Macro-invertebrate decline in surface water polluted with imidacloprid

Bacterial biodegradation of neonicotinoid pesticides in soil and water systems

Neonicotinoids are neurotoxic systemic insecticides used in plant protection worldwide. Unfortunately, application of neonicotinoids affects both beneficial and target insects indiscriminately. Being water soluble and persistent, these pesticides are capable of disrupting both food chains and biogeochemical cycles. This review focuses on the biodegradation of neonicotinoids in soil and water systems by the bacterial community. Several bacterial strains have been isolated and identified as capable of transforming neonicotinoids in the presence of an additional carbon source. Environmental parameters have been established for accelerated transformation in some of these strains. Studies have also indicated that enhanced biotransformation of these pesticides can be accomplished by mixed microbial populations under optimised environmental conditions. Substantial research into the identification of neonicotinoid-mineralising bacterial strains and identification of the genes and enzymes responsible for neonicotinoid degradation is still required to complete the understanding of microbial biodegradation pathways, and advance bioremediation efforts.

Sensitivity of the early-life stages of freshwater mollusks to neonicotinoid and butenolide insecticides

Neonicotinoid insecticides can be transported from agricultural fields, where they are used as foliar sprays or seed treatments, to surface waters by surface or sub-surface runoff. Few studies have investigated the toxicity of neonicotinoid or the related butenolide insecticides to freshwater mollusk species. The current study examined the effect of neonicotinoid and butenolide exposures to the early-life stages of the ramshorn snail, Planorbella pilsbryi, and the wavy-rayed lampmussel, Lampsilis fasciola. Juvenile P. pilsbryi were exposed to imidacloprid, clothianidin, or thiamethoxam for 7 or 28 d and mortality, growth, and biomass production were measured. The viability of larval (glochidia) L. fasciola was monitored during a 48 h exposure to six neonicotinoids (imidacloprid, thiamethoxam, clothianidin, acetamiprid, thiacloprid, or dinotefuran), or a butenolide (flupyradifurone). The 7-d LC50s of P. pilsbryi for imidacloprid, clothianidin, and thiamethoxam were ≥4000 μg/L and the 28-d LC50s were ≥182 μg/L. Growth and biomass production were considerably more sensitive endpoints than mortality with EC50s ranging from 33.2 to 122.0 μg/L. The 48-h LC50s for the viability of glochidia were ≥456 μg/L for all seven insecticides tested. Our data indicate that neonicotinoid and butenolide insecticides pose less of a hazard with respect to mortality of the two species of mollusk compared to the potential hazard to other non-target aquatic insects.

Can't take the heat: Temperature-enhanced toxicity in the mayfly Isonychia bicolor exposed to the neonicotinoid insecticide imidacloprid

Neonicotinoid insecticide usage has increased globally in recent decades. Neonicotinoids, such as imidacloprid, are potent insect neurotoxicants that may pose a threat to non-target aquatic organisms, such as aquatic insects. In nature, insects typically live in thermally fluctuating conditions, which may significantly alter both contaminant exposures and affects. Here we investigate the relationship between temperature and time-to-effect for imidacloprid toxicity with the aquatic insect Isonychia bicolor, a lotic mayfly. Additionally, we examined the mechanisms driving temperature-enhanced toxicity including metabolic rate, imidacloprid uptake rate, and tissue bioconcentration. Experiments included acute toxicity tests utilizing sublethal endpoints and mortality, as well as respirometry and radiotracer assays with [(14)C] imidacloprid. Further, we conducted additional uptake experiments with a suite of aquatic invertebrates (including I. bicolor, Neocloeon triangulifer, Macaffertium modestum, Pteronarcys proteus, Acroneuria carolinensis, and Pleuroceridae sp) to confirm and contextualize our findings from initial experiments. The 96h EC50 (immobility) for I. bicolor at 15°C was 5.81μg/L which was approximately 3.2 fold lower than concentrations associated with 50% mortality. Assays examining the impact of temperature were conducted at 15, 18, 21, and 24°C and demonstrated that time-to-effect for sublethal impairment and immobility was significantly decreased with increasing temperature. Uptake experiments with [(14)C] imidacloprid revealed that initial uptake rates were significantly increased with increasing temperature for I. bicolor, as were oxygen consumption rates. Further, in the separate experiment with multiple species across temperatures 15, 20, and 25°C, we found that all the aquatic insects tested had significantly increased imidacloprid uptake with increasing temperatures, with N. triangulifer accumulating the most imidacloprid on a mass-specific basis. Our acute toxicity results highlight the importance of evaluating sublethal endpoints, as profound impairments of motor function were evident far before mortality. Further, we demonstrate that temperature is a powerful modulator of sublethal toxicity within a range of environmentally relevant temperatures, impacting both uptake rates and metabolic rates of I. bicolor. Finally, we show that temperature alters imidacloprid uptake across a range of species, highlighting the physiological variation present within aquatic invertebrate communities and the challenge associated with relying solely on surrogate species. Taken together, this research points to the need to consider the role of temperature in toxicity assessments.

The influence of insecticide exposure and environmental stimuli on the movement behaviour and dispersal of a freshwater isopod

Behaviour links physiological function with ecological processes and can be very sensitive towards environmental stimuli and chemical exposure. As such, behavioural indicators of toxicity are well suited for assessing impacts of pesticides at sublethal concentrations found in the environment. Recent developments in video-tracking technologies offer the possibility of quantifying behavioural patterns, particularly locomotion, which in general has not been studied and understood very well for aquatic macroinvertebrates to date. In this study, we aim to determine the potential effects of exposure to two neurotoxic pesticides with different modes of action at different concentrations (chlorpyrifos and imidacloprid) on the locomotion behaviour of the water louse Asellus aquaticus. We compare the effects of the different exposure regimes on the behaviour of Asellus with the effects that the presence of food and shelter exhibit to estimate the ecological relevance of behavioural changes. We found that sublethal pesticide exposure reduced dispersal distances compared to controls, whereby exposure to chlorpyrifos affected not only animal activity but also step lengths while imidacloprid only slightly affected step lengths. The presence of natural cues such as food or shelter induced only minor changes in behaviour, which hardly translated to changes in dispersal potential. These findings illustrate that behaviour can serve as a sensitive endpoint in toxicity assessments. However, under natural conditions, depending on the exposure concentration, the actual impacts might be outweighed by environmental conditions that an organism is subjected to. It is, therefore, of importance that the assessment of toxicity on behaviour is done under relevant environmental conditions.

Regulation of Hydroxylation and Nitroreduction Pathways during Metabolism of the Neonicotinoid Insecticide Imidacloprid by Pseudomonas putida

Imidacloprid (IMI) is mainly metabolized via nitroreduction and hydroxylation pathways, which produce different metabolites that are toxic to mammals and insects. However, regulation of IMI metabolic flux between nitroreduction and hydroxylation pathways is still unclear. In this study, Pseudomonas putida was found to metabolize IMI to 5-hydroxy and nitroso IMI and was therefore used for investigating the regulation of IMI metabolic flux. The cell growth time, cosubstrate, dissolved oxygen concentration, and pH showed significant effect on IMI degradation and nitroso and 5-hydroxy IMI formation. Gene cloning and overexpression in Escherichia coli proved that P. putida KT2440 aldehyde oxidase mediated IMI nitroreduction to nitroso IMI, while cytochrome P450 monooxygenase (CYP) failed to improve IMI hydroxylation. Moreover, E. coli cells without CYP could hydroxylate IMI, demonstrating the role of a non-CYP enzyme in IMI hydroxylation. Thus, the present study helps to further understand the environmental fate of IMI and its underlying mechanism.

Mass Balance Assessment for Six Neonicotinoid Insecticides During Conventional Wastewater and Wetland Treatment: Nationwide Reconnaissance in United States Wastewater

Occurrence and removal of six high-production high-volume neonicotinoids was investigated in 13 conventional wastewater treatment plants (WWTPs) and one engineered wetland. Flow-weighted daily composites were analyzed by isotope dilution liquid chromatography tandem mass spectrometry, revealing the occurrence of imidacloprid, acetamiprid, and clothianidin at ng/L concentrations in WWTP influent (60.5 ± 40.0; 2.9 ± 1.9; 149.7 ± 289.5, respectively) and effluent (58.5 ± 29.1; 2.3 ± 1.4; 70.2 ± 121.8, respectively). A mass balance showed insignificant removal of imidacloprid (p = 0.09, CI = 95%) and limited removal of the sum of acetamiprid and its degradate, acetamiprid-N-desmethyl (18 ± 4%, p = 0.01, CI = 95%). Clothianidin was found only intermittently, whereas thiamethoxam, thiacloprid, and dinotefuran were never detected. In the wetland, no removal of imidacloprid or acetamiprid was observed. Extrapolation of data from 13 WWTPs to the nation as a whole suggests annual discharges on the order of 1000-3400 kg/y of imidacloprid contained in treated effluent to surface waters nationwide. This first mass balance and first United States nationwide wastewater reconnaissance identified imidacloprid, acetamiprid, and clothianidin as recalcitrant sewage constituents that persist through wastewater treatment to enter water bodies at significant loadings, potentially harmful to sensitive aquatic invertebrates.

Metabolism, bioaccumulation, and toxicity of pesticides in aquatic insect larvae

Aquatic insects having a high diversity are good biotic indicators for freshwater quality. Their larvae living in freshwater are sensitive to pesticides, and its impacts has been examined not only through laboratory toxicity studies using water and sediment exposure but also through higher-tier micro-/mesocosm studies and field monitoring. Many sophisticated statistical methods have been applied to assess the impacts of pesticides at levels from species to community, but their body burden has been studied much less, especially in relation to toxicity. We review the uptake, metabolism with relevant detoxifying enzymes, and depuration of pesticides in aquatic insect larvae, which determine their body burden and help to understand the toxicity profiles specific to each chemical class. We also discuss experimental conditions, environmental factors, and species sensitivity in relation to the bioconcentration/-accumulation and toxicity of pesticides.

Imidacloprid Extraction from Citrus Leaves and Analysis by Liquid Chromatography-Mass Spectrometry (HPLC-MS/MS)

A procedure was developed to extract Imidacloprid (IMD) from newly-flushed and fully-expanded citrus leaves. The extraction was conducted in a bullet blender, using a small sample mass (0.5 g of fresh tissue), stainless-steel beads (24 g), and methanol as extractant (10 mL). The extracts did not require further clean-up before analysis by HPLC-MS/MS. The method was validated with control samples from IMD-untreated Hamlin orange trees. The method limit of detection and limit of quantitation were 0.04 and 0.12 μg g(-1), respectively. IMD recoveries from fortified leaf tissue were between 92 % and 102 %, with relative standard deviations of <8 %. The method was further evaluated by extracting leaves from Hamlin orange trees treated with IMD. The treated trees showed maximum concentrations of 10.8 and 21.8 µg g(-1), observed at 20 days after applying two soil-drenching rates (0.51 and 1.02 kg IMD ha(-1)), respectively. This extraction technique will generate useful data on IMD plant uptake, foliar concentration, and correlations with Asian citrus psyllid (ACP) mortality or control. The method could be used to generate baseline data to improve IMD soil-drenching applications as the main management practice to control the ACP.

Development and Validation of Chronopotentiometric Method for Imidacloprid Determination in Pesticide Formulations and River Water Samples

A new electrochemical method for determination of imidacloprid using chronopotentiometry on thin film mercury and glassy carbon electrode was presented. The most important experimental parameters of chronopotentiometry were examined and optimized with respect to imidacloprid analytical signal. Imidacloprid provided well-defined reduction peak in Britton-Robinson buffer on thin film mercury electrode at -1.0 V (versus Ag/AgCl (KCl, 3.5 mol/L)) and on glassy carbon electrode at -1.2 V (versus Ag/AgCl (KCl, 3.5 mol/L)). The reduction time was linearly proportional to concentrations from 0.8 to 30.0 mg/L on thin film mercury electrode and from 7.0 to 70.0 mg/L on glassy carbon electrode. The detection limits were 0.17 mg/L and 0.93 mg/L for thin film mercury and glassy carbon electrode, respectively. The estimation of method precision as a function of repeatability and reproducibility showed relative standard deviations values lower than 3.73%. Recovery values from 97.3 to 98.1% confirmed the accuracy of the proposed method, while the constancy of the transition time with deliberated small changes in the experimental parameters indicated a very good robustness. A minor influence of possible interfering compounds proved good selectivity of the method. Developed method was applied for imidacloprid determination in commercial pesticide formulations and river water samples.

Field data reveal low critical chemical concentrations for river benthic invertebrates

River ecosystems are of immense ecological and social importance. Despite the introduction of wastewater treatment plants and advanced chemical authorization procedures in Europe, chemical pollution is still a major threat to freshwater ecosystems. Here, large-scale monitoring data was exploited to identify taxon-specific chemical concentrations beyond which benthic invertebrate taxa are unlikely to occur using Threshold Indicator Taxa Analysis (TITAN). 365 invertebrate taxa and 25 organic chemicals including pesticides, pharmaceuticals, plasticisers, flame retardants, complexing agents, a surfactant and poly- and monocyclic aromatic hydrocarbons from a total of 399 sites were analysed. The number of taxa that responded to each of these chemicals varied between 0% and 21%. These sensitive taxa belonged predominantly to the groups Plecoptera, Coleoptera, Trichoptera, Ephemeroptera, Turbellaria, Megaloptera, Crustacea, and Diptera. Strong effects were observed in response to wastewater-associated compounds, confirming that wastewater is an important cause of biological degradation. The majority of change points identified for each compound were well below predicted no-effect concentrations derived from laboratory toxicity studies. Thus, the results show that chemicals are likely to induce effects in the environment at concentrations much lower than expected based on laboratory experiments. Overall, it is confirmed that chemical pollution is still an important factor shaping the distribution of invertebrate taxa, suggesting the need for continued efforts to reduce chemical loads in rivers.

Field-scale examination of neonicotinoid insecticide persistence in soil as a result of seed treatment use in commercial maize (corn) fields in southwestern Ontario

Neonicotinoid insecticides, especially as seed treatments, have raised concerns about environmental loading and impacts on pollinators, biodiversity, and ecosystems. The authors measured concentrations of neonicotinoid residues in the top 5 cm of soil before planting of maize (corn) in 18 commercial fields with a history of neonicotinoid seed treatment use in southwestern Ontario in 2013 and 2014 using liquid chromatography-tandem mass spectrometry with electrospray ionization. A simple calculator based on first-order kinetics, incorporating crop rotation, planting date, and seed treatment history from the subject fields, was used to estimate dissipation rate from the seed zone. The estimated half-life (the time taken for 50% of the insecticide to have dissipated by all mechanisms) based on 8 yr of crop history was 0.64 (range, 0.25-1.59) yr and 0.57 (range, 0.24-2.12) yr for 2013 and 2014, respectively. In fields where neonicotinoid residues were measured in both years, the estimated mean half-life between 2013 and 2014 was 0.4 (range, 0.27-0.6) yr. If clothianidin and thiamethoxam were used annually as a seed treatment in a typical crop rotation of maize, soybean, and winter wheat over several years, residues would plateau rather than continue to accumulate. Residues of neonicotinoid insecticides after 3 yr to 4 yr of repeated annual use tend to plateau to a mean concentration of less than 6 ng/g in agricultural soils in southwestern Ontario.

Pesticide impact on aquatic invertebrates identified with Chemcatcher® passive samplers and the SPEAR(pesticides) index

Pesticides negatively affect biodiversity and ecosystem function in aquatic environments. In the present study, we investigated the effects of pesticides on stream macroinvertebrates at 19 sites in a rural area dominated by forest cover and arable land in Central Germany. Pesticide exposure was quantified with Chemcatcher® passive samplers equipped with a diffusion-limiting membrane. Ecological effects on macroinvertebrate communities and on the ecosystem function detritus breakdown were identified using the indicator system SPEARpesticides and the leaf litter degradation rates, respectively. A decrease in the abundance of pesticide-vulnerable taxa and a reduction in leaf litter decomposition rates were observed at sites contaminated with the banned insecticide Carbofuran (Toxic Units≥-2.8), confirming the effect thresholds from previous studies. The results show that Chemcatcher® passive samplers with a diffusion-limiting membrane reliably detect ecologically relevant pesticide pollution, and we suggest Chemcatcher® passive samplers and SPEARpesticides as a promising combination to assess pesticide exposure and effects in rivers and streams.

Metabolomics to Explore Imidacloprid-Induced Toxicity in the Central Nervous System of the Freshwater Snail Lymnaea stagnalis

Modern toxicology is seeking new testing methods to better understand toxicological effects. One of the most concerning chemicals is the neonicotinoid pesticide imidacloprid. Although imidacloprid is designed to target insects, recent studies have shown adverse effects on nontarget species. Metabolomics was applied to investigate imidacloprid-induced sublethal toxicity in the central nervous system of the freshwater snail Lymnaea stagnalis. The snails (n = 10 snails) were exposed for 10 days to increasing imidacloprid concentrations (0.1, 1, 10, and 100 μg/L). The comparison between control and exposure groups highlighted the involvement and perturbation of many biological pathways. The levels of several metabolites belonging to different metabolite classes were significantly changed by imidacloprid exposure. A change in the amino acids and nucleotide metabolites like tryptophan, proline, phenylalanine, uridine, and guanosine was found. Many fatty acids were down-regulated, and the levels of the polyamines, spermidine and putrescine, were found to be increased which is an indication of neuron cell injury. A turnover increase between choline and acetylcholine led us to hypothesize an increase in cholinergic gene expression to overcome imidacloprid binding to the nicotinic acetylcholine receptors. Metabolomics revealed imidacloprid induced metabolic changes at low and environmentally relevant concentration in a nontarget species and generated a novel mechanistic hypothesis.

Pesticide authorization in the EU-environment unprotected?

Pesticides constitute an integral part of high-intensity European agriculture. Prior to their authorization, a highly elaborated environmental risk assessment is mandatory according to EU pesticide legislation, i.e., Regulation (EC) No. 1107/2009. However, no field data-based evaluation of the risk assessment outcome, i.e., the regulatory acceptable concentrations (RACs), and therefore of the overall protectiveness of EU pesticide regulations exists. We conducted here a comprehensive meta-analysis using peer-reviewed literature on agricultural insecticide concentrations in EU surface waters and evaluated associated risks using the RACs derived from official European pesticide registration documents. As a result, 44.7 % of the 1566 cases of measured insecticide concentrations (MICs) in EU surface waters exceeded their respective RACs. It follows that current EU pesticide regulations do not protect the aquatic environment and that insecticides threaten aquatic biodiversity. RAC exceedances were significantly higher for insecticides authorized using conservative tier-I RACs and for more recently developed insecticide classes, i.e., pyrethroids. In addition, we identified higher risks, e.g., for smaller surface waters that are specifically considered in the regulatory risk assessment schemes. We illustrate the shortcomings of the EU regulatory risk assessment using two case studies that contextualize the respective risk assessment outcomes to field exposure. Overall, our meta-analysis challenges the field relevance and protectiveness of the regulatory environmental risk assessment conducted for pesticide authorization in the EU and indicates that critical revisions of related pesticide regulations and effective mitigation measures are urgently needed to substantially reduce the environmental risks arising from agricultural insecticide use.

The Role of Epigenetics in the Latent Effects of Early Life Exposure to Obesogenic Endocrine Disrupting Chemicals

Recent research supports a role for exposure to endocrine-disrupting chemicals (EDCs) in the global obesity epidemic. Obesogenic EDCs have the potential to inappropriately stimulate adipogenesis and fat storage, influence metabolism and energy balance and increase susceptibility to obesity. Developmental exposure to obesogenic EDCs is proposed to interfere with epigenetic programming of gene regulation, partly by activation of nuclear receptors, thereby influencing the risk of obesity later in life. The goal of this minireview is to briefly describe the epigenetic mechanisms underlying developmental plasticity and to evaluate the evidence of a mechanistic link between altered epigenetic gene regulation by early life EDC exposure and latent onset of obesity. We summarize the results of recent in vitro, in vivo, and transgenerational studies, which clearly show that the obesogenic effects of EDCs such as tributyltin, brominated diphenyl ether 47, and polycyclic aromatic hydrocarbons are mediated by the activation and associated altered methylation of peroxisome proliferator-activated receptor-γ, the master regulator of adipogenesis, or its target genes. Importantly, studies are emerging that assess the effects of EDCs on the interplay between DNA methylation and histone modifications in altered chromatin structure. These types of studies coupled with genome-wide rather than gene-specific analyses are needed to improve mechanistic understanding of epigenetic changes by EDC exposure. Current advances in the field of epigenomics have led to the first potential epigenetic markers for obesity that can be detected at birth, providing an important basis to determine the effects of developmental exposure to obesogenic EDCs in humans.

Ecological and Landscape Drivers of Neonicotinoid Insecticide Detections and Concentrations in Canada's Prairie Wetlands

Neonicotinoids are commonly used seed treatments on Canada's major prairie crops. Transported via surface and subsurface runoff into wetlands, their ultimate aquatic fate remains largely unknown. Biotic and abiotic wetland characteristics likely affect neonicotinoid presence and environmental persistence, but concentrations vary widely between wetlands that appear ecologically (e.g., plant composition) and physically (e.g., depth) similar for reasons that remain unclear. We conducted intensive surveys of 238 wetlands, and documented 59 wetland (e.g., dominant plant species) and landscape (e.g., surrounding crop) characteristics as part of a novel rapid wetland assessment system. We used boosted regression tree (BRT) analysis to predict both probability of neonicotinoid analytical detection and concentration. BRT models effectively predicted the deviance in neonicotinoid detection (62.4%) and concentration (74.7%) from 21 and 23 variables, respectively. Detection was best explained by shallow marsh plant species identity (34.8%) and surrounding crop (13.9%). Neonicotinoid concentration was best explained by shallow marsh plant species identity (14.9%) and wetland depth (14.2%). Our research revealed that plant composition is a key indicator and/or driver of neonicotinoid presence and concentration in Prairie wetlands. We recommend wetland buffers consisting of diverse native vegetation be retained or restored to minimize neonicotinoid transport and retention in wetlands, thereby limiting their potential effects on wetland-dependent organisms.

An Observational Study of Honey Bee Colony Winter Losses and Their Association with Varroa destructor, Neonicotinoids and Other Risk Factors

This article presents results of an analysis of honey bee losses over the winter of 2011-2012 in the Netherlands, from a sample of 86 colonies, located at 43 apiaries. The apiaries were selected using spatially stratified random sampling. Colony winter loss data were collected and related to various measures of colony strength recorded in summer, as well as data from laboratory analysis of sample material taken from two selected colonies in each of the 43 apiaries. The logistic regression model which best explained the risk of winter loss included, in order of statistical importance, the variables (1) Varroa destructor mite infestation rate in October 2011, (2) presence of the cyano-substituted neonicotinoids acetamiprid or thiacloprid in the first 2 weeks of August 2011 in at least one of the honey bee matrices honey, bees or bee bread (pollen), (3) presence of Brassica napus (oilseed rape) or Sinapis arvensis (wild mustard) pollen in bee bread in early August 2011, and (4) a measure of the unexplained winter losses for the postal code area where the colonies were located, obtained from a different dataset. We consider in the discussion that reduced opportunities for foraging in July and August because of bad weather may have added substantially to the adverse effects of acetamiprid and thiacloprid. A novel feature of this work is its use of postal code random effects from two other independent datasets collected in the annual national monitoring by questionnaires of winter losses of honey bees in the Netherlands. These were used to plan the sample selection and also in the model fitting of the data in this study. It should however be noted that the results of the present pilot study are based on limited data, which may consequently reveal strong factors but fail to demonstrate possible interaction effects.

Control of Pierce's Disease by Phage

Pierce's Disease (PD) of grapevines, caused by Xylella fastidiosa subsp. fastidiosa (Xf), is a limiting factor in the cultivation of grapevines in the US. There are presently no effective control methods to prevent or treat PD. The therapeutic and prophylactic efficacy of a phage cocktail composed of four virulent (lytic) phages was evaluated for control of PD. Xf levels in grapevines were significantly reduced in therapeutically or prophylactically treated grapevines. PD symptoms ceased to progress one week post-therapeutic treatment and symptoms were not observed in prophylactically treated grapevines. Cocktail phage levels increased in grapevines in the presence of the host. No in planta phage-resistant Xf isolates were obtained. Moreover, Xf mutants selected for phage resistance in vitro did not cause PD symptoms. Our results indicate that phages have great potential for biocontrol of PD and other economically important diseases caused by Xylella.

Isolation and Characterization of a Novel Imidacloprid-Degrading Mycobacterium sp. Strain MK6 from an Egyptian Soil

Thus far, only a small number and types of bacteria with limited ability in degrading imidacloprid have been reported. Also, genes regulating imidacloprid (IMDA) degradation have yet to be discovered. To study this in more detail, an enrichment technique was used to isolate consortia and pure cultures of IMDA-degrading bacteria. Through this approach, we successfully isolated a novel bacterium capable of completely degrading IMDA as a sole nitrogen source. The bacterium was subsequently identified as Mycobacterium sp. strain MK6 by sequence analysis of its 16S rRNA gene (Genbank accession number KR052814 ). BLASTn searches indicated that 16S rRNA gene from Mycobacterium sp. strain MK6 was 99% identical to several Mycobacterium spp. Mycobacterium sp. strain MK6 transformed 99.7% added IMDA (150 μg mL(-1)) in <2 weeks (t1/2 = 1.6 days) to 6-chloronicotinic acid (6-CNA) as its major metabolite. Although the isolated strain and mixed bacterial consortia were able to degrade IMDA, they failed to grow further on 6-CNA, indicating a lack of IMDA mineralization to carbon dioxide. Small amounts of the desnitro-olefin and desnitro-degradates of IMDA were observed during the incubation but did not accumulate in culture medium.

Neonicotinoid-Coated Zea mays Seeds Indirectly Affect Honeybee Performance and Pathogen Susceptibility in Field Trials

Thirty-two honeybee (Apis mellifera) colonies were studied in order to detect and measure potential in vivo effects of neonicotinoid pesticides used in cornfields (Zea mays spp) on honeybee health. Honeybee colonies were randomly split on four different agricultural cornfield areas located near Quebec City, Canada. Two locations contained cornfields treated with a seed-coated systemic neonicotinoid insecticide while the two others were organic cornfields used as control treatments. Hives were extensively monitored for their performance and health traits over a period of two years. Honeybee viruses (brood queen cell virus BQCV, deformed wing virus DWV, and Israeli acute paralysis virus IAPV) and the brain specific expression of a biomarker of host physiological stress, the Acetylcholinesterase gene AChE, were investigated using RT-qPCR. Liquid chromatography-mass spectrometry (LC-MS) was performed to detect pesticide residues in adult bees, honey, pollen, and corn flowers collected from the studied hives in each location. In addition, general hive conditions were assessed by monitoring colony weight and brood development. Neonicotinoids were only identified in corn flowers at low concentrations. However, honeybee colonies located in neonicotinoid treated cornfields expressed significantly higher pathogen infection than those located in untreated cornfields. AChE levels showed elevated levels among honeybees that collected corn pollen from treated fields. Positive correlations were recorded between pathogens and the treated locations. Our data suggests that neonicotinoids indirectly weaken honeybee health by inducing physiological stress and increasing pathogen loads.

Large-scale deployment of seed treatments has driven rapid increase in use of neonicotinoid insecticides and preemptive pest management in US field crops

Neonicotinoids are the most widely used class of insecticides worldwide, but patterns of their use in the U.S. are poorly documented, constraining attempts to understand their role in pest management and potential nontarget effects. We synthesized publicly available data to estimate and interpret trends in neonicotinoid use since their introduction in 1994, with a special focus on seed treatments, a major use not captured by the national pesticide-use survey. Neonicotinoid use increased rapidly between 2003 and 2011, as seed-applied products were introduced in field crops, marking an unprecedented shift toward large-scale, preemptive insecticide use: 34-44% of soybeans and 79-100% of maize hectares were treated in 2011. This finding contradicts recent analyses, which concluded that insecticides are used today on fewer maize hectares than a decade or two ago. If current trends continue, neonicotinoid use will increase further through application to more hectares of soybean and other crop species and escalation of per-seed rates. Alternatively, our results, and other recent analyses, suggest that carefully targeted efforts could considerably reduce neonicotinoid use in field crops without yield declines or economic harm to farmers, reducing the potential for pest resistance, nontarget pest outbreaks, environmental contamination, and harm to wildlife, including pollinator species.

Neonicotinoid insecticide residues in surface water and soil associated with commercial maize (corn) fields in southwestern Ontario

Neonicotinoid insecticides have come under scrutiny for their potential unintended effects on non-target organisms, particularly pollinators in agro-ecosystems. As part of a larger study of neonicotinoid residues associated with maize (corn) production, 76 water samples within or around the perimeter of 18 commercial maize fields and neighbouring apiaries were collected in 5 maize-producing counties of southwestern Ontario. Residues of clothianidin (mean = 2.28, max. = 43.60 ng/mL) and thiamethoxam (mean = 1.12, max. = 16.50 ng/mL) were detected in 100 and 98.7% of the water samples tested, respectively. The concentration of total neonicotinoid residues in water within maize fields increased six-fold during the first five weeks after planting, and returned to pre-plant levels seven weeks after planting. However, concentrations in water sampled from outside the fields were similar throughout the sampling period. Soil samples from the top 5 cm of the soil profile were also collected in these fields before and immediately following planting. The mean total neonicotinoid residue was 4.02 (range 0.07 to 20.30) ng/g, for samples taken before planting, and 9.94 (range 0.53 to 38.98) ng/g, for those taken immediately after planting. Two soil samples collected from within an conservation area contained detectable (0.03 and 0.11 ng/g) concentrations of clothianidin. Of three drifted snow samples taken, the drift stratum containing the most wind-scoured soil had 0.16 and 0.20 ng/mL mainly clothianidin in the melted snow. The concentration was at the limit of detection (0.02 ng/mL) taken across the entire vertical profile. With the exception of one sample, water samples tested had concentrations below those reported to have acute, chronic or sublethal effects to honey bees. Our results suggest that neonicotinoids may move off-target by wind erosion of contaminated soil. These results are informative to risk assessment models for other non-target species in maize agro-ecosytems.

Oxidative stress and DNA damage induced by imidacloprid in zebrafish (Danio rerio)

Imidacloprid is a neonicotinoid insecticide that can have negative effects on nontarget animals. The present study was conducted to assess the toxicity of various imidacloprid doses (0.3, 1.25, and 5 mg/mL) on zebrafish sampled after 7, 14, 21, and 28 days of exposure. The levels of catalase (CAT), superoxide dismutase (SOD), reactive oxygen species (ROS), glutathione-S-transferase (GST), and malondialdehyde (MDA) and the extent of DNA damage were measured to evaluate the toxicity of imidacloprid on zebrafish. SOD and GST activities were noticeably increased during early exposure but were inhibited toward the end of the exposure period. In addition, the CAT levels decreased to the control level following their elevation during early exposure. High concentrations of imidacloprid (1.25 and 5 mg/L) induced excessive ROS production and markedly increased MDA content on the 21st day of exposure. DNA damage was dose- and time-dependent. In conclusion, the present study showed that imidacloprid can induce oxidative stress and DNA damage in zebrafish.

Neonicotinoids in the Canadian aquatic environment: a literature review on current use products with a focus on fate, exposure, and biological effects

Developed to replace organophosphate and carbamate insecticides, neonicotinoids are structurally similar to nicotine. The three main neonicotinoid insecticides, imidacloprid, clothianidin, and thiamethoxam, are being re-evaluated by Health Canada's Pest Management Regulatory Agency (PMRA). An important aspect of the re-evaluation is the potential for effects in non-target organisms, including aquatic organisms. Leaching into surface waters is one of the major concerns surrounding extensive use of neonicotinoids, especially in close proximity to water bodies. The PMRA has classified IMI as 'persistent' with a 'high' leaching potential. Globally, neonicotinoids have been detected in a variety of water bodies, typically at concentrations in the low μg/L range. While IMI has been included in some monitoring exercises, there are currently very few published data for the presence of CLO and THM in Canadian water bodies. The majority of neonicotinoid toxicity studies have been conducted with IMI due to its longer presence on the market and high prevalence of use. Aquatic insects are particularly vulnerable to neonicotinoids and chronic toxicity has been observed at concentrations of IMI below 1 μg/L. Acute toxicity has been reported at concentrations below 20 μg/L for the most sensitive species, including Hyalella azteca, ostracods, and Chironomus riparius. Fish, algae, amphibians, and molluscs are relatively insensitive to IMI. However, the biological effects of THM and CLO have not been as well explored. The Canadian interim water quality guideline for IMI is 0.23 μg/L, but there is currently insufficient use, fate, and toxicological information available to establish guidelines for CLO and THM. Based on concentrations of neonicotinoids reported in surface waters in Canada and globally, there is potential for aquatic invertebrates to be negatively impacted by neonicotinoids. Therefore, it is necessary to address knowledge gaps to inform decisions around guidelines and registration status for neonicotinoid insecticides in Canada to protect our aquatic ecosystems.

A review of the direct and indirect effects of neonicotinoids and fipronil on vertebrate wildlife

Concerns over the role of pesticides affecting vertebrate wildlife populations have recently focussed on systemic products which exert broad-spectrum toxicity. Given that the neonicotinoids have become the fastest-growing class of insecticides globally, we review here 150 studies of their direct (toxic) and indirect (e.g. food chain) effects on vertebrate wildlife--mammals, birds, fish, amphibians and reptiles. We focus on two neonicotinoids, imidacloprid and clothianidin, and a third insecticide, fipronil, which also acts in the same systemic manner. Imidacloprid and fipronil were found to be toxic to many birds and most fish, respectively. All three insecticides exert sub-lethal effects, ranging from genotoxic and cytotoxic effects, and impaired immune function, to reduced growth and reproductive success, often at concentrations well below those associated with mortality. Use of imidacloprid and clothianidin as seed treatments on some crops poses risks to small birds, and ingestion of even a few treated seeds could cause mortality or reproductive impairment to sensitive bird species. In contrast, environmental concentrations of imidacloprid and clothianidin appear to be at levels below those which will cause mortality to freshwater vertebrates, although sub-lethal effects may occur. Some recorded environmental concentrations of fipronil, however, may be sufficiently high to harm fish. Indirect effects are rarely considered in risk assessment processes and there is a paucity of data, despite the potential to exert population-level effects. Our research revealed two field case studies of indirect effects. In one, reductions in invertebrate prey from both imidacloprid and fipronil uses led to impaired growth in a fish species, and in another, reductions in populations in two lizard species were linked to effects of fipronil on termite prey. Evidence presented here suggests that the systemic insecticides, neonicotinoids and fipronil, are capable of exerting direct and indirect effects on terrestrial and aquatic vertebrate wildlife, thus warranting further review of their environmental safety.

Neonicotinoid contamination of global surface waters and associated risk to aquatic invertebrates: a review

Neonicotinoids, broad-spectrum systemic insecticides, are the fastest growing class of insecticides worldwide and are now registered for use on hundreds of field crops in over 120 different countries. The environmental profile of this class of pesticides indicate that they are persistent, have high leaching and runoff potential, and are highly toxic to a wide range of invertebrates. Therefore, neonicotinoids represent a significant risk to surface waters and the diverse aquatic and terrestrial fauna that these ecosystems support. This review synthesizes the current state of knowledge on the reported concentrations of neonicotinoids in surface waters from 29 studies in 9 countries world-wide in tandem with published data on their acute and chronic toxicity to 49 species of aquatic insects and crustaceans spanning 12 invertebrate orders. Strong evidence exists that water-borne neonicotinoid exposures are frequent, long-term and at levels (geometric means=0.13μg/L (averages) and 0.63μg/L (maxima)) which commonly exceed several existing water quality guidelines. Imidacloprid is by far the most widely studied neonicotinoid (66% of the 214 toxicity tests reviewed) with differences in sensitivity among aquatic invertebrate species ranging several orders of magnitude; other neonicotinoids display analogous modes of action and similar toxicities, although comparative data are limited. Of the species evaluated, insects belonging to the orders Ephemeroptera, Trichoptera and Diptera appear to be the most sensitive, while those of Crustacea (although not universally so) are less sensitive. In particular, the standard test species Daphnia magna appears to be very tolerant, with 24-96hour LC50 values exceeding 100,000μg/L (geometric mean>44,000μg/L), which is at least 2-3 orders of magnitude higher than the geometric mean of all other invertebrate species tested. Overall, neonicotinoids can exert adverse effects on survival, growth, emergence, mobility, and behavior of many sensitive aquatic invertebrate taxa at concentrations at or below 1μg/L under acute exposure and 0.1μg/L for chronic exposure. Using probabilistic approaches (species sensitivity distributions), we recommend here that ecological thresholds for neonicotinoid water concentrations need to be below 0.2μg/L (short-term acute) or 0.035μg/L (long-term chronic) to avoid lasting effects on aquatic invertebrate communities. The application of safety factors may still be warranted considering potential issues of slow recovery, additive or synergistic effects and multiple stressors that can occur in the field. Our analysis revealed that 81% (22/27) and 74% (14/19) of global surface water studies reporting maximum and average individual neonicotinoid concentrations respectively, exceeded these thresholds of 0.2 and 0.035μg/L. Therefore, it appears that environmentally relevant concentrations of neonicotinoids in surface waters worldwide are well within the range where both short- and long-term impacts on aquatic invertebrate species are possible over broad spatial scales.

Risks of large-scale use of systemic insecticides to ecosystem functioning and services

Large-scale use of the persistent and potent neonicotinoid and fipronil insecticides has raised concerns about risks to ecosystem functions provided by a wide range of species and environments affected by these insecticides. The concept of ecosystem services is widely used in decision making in the context of valuing the service potentials, benefits, and use values that well-functioning ecosystems provide to humans and the biosphere and, as an endpoint (value to be protected), in ecological risk assessment of chemicals. Neonicotinoid insecticides are frequently detected in soil and water and are also found in air, as dust particles during sowing of crops and aerosols during spraying. These environmental media provide essential resources to support biodiversity, but are known to be threatened by long-term or repeated contamination by neonicotinoids and fipronil. We review the state of knowledge regarding the potential impacts of these insecticides on ecosystem functioning and services provided by terrestrial and aquatic ecosystems including soil and freshwater functions, fisheries, biological pest control, and pollination services. Empirical studies examining the specific impacts of neonicotinoids and fipronil to ecosystem services have focused largely on the negative impacts to beneficial insect species (honeybees) and the impact on pollination service of food crops. However, here we document broader evidence of the effects on ecosystem functions regulating soil and water quality, pest control, pollination, ecosystem resilience, and community diversity. In particular, microbes, invertebrates, and fish play critical roles as decomposers, pollinators, consumers, and predators, which collectively maintain healthy communities and ecosystem integrity. Several examples in this review demonstrate evidence of the negative impacts of systemic insecticides on decomposition, nutrient cycling, soil respiration, and invertebrate populations valued by humans. Invertebrates, particularly earthworms that are important for soil processes, wild and domestic insect pollinators which are important for plant and crop production, and several freshwater taxa which are involved in aquatic nutrient cycling, were all found to be highly susceptible to lethal and sublethal effects of neonicotinoids and/or fipronil at environmentally relevant concentrations. By contrast, most microbes and fish do not appear to be as sensitive under normal exposure scenarios, though the effects on fish may be important in certain realms such as combined fish-rice farming systems and through food chain effects. We highlight the economic and cultural concerns around agriculture and aquaculture production and the role these insecticides may have in threatening food security. Overall, we recommend improved sustainable agricultural practices that restrict systemic insecticide use to maintain and support several ecosystem services that humans fundamentally depend on.

Effects of neonicotinoids and fipronil on non-target invertebrates

We assessed the state of knowledge regarding the effects of large-scale pollution with neonicotinoid insecticides and fipronil on non-target invertebrate species of terrestrial, freshwater and marine environments. A large section of the assessment is dedicated to the state of knowledge on sublethal effects on honeybees (Apis mellifera) because this important pollinator is the most studied non-target invertebrate species. Lepidoptera (butterflies and moths), Lumbricidae (earthworms), Apoidae sensu lato (bumblebees, solitary bees) and the section "other invertebrates" review available studies on the other terrestrial species. The sections on freshwater and marine species are rather short as little is known so far about the impact of neonicotinoid insecticides and fipronil on the diverse invertebrate fauna of these widely exposed habitats. For terrestrial and aquatic invertebrate species, the known effects of neonicotinoid pesticides and fipronil are described ranging from organismal toxicology and behavioural effects to population-level effects. For earthworms, freshwater and marine species, the relation of findings to regulatory risk assessment is described. Neonicotinoid insecticides exhibit very high toxicity to a wide range of invertebrates, particularly insects, and field-realistic exposure is likely to result in both lethal and a broad range of important sublethal impacts. There is a major knowledge gap regarding impacts on the grand majority of invertebrates, many of which perform essential roles enabling healthy ecosystem functioning. The data on the few non-target species on which field tests have been performed are limited by major flaws in the outdated test protocols. Despite large knowledge gaps and uncertainties, enough knowledge exists to conclude that existing levels of pollution with neonicotinoids and fipronil resulting from presently authorized uses frequently exceed the lowest observed adverse effect concentrations and are thus likely to have large-scale and wide ranging negative biological and ecological impacts on a wide range of non-target invertebrates in terrestrial, aquatic, marine and benthic habitats.

Environmental fate and exposure; neonicotinoids and fipronil

Systemic insecticides are applied to plants using a wide variety of methods, ranging from foliar sprays to seed treatments and soil drenches. Neonicotinoids and fipronil are among the most widely used pesticides in the world. Their popularity is largely due to their high toxicity to invertebrates, the ease and flexibility with which they can be applied, their long persistence, and their systemic nature, which ensures that they spread to all parts of the target crop. However, these properties also increase the probability of environmental contamination and exposure of nontarget organisms. Environmental contamination occurs via a number of routes including dust generated during drilling of dressed seeds, contamination and accumulation in arable soils and soil water, runoff into waterways, and uptake of pesticides by nontarget plants via their roots or dust deposition on leaves. Persistence in soils, waterways, and nontarget plants is variable but can be prolonged; for example, the half-lives of neonicotinoids in soils can exceed 1,000 days, so they can accumulate when used repeatedly. Similarly, they can persist in woody plants for periods exceeding 1 year. Breakdown results in toxic metabolites, though concentrations of these in the environment are rarely measured. Overall, there is strong evidence that soils, waterways, and plants in agricultural environments and neighboring areas are contaminated with variable levels of neonicotinoids or fipronil mixtures and their metabolites (soil, parts per billion (ppb)-parts per million (ppm) range; water, parts per trillion (ppt)-ppb range; and plants, ppb-ppm range). This provides multiple routes for chronic (and acute in some cases) exposure of nontarget animals. For example, pollinators are exposed through direct contact with dust during drilling; consumption of pollen, nectar, or guttation drops from seed-treated crops, water, and consumption of contaminated pollen and nectar from wild flowers and trees growing near-treated crops. Studies of food stores in honeybee colonies from across the globe demonstrate that colonies are routinely and chronically exposed to neonicotinoids, fipronil, and their metabolites (generally in the 1-100 ppb range), mixed with other pesticides some of which are known to act synergistically with neonicotinoids. Other nontarget organisms, particularly those inhabiting soils, aquatic habitats, or herbivorous insects feeding on noncrop plants in farmland, will also inevitably receive exposure, although data are generally lacking for these groups. We summarize the current state of knowledge regarding the environmental fate of these compounds by outlining what is known about the chemical properties of these compounds, and placing these properties in the context of modern agricultural practices.

Neonicotinoid-contaminated puddles of water represent a risk of intoxication for honey bees

In recent years, populations of honey bees and other pollinators have been reported to be in decline worldwide. A number of stressors have been identified as potential contributing factors, including the extensive prophylactic use of neonicotinoid insecticides, which are highly toxic to bees, in agriculture. While multiple routes of exposure to these systemic insecticides have been documented for honey bees, contamination from puddle water has not been investigated. In this study, we used a multi-residue method based on LC-MS/MS to analyze samples of puddle water taken in the field during the planting of treated corn and one month later. If honey bees were to collect and drink water from these puddles, our results showed that they would be exposed to various agricultural pesticides. All water samples collected from corn fields were contaminated with at least one neonicotinoid compound, although most contained more than one systemic insecticide. Concentrations of neonicotinoids were higher in early spring, indicating that emission and drifting of contaminated dust during sowing raises contamination levels of puddles. Although the overall average acute risk of drinking water from puddles was relatively low, concentrations of neonicotinoids ranged from 0.01 to 63 µg/L and were sufficient to potentially elicit a wide array of sublethal effects in individuals and colony alike. Our results also suggest that risk assessment of honey bee water resources underestimates the foragers' exposure and consequently miscalculates the risk. In fact, our data shows that honey bees and native pollinators are facing unprecedented cumulative exposure to these insecticides from combined residues in pollen, nectar and water. These findings not only document the impact of this route of exposure for honey bees, they also have implications for the cultivation of a wide variety of crops for which the extensive use of neonicotinoids is currently promoted.

Widespread occurrence of neonicotinoid insecticides in streams in a high corn and soybean producing region, USA

Neonicotinoid insecticides are of environmental concern, but little is known about their occurrence in surface water. An area of intense corn and soybean production in the Midwestern United States was chosen to study this issue because of the high agricultural use of neonicotinoids via both seed treatments and other forms of application. Water samples were collected from nine stream sites during the 2013 growing season. The results for the 79 water samples documented similar patterns among sites for both frequency of detection and concentration (maximum:median) with clothianidin (75%, 257 ng/L:8.2 ng/L) > thiamethoxam (47%, 185 ng/L:<2 ng/L) > imidacloprid (23%, 42.7 ng/L: <2 ng/L). Neonicotinoids were detected at all nine sites sampled even though the basin areas spanned four orders of magnitude. Temporal patterns in concentrations reveal pulses of neonicotinoids associated with rainfall events during crop planting, suggesting seed treatments as their likely source.

How a complete pesticide screening changes the assessment of surface water quality

A comprehensive assessment of pesticides in surface waters is challenging due to the large number of potential contaminants. Most scientific studies and routine monitoring programs include only 15-40 pesticides, which leads to error-prone interpretations. In the present study, an extensive analytical screening was carried out using liquid chromatography-high-resolution mass spectrometry, covering 86% of all polar organic pesticides sold in Switzerland and applied to agricultural or urban land (in total 249 compounds), plus 134 transformation products; each of which could be quantified in the low ng/L range. Five medium-sized rivers, containing large areas of diverse crops and urban settlements within the respective catchments, were sampled between March and July 2012. More than 100 parent compounds and 40 transformation products were detected in total, between 30 and 50 parent compounds in each two-week composite sample in concentrations up to 1500 ng/L. The sum of pesticide concentrations was above 1000 ng/L in 78% of samples. The chronic environmental quality standard was exceeded for 19 single substances; using a mixture toxicity approach, exceedances occurred over the whole measurement period in all rivers. With scenario calculations including only 30-40 frequently measured pesticides, the number of detected substances and the mixture toxicity would be underestimated on average by a factor of 2. Thus, selecting a subset of substances to assess the surface water quality may be sufficient, but a comprehensive screening yields substantially more confidence.

Requiring pollutant discharge permits for pesticide applications that deposit residues in surface waters

Agricultural producers and public health authorities apply pesticides to control pests that damage crops and carry diseases. Due to the toxic nature of most pesticides, they are regulated by governments. Regulatory provisions require pesticides to be registered and restrictions operate to safeguard human health and the environment. Yet pesticides used near surface waters pose dangers to non-target species and drinking water supplies leading some governments to regulate discharges of pesticides under pollution discharge permits. The dual registration and discharge permitting provisions are burdensome. In the United States, agricultural interest groups are advancing new legislation that would exempt pesticide residues from water permitting requirements. An analysis of the dangers posed by pesticide residues in drinking water leads to a conclusion that both pesticide registration and pollutant discharge permitting provisions are needed to protect human health and aquatic species.

Widespread use and frequent detection of neonicotinoid insecticides in wetlands of Canada's Prairie Pothole Region

Neonicotinoids currently dominate the insecticide market as seed treatments on Canada's major Prairie crops (e.g., canola). The potential impact to ecologically significant wetlands in this dominantly agro-environment has largely been overlooked while the distribution of use, incidence and level of contamination remains unreported. We modelled the spatial distribution of neonicotinoid use across the three Prairie Provinces in combination with temporal assessments of water and sediment concentrations in wetlands to measure four active ingredients (clothianidin, thiamethoxam, imidacloprid and acetamiprid). From 2009 to 2012, neonicotinoid use was increasing; by 2012, applications covered an estimated ∼11 million hectares (44% of Prairie cropland) with >216,000 kg of active ingredients. Thiamethoxam, followed by clothianidin, were the dominant seed treatments by mass and area. Areas of high neonicotinoid use were identified as high density canola or soybean production. Water sampled four times from 136 wetlands (spring, summer, fall 2012 and spring 2013) across four rural municipalities in Saskatchewan similarly revealed clothianidin and thiamethoxam in the majority of samples. In spring 2012 prior to seeding, 36% of wetlands contained at least one neonicotinoid. Detections increased to 62% in summer 2012, declined to 16% in fall, and increased to 91% the following spring 2013 after ice-off. Peak concentrations were recorded during summer 2012 for both thiamethoxam (range: <LOQ - 1490 ng/L, canola) and clothianidin (range: <LOQ – 3110 ng/L, canola). Sediment samples collected during the same period rarely (6%) contained neonicotinoid concentrations (which did not exceed 20 ng/L). Wetlands situated in barley, canola and oat fields consistently contained higher mean concentrations of neonicotinoids than in grasslands, but no individual crop singularly influenced overall detections or concentrations. Distribution maps indicate neonicotinoid use is increasing and becoming more widespread with concerns for environmental loading, while frequently detected neonicotinoid concentrations in Prairie wetlands suggest high persistence and transport into wetlands.

Detection and analysis of neonicotinoids in river waters--development of a passive sampler for three commonly used insecticides

Increasing and widespread use of neonicotinoid insecticides all over the world, together with their environmental persistence mean that surface and ground waters need to be monitored regularly for their residues. However, current multi-residue analytical methods for waters are inadequate for trace residue analysis of these compounds, while passive sampling devices are unavailable. A new method using UltraPerformance Liquid Chromatography provided good separation of the five most common neonicotinoid compounds, with limits of quantitation in the range 0.6-1.0ng. The method was tested in a survey of rivers around Sydney (Australia), where 93% of samples contained two or more neonicotinoids in the range 0.06-4.5μgL(-1). Styrenedivinylbenzene-reverse phase sulfonated Empore™ disks were selected as the best matrix for use in passive samplers. Uptake of clothianidin, imidacloprid and thiacloprid in a flow-through laboratory system for 3weeks was linear and proportional to their water concentrations over the range 1-10μgL(-1). Sampling rates of 8-15mLd(-1) were correlated to the hydrophobicity of the individual compounds. The passive samplers and analytical methods presented here can detect trace concentrations of neonicotinoids in water.

Macro-invertebrate decline in surface water polluted with imidacloprid: a rebuttal and some new analyses

Imidacloprid, the largest selling insecticide in the world, has received particular attention from scientists, policymakers and industries due to its potential toxicity to bees and aquatic organisms. The decline of aquatic macro-invertebrates due to imidacloprid concentrations in the Dutch surface waters was hypothesised in a recent paper by Van Dijk, Van Staalduinen and Van der Sluijs (PLOS ONE, May 2013). Although we do not disagree with imidacloprid's inherent toxicity to aquatic organisms, we have fundamental concerns regarding the way the data were analysed and interpreted. Here, we demonstrate that the underlying toxicity of imidacloprid in the field situation cannot be understood except in the context of other co-occurring pesticides. Although we agree with Van Dijk and co-workers that effects of imidacloprid can emerge between 13 and 67 ng/L we use a different line of evidence. We present an alternative approach to link imidacloprid concentrations and biological data. We analysed the national set of chemical monitoring data of the year 2009 to estimate the relative contribution of imidacloprid compared to other pesticides in relation to environmental quality target and chronic ecotoxicity threshold exceedances. Moreover, we assessed the relative impact of imidacloprid on the pesticide-induced potential affected fractions of the aquatic communities. We conclude that by choosing to test a starting hypothesis using insufficient data on chemistry and biology that are difficult to link, and by ignoring potential collinear effects of other pesticides present in Dutch surface waters Van Dijk and co-workers do not provide direct evidence that reduced taxon richness and abundance of macroinvertebrates can be attributed to the presence of imidacloprid only. Using a different line of evidence we expect ecological effects of imidacloprid at some of the exposure profiles measured in 2009 in the surface waters of the Netherlands.

Widespread use and frequent detection of neonicotinoid insecticides in wetlands of Canada's Prairie Pothole Region

Neonicotinoids currently dominate the insecticide market as seed treatments on Canada's major Prairie crops (e.g., canola). The potential impact to ecologically significant wetlands in this dominantly agro-environment has largely been overlooked while the distribution of use, incidence and level of contamination remains unreported. We modelled the spatial distribution of neonicotinoid use across the three Prairie Provinces in combination with temporal assessments of water and sediment concentrations in wetlands to measure four active ingredients (clothianidin, thiamethoxam, imidacloprid and acetamiprid). From 2009 to 2012, neonicotinoid use was increasing; by 2012, applications covered an estimated ∼11 million hectares (44% of Prairie cropland) with >216,000 kg of active ingredients. Thiamethoxam, followed by clothianidin, were the dominant seed treatments by mass and area. Areas of high neonicotinoid use were identified as high density canola or soybean production. Water sampled four times from 136 wetlands (spring, summer, fall 2012 and spring 2013) across four rural municipalities in Saskatchewan similarly revealed clothianidin and thiamethoxam in the majority of samples. In spring 2012 prior to seeding, 36% of wetlands contained at least one neonicotinoid. Detections increased to 62% in summer 2012, declined to 16% in fall, and increased to 91% the following spring 2013 after ice-off. Peak concentrations were recorded during summer 2012 for both thiamethoxam (range: <LOQ--1490 ng/L, canola) and clothianidin (range: <LOQ--3110 ng/L, canola). Sediment samples collected during the same period rarely (6%) contained neonicotinoid concentrations (which did not exceed 20 ng/L). Wetlands situated in barley, canola and oat fields consistently contained higher mean concentrations of neonicotinoids than in grasslands, but no individual crop singularly influenced overall detections or concentrations. Distribution maps indicate neonicotinoid use is increasing and becoming more widespread with concerns for environmental loading, while frequently detected neonicotinoid concentrations in Prairie wetlands suggest high persistence and transport into wetlands.

A horizon scan of global conservation issues for 2014

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This is the fifth in our annual series of horizon scans published in TREE.

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We identify 15 issues that we considered insufficiently known by the conservation community.

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These cover a wide range of issues. Four relate to climate change, two to invasives and two to disease spread.

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This exercise has been influential in the past.

This paper presents the output of our fifth annual horizon-scanning exercise, which aims to identify topics that increasingly may affect conservation of biological diversity, but have yet to be widely considered. A team of professional horizon scanners, researchers, practitioners, and a journalist identified 15 topics which were identified via an iterative, Delphi-like process. The 15 topics include a carbon market induced financial crash, rapid geographic expansion of macroalgal cultivation, genetic control of invasive species, probiotic therapy for amphibians, and an emerging snake fungal disease.

Preliminary aquatic risk assessment of imidacloprid after application in an experimental rice plot

The potential aquatic risk of application of the neonicotinoid insecticide imidacloprid for aphid control in rice was assessed. To this end, imidacloprid was applied as Confidor(®) 200 SC at the recommended field dose of 100g a.i./ha to a Portuguese rice plot. Subsequently, fate of the test compound in water and potential effects of water samples on a battery of test species were determined. As compared to the first-tier predicted environmental concentrations (PECs) calculated using MED-Rice (around 30µg/L depending on the scenario used) and US-EPA (78µg/L) simulations, the actual peak concentration measured in the paddy water (52µg/L) was higher and lower, respectively. As was anticipated based on 50% effect concentrations (EC50 values) for Daphnia magna published in the open literature and that calculated in the present study (48h-EC50 immobility=84mg/L), no effects were observed of field water samples on daphnids. The sediment-dwelling ostracod Heterocypris incongruens, however, appeared relatively sensitive towards imidacloprid (6d-EC50 growth inhibition=0.01-0.015mg/L) and a slight effect was indeed noted in field samples taken the first week after application. Species sensitivity distributions based on published EC50 and NOEC values also revealed that other species are likely to be affected at the peak and time-weighted average imidacloprid concentrations, respectively. By applying the relative tolerance approach (i.e. by dividing the EC50 value of a certain species with that of Daphnia magna), ostracods appear to contain the most sensitive taxa to imidacloprid, followed by EPT (Ephemeroptera, Plecoptera and Trichoptera) taxa. Future field studies into (higher-tier) fate modelling of pesticides in rice paddies and effect assessment on field communities are required to ensure protection of aquatic life and wildlife (e.g. birds) from pesticide stress.

Alleviating the reference standard dilemma using a systematic exact mass suspect screening approach with liquid chromatography-high resolution mass spectrometry

In this study, the efficiency of a suspect screening strategy using liquid chromatography-high resolution mass spectrometry (LC-HRMS) without the prior purchase of reference standards was systematically optimized and evaluated for assessing the exposure of rarely investigated pesticides and their transformation products (TPs) in 76 surface water samples. Water-soluble and readily ionizable (electrospray ionization) substances, 185 in total, were selected from a list of all insecticides and fungicides registered in Switzerland and their major TPs. Initially, a solid phase extraction-LC-HRMS method was established using 45 known, persistent, and high sales volume pesticides. Seventy percent of these target substances had limit of quantitation (LOQ) < 5 ng L(-1). This compound set was then used to develop and optimize a HRMS suspect screening method using only the exact mass as a priori information. Thresholds for blank subtraction, peak area, peak shape, signal-to-noise, and isotopic pattern were applied to automatically filter the initially picked peaks. The success rate was 70%; false negatives mainly resulted from low intense peaks. The optimized approach was applied to the remaining 140 substances. Nineteen additional substances were detected in environmental samples, two TPs for the first time in the environment. Sixteen substances were confirmed with reference standards purchased subsequently, while three TP standards could be obtained from industry or other laboratories. Overall, this screening approach was fast and very successful and can easily be expanded to other micropollutant classes for which reference standards are not readily accessible such as TPs of household chemicals.