Toxicity of environmentally realistic concentrations of chlorpyrifos and terbuthylazine in indoor microcosms

A comparative study on targeted gene expression in zebrafish and its gill cell line exposed to chlorpyrifos

Chlorpyrifos (CPF) is an organophosphorus-based insecticide, which is known to pose a serious risk to aquatic animals. However, the mechanisms of CPF toxicity in animals still remain unclear. The present investigation aimed to compare the potential effects of CPF in zebrafish (Danio rerio) and its gill cell line (DrG cells). Based on the in vivo study, the LC50 was calculated as 18.03 µg/L and the chronic toxic effect of CPF was studied by exposing the fish to 1/10th (1.8 µg/L) and 1/5th (3.6 µg/L) of the LC50 value. Morphological changes were observed in fish and DrG cells which were exposed to sublethal concentrations of CPF. The results of MTT and NR assays showed significant decline in the survival of cells exposed to CPF at 96 h. The production of reactive oxygen species in DrG cells and expression levels of antioxidant markers, inflammatory response genes (cox2a and cox2b), cyp1a, proapoptotic genes (bax), antiapoptotic gene (bcl2), apoptotic genes (cas3 and p53), and neuroprotective gene (ache) were determined in vivo using zebrafish and in vitro using DrG cells after exposure to CPF. Significant changes were found in the ROS production (DrG cells) and in the expression of inflammatory, proapoptotic, and apoptotic genes. This study showed that DrG cells are potential alternative tools to replace the use of whole fish for toxicological studies.

Evaluating the Impact of Individual and Combined Toxicity of Imidacloprid, Cycloxaprid, and Tebuconazole on Daphnia magna

The risks posed by chemicals in the environment are typically assessed on a substance-by-substance basis, often neglecting the effects of mixtures. This may lead to an underestimation of the actual risk. In our study, we investigated the effects of three commonly used pesticides-imidacloprid (IMI), cycloxaprid (CYC), and tebuconazole (TBZ)-both individually and in combination, using various biomarkers to assess their impact on daphnia. Our findings indicated that the order of toxicity, from highest to lowest, was TBZ, IMI, and CYC, as determined by acute toxicity as well as reproduction. The effects of the ITmix (IMI and TBZ) and CTmix (CYC and TBZ) combinations on immobilization and reproduction were evaluated by MIXTOX, revealing a higher risk of immobilization at low concentrations for ITmix. The effect on reproduction differed depending on the ration of pesticides in the mixture, with synergism observed, which may be caused mainly by IMI. However, CTmix showed antagonism for acute toxicity, with the effect on reproduction depending upon the composition of the mixture. The response surface also exhibited a switch between antagonism and synergism. Additionally, the pesticides extended the body length and inhibited the development period. The activities of superoxide dismutase (SOD) and catalase (CAT) content was also significantly induced at different dosage points in both the single and combination groups, indicating changes in the metabolic capabilities of detoxifying enzymes and target site sensitivity. These findings highlight the need for more attention to be focused on the effects of pesticide mixtures.

Assessing the colonization by Daphnia magna of pesticide-disturbed habitats (chlorpyrifos, terbuthylazine and their mixtures) and the behavioral and neurotoxic effects

The spread of pesticides in water bodies integrated into agricultural landscapes may prevent some areas from being colonized. In this study, the effects on the colonization responses of D. magna exerted by gradients of realistic environmental concentrations of the pesticides chlorpyrifos, terbuthylazine and their mixtures were tested in a novel multicompartment non-forced exposure system. Furthermore, the effects of both pesticides and their mixtures on the swimming behavior and the neurotransmission activity of D. magna were analyzed using a traditional forced exposure system. The synthesis and concentration of the main environmental metabolites of terbuthylazine were also analyzed. Results confirmed that D. magna exposed to mixture gradients were able to detect the pollutants and their colonization dynamics were drastically inhibited. The swimming behavior increased in D. magna exposed to the highest concentration of the mixture treatment. AChE activity was only significantly inhibited in the D. magna exposed to the highest concentration of chlorpyrifos. Changes in swimming behavior could not be directly related to the effects on AChE. Furthermore, the synthesis of the metabolite terbuthylazine 2-hydroxy during the course of the experiments was confirmed. These results demonstrate the importance of integrating pesticide mixtures in both non-forced and forced exposure systems during ecotoxicological assays.

Influence of temperature on the toxicity of the elutriate from a pesticide contaminated soil to two cladoceran species

Brazil has become one of the largest consumers of pesticides in the world. However, there are still few studies evaluating pesticide toxicity integrating local aquatic and terrestrial environments. In addition, there is growing concern about the influence of temperature conditions related with climate change on contaminants toxicity. The aim of the present study was to evaluate the elutriate toxicity of the insecticide Kraft^® 36 EC (a.i. abamectin), the fungicide Score^® 250 EC (a.i. difenoconazole) and their mixture to the cladocerans Ceriodaphnia silvestrii and Daphnia similis, using model ecosystems (mesocosms). To this end, mesocosms were filled with natural soil and subjected to the following treatments: Control (Milli-Q water), Kraft (10.8 g abamectin ha^-1), Score (20 g difenoconazole ha^-1), and Kraft + Score (10.8 g abamectin ha^-1 + 20 g difenoconazole ha^-1). The experiment lasted 18 days, and the applications were made on days 1, 8, and 15; the occurrence of rainfall was simulated on days 1, 8, and 15 after applications and only rainfall simulation on days 4, 11, and 18. The experiment was conducted under two different temperatures: 23 °C and 33 °C. At 23 °C, single Kraft treatment and in combination with Score showed high toxicity to both cladocerans. At 33 °C, elutriate of the Kraft^® and mixture treatments were highly toxic to D. similis but not to C. silvestrii. The results indicate that while Kraft had higher toxicity than Score to both cladocerans, this toxicity was counteracted at 33 °C only for the exotic species, D. similis. The results portray the complexity of pesticide toxicity when considering realistic experimental settings including different organisms and temperature treatments.

Effects of Environmental Concentrations of Total Phosphorus on the Plankton Community Structure and Function in a Microcosm Study

The excessive nutrients in freshwater have been proven to promote eutrophication and harmful algae blooms, which have become great threats to water quality and human health. To elucidate the responses of the plankton community structure and function to total phosphorus (TP) at environmental concentrations in the freshwater ecosystem, a microcosm study was implemented. The results showed that plankton communities were significantly affected by the TP concentration ≥ 0.1 mg/L treatments. In terms of community structure, TP promoted the growth of Cyanophyta. This effect was transmitted to the zooplankton community, resulting in the promotion of Cladocera growth from day 42. The community diversities of phytoplankton and zooplankton had been continuously inhibited by TP. The principal response curve (PRC) analysis results demonstrated that the species composition of phytoplankton and zooplankton community in TP enrichment treatments significantly (p ≤ 0.05) deviated from the control. For community function, TP resulted in the decline in phytoplankton photosynthesis. The chlorophyll fluorescence parameters were significantly inhibited when TP concentration reached 0.4 mg/L. In TP ≥ 0.1 mg/L treatments, the reductions in total phytoplankton abundances led to a continuous decrease in pH. This study can directly prove that the plankton community changes significantly when TP concentrations are greater than 0.1 mg/L and can help managers to establish specific nutrient management strategies for surface water.

Nutrient potentiate the responses of plankton community structure and metabolites to cadmium: A microcosm study

Metal pollution is a worldwide concern and may pose risks to aquatic organisms, communities, and ecosystems. The toxic effects of metals at the organism level are relatively clear. However, their impacts at the community level are still poorly understood, especially with concurred eutrophication in surface water. In the present study, the effects of Cd on the plankton community structure and function under varying nutrient conditions were evaluated using a microcosm study. The employed concentrations of Cd and nutrient were based on the values currently measured in the freshwater ecosystem. For the plankton structure, our results showed that the Chl a concentration, the abundances of total phytoplankton, Cyanophyta, and Chlorophyta, and the abundance of Copepoda decreased by Cd consistently. The Cyanophyta Oscillatoria tenuis and Copepoda nauplius were the most sensitive species to Cd in the phytoplankton and zooplankton community, respectively. For the community effects, we found the inhibitory effects of Cd on the photosystem II (PSII) activity of phytoplankton community because of the consistent decrease in the chlorophyll fluorescence parameters (F_v/F_m, Y(Ⅱ), and ETR). Furthermore, the reductions of DOC and pH by Cd were only found in the high nutrient condition, which indicated that the toxic effects of Cd on the community structure and community metabolites were aggravated by the increased nutrient. This study emphasizes the importance of considering nutrient conditions when assessing the metal ecotoxicological effects at environmentally relevant concentrations.

Multiple stressors in Mediterranean coastal wetland ecosystems: Influence of salinity and an insecticide on zooplankton communities under different temperature conditions

Temperature increase, salinity intrusion and pesticide pollution have been suggested to be among the main stressors affecting the biodiversity of coastal wetland ecosystems. Here we assessed the single and combined effects of these stressors on zooplankton communities collected from a Mediterranean coastal lagoon. An indoor microcosm experiment was designed with temperature variation (20 °C and 30 °C), salinity (no addition, 2.5 g/L NaCl) and the insecticide chlorpyrifos (no addition, 1 μg/L) as treatments. The impact of these stressors was evaluated on water quality variables and on the zooplankton comunity (structure, diversity, abundance and taxa responses) for 28 days. This study shows that temperature is the main driver for zooplankton community change, followed by salinity and chlorpyrifos. The three stressors contributed to a decrease on zooplankton diversity. The increase of temperature contributed to an increase of zooplankton abundance. Salinity generally affected Cladocera, which resulted in a Copepoda increase at 20 °C, and a reduction in the abundance of all major zooplankton groups at 30 °C. The insecticide chlorpyrifos affected primarily Cladocera, altough the magnitude and duration of the direct and indirect effects caused by the insecticide substantially differed between the two temperature scenarios. Chlorpyrifos and salinity resulted in antagonistic effects on sensitive taxa (Cladocera) at 20 °C and 30 °C. This study shows that temperature can influence the direct and indirect effects of salinity and pesticides on zooplankton communities in Mediterranean coastal wetlands, and highlights vulnerable taxa and ecological responses that are expected to dominate under future global change scenarios.

Prioritization of Pesticides for Assessment of Risk to Aquatic Ecosystems in Canada and Identification of Knowledge Gaps

Pesticides can enter aquatic environments via direct application, via overspray or drift during application, or by runoff or leaching from fields during rain events, where they can have unintended effects on non-target aquatic biota. As such, Fisheries and Oceans Canada identified a need to prioritize current-use pesticides based on potential risks towards fish, their prey species, and habitats in Canada. A literature review was conducted to: (1) Identify current-use pesticides of concern for Canadian marine and freshwater environments based on use and environmental presence in Canada, (2) Outline current knowledge on the biological effects of the pesticides of concern, and (3) Identify general data gaps specific to biological effects of pesticides on aquatic species. Prioritization was based upon recent sales data, measured concentrations in Canadian aquatic environments between 2000 and 2020, and inherent toxicity as represented by aquatic guideline values. Prioritization identified 55 pesticides for further research nationally. Based on rank, a sub-group of seven were chosen as the top-priority pesticides, including three herbicides (atrazine, diquat, and S-metolachlor), three insecticides (chlorpyrifos, clothianidin, and permethrin), and one fungicide (chlorothalonil). A number of knowledge gaps became apparent through this process, including gaps in our understanding of sub-lethal toxicity, environmental fate, species sensitivity distributions, and/or surface water concentrations for each of the active ingredients reviewed. More generally, we identified a need for more baseline fish and fish habitat data, ongoing environmental monitoring, development of marine and sediment-toxicity benchmarks, improved study design including sufficiently low method detection limits, and collaboration around accessible data reporting and management.

Unravelling the effects of multiple stressors on diatom and macroinvertebrate communities in European river basins using structural and functional approaches

Rivers suffer from more severe decreases in species diversity compared to other aquatic and terrestrial ecosystems due to a variety of pressures related to human activities. Species provide different roles in the functioning of the ecosystem, and their loss may reduce the capacity of the ecosystems to respond to multiple stressors. The effects on diversity will differ based on the type, combination and severity of stressors, as well as on the characteristics of the community composition and tolerance. Multiple trait-based approaches (MTBAs) can help to unravel the effects of multiple stressors on communities, providing a mechanistic interpretation, and, thus, complementing traditional biodiversity assessments using community structure. We studied the relationships between diversity indexes and trait composition of macroinvertebrate and diatom communities, as well as environmental variables that described the hydrological and geomorphological alterations and toxic pollution (pesticides and pharmaceuticals) of three different European river basins: the Adige, the Sava, and the Evrotas. These river basins can be considered representative cases of different situations in European freshwater systems. Hydrological variables were the main drivers determining the community structure and function in the rivers, for both diatoms and macroinvertebrates. For diatom communities, pharmaceutical active compound (PhAC) toxic units were also identified as a very important driver of diversity changes, explaining up to 57% of the variance in taxonomic richness. For macroinvertebrates, river geomorphology was an important driver of structural changes, particularly affecting Plecoptera richness. In addition, PhAC and pesticide toxic units were also identified as stressors for macroinvertebrate communities. MTBA provided a detailed picture of the effects of the stressors on the communities and confirmed the importance of hydrological variables in shaping the functional attributes of the communities.

Multi-class analysis of 46 antimicrobial drug residues in pond water using UHPLC-Orbitrap-HRMS and application to freshwater ponds in Flanders, Belgium

Increasing anthropogenic pressure and agricultural pollution raises concerns regarding antimicrobial resistance and biodiversity loss in aquatic environments. In order to protect and restore water resources and biodiversity, antimicrobial drug residues should be monitored in all aquatic environments including pond water. Consequently, the objective of this research was to develop and validate a novel multi-residue method for the simultaneous quantification of 46 targeted human and veterinary antimicrobial drugs in pond water. A suitable extraction method based on solid-phase extraction (SPE) was developed, assisted by a fractional factorial design. A broad polarity range of compounds was covered (log P from -4.05 to 4.38), including major representatives of the following classes: sulfonamides, tetracyclines, quinolones, macrolides, lincosamides, nitrofurans, penicillins, cephalosporins, diaminopyrimidines, pleuromutilins and phenicols. All analytes were separated using ultra-high performance liquid chromatography (UHPLC) and detected in full-scan by Orbitrap high resolution mass spectrometry (Orbitrap-HRMS). Good linearity was obtained for all compounds with R² ≥ 0.993 and goodness-of-fit coefficient (g) ≤ 11.56%. Method detection limits ranged from 10 to 50 ng L^-1 and method quantification limits were 50 ng L^-1 for all compounds. Acceptable values were obtained for within-day and between-day apparent recoveries (i.e. between 50 and 120%), precision (< 30% and < 45%) and measurement uncertainty (< 50%). Targeted analysis of 18 freshwater ponds throughout Flanders was performed to demonstrate the applicability of the newly developed UHPLC-HRMS method. Overall, 20 antimicrobial drugs were detected with highest concentrations observed for tetracyclines and their transformation products ranging between 51 and 248 ng L^-1. Finally, suspect screening was performed suggesting the presence of 14 additional pharmaceuticals including 3 antimicrobial degradation products (e.g. apo-oxytetracycline, amoxicillin penicilloic acid and penilloic acid) and 11 pesticides.

Effects of chlorpyrifos on cell death and cellular phenotypic specification of human neural stem cells

Chlorpyrifos (CPF) is an organophosphate pesticide widely used in agriculture, whose traditional and well-known mechanism of action is the inhibition of the enzyme Acetylcholinesterase (AChE). Subacute exposures to CPF have been associated with alterations different from the inhibition of AChE. Because of the vulnerability of the developing nervous system, prenatal and early postnatal exposures are of special concern. Human neural stem cells (hNSC) provide the opportunity to study early stages of neural development and may be a valuable tool for developmental neurotoxicology (DNT). In the current work, the cell line hNS1 was used as a model system with the aim of validating this cell line as a reliable testing method. To evaluate the effects of CPF on early developmental stages, hNS1 cells were exposed to different concentrations of the pesticide and cell death, proliferation and cell fate specification were analyzed under differentiation conditions. Since hNS1 cells responded to CPF in a similar way to other human cell lines, we consider it may be a valid model for DNT chemical assessment. CPF induced apoptotic cell death only at the highest doses tested, suggesting that it is not toxic for the specific developmental stage here addressed under short term exposure. In addition, the higher doses of CPF promoted the generation of astroglial cells, without affecting neurogenesis.

Effects of the insecticide esfenvalerate on zooplankton in an indoor synthetic model ecosystem

Effects of esfenvalerate on zooplankton and their recovery potential were studied using an indoor synthetic model ecosystem. Esfenvalerate was applied to the system by direct spiking to overlying water or the introduction of treated slurry soil to imitate drift and run-off exposure. Four zooplankton taxa, Daphnia magna (Cladocera), Heterocypris incongruens (Ostracoda), Cyclops sp. (Copepoda), and Brachionus calyciflorus (Rotifera), were exposed to esfenvalerate with Raphidocelis subcapitata (green alga). In a drift scenario, lower doses (0.02-0.5 µg/L) showed slight or negligible effects, but the results for the highest dose (5 µg/L) indicated direct effects, as remarkable population decreases were observed for three taxa (except rotifera). However, for the latter dose, results of weekly or single (Day-15) zooplankton re-introductions after dosing demonstrated resilient recovery. In a run-off scenario, a nominal dose of 20 µg/L, in which the measured water concentrations remained at 3-6%, had effects similar to those of the high drift exposure scenario for cladocera and ostracoda.

Sensitivity of tropical cladocerans to chlorpyrifos and other insecticides as compared to their temperate counterparts

The use of temperate toxicity data in tropical risk assessments has often been disputed. Previous sensitivity comparisons between temperate and tropical species, however, have not shown a consistent sensitivity difference between climatically-distinct species. Such comparisons were often limited by a small tropical toxicity dataset. In addition, differences in the taxonomic compositions of the temperate and tropical species assemblages used to construct species sensitivity distributions curves also hampered direct comparisons (e.g. type and ration of crustaceans and insects). The aim of the present study was to compare the sensitivity of temperate and tropical cladocerans to insecticides. Acute laboratory toxicity tests were conducted with five Neotropical cladocerans exposed to a concentration series of the insecticide chlorpyrifos. Subsequently, their EC₅₀ values were compared with those reported in the literature for non-tropical cladocerans. An additional literature toxicity data search for insecticides other than chlorpyrifos was also conducted for both temperate and tropical cladocerans to enable a comparison for a wider range of insecticides and taxa. The order of sensitivity of the native cladocerans to chlorpyrifos was Ceriodaphnia silvestrii (0.039 μg L^-1) > Diaphanosoma birgei (0.211 μg L^-1) = Daphnia laevis (0.216 μg L^-1) > Moina micrura (0.463 μg L^-1) = Macrothrix flabelligera (0.619 μg L^-1). A regulatory acceptable concentration based on temperate cladoceran toxicity data of both chlorpyrifos and other insecticides also appeared to be sufficiently protective for tropical cladoceran species. Implications for the use of temperate toxicity data in tropical risk assessments and indications for tropical cladoceran test species selection are discussed.

Effects of imidacloprid and a neonicotinoid mixture on aquatic invertebrate communities under Mediterranean conditions

Neonicotinoid insecticides are considered contaminants of concern due to their high toxicity potential to non-target terrestrial and aquatic organisms. In this study we evaluated the sensitivity of aquatic invertebrates to a single application of imidacloprid and an equimolar mixture of five neonicotinoids (imidacloprid, acetamiprid, thiacloprid, thiamethoxam, clothianidin) using mesocosms under Mediterranean conditions. Cyclopoida, Cloeon dipterum and Chironomini showed the highest sensitivity to neonicotinoids, with calculated NOECs below 0.2 μg/L. The sensitivity of these taxa was found to be higher than that reported in previous studies performed under less warm conditions, proving the high influence of temperature on neonicotinoid toxicity. The short-term responses of the zooplankton and the macroinvertebrate communities to similar imidacloprid and neonicotinoid mixture concentrations were very similar, suggesting that the concentration addition model can be used as a plausible hyphotesis to assess neonicotinoid mixture effects in aquatic ecosystems. Long-term mixture toxicity assessments, however, should consider the fate of the evaluated substances in the environment of concern. As part of this study, we also demonstrated that Species Sensitivity Distributions constructed with chronic laboratory toxicity data and calculated (multi-substance) Potentially Affected Fractions provide an accurate estimation to asssess the ecotoxicologial risks of imidacloprid and neonicotinoid mixtures to aquatic invertebrate species assemblages.

Mechanochemical enhancement of the natural attenuation capacity of soils using two organophosphate biocides as models

Mechanochemical treatment by high energy ball milling is a promising technology to safely destroy organic pollutants in contaminated soil and allow its possible beneficial reuse. The present study investigates the mechanochemical activation of four major soil components, which induces generation of electrons on particle surfaces. Such phenomenon is demonstrated to occur on oxides by formation of trapped electrons in oxygen vacancies (following a zeroth-order kinetics), as well as on quartz and clayey materials to form fresh electron-rich surfaces by homolytic bond rapture (according to a first-order kinetics). Two toxic organophosphate biocides (i.e. chlorpyrifos and glyphosate) are used as model pollutants. Results show that the aromatic structure of chlorpyrifos determines a faster degradation rate, compared to the aliphatic one of glyphosate, because of the higher stability of generated radical intermediates. Moreover, the aromatic moiety facilitates adsorption on clays, thus temporarily sequestering the molecule and delaying its degradation. The many heteroatoms in both organophosphates have analogous fate: mineralization to inorganic form.

Sensitivities of three tropical indigenous freshwater invertebrates to single and mixture exposures of diuron and carbofuran and their commercial formulations

As compared to their temperate counterparts, few toxicity tests have been conducted so far into the evaluation of the sensitivity of indigenous tropical species to pesticides. Especially mixture toxicity assessments appear to be scarce. To contribute to increase our knowledge in this arena, we evaluated the acute toxicity of diuron and carbofuran and their mixtures to the neotropical oligochaetes Allonais inaequalis and Dero furcatus, and the ostracod Strandesia trispinosa. Tests were performed with both the pure active ingredients, as well as their formulated products. The toxicity of the latter to the three test organisms was generally greater than that of the pure active ingredients, although absolute differences were rather small. The sensitivity of the indigenous species was slightly greater than temperate test species from the same taxonomic groups. The concentration addition conceptual model best described the results of the mixture toxicity data. Derived deviations of this model appeared to be dependent on the test organism and as to whether the pesticides were applied as active ingredients or their commercial products. Reported field concentrations of the two pesticides indicate risks to freshwater biota, especially if they are both present. The test species used in the present study are concluded to be suitable candidates as surrogate test organisms in local pesticide risk evaluations.

Toxicity prediction and assessment of an environmentally realistic pesticide mixture to Daphnia magna and Raphidocelis subcapitata

In a regulatory perspective addressing the cumulative effect of co-occurring chemicals is the first and most important step in providing a more realistic hazard assessment of chemical cocktails to both man and environment. This study was conducted to show if joint effects on the immobilisation of the crustacean Daphnia magna and on the growth inhibition of algae Raphidocelis subcapitata follow additivity (concentration addition (CA) or independent action (IA) predictions) or if there is an interaction between chemicals in the organisms upon exposure to an environmentally realistic mixture of chlorpyrifos and terbuthylazine, with expected different molecular sites of action. A pattern of antagonism at lower doses and synergism at higher doses was found for acute immobility data, while no deviation from the additive conceptual models was observed in the algae inhibition test. Results in relation to the relevant set of regulatory acceptable concentrations (RACs) and environmental quality standards (EQSs) derived for individual chlorpyrifos and terbuthylazine were evaluated.

Ecotoxicological and biochemical mixture effects of an herbicide and a metal at the marine primary producer diatom Thalassiosira weissflogii and the primary consumer copepod Acartia tonsa

Mixture effects of chemicals and their potential synergistic interactions are of great concern to the public and regulatory authorities worldwide. Intensive agricultural activities are leading to discharges of chemical mixtures to nearby estuarine and marine waters with possible adverse effects on the aquatic communities and for the trophic food web interlinking these communities. Further information about the impacts of these stressors on aquatic organisms is needed. This study addresses ecotoxicological and biochemical effects of single and mixtures of the metal copper and the herbicide Primextra® Gold TZ on the marine diatom Thalassiosira weissflogii and on the estuarine calanoid copepod Acartia tonsa by determining growth rate and survival, respectively, and changes on fatty acid(FA) profiles in both species. Mixture effects on diatom species revealed that copper and Primextra® acted most likely additively with respect to the concentration addition (CA) and independent action (IA) models with model deviation ratios (MDR), 0.752 and 1.063, respectively. For the copepod species, copper and Primextra® were most likely non-interactive with respect to the CA model (MDR = 1.521) but acted most likely synergistically with respect to the IA model (MDR = 2.026). A significant decline in the absolute FA concentration was observed for copepod species after mixture exposure including a considerable decrease of essential FAs that cannot be synthesized de novo by these grazers. We concluded that the mixture effects are more hazardous for primary consumer than for primary producer species in terms of both abundance and biomass quality, suggesting a potential for harmful effects for higher trophic levels and thus a decrease in energy flow through the ecosystem.

Toxicity assessment of chlorpyrifos-degrading fungal bio-composites and their environmental risks

Bioremediation techniques coupling with functional microorganisms have emerged as the most promising approaches for in-situ elimination of pesticide residue. However, the environmental safety of bio-products based on microorganisms or engineered enzymes was rarely known. Here, we described the toxicity assessment of two previously fabricated fungal bio-composites which were used for the biodegradation of chlorpyrifos, to clarify their potential risks on the environment and non-target organisms. Firstly, the acute and chronic toxicity of prepared bio-composites were evaluated using mice and rabbits, indicating neither acute nor chronic effect was induced via short-term or continuous exposure. Then, the acute mortality on zebrafish was investigated, which implied the application of fungal bio-composites had no lethal risk on aquatic organisms. Meanwhile, the assessment on soil organic matters suggested that no threat was posed to soil quality. Finally, by monitoring, the germination of cabbage was not affected by the exposure to two bio-products. Therefore, the application of fungal bio-composites for chlorpyrifos elimination cannot induce toxic risk to the environment and non-target organisms, which insured the safety of these engineered bio-products for realistic management of pesticide residue, and provided new insights for further development of bioremediation techniques based on functional microorganisms.