbana was inhibited and the photosynthetic parameters were uplifted with the increased exposure duration and FFC concentration. Furthermore, superoxide dismutase (SOD), catalase (CAT) activity significantly dropped at 0.01–20 mg/L FFC, while the contents of malondialdehyde (MDA), glutathione (GSH) and reactive oxygen species (ROS) increased after 72 h exposure, indicating that FFC at high concentrations caused a serious oxidative stress on algae. The simultaneous increase of ROS disrupted the equilibration between oxidants and antioxidant systems. Under the high concentration of FFC, the excessive of ROS was generated in algae which affected the membrane permeability and further decreased the cell biomass. Present study showed that acute exposure (72 h) at the environmental relevant concentration (0.01 mg/L) cannot induce the physiological dysfunction of the microalgae I. galbana, but the feeding concentration (20 mg/L) can. Additionally, this study hinted the possible negative impacts on ecosystems with the chronic exposure even at low FFC concentration or with the uncontrolled use of FFC.