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

Pollution and partitioning of neonicotinoid insecticides in free-grazing ducks and their eggs: Implications for human health

Neonicotinoid insecticides are used extensively in many pest control schemes across the globe; but little is known about their impacts on free-grazing domestic birds and the quality of meat or eggs produced from such birds. This study assessed the pollution and partitioning of neonicotinoids in serum and eggs of free-grazing ducks from 5 provinces of Thailand and elucidated the associated human health implications. Biological samples (duck serum, egg albumins, and egg yolks) and environmental samples (soil, water, feed) were collected from 9 duck farms in Thailand and subjected to LC/MS/MS analysis. Out of 6 neonicotinoid compounds targeted, five were detected in duck serum. Imidacloprid had the greatest median concentration of 1.4 ng/mL and the highest detection frequency (df) of 85.8 % in the ducks' serum, followed by acetamiprid (median concentration = 0.4 ng/mL; df = 2.8 %), clothianidin (median concentration = 0.2 ng/mL; df = 9.4 %) or thiamethoxam (median concentration = 0.2 ng/mL; df = 7.5 %) and dinotefuran (only one sample was contaminated with 6.3 ng/mL of dinotefuran). The neonicotinoids were similarly detected in soil, water, and feed samples obtained from the duck farms, suggesting that the ducks were exposed to the insecticides from the nearby agricultural fields. The neonicotinoid compounds selectively accumulated in the albumin of duck eggs compared to yolk. The median concentration ratios of albumin to yolk obtained for imidacloprid, dinotefuran, thiamethoxam, clothianidin, and acetamiprid were 694, 463, 458, 382, and 263, respectively. However, upon human health risk analysis, levels of neonicotinoids detected in duck eggs were not found to present any appreciable risks to duck egg consumers.

Heatwaves, elevated temperature, and insecticide-induced effects at different trophic levels of a freshwater ecosystem

Heatwaves and increasing average temperatures associated with climate change pose severe stress on nature, including freshwater ecosystems. As these thermal stressors do not act in isolation over temporal or spatial scales, interactions with other stressors, like pesticides, may lead to unpredictable combined effects. Empirical studies investigating multiple stressor effects across different trophic levels are scarce and often lack environmental realism. Here, we performed a multiple stressor experiment using outdoor freshwater mesocosms and realistic pond assemblages including microbes, phytoplankton, macrophytes, and invertebrates. The effects of the pesticide imidacloprid at three dosings (0, 1, 10 μg/L) were examined in combination with three temperature scenarios comprising natural ambient, elevated temperatures (+4 °C), and repeated heatwaves (+8 °C). Our results reveal fast imidacloprid dissipation for all temperature treatments with the lowest average dissipation half-lives (DT50: 6 days) in the heatwave treatment. Imidacloprid induced a series of significant effects on the macroinvertebrate community at 10 μg/L across the temperature treatments. Significant declines in abundance appeared throughout the experiment for the most sensitive taxa Cloeon dipterum, Caenis sp., Chironomini, and Dero sp., whereas significant imidacloprid effects on Tanytarsini, Chironomus, and Gammarus pulex occurred only after each dosing. Only Zygoptera showed an imidacloprid-related increase in abundance, whereas significantly adverse time-cumulative effects on abundance occurred for Asellus aquaticus. The zooplankton community showed imidacloprid tolerance (10 μg/L) with increasing abundances of Chydorus sphaericus, Acroperus harpae, and Ascomorpha. Heatwaves induced significantly meliorating effects on Dero sp. and adverse effects on Caenis sp., Tanytarsini, G. pulex, and A. harpae. The macroinvertebrate community demonstrated faster post-exposure recovery dynamics in the highest imidacloprid treatment when previously exposed to heatwaves and elevated temperatures compared to ambient conditions. Overall, heatwaves amplified the effects of imidacloprid on the invertebrate community, manifesting in manifold effects that adversely impacted multiple trophic levels.

Neonicotinoid pesticides in African agriculture: What do we know and what should be the focus for future research?

This review provides a comprehensive overview of the direct and indirect effects of neonicotinoid pesticides (NEO-P) within African agricultural ecosystems and identifies research gaps, particularly in the monitoring and regulation of pesticide use. We observed a decline in the numbers of NEO-P studies conducted in Africa since 2019 with 40.7% of the countries reporting at least one study to date. Imidacloprid (33.5%), acetamiprid (23.3%), and thiamethoxam (25.0%) are the most reported NEO-P across the continent with concentrations range from 9.0 × 10-5 to 7.2 × 107 mg kg-1, 1.7 × 10-5 to 2.1 × 103 mg kg-1, and 1.0 × 10-5 to 4.7 × 104 mg kg-1, respectively. NEO-P have been reported in honey, water, vegetables, fruits, and staple foods in most countries and in 92-100% of human urine samples collected in Ghana and Cameroon. This widespread presence indicates a potential food safety and public health concern, warranting further study. Studies on NEO-P interactions with bees have emanated mainly from North Africa (35.3% published studies) while Central/Middle, and Southern Africa accounted for 11.8% each of these studies, all of which were conducted in Cameroon and South Africa, respectively. It is important to have contextual evidence to understand neonicotinoids-pollinator interactions across specific African regions and countries; however, literature regarding the extent of NEO-P toxicities/effects on pollinators is required in 44 African countries. The environmental persistence of NEO-P and their broad-spectrum impact necessitate a re-evaluation of current regulatory practices and adoption of more sustainable pest management strategies across the continent. Furthermore, future studies should focus on investigating the long-term exposure to NEO-P, advanced computational methods in ecological risk assessments and eco-friendly alternatives to NEO-P.

Impacts of neonicotinoids on biodiversity: a critical review

Neonicotinoids are the most widely used class of insecticides in the world, but they have raised numerous concerns regarding their effects on biodiversity. Thus, the objective of this work was to do a critical review of the contamination of the environment (soil, water, air, biota) by neonicotinoids (acetamiprid, clothianidin, imidacloprid, thiacloprid, thiamethoxam) and of their impacts on terrestrial and aquatic biodiversity. Neonicotinoids are very frequently detected in soils and in freshwater, and they are also found in the air. They have only been recently monitored in coastal and marine environments, but some studies already reported the presence of imidacloprid and thiamethoxam in transitional or semi-enclosed ecosystems (lagoons, bays, and estuaries). The contamination of the environment leads to the exposure and to the contamination of non-target organisms and to negative effects on biodiversity. Direct impacts of neonicotinoids are mainly reported on terrestrial invertebrates (e.g., pollinators, natural enemies, earthworms) and vertebrates (e.g., birds) and on aquatic invertebrates (e.g., arthropods). Impacts on aquatic vertebrate populations and communities, as well as on microorganisms, are less documented. In addition to their toxicity to directly exposed organisms, neonicotinoid induce indirect effects via trophic cascades as demonstrated in several species (terrestrial and aquatic invertebrates). However, more data are needed to reach firmer conclusions and to get a clearer picture of such indirect effects. Finally, we identified specific knowledge gaps that need to be filled to better understand the effects of neonicotinoids on terrestrial, freshwater, and marine organisms, as well as on ecosystem services associated with these biotas.

Evaluating the impact of neonicotinoids on aquatic non-target species: A comprehensive review

Neonicotinoid insecticides (NNIs) are the fastest-growing class in agricultural protection. They target nicotinic acetylcholine receptors (nAChR) in pests, stimulating the nervous system at low doses and causing paralysis and death at higher concentrations. NNIs are used in crop protection, seed treatment, forestry, agriculture, and flea control in domestic cattle. Effective at lower concentrations and offering long-term control, NNIs are favoured for their systemic activity. However, due to their water solubility, mobility, and moderate persistence, NNIs easily contaminate adjacent aquatic environments via runoff, leaching, or spray drift. While less toxic to vertebrates, their widespread use poses threats to aquatic and terrestrial organisms, causing neurotoxicity, nephrotoxicity, cytotoxicity, genotoxicity, immunotoxicity, hepatotoxicity, endocrine disruption, and reproductive malformations. This review synthesizes research to address knowledge gaps on the environmental impact of NNIs and proposes policies to mitigate their harmful effects on aquatic non-target species.

Field-realistic doses of the neonicotinoid acetamiprid impact natural soil arthropod community diversity and structure

The neonicotinoid acetamiprid is used as a foliar insecticide spray, which results in direct exposure of a wide variety of soil organisms. Laboratory testing indicated that acetamiprid is toxic to the Collembola (springtails) species Folsomia candida, while Acari (mites) seem relatively insensitive to neonicotinoids. Since such opposing effects on different soil arthropods might imbalance natural arthropod communities, this study determined: (i) if field-realistic doses of acetamiprid affect the abundance and diversity in soil arthropod communities, and (ii) whether these potential effects are short-term or persist after degradation of acetamiprid. Intact soil cores collected from an untreated grassland field were placed in the mesocosm set up 'CLIMECS', and the naturally sourced communities were exposed to a control and increasing field-realistic doses of acetamiprid (i.e. 0, 0.05, 0.2, 0.8 mg a.s./kg dry soil). Before and 7 and 54 days after spraying the insecticide, the abundance of mites and springtails and springtail diversity were assessed. Springtail and mite abundances were similar at the start of the experiment, but springtail abundance was significantly lowered while mite abundance increased shortly after exposure to increasing doses of acetamiprid. At the highest dose, springtail numbers decreased by 53% on average while the number of mites increased by 26%. This effect was no longer visible after 54 days, suggesting recovery of the community as a whole reflected by observed changes in community dissimilarity: shortly after application springtail communities clearly diverged from the control in terms of species composition, while communities converged again in the long-term. With our results, we are the first to show that field-realistic applications of N-nitroguanidine neonicotinoids can significantly impact natural soil fauna communities, which might have implications for soil ecosystem functioning.

Occurrence of emerging contaminants in three river basins impacted by wastewater treatment plant effluents: Spatio-seasonal patterns and environmental risk assessment

The concern on the fate and distribution of contaminants of emerging concern (CECs) is a burning topic due to their widespread occurrence and potential harmful effects. Particularly, antibiotics have received great attention due to their implications in antimicrobial resistance occurrence. The impact of wastewater treatment plants (WWTP) is remarkable, being one of the main pathways for the introduction of CECs into aquatic systems. The combination of novel analytical methodologies and risk assessment strategies is a promising tool to find out environmentally relevant compounds posing major concerns in freshwater ecosystems impacted by those wastewater effluents. Within this context, a multi-target approach was applied in three Spanish river basins affected by different WWTP treated effluents for spatio-temporal monitoring of their chemical status. Solid phase extraction followed by ultra-high-performance liquid chromatography were used for the quantification of a large panel of compounds (n = 270), including pharmaceuticals and other consumer products, pesticides and industrial chemicals. To this end, water samples were collected in four sampling campaigns at three locations in each basin: (i) upstream from the WWTPs; (ii) WWTP effluent discharge points (effluent outfall); and (iii) downstream from the WWTPs (500 m downriver from the effluent outfall). Likewise, 24-h composite effluent samples from each of the WWTPs were provided in all sampling periods. First the occurrence and distribution of these compounds were assessed. Diverse seasonal trends were observed depending on the group of emerging compounds, though COVID-19 outbreak affected variations of certain pharmaceuticals. Detection frequencies and concentrations in effluents generally exceeded those in river samples and concentrations measured upstream WWTPs were generally low or non-quantifiable. Finally, risks associated with maximum contamination levels were evaluated using two different approaches to account for antibiotic resistance selection as well. From all studied compounds, 89 evidenced environmental risk on at least one occasion in this study.

Effects of the insecticide imidacloprid on aquatic invertebrate communities of the Ecuadorian Amazon

Imidacloprid is a neonicotinoid insecticide that has received particular attention due to its widespread use and potential adverse effects for aquatic and terrestrial ecosystems. Its toxicity to aquatic organisms has been evaluated in central and southern Europe as well as in (sub-)tropical regions of Africa and Asia, showing high toxic potential for some aquatic insects and zooplankton taxa. However, its toxicity to aquatic organisms representative of tropical regions of Latin America has never been evaluated. To fill this knowledge gap, we carried out a mesocosm experiment to assess the short- and long-term effects of imidacloprid on freshwater invertebrate communities representative of the Ecuadorian Amazon. A mesocosm experiment was conducted with five weekly applications of imidacloprid at four nominal concentrations (0.01 μg/L, 0.1 μg/L, 1 μg/L and 10 μg/L). Toxic effects were evaluated on zooplankton and macroinvertebrate populations and communities, as well as on water quality parameters for 70 days. Given the climatic conditions prevailing in the study area, characterized by a high solar radiation and abundant rainfall that resulted in mesocosm overflow, there was a rapid dissipation of the test compound from the water column (half-life: 4 days). The macroinvertebrate taxa Callibaetis pictus (Ephemeroptera), Chironomus sp. (Diptera), and the zooplankton taxon Macrocyclops sp., showed population declines caused by the imidacloprid treatment, with a 21-d Time Weighted Average No Observed Effect Concentrations (21-d TWA NOEC) of 0.46 μg/L, except for C. pictus which presented a 21-d TWA NOEC of 0.05 μg/L. In general terms, the sensitivity of these taxa to imidacloprid was greater than that reported for surrogate taxa in temperate zones and similar to that reported in other (sub-)tropical regions. These results confirm the high sensitivity of tropical aquatic invertebrates to this compound and suggest the need to establish regulations for the control of imidacloprid contamination in Amazonian freshwater ecosystems.

Physiological and gene expression responses of Protohermes xanthodes (Megaloptera: Corydalidae) larvae to imidacloprid

Megaloptera larvae are important bioindicator species and potential resource insects. To further cultivate their economic role, their living environment must be examined in more detail. In this study, we analyzed the physiological and biochemical effects of a sublethal dose of imidacloprid, a widely used neonicotinoid insecticide, on the larvae of Protohermes xanthodes. After treatment with imidacloprid, P. xanthodes larvae exhibited clear symptoms of poisoning, including the head curling up toward the ventral surface. Additionally, the activity of acetylcholinesterase was significantly inhibited following exposure. The activities of glutathione S-transferases initially continuously increased but showed a slight decrease after 8 days. Catalase activity initially increased and then decreased following imidacloprid treatment; superoxide dismutase activity fluctuated over time, and peroxidase activity continuously increased. The expression levels of HSP70s genes were evaluated using qRT-PCR. These results indicate that P. xanthodes larvae exhibit a toxic response to imidacloprid exposure, manifested as oxidative stress, as observed through behavioral and physiological indicators.

Fingerprinting of emerging contaminants in L'Albufera natural park (Valencia, Spain): Implications for wetland ecosystem health

Wetlands are crucial ecosystems that are increasingly threatened by anthropogenic activities. L'Albufera Natural Park, the second-largest coastal wetland in Spain, faces significant pressures from surrounding agricultural lands, industrial activities, human settlements, and associated infrastructures, including treated wastewater inputs. This study aimed at (i) establishing pathways of emerging pollutants entering the natural wetland using both target and non-target screening (NTS) for management purposes, (ii) distinguishing specific contamination hotspots through Geographic Information System (GIS) and (iii) performing basic ecological risk assessment to evaluate ecosystem health. Two sampling campaigns were conducted in the spring and summer of 2019, coinciding with the start and end of the rice cultivation season, the region's primary agricultural activity. Each campaign involved the collection of 51 samples. High-resolution mass spectrometry (HRMS) was employed, using a simultaneous NTS approach with optimized gradients for pesticides and moderately polar compounds, along with complementary NTS methods for polar compounds, to identify additional contaminants of emerging concern (CECs). Quantitative analysis revealed that fungicides comprised a substantial portion of detected CECs, constituting approximately 50% of the total quantified pesticides. Tebuconazole emerged as the predominant fungicide, with the highest mean concentration (>16.9 μg L-1), followed by azoxystrobin and tricyclazole. NTS tentatively identified 16 pesticides, 43 pharmaceuticals and personal care products (PPCPs), 24 industrial compounds, and 12 other CECs with high confidence levels. Spatial distribution analysis demonstrated significant contamination predominantly in the southwestern region of the park, gradually diminishing towards the north-eastern outlet. The composition of contaminants varied between water and sediment samples, with pharmaceuticals predominating in water and industrial compounds in sediments. Risk assessment, evaluated through risk quotient calculations based on parent compound concentrations, revealed a decreasing trend towards the outlet, suggesting wetland degradation capacity. However, significant risk levels persist throughout much of the Natural Park, highlighting the urgent need for mitigation measures to safeguard the integrity of this vital ecosystem.

Pesticides in the Great Barrier Reef catchment area: Plausible risks to fish populations

Waterways that drain the Great Barrier Reef catchment area (GBRCA) transport pollutants to marine habitats, provide a critical corridor between freshwater and marine habitats for migratory fish species, and are of high socioecological value. Some of these waterways contain concentrations of pesticide active ingredients (PAIs) that exceed Australian ecotoxicity threshold values (ETVs) for ecosystem protection. In this article, we use a "pathway to harm" model with five key criteria to assess whether the available information supports the hypothesis that PAIs are or could have harmful effects on fish and arthropod populations. Strong evidence of the first three criteria and circumstantial weaker evidence of the fourth and fifth criteria are presented. Specifically, we demonstrate that exceedances of Australian and New Zealand ETVs for ecosystem protection are widespread in the GBRCA, that the PAI contaminated water occurs (spatially and temporally) in important habitats for fisheries, and that there are clear direct and indirect mechanisms by which PAIs could cause harmful effects. The evidence of individuals and populations of fish and arthropods being adversely affected species is more circumstantial but consistent with PAIs causing harmful effects in the freshwater ecosystems of Great Barrier Reef waterways. We advocate strengthening the links between PAI concentrations and fish health because of the cultural values placed on the freshwater ecosystems by relevant stakeholders and Traditional Owners, with the aim that stronger links between elevated PAI concentrations and changes in recreationally and culturally important fish species will inspire improvements in water quality. Integr Environ Assess Manag 2024;20:1256-1279. © 2023 Commonwealth of Australia and The Commonwealth Scientific and Industrial Research Organisation. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Combined stress of an insecticide and heatwaves or elevated temperature induce community and food web effects in a Mediterranean freshwater ecosystem

Ongoing global climate change will shift nature towards Anthropocene's unprecedented conditions by increasing average temperatures and the frequency and severity of extreme events, such as heatwaves. While such climatic changes pose an increased threat for freshwater ecosystems, other stressors like pesticides may interact with warming and lead to unpredictable effects. Studies that examine the underpinned mechanisms of multiple stressor effects are scarce and often lack environmental realism. Here, we conducted a multiple stressors experiment using outdoor freshwater mesocosms with natural assemblages of macroinvertebrates, zooplankton, phytoplankton, macrophytes, and microbes. The effects of the neonicotinoid insecticide imidacloprid (1 µg/L) were investigated in combination with three temperature scenarios representing ambient, elevated temperatures (+4 °C), and heatwaves (+0 to 8 °C), the latter two having similar energy input. We found similar imidacloprid dissipation patterns for all temperature treatments with lowest average dissipation half-lives under both warming scenarios (DT50: 3 days) and highest under ambient temperatures (DT50: 4 days) throughout the experiment. Amongst all communities, only the zooplankton community was significantly affected by the combined treatments. This community demonstrated low chemical sensitivity with lagged and significant negative imidacloprid effects only for cyclopoids. Heatwaves caused early and long-lasting significant effects on the zooplankton community as compared to elevated temperatures, with Polyarthra, Daphnia longispina, Lecanidae, and cyclopoids being the most negatively affected taxa, whereas Ceriodaphnia and nauplii showed positive responses to temperature. Community recovery from imidacloprid stress was slower under heatwaves, suggesting temperature-enhanced toxicity. Finally, microbial and macrofauna litter degradation were significantly enhanced by temperature, whereas the latter was also negatively affected by imidacloprid. A structural equation model depicted cascading food web effects of both stressors with stronger relationships and significant negative stressor effects at higher than at lower trophic levels. Our study highlights the threat of a series of heatwaves compared to elevated temperatures for imidacloprid-stressed freshwaters.

Prediction of Potential Risk for Flupyradifurone and Its Transformation Products to Hydrobionts

Flupyradifurone (FPF) is considered the latest generation of neonicotinoid insecticides. Here, we investigated the toxicity and ecological risk of FPF and its aerobic transformation products (TPs) to aquatic species using the method of prediction. We found that FPF exhibited moderate or high toxicity to some aquatic species. The 5% hazardous concentration of FPF was 3.84 μg/L for aquatic organisms. We obtained 91 aerobic TPs for FPF, and almost half of FPF TPs exhibited toxicity to fish or Daphnia. Eleven of the TPs of FPF exhibited a high or moderate risk to aquatic ecosystems. All FPF TPs with high and moderate risks contained a 6-chloropyridine ring structure, indicating that the derivant of a pyridine ring exhibits potential risks to aquatic ecosystems. Our results provide insight into the potential risk of FPF to aquatic ecosystems and could be used to help set criteria to control pollution caused by FPF.

Organophosphate pesticide residue impact on water quality and changes in macroinvertebrate community in an Afrotropical stream flowing through farmlands

River Chanchaga has experienced significant agricultural practices around its catchment, which involved the indiscriminate use of pesticides. However, residents of the study area are not well aware of the negative impact of pesticides on water quality and macroinvertebrates. In this study, the first report on the influence of organophosphate pesticide contamination on the abundance of the macroinvertebrate community was provided. Sampling for the determination of organophosphate pesticide residues was carried out during the peak of the two seasons, while macroinvertebrates and physicochemical variables were observed for 6 months. We examined 11 organophosphate pesticide residues using gas chromatography coupled with mass spectrometry, 12 water quality variables, and 625 macroinvertebrate individuals. The concentration of recorded organophosphate pesticide residues ranged from 0.01 to 0.52 μg/L. From the Canonical Correspondence Analysis plot, malathion, chlorine, and paraffin show a positive correlation with Unima sp., Hydrocanthus sp., Chironomus sp., and Potadoma sp. At station 3, depth shows a positive correlation with Biomphalaria sp. and Zyxomma sp., indicating poor water quality as most of these macroinvertebrates are indicators of water pollution. Diuron and carbofuran show a negative correlation with Lestes sp. and Pseudocloeon sp., and these are pollution-sensitive macroinvertebrates. The total mean concentration of organophosphate pesticide residues was above international drinking water standards set by the World Health Organization except for paraffin, chlorpyrifos, and diuron. In conclusion, the observations recorded from this research are useful in managing pesticide applications around the river catchment.

A fluorescent magnetic nanosensor for imidacloprid based on the incorporation of polymer dots and Fe3 O4 nanoparticles into the covalent organic framework

A magnetic nanoprobe was designed for imidacloprid by encapsulating nonconjugated polymer dots (NCPDs) and Fe3 O4 nanoparticles in the covalent organic framework (COF). The fluorescence intensity of the COF-based nanocomposite is markedly suppressed by imidacloprid. As the absorption spectrum of imidacloprid was close to the band-gap of the NCPDs, and due to the presence of a nitro group (as an electron acceptor), the electrons can be easily transferred from the conduction band of NCPDs to the LUMO of imidacloprid, so fluorescence quenching was more likely to have been caused by the electron transfer process. The COF-based nanosensor was used for the determination of imidacloprid in the linear range 1.3-130 nM with a detection limit of 1.2 nM. The high sensitivity of the nanoprobe for imidacloprid is due to the combination of COF benefits (accumulation of the imidacloprid into the COF cavities) and the high adsorption ability of the Fe3 O4 nanoparticles, which leads to further enrichment of imidacloprid. The magnetic nature of the nanocomposite enables the preconcentration and easy separation of the analyte, and so reduces matrix interference and lowers the detection limits. The practicality of this nanoprobe was confirmed by quantification of imidacloprid in the wastewater and fruit juice samples.

Neonicotinoid mixture alters trophic interactions in a freshwater aquatic invertebrate community

Neonicotinoids are increasingly and widely used systemic insecticides in agriculture, residential applications, and elsewhere. These pesticides can sometimes occur in small water bodies in exceptionally high concentrations, leading to downstream non-target aquatic toxicity. Although insects appear to be the most sensitive group to neonicotinoids, other aquatic invertebrates may also be affected. Most existing studies focus on single-insecticide exposure and very little is known concerning the impact of neonicotinoid mixtures on aquatic invertebrates at the community level. To address this data gap and explore community-level effects, we performed an outdoor mesocosm experiment that tested the effect of a mixture of three common neonicotinoids (formulated imidacloprid, clothianidin and thiamethoxam) on an aquatic invertebrate community. Exposure to the neonicotinoid mixture induced a top-down cascading effect on insect predators and zooplankton, ultimately increasing phytoplankton. Our results highlight complexities of mixture toxicity occurring in the environment that may be underestimated with traditional mono-specific toxicological approaches.

Effects of intensive agriculture and urbanization on water quality and pesticide risks in freshwater ecosystems of the Ecuadorian Amazon

The Ecuadorian Amazon has experienced a significant land use change due to the demographic increase and the expansion of the agricultural frontier. Such changes in land use have been associated to water pollution problems, including the emission of untreated urban wastewater and pesticides. Here we provide the first report on the influence of urbanization and intensive agriculture expansion on water quality parameters, pesticide contamination and the ecological status of Amazonian freshwater ecosystems of Ecuador. We monitored 19 water quality parameters, 27 pesticides, and the macroinvertebrate community in 40 sampling locations of the Napo River basin (northern Ecuador), including a nature conservation reserve and sites in areas influenced by African palm oil production, corn production and urbanization. The ecological risks of pesticides were assessed using a probabilistic approach based on species sensitivity distributions. The results of our study show that urban areas and areas dominated by African palm oil production have a significant influence on water quality parameters, affecting macroinvertebrate communities and biomonitoring indices. Pesticide residues were detected in all sampling sites, with carbendazim, azoxystrobin, diazinon, propiconazole and imidacloprid showing the largest prevalence (>80% of the samples). We found a significant effect of land use on water pesticide contamination, with residues of organophosphate insecticides correlating with African palm oil production and some fungicides with urban areas. The pesticide risk assessment indicated organophosphate insecticides (ethion, chlorpyrifos, azinphos-methyl, profenofos and prothiophos) and imidacloprid as the compounds posing the largest ecotoxicological hazard, with pesticide mixtures potentially affecting up to 26-29% of aquatic species. Ecological risks of organophosphate insecticides were more likely to occur in rivers surrounded by African palm oil plantations, while imidacloprid risks were identified in corn crop areas as well as in natural areas. Future investigations are needed to clarify the sources of imidacloprid contamination and to assess its effects for Amazonian freshwater ecosystems.

Chronic toxicity of three formulations of neonicotinoid insecticides and their mixture on two daphniid species: Daphnia magna and Ceriodaphnia dubia

Neonicotinoid insecticides represent nearly a quarter of the global insecticide market and are widely used in agriculture but also for lawn, garden care, and pest control. They are highly water-soluble, persistent in soil, may enter the aquatic compartment via spray drift, runoff, or leaching, and contribute to downstream aquatic toxicity. Although insects appear to be the most sensitive group to neonicotinoids, other groups, such as crustaceans, may also be affected. Furthermore, most studies focus on single-insecticide exposure and very little is known concerning the impact of neonicotinoid mixtures on aquatic invertebrates. The present study was designed to test potential toxicological effects of an environmentally relevant mixture of imidacloprid, clothianidin, and thiamethoxam on populations of Ceriodaphnia dubia and Daphnia magna under controlled conditions. Chronic toxicity tests were conducted in the laboratory, and survival and reproduction were measured for both species under environmentally relevant, 'worst-case' concentrations for each compound separately and in combination as pesticides are often detected as mixtures in aquatic environments. The neonicotinoids did not appear to affect the survival of C. dubia and D. magna. Reproduction of C. dubia was affected by the mixture whereas all three individual insecticides as well as the mixture caused a significant reduction in the reproduction of D. magna. Our results highlight the complexity of pesticide toxicity and show that traditional toxicological approaches such as, acute mortality studies and tests with single compounds can underestimate negative impacts that occur in the environment.

Physiological Dependency Explains Temperature Differences in Sensitivity Towards Chemical Exposure

In chemical risk assessment, extrapolations from laboratory tests to more realistic conditions are essential to address the toxic effects of pesticides on individuals and populations under field conditions. To transfer toxicological laboratory tests to differing temperature conditions, or outdoor field scenarios, the consideration of temperature dependence is essential and increases realism. Special consideration is given to the impact of temperature on direct sensitivity of organisms to pesticides, for which there are only few modelling approaches available so far. We present a concept for applying physiological temperature dependencies to toxicokinetic-toxicodynamic (TKTD) parameters in the General Uniformed Threshold model of Survival (GUTS). To test this approach in an exemplary study, temperature dependencies from studies on the developmental rate of the mayfly Cloeon dipterum were applied to the parameters of a previously parameterised TKTD model of this species after exposure to imidacloprid. Using a physiologically derived temperature correction for the TKTD rate constants, model predictions for independently conducted toxicology experiments with temperature ranges between 7.8 and 26.4 °C were performed for validation. Our approach demonstrates the successful transfer of a physiological observed temperature dependency on toxicity parameters and survival patterns for Cloeon dipterum and imidacloprid as a case study.

Mixture effects of imidacloprid and difenconazole on enzymatic activity and gene expression in small yellow croakers (Larimichthys polyactis)

Agrochemicals usually exist as mixtures in aqueous ecosystems and have harmful impacts on the natural environment. Nonetheless, the combined effects and underlying mechanisms of agrochemicals on aqueous organisms remain poorly understood. In the present study, the interactive effects of imidacloprid (IMI) and difenconazole (DIF) on the embryos of small yellow croakers (Larimichthys polyactis) were assessed using various toxicological assays, including acute toxicity, enzymatic activity, and gene expression changes. The results showed that DIF (72-h LC₅₀ value of 0.20 mg L^-1) had higher toxicity than IMI (72-h LC₅₀ value of 12.5 mgL^-1). Simultaneously, combinations of IMI and DIF exerted synergistic acute effects on the embryos of L. polyactis. In addition, the SOD, CAT, GST, and CarE activities were noticeably altered in most single and mixed exposures, relative to the untreated control. The expression of four genes (cyp19a1b, ngln2, klf2a, and socs3a) related to the immune system, endocrine system, and neurodevelopment was also surprisingly altered when the embryos of L. polyactis were subjected to individual and combined exposures relative to the untreated control. Changes in enzymatic activity and gene expression might provide early warning indices for the identification of agrochemical co-exposure. The results of this study provide valuable insights into the comprehensive toxicity of agrochemical mixtures to L. polyactis. Further studies on the long-term effects of agrochemical mixtures on marine fish should be conducted to formulate definitive conclusions concerning hazards.

Two constructed wetlands within a Mediterranean natural park immersed in an agrolandscape reduce most heavy metal water concentrations and dampen the majority of pesticide presence

The water concentrations of 12 heavy and other metals/metalloids were analyzed seasonally along two horizontal-flow constructed wetlands (CWs) (Tancat Mília-TM and Tancat l'Illa-TLI) located within the Mediterranean Albufera de València Natural Park during 2020-2021. A wide-scope screening of pesticides present in waters was also performed. The two CWs were created to improve water quality and increase biodiversity. They currently receive effluent waters from two different tertiary-treatment wastewater plants, and the water flows along the CWs before being discharged into the main lagoon and a smaller lagoon in TM and TLI, respectively. TLI manages to reduce (Mn) or maintain the concentration of most of the studied elements (Zn, Ni, Hg, Cr, Fe Cd, Cu) at the same level as outside (67%). Only Al, Pb, B, and As remain at a higher concentration. TM also reduces Zn and Cu and keeps the concentration of Cr, Cd, and Hg (representing 42%). Al, Pb, B, and As remain at higher concentrations, as in TLI, but Ni, Fe, and Mn are also at higher concentrations. Although both CWs vary in their ability to remove elements, no risks to human health or the environment have been detected due to the low metal concentration in their outlets, all of them (except Hg) below the legal limits for environmental quality in the European Union. With the detection of 71 compounds in water in each CW area (26 herbicides, 26 insecticides, and 19 fungicides in TLI, and 29 herbicides, 23 insecticides, and 19 fungicides in TM), we also provide evidence of the impact of pesticides, which depends on the application method (helicopter, tractor), originated from areas with high agricultural pressure (chiefly rice crops) on systems (mainly TM) created to preserve biodiversity. Nevertheless, both systems provide crucial environmental services in water quality in this agrolandscape.

Comparing the acute and chronic toxicity of flupyradifurone and imidacloprid to non-target aquatic arthropod species

Flupyradifurone (FPF) is a new type of butenolide insecticide. It was launched on the market in 2015 and is considered an alternative to the widely used neonicotinoids, like imidacloprid (IMI), some of which are banned from outdoor use in the European Union. FPF is claimed to be safe for bees, but its safety for aquatic organisms is unknown. Its high water solubility, persistence in the environment, and potential large-scale use make it urgent to evaluate possible impacts on aquatic systems. The current study assessed the acute and chronic toxicity of FPF for aquatic arthropod species and compared these results with those of imidacloprid. Besides, toxicokinetics and toxicokinetic-toxicodynamic models were used to understand the mechanisms of the toxicity of FPF. The present study results showed that organisms take up FPF slower than IMI and eliminate it faster. In addition, the hazardous concentration 5th percentiles (HC₀₅) value of FPF derived from a species sensitivity distribution (SSD) based on acute toxicity was found to be 0.052 µmol/L (corresponding to 15 µg/L), which was 37 times higher than IMI (0.0014 µmol/L, corresponding to 0.36 µg/L). The chronic 28 days EC₁₀ of FPF for Cloeon dipterum and Gammarus pulex were 7.5 µg/L and 2.9 µg/L, respectively. For G. pulex, after 28 days of exposure, the no observed effect concentration (NOEC) of FPF for food consumption was 0.3 µg/L. A toxicokinetic-toxicodynamic (TKTD) model parameterised on the acute toxicity data well predicted the observed chronic effects of FPF on G. pulex, indicating that toxicity mechanisms of FPF did not change with prolonged exposure time, which is not the case for IMI.

A critical review of effect modeling for ecological risk assessment of plant protection products

A wide diversity of plant protection products (PPP) is used for crop protection leading to the contamination of soil, water, and air, which can have ecotoxicological impacts on living organisms. It is inconceivable to study the effects of each compound on each species from each compartment, experimental studies being time consuming and cost prohibitive, and animal testing having to be avoided. Therefore, numerous models are developed to assess PPP ecotoxicological effects. Our objective was to provide an overview of the modeling approaches enabling the assessment of PPP effects (including biopesticides) on the biota. Six categories of models were inventoried: (Q)SAR, DR and TKTD, population, multi-species, landscape, and mixture models. They were developed for various species (terrestrial and aquatic vertebrates and invertebrates, primary producers, micro-organisms) belonging to diverse environmental compartments, to address different goals (e.g., species sensitivity or PPP bioaccumulation assessment, ecosystem services protection). Among them, mechanistic models are increasingly recognized by EFSA for PPP regulatory risk assessment but, to date, remain not considered in notified guidance documents. The strengths and limits of the reviewed models are discussed together with improvement avenues (multigenerational effects, multiple biotic and abiotic stressors). This review also underlines a lack of model testing by means of field data and of sensitivity and uncertainty analyses. Accurate and robust modeling of PPP effects and other stressors on living organisms, from their application in the field to their functional consequences on the ecosystems at different scales of time and space, would help going toward a more sustainable management of the environment. Graphical Abstract Combination of the keyword lists composing the first bibliographic query. Columns were joined together with the logical operator AND. All keyword lists are available in Supplementary Information at https://doi.org/10.5281/zenodo.5775038 (Larras et al. 2021).

A rapid evidence assessment of the potential risk to the environment presented by active ingredients in the UK's most commonly sold companion animal parasiticides

A number of parasiticides are commercially available as companion animal treatments to protect against parasite infestation and are sold in large volumes. These treatments are not intended to enter the wider environment but may be washed off or excreted by treated animals and have ecotoxic impacts. A systematic literature review was conducted to identify the existing evidence for the toxicity of the six most used parasiticides in the UK: imidacloprid, fipronil, fluralaner, afoxolaner, selamectin, and flumethrin. A total of 17,207 published articles were screened, with 690 included in the final evidence synthesis. All parasiticides displayed higher toxicity towards invertebrates than vertebrates, enabling their use as companion animal treatments. Extensive evidence exists of ecotoxicity for imidacloprid and fipronil, but this focuses on exposure via agricultural use and is not representative of environmental exposure that results from use in companion animal treatments, especially in urban greenspace. Little to no evidence exists for the ecotoxicity of the remaining parasiticides. Despite heavy usage, there is currently insufficient evidence to understand the environmental risk posed by these veterinary treatments and further studies are urgently needed to quantify the levels and characterise the routes of environmental exposure, as well as identifying any resulting environmental harm.

Pesticide contamination of fish ponds in relation to crop area in a mixed farmland-pond landscape (Dombes area, France)

Pesticides are still widely used by agriculture, leading to the exposure of surface water. This may be the case for fish ponds located in farmland landscapes. To address this issue, the present study investigated the contamination by pesticides of fish ponds located in the mixed agriculture-pond landscape of the Dombes area, France. Ten ponds were selected in water catchments with a gradient of 3-57 ha of cropland with maize and winter cereals as the dominant crops. A total of 197 water samples were collected in the ponds during the fish production season over 3 years. Recently used pesticides were the most frequent residues occurring. Occurrences greater than 0.1 µgL^-1 particularly concerned chlorotoluron and S-metolachlor. Maximum observed concentrations were slightly above 3 µgL^-1 for S-metolachlor, acetochlor, and dimethenamide, all herbicides allowed for maize cultivation. Isoproturon and chlorotoluron, herbicides allowed in cereal crops, reached up to 1.2 and 1.0 µgL^-1, respectively. We found a significant positive effect of crop area in catchments on the pond contamination frequency by pesticides and more significantly on the contamination frequency by broad-spectrum herbicides (glyphosate and AMPA residues). The cumulative antecedent rainfall was best correlated to the frequency of highest contaminations (> 0.5 µgL^-1). In such a hydrological context, the crop area within catchment was identified as a good indicator of fish pond exposure to pesticide residues. Finally, we proposed to adapt some mitigation measures to reduce fish pond contamination.

Biodiversity impacts by multiple anthropogenic stressors in Mediterranean coastal wetlands

Mediterranean coastal wetlands are considered biodiversity hot-spots and contain a high number of endemic species. The biodiversity of these ecosystems is endangered by several pressures resulting from agricultural and urban expansion, climate change, and the alteration of their hydrological cycle. In this study we assess the state-of-the-art regarding the impact of several stressor groups on the biodiversity of Mediterranean coastal wetlands (i.e., lagoons, marshes, estuaries). Particularly, we describe the impacts of eutrophication, chemical pollution, invasive species, salinization, and temperature rise, and analyze the existing literature regarding the impact of multiple stressors on these ecosystems. Our study denotes a clear asymmetry both in terms of study areas and stressors evaluated. The majority of studies focus on lagoons and estuaries of the north-west parts of the Mediterranean basin, while the African and the Asian coast have been less represented. Eutrophication and chemical pollution were the most studied stressors compared to others like temperature rise or species invasions. Most studies evaluating these stressors individually show direct or indirect effects on the biodiversity of primary producers and invertebrate communities, and changes in species dominance patterns that contribute to a decline of endemic populations. The few available studies addressing stressor interactions have shown non-additive responses, which are important to define appropriate ecosystem management and restoration measures. Finally, we propose research needs to advance our understanding on the impacts of anthropogenic stressors on Mediterranean coastal wetlands and to guide future interventions to protect biodiversity.

Temporal and spatial analysis of benomyl/carbendazim in water and its possible impact on Nile tilapia (Oreochromis niloticus) from Tenango dam, Puebla, Mexico

Activities like agriculture contribute to the pollution of aquatic systems by fungicides, such as benomyl/carbendazim. This chemical inhibits the activity of acetylcholinesterase (AChE), having teratogenic, oncogenic, reproductive, and hepatic effects on aquatic and soil organisms. This paper presents the results of a study conducted in the Tenango dam, Mexico, aimed at detecting and determining the spatial and temporal variability of benomyl/carbendazim fungicide in the dam's water and its possible impact on Nile tilapia (Oreochromis niloticus), farmed and commercialized in the site. Five site visits were made during 2015. Benomyl/carbendazim was quantified at 34 georeferenced stations. Thirty O. niloticus specimens were collected per visit. The quality of water and O. niloticus specimens was evaluated according to the Mexican standards. The fungicide concentrations in the O. niloticus muscle and the AChE activity were measured. Seasonal and spatial variations of benomyl/carbendazim were determined using geostatistical methods (ordinary kriging [OK] and universal kriging [UK]). Geostatistical analyses demonstrated that agriculture contributes to the increased amounts of the chemical in specific areas. Even though the fungicide levels in water varied over time, they did not represent a risk to O. niloticus according to the current standards. The specimens met the quality criteria for their commercialization; however, they had low weights and small sizes. The benomyl/carbendazim concentration in the muscle increased with the size and exhibited a negative correlation with the AChE activity, thus indicating a potential harmful effect.

Imbalance of intestinal microbial homeostasis caused by acetamiprid is detrimental to resistance to pathogenic bacteria in Bombyx mori

The neonicotinoid insecticide acetamiprid is widely applied for pest control in agriculture production, and its exposure often results in adverse effects on a non-target insect, Bombyx mori. However, only few studies have investigated the effects of exposure to sublethal doses of neonicotinoid insecticides on gut microbiota and susceptibility to pathogenic bacteria. In this study, we aimed to explore the possible mechanisms underlying the acetamiprid-induced compositional changes in gut microbiota of silkworm and reduced host resistance against detrimental microbes. This study indicated that sublethal dose of acetamiprid activated the dual oxidase-reactive oxygen species (Duox-ROS) system and induced ROS accumulation, leading to dysregulation of intestinal immune signaling pathways. The evenness and structure of bacterial community were altered. Moreover, after 96 h of exposure to sublethal dose of acetamiprid, several bacteria, such as Pseudomonas sp (Biotype A, DOP-1a, XW34) and Staphylococcus sp (RCB1054, RCB314, X302), invaded the silkworm hemolymph. The survival rate and bodyweight of the acetamiprid treated silkworm larvae inoculated with Enterobacter cloacae (E. cloacae) were significantly lower than the acetamiprid treatment group, suggesting that acetamiprid reduced silkworm resistance against pathogens. These findings indicated that acetamiprid disturbed gut microbial homeostasis of Bombyx mori, resulting in changes in gut microbial community and susceptibility to detrimental microbes.

Experimental evidence for neonicotinoid driven decline in aquatic emerging insects

Survey data show a large-scale decline in insects. This global decline is often linked to human actions in intensive agricultural areas. To investigate whether this decline has a causal relationship with neonicotinoid insecticides, we performed an outdoor experiment with representative surface water concentrations of the neonicotinoid thiacloprid. We exposed naturally formed aquatic communities to increasing neonicotinoid concentrations and monitored insect emergence during a 3-mo period. We show that increasing neonicotinoid concentrations strongly decreased the abundance and biomass of five major insect orders that together comprised >99% of the 55,574 collected insects as well as the diversity of the most species-rich freshwater family, thus showing a causal relation between insect decline and neonicotinoids.

There is an ongoing unprecedented loss in insects, both in terms of richness and biomass. The usage of pesticides, especially neonicotinoid insecticides, has been widely suggested to be a contributor to this decline. However, the risks of neonicotinoids to natural insect populations have remained largely unknown due to a lack of field-realistic experiments. Here, we used an outdoor experiment to determine effects of field-realistic concentrations of the commonly applied neonicotinoid thiacloprid on the emergence of naturally assembled aquatic insect populations. Following application, all major orders of emerging aquatic insects (Coleoptera, Diptera, Ephemeroptera, Odonata, and Trichoptera) declined strongly in both abundance and biomass. At the highest concentration (10 µg/L), emergence of most orders was nearly absent. Diversity of the most species-rich family, Chironomidae, decreased by 50% at more commonly observed concentrations (1 µg/L) and was generally reduced to a single species at the highest concentration. Our experimental findings thereby showcase a causal link of neonicotinoids and the ongoing insect decline. Given the urgency of the insect decline, our results highlight the need to reconsider the mass usage of neonicotinoids to preserve freshwater insects as well as the life and services depending on them.

Imidacloprid treatments induces cyanobacteria blooms in freshwater communities under sub-tropical conditions

Imidacloprid is one of the most used neonicotinoid insecticides all over the world and is considered as a contaminant of concern due to its high toxicity potential to aquatic organisms. However, the majority of the studies that have evaluated the effects of imidacloprid on aquatic organisms were conducted under temperate conditions. In the present study, a mesocosm experiment was conducted under sub-tropical conditions to assess the effects of imidacloprid on the structure (macroinvertebrates, zooplankton and phytoplankton) and functional endpoints of an aquatic ecosystem and to compare the results with similar temperate and (sub-)tropical mesocosm studies. Imidacloprid (0, 0.03, 0.3 and 3 µg/L) was applied to 13 mesocosms weekly over a period of 4 weeks, followed by a one month recovery period. At the community level a lowest NOEC_community of 0.03 µg/L was calculated for the zooplankton, phytoplankton and macroinvertebrate communities. The highest sensitivity to imidacloprid (NOEC < 0.03 µg/L) were observed for Gerris sp., Diaptomus sp. and Brachionus quadridentatus. Imidacloprid induced population declines of the larger zooplankton species (Diaptomus sp. and Ostracoda) resulted in increased rotifer abundances and shifted the phytoplankton community to a graze resistant gelatinous cyanobacteria dominated ecosystem. These cyanobacteria blooms occurred at all different concentrations and could pose an important public health and environmental concern. Although there are some differences in species and community sensitivity between the present and the other (sub-)topical mesocosm studies, it can be observed that all show a similar general community response to imidacloprid. Under (sub-)tropical conditions, the toxic effects of imidacloprid occur at lower concentrations than found for temperate ecosystems.

Warming and imidacloprid pulses determine macroinvertebrate community dynamics in experimental streams

Sustainable management of freshwater and pesticide use is essential for mitigating the impacts of intensive agriculture in the context of a changing climate. To better understand how climate change will affect the vulnerability of freshwater ecosystems to chemical pollutants, more empirical evidence is needed on the combined effects of climatic and chemical stressors in environmentally realistic conditions. Our experiment provides the first empirical evaluation of stream macroinvertebrate community dynamics in response to one of the world's most widely used insecticides, imidacloprid, and increased water temperature. In a 7-week streamside experiment using 128 flow-through circular mesocosms, we investigated the effects of pulsed imidacloprid exposure (four environmentally relevant levels between 0 and 4.6 µg/L) and raised water temperature (ambient, 3°C above) on invertebrate communities representative of fast- and slow-flowing microhabitats. Invertebrate drift and insect emergence were monitored during three pesticide pulses (10 days apart), and benthic invertebrate communities were sampled after 24 days of heating and pesticide manipulations. All three manipulated factors strongly affected drift community composition. The first imidacloprid pulse and increased temperature had a greater impact on communities in fast-flowing mesocosms, which contained more pollution-sensitive EPT taxa (mayflies, stoneflies and caddisflies). Heating and imidacloprid caused increased emigration by drift, weak reductions in emergence, and negatively affected the benthic community. The combined effect of stressor manipulations and a 10-day natural heatwave drastically reduced relative abundances of EPT and insects overall and caused a shift to oligochaete-, crustacean- and gastropod-dominated communities. Contrary to our hypothesis, the very high yet realistic water temperatures reached in our experiment meant the negative effects of imidacloprid were clearest at ambient temperatures and fast flow. These findings demonstrate the potential combined impacts of imidacloprid contamination and heatwaves on freshwater invertebrate communities under future climate scenarios and highlight the need for more countries to take regulatory action to control neonicotinoid use.

Physiological Effects of Neonicotinoid Insecticides on Non-Target Aquatic Animals-An Updated Review

In this paper, we review the effects of large-scale neonicotinoid contaminations in the aquatic environment on non-target aquatic invertebrate and vertebrate species. These aquatic species are the fauna widely exposed to environmental changes and chemical accumulation in bodies of water. Neonicotinoids are insecticides that target the nicotinic type acetylcholine receptors (nAChRs) in the central nervous systems (CNS) and are considered selective neurotoxins for insects. However, studies on their physiologic impacts and interactions with non-target species are limited. In researches dedicated to exploring physiologic and toxic outcomes of neonicotinoids, studies relating to the effects on vertebrate species represent a minority case compared to invertebrate species. For aquatic species, the known effects of neonicotinoids are described in the level of organismal, behavioral, genetic and physiologic toxicities. Toxicological studies were reported based on the environment of bodies of water, temperature, salinity and several other factors. There exists a knowledge gap on the relationship between toxicity outcomes to regulatory risk valuation. It has been a general observation among studies that neonicotinoid insecticides demonstrate significant toxicity to an extensive variety of invertebrates. Comprehensive analysis of data points to a generalization that field-realistic and laboratory exposures could result in different or non-comparable results in some cases. Aquatic invertebrates perform important roles in balancing a healthy ecosystem, thus rapid screening strategies are necessary to verify physiologic and toxicological impacts. So far, much of the studies describing field tests on non-target species are inadequate and in many cases, obsolete. Considering the current literature, this review addresses important information gaps relating to the impacts of neonicotinoids on the environment and spring forward policies, avoiding adverse biological and ecological effects on a range of non-target aquatic species which might further impair the whole of the aquatic ecological web.

Integrated non-targeted lipidomics and metabolomics analyses for fluctuations of neonicotinoids imidacloprid and acetamiprid on Neuro-2a cells

Neonicotinoid insecticides are widely used for pest control. However, they are highly water-soluble and easily ingested by organisms, posing potential health risks. In this study, cytotoxicity evaluations of imidacloprid and acetamiprid were conducted in Neuro-2a cells by obtaining their half maximal inhibitory concentration (IC₅₀ values) (1152.1 and 936.5 μM, respectively). The toxic effects at the IC₁₀ and IC₂₀ on cell metabolism were determined by integrated non-targeted lipidomics and metabolomics analyses. Changes in the concentration of acetamiprid caused the most drastic perturbations of metabolism in Neuro-2a cells. Altogether, the detected lipids were mainly attributed to triglyceride, phosphatidylcholine (PC), and diglyceride. These three categories of lipids accounted for more than 67% of the sum in Neuro-2a cells. A total of 14 lipids and other 40 metabolites were screened as differential metabolites based on multivariate data analysis, and PCs were most frequently observed with a proportion of 25.9%. The results demonstrated that lipid metabolism should be paid considerable attention after imidacloprid and acetamiprid exposure. Pathway analysis showed that the metabolisms of glycerophospholipid, sphingolipid, and glutathione were the dominant pathways that were interfered. The present study is the first to investigate the cellular toxic mechanisms after separate imidacloprid and acetamiprid exposure by using lipidomics and metabolomics simultaneously. This research also provides novel insights into the evaluation of the ecological risk of imidacloprid and acetamiprid and contribute to the study of toxicity mechanism of these neonicotinoid insecticides to animals and humans in the future.

Ecological effects of imidacloprid on a tropical freshwater ecosystem and subsequent recovery dynamics

This study aimed to investigate the effect of imidacloprid on structural (invertebrates and primary producers) and functional (organic matter decomposition and physicochemical parameters) characteristics of tropical freshwaters using acute single species and mesocosm studies performed in Ethiopia. The recovery of affected endpoints was also studied by using a mesocosm study period of 21 weeks. Our acute toxicity test showed that Cloeon dipterum (96-h EC50 = 1.5 μg/L) and Caenis horaria (96-h EC50 = 1.9 μg/L) are relatively sensitive arthropods to imidacloprid. The mesocosm experiment evaluated the effects of four applications of imidacloprid with a weekly interval and the results showed that the macroinvertebrate and zooplankton community structure changed significantly due to imidacloprid contamination in mesocosms repeatedly dosed with ≥0.1 and ≥ 0.01 μg/L, respectively (time weighted average concentrations of 112 days (TWA_112d) of ≥0.124 and ≥ ≈0.02 μg/L, respectively). The largest responses were found for C. dipterum, C. horaria, Brachionus sp. and Filinia sp. Chlorophyll-a concentrations of periphyton and phytoplankton significantly increased in the ≥0.1 μg/L treatments levels which are indirect effects as a result of the release of grazing pressure. A significant, but quantitatively small, decrease of organic matter decomposition rate was observed in mesocosms treated with repeated doses of 1 μg/L (TWA_112d of 2.09 μg/L). No recovery was observed for the macroinvertebrates community during the study period of 21 weeks, but zooplankton recovered after 9 weeks. We observed spatio-temporal related toxicity differences between tropical and temperate aquatic taxa, with tropical taxa generally being more sensitive. This suggests that use of temperate toxicity data for the risk assessment of imidacloprid in tropical region is not recommended.

Ecological risk assessment of pesticides in the Mijares River (eastern Spain) impacted by citrus production using wide-scope screening and target quantitative analysis

The widespread use of pesticides, especially in agricultural areas, makes necessary to control their presence in surrounding surface waters. The current study was designed to investigate the occurrence and ecological risks of pesticides and their transformation products in a Mediterranean river basin impacted by citrus agricultural production. Nineteen sites were monitored in three campaigns distributed over three different seasons. After a qualitative screening, 24 compounds was selected for subsequent quantitative analysis. As expected, the lower section of the river was most contaminated, with total concentration >5 µg/L in two sites near to the discharge area of wastewater treatment plants. The highest concentrations were found in September, after agricultural applications and when the river flow is reduced. Ecological risks were calculated using two mixture toxicity approaches (Toxic Unit and multi-substance Potentially Affected Fraction), which revealed high acute and chronic risks of imidacloprid to invertebrates, moderate-to-high risks of diuron, simazine and 2,4-D for primary producers, and moderate-to-high risks of thiabendazole for invertebrates and fish. This study shows that intensive agricultural production and the discharge of wastewater effluents containing pesticide residues from post-harvest citrus processing plants are threatening freshwater biodiversity. Further actions are recommended to control pesticide use and to reduce emissions.

Emerging investigator series: municipal wastewater as a year-round point source of neonicotinoid insecticides that persist in an effluent-dominated stream

Neonicotinoids in aquatic systems have been predominantly associated with agriculture, but some are increasingly being linked to municipal wastewater. Thus, the aim of this work was to understand the municipal wastewater contribution to neonicotinoids in a representative, characterized effluent-dominated temperate-region stream. Our approach was to quantify the spatiotemporal concentrations of imidacloprid, clothianidin, thiamethoxam, and transformation product imidacloprid urea: 0.1 km upstream, the municipal wastewater effluent, and 0.1 and 5.1 km downstream from the wastewater outfall (collected twice-monthly for one year under baseflow conditions). Quantified results demonstrated that wastewater effluent was a point-source of imidacloprid (consistently) and clothianidin (episodically), where chronic invertebrate exposure benchmarks were exceeded for imidacloprid (36/52 samples; 3/52 > acute exposure benchmark) and clothianidin (8/52 samples). Neonicotinoids persisted downstream where mass loads were not significantly different than those in the effluent. The combined analysis of neonicotinoid effluent concentrations, instream seasonality, and registered uses in Iowa all indicate imidacloprid, and seasonally clothianidin, were driven by wastewater effluent, whereas thiamethoxam and imidacloprid urea were primarily from upstream non-point sources (or potential in-stream transformation for imidacloprid urea). This is the first study to quantify neonicotinoid persistence in an effluent-dominated stream throughout the year-implicating wastewater effluent as a point-source for imidacloprid (year-round) and clothianidin (seasonal). These findings suggest possible overlooked neonicotinoid indoor human exposure routes with subsequent implications for instream ecotoxicological exposure.

Neonicotinoid Insecticides from a Marine Perspective: Acute and Chronic Copepod Testing and Derivation of Environmental Quality Standards

Neonicotinoid insecticides have become of global concern for the aquatic environment. Harpacticoid copepods are among the organisms most sensitive to neonicotinoids. We exposed the brackish copepod Nitocra spinipes to 4 neonicotinoid insecticides (clothianidin, imidacloprid, thiacloprid, and thiamethoxam) to investigate acute toxicity on adults (96-h exposure) and effects on larval development (7-d exposure). We used these results in combination with publicly available ecotoxicity data to derive environmental quality standards (EQS). These EQS were ultimately used in a single-substance and mixture risk assessment for the Belgian part of the North Sea. Acute toxicity testing revealed that immobilization is a more sensitive endpoint than mortality, with 96-h median effect concentration (EC50) values of 6.9, 7.2, 25, and 120 µg L^-1 for clothianidin, thiacloprid, imidacloprid, and thiamethoxam, respectively. In addition, the larval development tests resulted in 7-d no-observed-effect concentrations (NOECs) of 2.5, 2.7, 4.2, and >99 µg L^-1 for clothianidin, thiacloprid, imidacloprid, and thiamethoxam, respectively. The derived saltwater annual average (AA-)EQS were 0.05, 0.0048, 0.002, and 0.016 µg L^-1 for clothianidin, thiacloprid, imidacloprid, and thiamethoxam, respectively. Finally, the risk characterization revealed some exceedances of the AA-EQS in Belgian harbors for imidacloprid (number of exceedances, n = 2/4), for thiacloprid (n = 1/4), for thiamethoxam (n = 1/4), and for the mixture of the 4 neonicotinoids (n = 4/4), but not at the open sea. At the open sea site, the toxic unit sums relative to the AA-EQS were 0.72 and 0.22, suggesting no mixture risk, albeit with a relatively small margin of safety. Including short-term EC10 (96-h) values of N. spinipes for the AA-EQS derivation led to a refinement of the AA-EQS for clothianidin and thiamethoxam, suggesting their use for the AA-EQS derivation because one of the overarching goals of the definition of EQS is to protect species at the population level. Environ Toxicol Chem 2021;40:1353-1367. © 2021 SETAC.

Responses of Aquatic Nontarget Organisms in Experiments Simulating a Scenario of Contamination by Imidacloprid in a Freshwater Environment

Several studies have indicated the presence of the neonicotinoid insecticide imidacloprid (IMI) in aquatic ecosystems in concentrations up to 320.0 µg L^-1. In the present study, we evaluated the effects of the highest IMI concentration detected in surface water (320.0 µg L^-1) on the survival of Chironomus sancticaroli, Daphnia similis, and Danio rerio in three different scenarios of water contamination. The enzymatic activities of glutathione S-transferase (GST), catalase (CAT), and ascorbate peroxidase (APX) in D. rerio also were determined. For this evaluation, we have simulated a lotic environment using an indoor system of artificial channels developed for the present study. In this system, three scenarios of contamination by IMI (320.0 µg L^-1) were reproduced: one using reconstituted water (RW) and the other two using water samples collected in unpolluted (UW) and polluted (DW) areas of a river. The results indicated that the tested concentration was not able to cause mortality in D. similis and D. rerio in any proposed treatment (RW, UW, and DW). However, C. sancticaroli showed 100% of mortality in the presence of IMI in the three proposed treatments, demonstrating its potential to impact the community of aquatic nontarget insects negatively. Low IMI concentrations did not offer risks to D. rerio survival. However, we observed alterations in GST, CAT, and APX activities in treatments that used IMI and water with no evidence of pollution (i.e., RW and UW). These last results demonstrated that fish are more susceptible to the effects of IMI in unpolluted environments.

Impacts of Neonicotinoids on Molluscs: What We Know and What We Need to Know

The broad utilisation of neonicotinoids in agriculture has led to the unplanned contamination of adjacent terrestrial and aquatic systems around the world. Environmental monitoring regularly detects neonicotinoids at concentrations that may cause negative impacts on molluscs. The toxicity of neonicotinoids to some non-target invertebrates has been established; however, information on mollusc species is limited. Molluscs are likely to be exposed to various concentrations of neonicotinoids in the soil, food and water, which could increase their vulnerability to other sources of mortality and cause accidental exposure of other organisms higher in the food chain. This review examines the impacts of various concentrations of neonicotinoids on molluscs, including behavioural, physiological and biochemical responses. The review also identifies knowledge gaps and provides recommendations for future studies, to ensure a more comprehensive understanding of impacts from neonicotinoid exposure to molluscs.

Beyond the Headlines: The Influence of Insurance Pest Management on an Unseen, Silent Entomological Majority

For most of the last two decades, insect pest management in key grain and oilseed crops has relied heavily on an insurance-based approach. This approach mandates a suite of management tactics prior to planting and in the absence of pest data. Because there is little flexibility for using these tactics individually, most producers have adopted this full suite of practices despite mounting evidence that some components do not provide consistent benefits. In North America in particular, this preventive approach to insect pest management has led to steep increases in use of neonicotinoid insecticides and subsequent increases in neonicotinoids in soil and water within crop fields and beyond. These increases have been accompanied by a host of non-target effects that have been most clearly studied in pollinators and insect natural enemies. Less attention has been given to the effects of this practice upon the many thousands of aquatic insect species that are often cryptic and offer negligible, or undefined, clear benefits to humans and their commerce. A survey of the literature reveals that the non-target effects of neonicotinoids upon these aquatic species are often as serious as for terrestrial species, and more difficult to address. By focusing upon charismatic insect species that provide clearly defined services, we are likely dramatically under-estimating the effects of neonicotinoids upon the wider environment. Given the mounting evidence base demonstrating that the pest management and crop yield benefits of this approach are negligible, we advocate for a return to largely-abandoned IPM principles as a readily accessible alternative path.

Occurrence and ecological risks of pharmaceuticals in a Mediterranean river in Eastern Spain

Pharmaceuticals are biologically active molecules that may exert toxic effects to a wide range of aquatic organisms. They are considered contaminants of emerging concern due to their common presence in wastewaters and in the receiving surface waters, and the lack of specific regulations to monitor their environmental occurrence and risks. In this work, the environmental exposure and risks of pharmaceuticals have been studied in the Mijares River, Eastern Mediterranean coast (Spain). A total of 57 surface water samples from 19 sampling points were collected in three monitoring campaigns between June 2018 and February 2019. A list of 40 compounds was investigated using a quantitative target UHPLC-MS/MS method. In order to complement the data obtained, a wide-scope screening of pharmaceuticals and metabolites was also performed by UHPLC-HRMS. The ecological risks posed by the pharmaceutical mixtures were evaluated using species sensitivity distributions built with chronic toxicity data for aquatic organisms. In this study, up to 69 pharmaceuticals and 9 metabolites were identified, out of which 35 compounds were assessed using the quantitative method. The highest concentrations in water corresponded to acetaminophen, gabapentin, venlafaxine, valsartan, ciprofloxacin and diclofenac. The compounds that were found to exert the highest toxic pressure on the aquatic ecosystems were principally analgesic/anti-inflammatory drugs and antibiotics. These were: phenazone > azithromycin > diclofenac, and to a lower extent norfloxacin > ciprofloxacin > clarithromycin. The monitored pharmaceutical mixtures are expected to exert severe ecological risks in areas downstream of WWTP discharges, with the percentage of aquatic species affected ranging between 65% and 82% in 3 out of the 19 evaluated sites. In addition, five antibiotics were found to exceed antibiotic resistance thresholds, thus potentially contributing to resistance gene enrichment in environmental bacteria. This work illustrates the wide use and impact of pharmaceuticals in the area under study, and the vulnerability of surface waters if only conventional wastewater treatments are applied. Several compounds included in this study should be incorporated in future water monitoring programs to help in the development of future regulations, due to their potential risk to the aquatic environment.

Population-level variation in neonicotinoid tolerance in nymphs of the Heptageniidae

Anthropogenic activities can have significant ecological and evolutionary consequences on populations and communities. In the United States, neonicotinoid insecticides are widespread across the agricultural Midwest and frequently detected in stream systems. Their effect on Heptageniidae mayflies is a major concern because they are highly sensitive to neonicotinoids and have some of the lowest reported tolerance values of any organism. Our objective was to evaluate population-level variation in neonicotinoid sensitivity. We did so by conducting 96 h half maximal effective concentration (EC50_96-h) tests for the neonicotinoids clothianidin and thiamethoxam on populations of Stenacron, Stenonema, and Maccaffertium mayflies and testing for associations with agricultural landcover. Additionally, we collected water samples to assess temporal patterns of neonicotinoid presence in stream habitats. We found variation in neonicotinoid tolerance with EC50 values ranging from 4.9 μg/L to 32 μg/L and 19.8 μg/L to 86.5 μg/L for clothianidin and thiamethoxam, respectively. Agricultural landcover was associated with neonicotinoid tolerance for Stenacron and thiamethoxam but not for other comparisons. Moreover, water samples demonstrated that the amount of agricultural landcover was not a strong predictor of neonicotinoids presence in streams. Our data suggest that populations of Heptageniidae mayflies can vary substantially in neonicotinoid tolerance. Population-level variation should be considered in toxicity assessments and presents the potential for evolved tolerance.

Joint toxic impacts of cadmium and three pesticides on embryonic development of rare minnow (Gobiocypris rarus)

Although rare minnow (Gobiocypris rarus) has been employed in many toxicological investigations, most of them have only assessed the impacts of single chemical. In our current work, we investigated the single and joint toxic impacts of heavy metal cadmium (Cd) and three pesticides (thiamethoxam, bifenthrin, and tebuconazole) on G. rarus embryos. Results from the 96-h semi-static toxicity assay exhibited that bifenthrin possessed the highest intrinsic toxic effect on rare minnows with an LC₅₀ value of 1.86 mg L^-1, followed by tebuconazole with LC₅₀ values of 4.07 mg L^-1. Contrarily, thiamethoxam elicited the least toxic effect with an LC₅₀ value of 351.9 mg L^-1. Seven chemical mixtures (four binary mixtures of Cd-bifenthrin, thiamethoxam-bifenthrin, thiamethoxam-tebuconazole, and bifenthrin-tebuconazole, two ternary mixtures of Cd-thiamethoxam-tebuconazole and thiamethoxam-bifenthrin-tebuconazole, and one quaternary mixture of Cd-thiamethoxam-bifenthrin-tebuconazole) displayed synergistic impacts with equivalent concentration and equitoxic ratio on G. rarus. Our results offered valuable insights into ecological risk assessment of these chemical combinations to aquatic vertebrates. The simultaneous existence of a few chemicals in the aquatic ecosystem might result in elevated toxicity, leading to severe harm to the non-target organisms compared with single compound. The observed synergistic interactions underlined the necessity to revise water quality standards, in which the detrimental joint effects of these chemicals are likely to be underestimated.

Neonicotinoid-containing insecticide disruption of growth, locomotion, and fertility in Caenorhabditis elegans

Neonicotinoids, a class of insecticides structurally similar to nicotine that target biting and sucking insects, are the most widely used insecticides today, in part due to their supposed low toxicity in other organisms. However, a growing body of research has found that even low doses of neonicotinoids can induce unexpected negative effects on the physiology and survival of a wide range of non-target organisms. Importantly, no work has been done on the commercial formulations of pesticides that include imidacloprid as the active ingredient, but that also contain many other components. The present study examines the sublethal effects of "Tree and Shrub"™ ("T+S"), a commercial insecticide containing the neonicotinoid imidacloprid as its active ingredient, on Caenorhabditis elegans. We discovered that "T+S" significantly stunted the overall growth in wildtype nematodes, an effect that was exacerbated by concurrent exposure to heat stress. "T+S" also negatively impacted fecundity as measured by increased germline apoptosis, a decrease in egg-laying, and fewer viable offspring. Lastly, exposure to "T+S" resulted in degenerative changes in nicotinic cholinergic neurons in wildtype nematodes. As a whole, these findings demonstrate widespread toxic effects of neonicotinoids to critical functions in nematodes.

Losses of selected pesticides in drainage water from containerized ornamental plants

Limited research has focused on factors affecting pesticide losses from ornamental plant production nurseries. This project evaluated the effects of overhead irrigation or simulated rainfall intensity and formulation and application methods on the losses of acephate, bifenthrin, and imidacloprid in drainage water. The liquid formulation of each respective pesticide was applied to individual replicates (potted Ilex cornuta Lindl. & Paxton plant on a drainage collection saucer) as substrate-applied drenches or foliar sprays (acephate and bifenthrin only). Granular formulations of acephate and imidacloprid were spread across the tops of media in pots. After application of treatments, irrigation or simulated rainfall was applied daily for 19 consecutive days at rates of 42.3 ± 4.57, 56.7 ± 7.92, and 95.4 ± 19.47 ml min^-1 , and drainage water from individual replicates was collected for analysis. Irrigation or simulated rainfall intensity had no effects on losses of the pesticides under the conditions tested. Concentrations in drainage of all three pesticides were highest from the drench applications, whereas respective foliar spray applications resulted in the lowest active ingredient concentrations in drainage. The percentage of active ingredient lost in drainage water ranged from a minimum of 0.2 ± 0.05% (mean ± SE) for granular acephate to a maximum of 19.5 ± 3.14% (mean ± SE) for the imidacloprid drench. Most pesticide losses occurred within the first 2 d after application of drenches or sprays. Granular formulations had a longer period of release, indicating a risk of loss from overirrigation during an extended period. Results emphasize the need for careful water management after applications.

Ecological risks of imidacloprid to aquatic species in the Netherlands: Measured and estimated concentrations compared to species sensitivity distributions

Recent declines of insects' biomass have been a major point of interest. While several causes, including use of neonicotinoids like imidacloprid, have been suggested, scientific underpinning is limited. The aim of our study was to assess the potential risk of imidacloprid for freshwater fauna in the Netherlands and to validate the SimpleBox model to allow application elsewhere. To this end, we compared imidacloprid concentrations estimated from emissions using the SimpleBox model to measurements obtained from monitoring databases and calculated the ecological risk based on measured concentrations for aquatic fauna. Imidacloprid concentration estimations were within the range measured, opening opportunities for application of SimpleBox to regions where measurements are limited. Aquatic insects were found to be most sensitive to imidacloprid while amphibians and fish are least sensitive to imidacloprid. In particular, the ecological risk of measured imidacloprid concentration in the Netherlands was 1%, implying that concentrations frequently exceed levels that are lethal in short-term experiments. Hence, based on lab toxicity data, the present study suggests that imidacloprid concentrations can be high enough to explain insect decline observed in the same areas.

Neonicotinoids and fertilizers jointly structure naturally assembled freshwater macroinvertebrate communities

Although it is widely acknowledged that a decline of freshwater biodiversity jeopardizes the functioning of freshwater ecosystems, the large number of (human-induced) pressures jointly acting on these systems hampers managing its biodiversity. To disentangle the magnitude and the temporal effects of these single and interacting pressures, experiments are required that study how these pressures affect the structuring of natural communities. We performed experiments with naturally assembled invertebrate communities in 36 experimental ditches to assess the single and joint effects of environmentally relevant concentrations of two commonly co-occurring stressors: fertilizer inputs and neonicotinoid insecticides, in this case thiacloprid. Specifically, we explored whether these agrochemicals result in sustained changes in community structure by inspecting divergence, convergence and short- /long-lived dissimilarity of communities, when compared to a control treatment. Our results indicate strong impacts on the abundance of different taxa by exposure to the agrochemicals. However, we found no effect of any treatment on total abundance, taxon richness or convergence/divergence (measured as beta dispersion) of the communities. Moreover, we found contrasting responses when both joint stressors were present: when considering abundance of different taxa, we observed that fertilizer additions reduced some of the thiacloprid toxicity. But when assessing the community structure, we found that exposure to both stressors consistently resulted in a more dissimilar community compared to the control. This dissimilarity was persistent up to four months after applying the agrochemicals, even though there was a turnover in taxa explaining this dissimilarity. This turnover indicates that the persistent dissimilarity can potentially be attributed to a rippling effect in the community rather than continued toxicity. Such shifts in natural freshwater invertebrate communities, months after the actual exposure, suggests that stressors may have important long-term repercussions for which may subsequently lead to changes in ecosystem functioning.

Chronic Toxicities of Neonicotinoids to Nymphs of the Common New Zealand Mayfly Deleatidium spp

Neonicotinoid insecticides have been shown to have high chronic toxicity relative to acute toxicity, and therefore short-term toxicity tests ≤96 h in duration may underestimate their environmental risks. Among nontarget aquatic invertebrates, insects of the orders Diptera and Ephemeroptera have been found to be the most sensitive to neonicotinoids. To undertake a more accurate assessment of the risks posed by neonicotinoids to freshwater ecosystems, more data are needed from long-term tests employing the most sensitive taxa. Using nymphs of the common New Zealand mayfly genus Deleatidium spp., we performed 28-d static-renewal exposures with the widely used neonicotinoids imidacloprid, clothianidin, and thiamethoxam. We monitored survival, immobility, impairment, and mayfly moulting propensity at varying time points throughout the experiment. Imidacloprid and clothianidin exerted strong chronic toxicity effects on Deleatidium nymphs, with 28-d median lethal concentrations (LC50s) of 0.28 and 1.36 µg/L, respectively, whereas thiamethoxam was the least toxic, with a 28-d LC50 > 4 µg/L (highest concentration tested). Mayfly moulting propensity was also negatively affected by clothianidin (during 3 of 4 wk), imidacloprid (2 of 4 wk), and thiamethoxam (1 of 4 wk). Comparisons with published neonicotinoid chronic toxicity data for other mayfly taxa and larvae of the midge genus Chironomus showed similar sensitivities for mayflies and midges, suggesting that experiments using these taxa provide reliable assessments of the threats of neonicotinoids to the most vulnerable freshwater species. Environ Toxicol Chem 2019;38:2459-2471. © 2019 SETAC.

Community responses of aquatic insects in paddy mesocosms to repeated exposures of the neonicotinoids imidacloprid and dinotefuran

Pesticides are one of major threats to wetland environments and their communities, and thus the information about ecological impact assessment of agro-chemicals on ecosystems is essential for future effective pesticides management. Here, effects of the yearly application of two neonicotinoids, imidacloprid and dinotefuran on aquatic insect communities of experimental rice fields were assessed during two years of monitoring. Both neonicotinoid-treated fields and controls were monitored biweekly throughout the 5-month experimental period until harvest (late October) in each year. Maximum concentrations of imidacloprid (157.5 μg/l in 2014 and 138.0 μg/l in 2015) and dinotefuran (10.54 μg/l in 2014 and 54.05 μg/l in 2015) in water were relatively similar in both years, but maximum residues of imidacloprid (245.45 μg/kg) and dinotefuran (419.5 μg/kg) in the sediment in the second-year were 18 and 175 times higher than in the first year, respectively, with great variability of concentrations among sampling dates. In addition, remaining soil residues of both neonicotinoids were approximately 1 μg/kg (ppb) at the start of the second-year. A total of 6265 individuals of 18 aquatic species belonging to 7 orders were collected. No differences in the number of species between controls and the two neonicotinoids-treated paddies were found between years. However, clear differences in community structures of aquatic insects among the imidacloprid- and dinotefuran-treated mesocosms, and controls and between years were shown by PRC analysis. In particular, imidacloprid likely decreased Crocothemisia servilia mariannae nymphs, Chironominae spp. larvae, and Aedes albopictus larvae, whereas dinotefuran tended to decrease Guignotus japonicus, Orthetrum albistylum speciosum nymphs, and Tubiificidae spp. In addition, long-living species of Coleoptera and Odonata were most sensitive to both neonicotinoids. Changes in composition of feeding functional groups (FFGs) of aquatic insects were more prominent in the first year and became subtler in the second year. One of the possibilities of this phenomenon may be functional redundancy in which species that had low sensitivity to imidacloprid and dinotefuran replaced the vacant niche caused by decreases of other species with high susceptibility within the same feeding functions, although further studies are needed to verify this explanation. Thus, feeding functional traits can be a good indicator for evaluation of changes in ecosystem processes under pesticides exposures. Consequently, the current study emphasized that more realistic prediction of community properties after the repeated application of agrochemicals in successive years should consider for 1) long-term population monitoring, 2) cumulative effects at least over the years, and 3) species' functional traits.

A survey and risk assessment of neonicotinoids in water, soil and sediments of Belize

Usage of neonicotinoids is common in all agricultural regions of the world but data on environmental contamination in tropical regions is scarce. We conducted a survey of five neonicotinoids in soil, water and sediment samples along gradients from crops fields to protected lowland tropical forest, mangroves and wetlands in northern Belize, a region of high biodiversity value. Neonicotinoid frequency of detection and concentrations were highest in soil (68%) and lowest in water (12%). Imidacloprid was the most common residue reaching a maximum of 17.1 ng/g in soil samples. Concentrations in soils differed among crop types, being highest in melon fields and lowest in banana and sugarcane fields. Residues in soil declined with distance to the planted fields, with clothianidin being detected at 100 m and imidacloprid at more than 10 km from the nearest applied field. About half (47%) of the sediments collected contained residues of at least one compound up to 10 km from the source. Total neonicotinoid concentrations in sediments (range 0.014-0.348 ng/g d. w.) were about 10 times lower than in soils from the fields, with imidacloprid being the highest (0.175 ng/g). A probabilistic risk assessment of the residues in the aquatic environment indicates that 31% of sediment samples pose a risk to invertebrate aquatic and benthic organisms by chronic exposure, whereas less than 5% of sediment samples may incur a risk by acute exposure. Current residue levels in water samples do not appear to pose risks to the aquatic fauna. Fugacity modeling of the four main compounds detected suggest that most of the dissipation from the agricultural fields occurs via runoff and leaching through the porous soils of this region. We call for better monitoring of pesticide contamination and invertebrate inventories and finding alternatives to the use of neonicotinoids in agriculture.