Culmination of low-dose pesticide effects

A systems-based analysis to rethink the European environmental risk assessment of regulated chemicals using pesticides as a pilot case

A growing body of scientific literature stresses the need to advance current environmental risk assessment (ERA) methodologies and associated regulatory frameworks to better address the landscape-scale and long-term impact of pesticide use on biodiversity and the ecosystem. Moreover, more collaborative and integrative approaches are needed to meet sustainability goals. The One Health approach is increasingly applied by the European Food Safety Authority (EFSA) to support the transition towards safer, healthier and more sustainable food. To this end, EFSA commissioned the development of a roadmap for action to establish a European Partnership for next-generation, systems-based Environmental Risk Assessment (PERA). Here, we summarise the main conclusions and recommendations reported in the 2022 PERA Roadmap. This roadmap highlights that fragmentation of data, knowledge and expertise across regulatory sectors results in suboptimal processes and hinders the implementation of integrative ERA approaches needed to better protect the environment. To advance ERA, we revisited the underlying assumptions of the current ERA paradigm; that chemical risks are generally assessed and managed in isolation with a substance-by-substance, realistic worst-case and tiered approach. We suggest optimising the use of the vast amount of information and expertise available with pesticides as a pilot area. It is recommended to as soon as possible adopt a systems-based approach, i.e. within the current regulatory framework, to spark a step-wise transition towards an ERA framed at a system level of ecological and societal relevance. Tangible systems-based and integrative steps are available. For instance, the rich sources of existing data for prospective and retrospective ERA of pesticides could be used to reality-benchmark existing and new ERA methods. To achieve these goals, collaboration among stakeholders across scientific disciplines and regulatory sectors must be strengthened.

Predicting the Combined Effects of Multiple Stressors and Stress Adaptation in Gammarus pulex

Global change confronts organisms with multiple stressors causing nonadditive effects. Persistent stress, however, leads to adaptation and related trade-offs. The question arises: How can the resulting effects of these contradictory processes be predicted? Here we show that Gammarus pulex from agricultural streams were more tolerant to clothianidin (mean EC50 148 μg/L) than populations from reference streams (mean EC50 67 μg/L). We assume that this increased tolerance results from a combination of physiological acclimation, epigenetic effects, and genetic evolution, termed as adaptation. Further, joint exposure to pesticide mixture and temperature stress led to synergistic interactions of all three stressors. However, these combined effects were significantly stronger in adapted populations as shown by the model deviation ratio (MDR) of 4, compared to reference populations (MDR = 2.7). The pesticide adaptation reduced the General-Stress capacity of adapted individuals, and the related trade-off process increased vulnerability to combined stress. Overall, synergistic interactions were stronger with increasing total stress and could be well predicted by the stress addition model (SAM). In contrast, traditional models such as concentration addition (CA) and effect addition (EA) substantially underestimated the combined effects. We conclude that several, even very disparate stress factors, including population adaptations to stress, can act synergistically. The strong synergistic potential underscores the critical importance of correctly predicting multiple stresses for risk assessment.

Revealing the cascade of pesticide effects from gene to community

Global pesticide exposure in agriculture leads to biodiversity loss, even at ultra-low concentrations below the legal limits. The mechanisms by which the effects of toxicants act at such low concentrations are still unclear, particularly in relation to their propagation across the different biological levels. In this study, we demonstrate, for the first time, a cascade of effects from the gene to the community level. At the gene level, agricultural pesticide exposure resulted in reduced genetic diversity of field-collected Gammarus pulex, a dominant freshwater crustacean in Europe. Additionally, we identified alleles associated with adaptations to pesticide contamination. At the individual level, this genetic adaptation to pesticides was linked to a lower fecundity, indicating related fitness costs. At the community level, the combined effect of pesticides and competitors caused a decline in the overall number and abundance of pesticides susceptible macroinvertebrate competing with gammarids. The resulting reduction in interspecific competition provided an advantage for pesticide-adapted G. pulex to dominate macroinvertebrate communities in contaminated areas, despite their reduced fitness due to adaptation. These processes demonstrate the complex cascade of effects, and also illustrate the resilience and adaptability of biological systems across organisational levels to meet the challenges of a changing environment.

Passive sampling of herbicides above sediments at sites with losses of submerged macrophytes in a mesotrophic lake

Declines of submerged macrophytes (SUM) were monitored in littoral zones of the deep, mesotrophic lake Suhrer See (Northern Germany) since 2017. Drastic losses coincided with intense agriculture in sandy sub-catchments and precipitation. All lines of evidence pointed to a causal connection with subsurface discharge indicating that herbicide application might have caused the effects. Passive sampling was applied in 2022 to elucidate, whether herbicides were really present at sites of losses and if so, in ecotoxicological relevant concentrations. Samplers were exposed on top of lake sediments in 2 m depth and under worst case conditions, i.e., at sites, known for losses of the whole functional group of SUM and at the beginning of the vegetation period. At this time, SUM diaspores were most vulnerable to repression of development and the subsurface discharge was high in the same instance. The potential ecotoxicological relevance of detected herbicide concentrations was assessed with a toxic units (TU) approach, with reference to acute effect concentrations (EC50 of green algae, 72 h, growth). The TU ranged from 0.001 to 0.03. Most concentrations exceeded the threshold of relevance set by an assessment factor of 1000, i.e., TU > 0.001. Locally applied herbicides acted by suppressing developmental stages, and the sum of TU exceeded 0.02 at all sites, mainly due to diflufenican. Not applied locally, terbuthylazine and its relevant metabolites, including terbutryn, acted by inhibiting photosynthesis, and the sum of TU reached 0.005. On this base, diflufenican was assessed to be likely a main stressor, all other detected herbicides to be potentially relevant. Uncertainties and knowledge gaps were specified. The result of the chemical risk assessment was counterchecked for consistence with biological monitoring data within a whole lake perspective. Concepts of empirical and advanced causal attribution methodology were applied to get a grip to the ecological causal field and to protection.

Latent pesticide effects and their mechanisms

Short pulses of toxicants can cause latent effects that occur long after the contamination event and are currently unpredictable. Here, we introduce an analytical framework for mechanistically predicting latent effects considering interactive effects of multiple stressors and hormetic effect compensation. We conducted an extensive investigation using high temporal resolution microcosm data of the mayfly Cloeon dipterum exposed to the pyrethroid pesticide esfenvalerate for 1 h. For 6 pesticide concentrations and 3 food levels we identified daily general stress information and predicted their synergistic interactions using the Stress Addition Model (SAM). Our analysis revealed that, especially at low concentrations, latent effects contributed most to the overall effect. At low concentrations ranging from 1/100 to 1/10,000 of the acute LC50, resulting in a 30-15 % mortality, latent effects prevailed, accounting for 92 % to 100 % of the observed effects. Notably, the concentration causing 15 % mortality 29 days post-exposure was 1000 times lower than the concentration causing the same mortality 4 days post-exposure, emphasizing the time-dependent nature of this Latent-Effect-Amplification (LEA). We identified both acute mortality and latent effects of pesticides on emergence. Furthermore, we observed pesticide-induced compensation mechanisms at both individual and population levels, transforming the initial monotonic concentration-response relationship into a hormetic, tri-phasic response pattern. Combining these processes enabled a quantification of the underlying causes of latent effects. Our findings highlight that short-term pesticide exposures can lead to latent effects of particular significance, especially at low effect concentrations.

Ultra-low esfenvalerate exposure may disrupt interspecific competition

Field and mesocosm studies repeatedly show that higher tier processes reduce the predictive accuracy of toxicity evaluation and thus their value for pesticide risk assessment. Therefore, understanding the influence of ecological complexity on toxicant effects is crucial to improve realism of aquatic risk assessment. Here we investigate the influence of repeated exposure to ecologically realistic concentrations of esfenvalerate on the two similarly sensitive species Daphnia magna and Culex pipiens in a food limited and highly competitive environment. We show that significant perturbations in population development are only present at 100 ng/L (close to the EC50). In contrast, interspecific competition between species is already reduced at 0.1 ng/L (≤ 3 orders of magnitude below the acute lethal EC50). We conclude that extremely low, environmentally relevant concentrations can disrupt species interactions. This toxicant mediated alteration of competitive balances in ecological communities may be the underlying mechanism for shifts in species distribution at ultra-low pesticide concentrations. A realistic risk assessment should therefore consider these processes in order to predict potential pesticide effects on the structure of communities.

Increased bat hunting at polluted streams suggests chemical exposure rather than prey shortage

Streams and their riparian areas are important habitats and foraging sites for bats feeding on emergent aquatic insects. Chemical pollutants entering freshwater streams from agricultural and wastewater sources have been shown to alter aquatic insect emergence, yet little is known about how this impacts insectivorous bats in riparian areas. In this study, we investigate the relationships between the presence of wastewater effluent, in-stream pesticide toxicity, the number of emergent and flying aquatic insects, and the activity and hunting behaviour of bats at 14 streams in southwestern Germany. Stream sites were located in riparian forests, sheltered from direct exposure to pollutants from agricultural and urban areas. We focused on three bat species associated with riparian areas: Myotis daubentonii, M. cf. brandtii, and Pipistrellus pipistrellus. We found that streams with higher pesticide toxicity and more frequent detection of wastewater also tended to be warmer and have higher nutrient and lower oxygen concentrations. We did not observe a reduction of insect emergence, bat activity or hunting rates in association with pesticide toxicity and wastewater detections. Instead, the activity and hunting rates of Myotis spp. were higher at more polluted sites. The observed increase in bat hunting at more polluted streams suggests that instead of reduced prey availability, chemical pollution at the levels measured in the present study could expose bats to pollutants transported from the stream by emergent aquatic insects.

Chlorpyrifos toxicity and detoxifying enzymes activities in three native-aquatic species of macroinvertebrates from an agricultural area

Non-target species from agricultural areas might be exposed to sublethal pesticide concentrations favoring survival and reproduction of the resistance individuals. The objective of this study was to evaluate chlorpyrifos toxicity and detoxification enzymatic activities on three species (Hyalella curvispina, Heleobia parchappii and Girardia tigrina) from a drain channel with history of insecticide contamination (EF) and the Neuquén river (NR) in Argentina. Chlorpyrifos toxicity on amphipods (H. curvispina) and planarians (G. tigrina) from NR was about six- and two-fold higher than that of their counterparts from EF. Mean carboxylesterases (CarE) activities determined in the three species from NR were significantly different from EF, whereas mean glutathione-S-transferase (GST) activities were no significantly different. Finally, planarians from EF showed significantly higher mean 7-ethoxycoumarine O-deethylase (ECOD) activity than those from NR. Amphipods from both sites displayed similar ECOD activities. The present results suggest that chlorpyrifos resistance in amphipods from EF is not conferred by increased detoxification.

Time between Sequential Exposures to Multiple Stress Turns Antagonism into Synergism

Aquatic communities are exposed to repeated pulses of toxicants and environmental stressors. We hypothesize that the dose, order, and timing of stress events shape the interactions of these communities. For this, we conducted a fully-crossed, four-factorial, multiple stress exposure experiment to study the combined effects of Esfenvalerate and ultraviolet-B (UV-B) radiation related to the exposure timing and order on Daphnia magna. We revealed that initial exposure to low stress doses, independent of the stress type (UV-B or Esfenvalerate), significantly increased the resistance toward the second stressor. This beneficial effect was apparent only when the second stressor was applied immediately after the first stressor (p < 0.01). When the period between stressor applications was extended to 2 days, the antagonism between the two stressors turned into synergism. The stressor interaction could be predicted with an abstract-mechanistic model of the temporal dynamics of the early-stage stress response. With this model, the timing and order of exposures were able to successfully explain interactions observed in all treatments (model-R² = 1.0). We conclude that especially the duration of a break between exposures and the exposure dose have a decisive influence on interactions between toxicants and environmental stressors.

Environmental and human health at risk - Scenarios to achieve the Farm to Fork 50% pesticide reduction goals

The recently released Farm to Fork Strategy of the European Union sets, for the first time, pesticide reduction goals at the EU level: 50% reduction in overall use and risk of chemical pesticides and a 50% use reduction of more hazardous pesticides. However, there is little guidance provided as to how to achieve these targets. In this study, we compiled the characteristics of all 230 EU-approved, synthetic, open-field use active substances (AS) used as herbicides, fungicides and insecticides, and explored the potential of seven Farm to Fork-inspired pesticide use reduction scenarios to achieve the 50% reduction goals. The pesticide reduction scenarios were based on recommended AS application rates, pesticide type, soil persistence, presence on the candidate for substitution list, and hazard to humans and ecosystems. All 230 AS have been found to cause negative effects on humans or ecosystems depending on exposure levels. This is found despite the incomplete hazard profiles of several AS. 'No data available' situations are often observed for the same endpoints and specific organisms. The results of the scenarios indicate that only severe pesticide use restrictions, such as allowing only low-hazard substances, will result in the targeted 50% use and risk reductions. Over half of the 230 AS considered are top use or top hazard substances, however, the reduction actions depend on the still to be defined EC priority areas and action plans, also for other recent and related strategies. Broader scenario implications (on productivity, biodiversity or economy) and the response of farmers to the pesticide use restrictions should be explored in those plans to define effective actions. Our results emphasize the need for a re-evaluation of the approved AS and of their representative uses, and the call for open access to AS, crop and region-specific use data to refine scenarios and assess effective reductions.

Risk from pesticide mixtures - The gap between risk assessment and reality

Pesticide applications in agricultural crops often comprise a mixture of plant protection products (PPP), and single fields face multiple applications per year leading to complex pesticide mixtures in the environment. Restricted to single PPP, the current European Union PPP regulation, however, disregards the ecological risks of pesticide mixtures. To quantify this additional risk, we evaluated the contribution of single pesticide active ingredients to the additive mixture risk for aquatic risk indicators (invertebrates and algae) in 464 different PPP used, 3446 applications sprayed and 830 water samples collected in Central Europe, Germany. We identified an average number of 1.3 different pesticides in a single PPP, 3.1 for complete applications often involving multiple PPP and 30 in stream water samples. Under realistic worst-case conditions, the estimated stream water pesticide risk based on additive effects was 3.2 times higher than predicted from single PPP. We found that in streams, however, the majority of regulatory threshold exceedances was caused by single pesticides alone (69% for algae, 81% for invertebrates). Both in PPP applications and in stream samples, pesticide exposure occurred in repeated pulses each driven by one to few alternating pesticides. The time intervals between pulses were shorter than the 8 weeks considered for ecological recovery in environmental risk assessment in 88% of spray series and 53% of streams. We conclude that pesticide risk assessment should consider an additional assessment factor to account for the additive, but also potential synergistic simultaneous pesticide mixture risk. Additionally, future research and risk assessment need to address the risk from the frequent sequential pesticide exposure observed in this study.

Pesticides are the dominant stressors for vulnerable insects in lowland streams

Despite elaborate regulation of agricultural pesticides, their occurrence in non-target areas has been linked to adverse ecological effects on insects in several field investigations. Their quantitative role in contributing to the biodiversity crisis is, however, still not known. In a large-scale study across 101 sites of small lowland streams in Central Europe, Germany we revealed that 83% of agricultural streams did not meet the pesticide-related ecological targets. For the first time we identified that agricultural nonpoint-source pesticide pollution was the major driver in reducing vulnerable insect populations in aquatic invertebrate communities, exceeding the relevance of other anthropogenic stressors such as poor hydro-morphological structure and nutrients. We identified that the current authorisation of pesticides, which aims to prevent unacceptable adverse effects, underestimates the actual ecological risk as (i) measured pesticide concentrations exceeded current regulatory acceptable concentrations in 81% of the agricultural streams investigated, (ii) for several pesticides the inertia of the authorisation process impedes the incorporation of new scientific knowledge and (iii) existing thresholds of invertebrate toxicity drivers are not protective by a factor of 5.3 to 40. To provide adequate environmental quality objectives, the authorisation process needs to include monitoring-derived information on pesticide effects at the ecosystem level. Here, we derive such thresholds that ensure a protection of the invertebrate stream community.

Long-term effects of a catastrophic insecticide spill on stream invertebrates

Accidental spills or illegal discharges of pesticides in aquatic ecosystems can lead to exposure levels that strongly exceed authorized pesticide concentrations, causing major impacts on aquatic ecosystems. Such short-term events often remain undetected in regular monitoring programs with infrequent sampling. In early spring 2015, we identified a catastrophic pesticide spill with the insecticide cypermethrin in the Holtemme River, Germany. Based on existing pre-event macroinvertebrate community data, we monitored the effects and recovery of the macroinvertebrate community for more than two years after the spill. Strong short-term effects were apparent for all taxa with the exception of Chironomidae and Tubificidae. Effects could also be observed on the community level as total abundance, taxa number and biomass strongly decreased. Total abundance and taxa number showed a fast recovery. Regarding long-term effects, the total biomass remained substantially below the pre-contamination level (76%) until the end of the study. Also the abundances of three taxa (Gammarus, Leuctra, Limnius Ad.) did not return to levels prior to the spill even after 26 months. This lack of the taxon-specific recovery was likely due to their long generation time and a low migration ability due to a restricted connectivity between the contaminated site and uncontaminated stream sections. These factors proved to be stronger predictors for the recovery than the pesticide tolerance. We revealed that the biological indicators SPEARpesticides and share of Ephemeroptera, Plecoptera and Trichoptera (EPT) are not suitable for the identification of such extreme events, when nearly all taxa are eradicated. Both indicators are functioning only when repeated stressors initiate long-term competitive replacement of sensitive by insensitive taxa. We conclude that pesticide spills can have significant long-term effects on stream macroinvertebrate communities. Regular ecological monitoring is imperative to identify such ecosystem impairments, combined with analytical chemistry methods to identify the potential sources of spills.

High Tolerance and Delayed Responses of Daphnia magna to Neonicotinoid Insecticide Imidacloprid: Toxicokinetic and Toxicodynamic Modeling

Species sensitivity to neonicotinoids has been shown to be highly variable among aquatic invertebrates. Toxicokinetic and toxicodynamic (TKTD) models were constructed to mechanistically elucidate the susceptibility of Daphnia magna to imidacloprid. D. magna was highly tolerant to single short-term exposure to imidacloprid (96-h LC50 of 8.47 μg/mL), but delayed and carry-over toxicity occurred under repeated pulse exposures. Kinetic distribution of imidacloprid between exoskeleton and soft tissues of D. magna was evaluated using a newly developed method. Approximately 84% imidacloprid was distributed to soft tissues but was rapidly depurated from the tissue (t_1/2 of 1.2 h), resulting in low bioaccumulation and high tolerance. TKTD modeling also successfully simulated the survival of D. magna after pulsed exposures. The calculated recovery time was 45 d, indicating significant delayed and carry-over toxicity of the insecticide. While complete elimination of imidacloprid only took about 5 h (TK), slow damage recovery (45 d) caused slow organism recovery (TD). Consequently, although D. magna was tolerant to imidacloprid due to fast depuration from soft tissue, long damage recovery time significantly enhanced the toxicity under repeated pulse exposures. Our study highlights the necessity of integrating delayed and carry-over toxicity quantification in assessing the risk of neonicotinoids to aquatic invertebrates.

Daily temperature variation lowers the lethal and sublethal impact of a pesticide pulse due to a higher degradation rate

Daily temperature variation (DTV) is an important warming-related stressor that may magnify pesticide toxicity. Yet, it is unknown whether the pesticide impact under DTV is partly ameliorated by a faster pesticide degradation caused by cyclically higher temperatures under DTV. As synergisms may be more likely under energy-limiting conditions, the impact of the pesticide chlorpyrifos was tested under DTV on the mosquito Culex pipiens in the absence and presence of interspecific competition with the water flea Daphnia magna. Chlorpyrifos exposure at a constant temperature without interspecific competition caused considerable mortality, decreased development time, and increased pupal mass of C. pipiens. Competition with D. magna had negative sublethal effects, but it did not affect the toxicity of chlorpyrifos. In contrast, the presence of C. pipiens decreased the impact of chlorpyrifos on D. magna probably due to corporal absorption of chlorpyrifos by C. pipiens. A key finding was that chlorpyrifos no longer caused lethal effects on C. pipiens under DTV, despite DTV on its own being mildly lethal. Additionally, chlorpyrifos exposure under DTV decreased development time less and had no effect anymore on pupal mass compared to chlorpyrifos exposure at a constant temperature. Similarly, the negative chlorpyrifos impact on adult survival of D. magna was less under DTV than at the constant temperature. This could be explained by a faster chlorpyrifos degradation under DTV. This antagonism between pesticide exposure and DTV is likely widespread because organisms experience DTV, many pesticides are applied in pulses, and pesticide degradation is faster at higher temperatures.

Repeated insecticide pulses increase harmful effects on stream macroinvertebrate biodiversity and function

We exposed twelve mesocosm stream channels and four instream channels to one, two, and four pulses of the insecticide lambda-cyhalothrin (0.1 μg L-1) applied at two day intervals, each pulse lasting 90 min. Unexposed controls were included. We monitored macroinvertebrate taxonomic composition in the channels and in deployed leaf packs one day before and 29 days after the first exposure. Further, we measured drift in and out of the channels and leaf litter decomposition. Lambda-cyhalothrin exposures induced significantly increased drift in both experiments especially for Gammarus pulex, Amphinemura standfussi, and Leuctra spp. Macroinvertebrate taxonomic composition increasingly changed with increasing number of lambda-cyhalothrin exposures being most pronounced in the mesocosm channels. Further, leaf decomposition significantly decreased with increasing number of exposures in the mesocosm channels. Our study showed that species with predicted highest sensitivity to lambda-cyhalothrin were primary drivers of significant changes in taxonomic composition lasting for at least one month despite continuous recolonization of exposed channels from upstream parts of the natural stream and from the water inlet in the mesocosm channels. The overall results highlight the importance of sequential exposures to insecticides for understanding the full impact of insecticides on macroinvertebrates at the community level in streams.

How Do Indirect Effects of Contaminants Inform Ecotoxicology? A Review

Indirect effects in ecotoxicology are defined as chemical- or pollutant-induced alterations in the density or behavior of sensitive species that have cascading effects on tolerant species in natural systems. As a result, species interaction networks (e.g., interactions associated with predation or competition) may be altered in such a way as to bring about large changes in populations and/or communities that may further cascade to disrupt ecosystem function and services. Field studies and experimental outcomes as well as models indicate that indirect effects are most likely to occur in communities in which the strength of interactions and the sensitivity to contaminants differ markedly among species, and that indirect effects will vary over space and time as species composition, trophic structure, and environmental factors vary. However, knowledge of indirect effects is essential to improve understanding of the potential for chemical harm in natural systems. For example, indirect effects may confound laboratory-based ecological risk assessment by enhancing, masking, or spuriously indicating the direct effect of chemical contaminants. Progress to better anticipate and interpret the significance of indirect effects will be made as monitoring programs and long-term ecological research are conducted that facilitate critical experimental field and mesocosm investigations, and as chemical transport and fate models, individual-based direct effects models, and ecosystem/food web models continue to be improved and become better integrated.

Long-term effects of neonicotinoid insecticides on ants

The widespread prophylactic usage of neonicotinoid insecticides has a clear impact on non-target organisms. However, the possible effects of long-term exposure on soil-dwelling organisms are still poorly understood especially for social insects with long-living queens. Here, we show that effects of chronic exposure to the neonicotinoid thiamethoxam on black garden ant colonies, Lasius niger, become visible before the second overwintering. Queens and workers differed in the residue-ratio of thiamethoxam to its metabolite clothianidin, suggesting that queens may have a superior detoxification system. Even though thiamethoxam did not affect queen mortality, neonicotinoid-exposed colonies showed a reduced number of workers and larvae indicating a trade-off between detoxification and fertility. Since colony size is a key for fitness, our data suggest long-term impacts of neonicotinoids on these organisms. This should be accounted for in future environmental and ecological risk assessments of neonicotinoid applications to prevent irreparable damages to ecosystems.

Insecticides in agricultural streams exert pressure for adaptation but impair performance in Gammarus pulex at regulatory acceptable concentrations

Pesticide exposure in agricultural streams requires non-target species to adapt. However, pesticides may reduce performance in between exposure events due to long-term effects and physiological fitness costs of adaptation. Here, we investigated the long-term consequences of pesticide exposure to low concentrations in the widespread crustacean Gammarus pulex. We collected populations from six German streams covering no to moderate agricultural pesticide exposure. Peak concentrations ranged up to 1/400 of their acute median lethal concentration (Toxic Unit = -2.6), resulting in significant changes in the macroinvertebrate community composition (SPEAR_pesticides = up to 0.12). Acute toxicity tests revealed up to 2.5-fold increased tolerance towards the most frequently found insecticide clothianidin compared to populations from non-contaminated streams. However, populations showing increased insecticide tolerance were characterized by reduced survival, per capita growth and mating when cultured under pesticide-free conditions in the laboratory for three months. We conclude that pesticide pollution triggers adaptation both at the species and the community level even at concentrations considered to be safe according to the European pesticide legislation. In G. pulex, exposure and adaptation are associated with impaired performance which potentially affects ecosystem functions such as leaf litter degradation. These long-term impairments need to be considered in deriving safe concentrations.

Evaluation of Drimys winteri (Canelo) Essential Oil as Insecticide against Acanthoscelides obtectus (Coleoptera: Bruchidae) and Aegorhinus superciliosus (Coleoptera: Curculionidae)

Adverse effects caused by synthetic pesticides have increased interest in plant-derived insecticidal compounds, in particular essential oils, as a more compatible and ecofriendly alternative for pest control of economic importance. For this reason, the essential oil isolated from leaves and shoots of Drimys winteri (J.R. Forster & G. Forster)-also named canelo (CEO)-was investigated for its chemical profile and insecticidal action against Acanthoscelides obtectus (Say)-one of the most important post-harvest pests of dry beans in the world-and Aegorhinus superciliosus (Guérin)-a significant pest of fruit trees in Chile. The analysis by gas chromatography, paired with mass spectrometry (GC/MS) determined 56 compounds, corresponding to 92.28% of the detected compounds. Elemol (13.54%), γ-eudesmol (11.42%), β-eudesmol (8.49%), α-eudesmol (6.39%), α-pinene (7.92%) and β-pinene (5.17%) were the most abundant. Regarding the bioactivity of the CEO, the results demonstrated toxicological effects against A. obtectus. A concentration of 158.3 µL L^-1 had a mortality rate of 94% after 24 h exposure. The LC₅₀ and LC₉₀ values at 24 h were 60.1 and 163.0 µL L^-1. Moreover, behavioral bioassays showed a repellent effect against A. superciliosus with a dose of one microliter of CEO. Both sexes of the raspberry weevil stayed for very short times in the treated area with the oil (<0.8 min), showing a homogeneous repellency in the species. The overall data suggest that canelo leaves and shoots essential oil has an insecticide effect and is worth exploring to better understand the synergistic relationship between the compounds present in the essential oil.

Pesticide pollution in freshwater paves the way for schistosomiasis transmission

Schistosomiasis is a severe neglected tropical disease caused by trematodes and transmitted by freshwater snails. Snails are known to be highly tolerant to agricultural pesticides. However, little attention has been paid to the ecological consequences of pesticide pollution in areas endemic for schistosomiasis, where people live in close contact with non-sanitized freshwaters. In complementary laboratory and field studies on Kenyan inland areas along Lake Victoria, we show that pesticide pollution is a major driver in increasing the occurrence of host snails and thus the risk of schistosomiasis transmission. In the laboratory, snails showed higher insecticide tolerance to commonly found pesticides than associated invertebrates, in particular to the neonicotinoid Imidacloprid and the organophosphate Diazinon. In the field, we demonstrated at 48 sites that snails were present exclusively in habitats characterized by pesticide pollution and eutrophication. Our analysis revealed that insensitive snails dominated over their less tolerant competitors. The study shows for the first time that in the field, pesticide concentrations considered “safe” in environmental risk assessment have indirect effects on human health. Thus we conclude there is a need for rethinking the environmental risk of low pesticide concentrations and of integrating agricultural mitigation measures in the control of schistosomiasis.

A toxic effect at molecular level can be expressed at community level: A case study on toxic hierarchy

This study demonstrated hierarchical toxicity and addressed the relevance and differences of toxic effects at the molecular, individual, population, and community levels. Superoxide dismutase (SOD) activity, photosynthetic oxygen production, filtration rate, life span and densities of Platymonas helgolandica var. tsingtaoensis, Isochrysis galbana, and Brachionus plicatilis in single-species tests and customized community tests were examined in response to a concentration gradient of aniline ranging from 0 to 50.0 mg L^-1. The SOD activity was the most sensitive endpoint with the fastest response to aniline according to the calculated no-detection of toxic effect concentration (NDEC) and the EC₅₀. The individual- and population-level endpoints, showing a lower response to aniline, could be constructed from the SOD activity in a stepwise manner. A multi-scale hierarchical model with endpoints at 4 levels was used to characterize toxic effects, at the scales of time and size. Linkage of SOD activity to toxic effects at a community level was established level by level to express the change in the customized community with the concentration of aniline. The calculated threshold concentration of aniline for the customized community was nearly equal to the minimum NDEC, demonstrating as great an impact on interactions by the toxic effect at subpopulation-level as that at the community level. However, we identified a trend of higher sensitivities of measured endpoints at sub-population level, decreasing sensitivity at higher levels but a great variety of sensitivities at community level. Although the characteristics of toxic effects are different at different levels, the structure and process of endpoints at adjacent levels are related to and interact with each other. The resulted indirect effects, together with direct effect, determine the toxic effect at every levels of biological complexity. The toxic effects at adjacent levels should be studied at the same time to better understand the ecological risk of contaminants.

Food Shortage Amplifies Negative Sublethal Impacts of Low-Level Exposure to the Neonicotinoid Insecticide Imidacloprid on Stream Mayfly Nymphs

Interactions of pesticides with biotic or anthropogenic stressors affecting stream invertebrates are still poorly understood. In a three-factor laboratory experiment, we investigated effects of the neonicotinoid imidacloprid, food availability, and population density on the New Zealand mayfly Deleatidium spp. (Leptophlebiidae). Larval mayflies (10 or 20 individuals) were exposed to environmentally realistic concentrations of imidacloprid (controls, 0.97 and 2.67 μg L−1) for nine days following five days during which individuals were either starved or fed with stream algae. Imidacloprid exposure had severe lethal and sublethal effects on Deleatidium, with effects of the lower concentration occurring later in the experiment. The starvation period had delayed interactive effects, with prior starvation amplifying imidacloprid-induced increases in mayfly impairment (inability to swim or right themselves) and immobility (no signs of movement besides twitching appendages). Few studies have investigated interactions with other stressors that may worsen neonicotinoid impacts on non-target freshwater organisms, and experiments manipulating food availability or density-dependent processes are especially rare. Therefore, we encourage longer-term multiple-stressor experiments that build on our study, including mesocosm experiments involving realistic stream food webs.

A general model of hormesis in biological systems and its application to pest management

Hormesis, a phenomenon whereby exposure to high levels of stressors is inhibitory but low (mild, sublethal and subtoxic) doses are stimulatory, challenges decision-making in the management of cancer, neurodegenerative diseases, nutrition and ecotoxicology. In the latter, increasing amounts of a pesticide may lead to upsurges rather than declines of pests, ecological paradoxes that are difficult to predict. Using a novel re-formulation of the Ricker population equation, we show how interactions between intervention strengths and dose timings, dose–response functions and intrinsic factors can model such paradoxes and hormesis. A model with three critical parameters revealed hormetic biphasic dose and dose timing responses, either in a J-shape or an inverted U-shape, yielding a homeostatic change or a catastrophic shift and hormetic effects in many parameter regions. Such effects were enhanced by repeated pulses of low-level stimulations within one generation at different dose timings, thereby reducing threshold levels, maximum responses and inhibition. The model provides insights into the complex dynamics of such systems and a methodology for improved experimental design and analysis, with wide-reaching implications for understanding hormetic effects in ecology and in medical and veterinary treatment decision-making. We hypothesized that the dynamics of a discrete generation pest control system can be determined by various three-parameter spaces, some of which reveal the conditions for occurrence of hormesis, and confirmed this by fitting our model to both hormetic data from the literature and to a non-hormetic dataset on pesticidal control of mirid bugs in cotton.

Potential for insecticide-mediated shift in ecological dominance between two competing aphid species

Competition is a key structuring component of biological communities, which is affected by both biotic and abiotic environmental stressors. Among the latter, anthropic stressors and particularly pesticides are noteworthy due to their intrinsic toxicity and large use in agroecosystems. However this issue has been scarcely documented so far. In this context, we carried out experiments under laboratory conditions to evaluate stress imposed by the neonicotinoid insecticide imidacloprid on intra and interspecific competition among two major wheat pest aphids. The bird cherry-oat aphid Rhopalosiphum padi L. and the English grain aphid Sitobion avenae F. were subjected to competition on wheat seedlings under varying density combinations of both species and subjected or not to imidacloprid exposure. Intraspecific competition does take place without insecticide exposure, but so does interspecific competition between both aphid species with R. padi prevailing over S. avenae. Imidacloprid interfered with both intra and interspecific competition suppressing the former and even the latter for up to 14 days, but not afterwards when a shift in dominance takes place favoring S. avenae over R. padi, in contrast with the interspecific competition without imidacloprid exposure. These findings hinted that insecticides are indeed able to mediate species interaction and competition influencing community structure and raising management concerns for favoring potential secondary pest outbreaks.

Multigenerational effects of carbendazim in Daphnia magna: From a subcellular to a population level

Anthropogenic activities such as the use of pesticides may affect aquatic biota populations, due to potential agricultural runoffs or disposals. Carbendazim is one example of a widely used fungicide with a high potential to end up in aquatic ecosystems through runoff. Deleterious effects observed at the individual level are possibly explained by changes in homeostasis at the cellular level, and both factors can then be used to predict effects at the population level. In the present study, an isoclonal population of Daphnia magna (clone K6) was exposed to a concentration that mimics relevant levels of carbendazim in the environment over 12 generations. The effects of carbendazim were assessed in some generations using the following endpoints: biochemical biomarkers (cholinesterase, catalase, and glutathione-S-transferase), lipid peroxidation and energy-related parameters (carbohydrates, lipids, and proteins along with available energy and energy consumption), parental longevity, and population growth (r). Long-term exposure to carbendazim had no effect on the intrinsic rate of natural increase (r) of adult D. magna, but longevity was decreased at the F12 generation compared to that of control. Differences between the exposed and nonexposed populations were found for cholinesterase, glutathione-S-transferase, and lipid peroxidation. However, for catalase and energy-related parameters, no differences were observed between these 2 populations. Natural variability was seen throughout the test period, under control conditions, within the 12 generations. Overall, carbendazim induced some effects at the subcellular level that translated into changes in longevity but these later vanished in terms of population effects. Environ Toxicol Chem 2019;38:412-422. © 2018 SETAC.

Meta-Analysis of Insecticides in United States Surface Waters: Status and Future Implications

Agricultural insecticides occur in U.S. surface waters, yet our knowledge of their current and potential future large-scale risks for biodiversity is restricted. Here, we conducted a meta-analysis of measured insecticide concentrations (MICs; n = 5817; 1962-2017) in U.S. surface waters and sediments reported in 259 peer-reviewed scientific studies for 32 important insecticide compounds and their degradation products ( n = 6). To assess overall and substance-specific ecological risks and future implications, MICs were compared with official U.S. Environmental Protection Agency regulatory threshold levels (RTLs) and insecticide use trends. Approximately half of the MICs, i.e., 49.4% (at 69.7% of the 644 sites covered), exceeded their RTLs, indicating substantial risks to the integrity of U.S. aquatic ecosystems and potential shortcomings of regulatory risk assessment procedures. Overall, pyrethroids had the highest exceedance rate (80.7%; n = 1808), followed by organophosphates and carbamates (42.2%, n = 2618), and organochlorines (33.3%, n = 468). Pronounced increasing use trends were found for neonicotinoids, which exceeded their chronic RTLs, i.e., those of high relevance due to neonicotinoids̀ persistence in surface waters, for 56.8% of MICs (22.2% for acute RTLs). A regression analysis of insecticide use trends, although to be interpreted with care, indicated a future increase in applied amounts of several high risk insecticides such as pyrethroids and neonicotinoids, suggesting elevated prospective risks for U.S. surface waters, biodiversity, and endangered species.

Identification of pesticide exposure-induced metabolic changes in mosquito larvae

The European regulatory framework for pesticides generally applies an assessment factor of up to 100 below the acute median lethal concentration (LC50) in laboratory tests to predict the regulatory acceptable concentrations (RACs). However, long-term detrimental effects of pesticides in the environment occur far below the RACs. Here, we explored the metabolic changes induced by exposure to the neonicotinoid insecticide clothianidin in larvae of the mosquito Culex pipiens. We exposed the test organisms to the insecticide for 24 h and then measured the levels of 184 metabolites immediately and 48 h after the pulse contamination. We established a link between the exposure to clothianidin and changes in the level of three specific classes of metabolites involved in energy metabolism, namely, glycerophospholipids, acylcarnitines and biogenic amines. Remarkably, exposure to concentrations considered to be safe according to the regulatory framework (2-4 orders of magnitude lower than the acute LC50), induced longer-term effects than exposure to the highest concentration. These results suggest that a specific detoxification mechanism was only triggered by the highest concentration. We conclude that even very low insecticide concentrations increase the energy demands of exposed organisms, which potentially translates into a decline in sensitive species in the field.

Pesticide Body Burden of the Crustacean Gammarus pulex as a Measure of Toxic Pressure in Agricultural Streams

Risk assessments of toxicants in aquatic environments are typically based on the evaluation of concentrations in water or sediment. However, concentrations in water are highly variable, while the body burden may provide a better time-integrated measure of pesticide exposure and potential effects in aquatic organisms. Here, we quantified pesticide body burdens in a dominant invertebrate species from agricultural streams, Gammarus pulex, compared them with pesticide concentrations in water samples, and linked the pesticide contamination with observed ecological effects on macroinvertebrate communities. In total, 19 of 61 targeted analytes were found in the organisms, ranging from 0.037 to 93.94 ng g^-1 (wet weight). Neonicotinoids caused the highest toxic pressure among the pesticides detected in G. pulex. Using linear solvation energy relationships (LSERs), we derived equivalent pesticide concentrations in streamwater based on the body burden. These equivalent concentrations correlated with the concentrations in water samples collected after runoff (65% of variance explained). Pesticide pressure significantly affected the aquatic macroinvertebrate community structure, expressed as SPEAR_pesticides, and caused, on average, 3-fold increased insecticide tolerance in G. pulex as a result of adaptation. The toxic pressure derived from body burden and from water samples similarly explained the change in community structure (68% and 64%). However, the increased tolerance of G. pulex to pesticides was better explained by the toxicity derived from body burden (70%) than by the toxicity from water samples (53%). We conclude that the internal body burden of macroinvertebrates is suitable to assess the overall pesticide exposure and effects in agricultural streams.

Controlling Culex pipiens: antagonists are more efficient than a neonicotinoid insecticide

Species vulnerability to pesticides depends on physiological sensitivity, the potential to recover, and the ecological context. We assessed the vulnerability of the mosquito Culex pipiens to a repeated treatment with thiacloprid in outdoor microcosms with and without antagonists (competitive and predatory invertebrates). Microcosms were treated repeatedly (three times) with thiacloprid at a concentration of 0.1, 1, or 10 µg/liter. In microcosms without antagonists, the abundance of Cx. pipiens larvae decreased moderately after the second and the third exposures to 10 µg/liter thiacloprid. In microcosms with antagonists, the abundance of Cx. pipiens larvae declined to approximately zero in the control group and the low concentration treatments during the five weeks of observation. By contrast, the abundance of Cx. pipiens larvae temporarily increased at 10 µg/liter thiacloprid after the second and third contamination. We explained this positive effect on the development of Cx. pipiens because of the decrease in competition due to the elimination of sensitive antagonists combined with the high recovery potential of Cx. pipiens. Based on these results, natural antagonists must be supported for the sustainable control of mosquitoes.

Combined use of the entomopathogenic fungus, Metarhizium brunneum, and the mosquito predator, Toxorhynchites brevipalpis, for control of mosquito larvae: Is this a risky biocontrol strategy?

Mosquitoes transmit several diseases, which are of global significance (malaria, dengue, yellow fever, Zika). The geographic range of mosquitoes is increasing due to climate change, tourism and trade. Both conidial and blastospore formulations of the entomopathogenic fungus, Metarhizium brunneum ARSEF 4556, are being investigated as mosquito larvicides. However, concerns have been raised over possible non-target impacts to arthropod mosquito predators such as larvae of Toxorhynchites brevipalpis which feed on larvae of mosquito vector species. Laboratory-based, small container bioassays showed, that T. bevipalpis larvae are susceptible to relatively high concentrations (i.e. ≥10⁷ spores ml^-1) of inoculum with blastospores being significantly more virulent than conidia. At lower concentrations (e.g. <10⁷ spores ml^-1), it appears that M. brunneum complements T. brevipalpis resulting in higher control than if either agent was used alone. At a concentration of 10⁵ spores ml^-1, the LT₅₀ of for conidia and blastospores alone was 5.64 days (95% CI: 4.79-6.49 days) and 3.89 days (95% CI: 3.53-4.25 days), respectively. In combination with T. brevipalpis, this was reduced to 3.15 days (95% CI: 2.82-3.48 days) and 2.82 days (95% CI: 2.55-3.08 days). Here, combined treatment with the fungus and predator was beneficial but weaker than additive. At 10⁷ and 10⁸ blastospores ml^-1, mosquito larval mortality was mostly due to the fungal pathogen when the predator was combined with blastospores. However, with conidia, the effects of combined treatment were additive/synergistic at these high concentrations. Optimisation of fungal concentration and formulation will reduce: (1) risk to the predator and (2) application rates and costs of M. brunneum for control of mosquito larvae.

Sequential exposure to low levels of pesticides and temperature stress increase toxicological sensitivity of crustaceans

Frequent pesticide-related impacts on ecosystems at concentrations considered environmentally safe indicate that the current risk assessment framework for registration of pesticides is not protective enough. Causes may include difficulties in assessing the effects of sequential pesticide pulses and their interaction with environmental stressors. By contrast to such realistic scenarios, risk assessment for registration of pesticides is typically based on tests of a single exposure period under benign laboratory conditions. Here, we investigated the toxicological sensitivity of Gammarus pulex, an ecologically relevant crustacean, from uncontaminated control streams and pesticide-contaminated agricultural streams by exposing them to pesticide contamination in the laboratory. Individuals from contaminated streams were 2.7-fold more sensitive to pesticide exposure than individuals from the reference streams. We revealed that this increase in sensitivity was the result of a synergistic interaction of sequential pesticide exposure and temperature stress. Such multiple stressor scenarios are typical for agricultural streams. We conclude that the interactive effects of sequential toxicant exposure and additional environmental stressors need to be considered in a realistic risk assessment framework.

Towards a holistic and solution-oriented monitoring of chemical status of European water bodies: how to support the EU strategy for a non-toxic environment?

The definition of priority substances (PS) according to the Water Framework Directive (WFD) helped to remove many of these chemicals from the market and to reduce their concentrations in the European water bodies. However, it could not prevent that many of these chemicals have been replaced by others with similar risks. Today, monitoring of the PS-based chemical status according to WFD covers only a tiny fraction of toxic risks, extensively ignores mixture effects and lacks incentives and guidance for abatement. Thus, we suggest complement this purely status-related approach with more holistic and solution-oriented monitoring, which at the same time helps to provide links to the ecological status. Major elements include (1) advanced chemical screening techniques supporting mixture risk assessment and unraveling of source-related patterns in complex mixtures, (2) effect-based monitoring for the detection of groups of chemicals with similar effects and the establishment of toxicity fingerprints, (3) effect-directed analysis of drivers of toxicity and (4) to translate chemical and toxicological fingerprints into chemical footprints for prioritization of management measures. The requirement of more holistic and solution-oriented monitoring of chemical contamination is supported by the significant advancement of appropriate monitoring tools within the last years. Non-target screening technology, effect-based monitoring and basic understanding of mixture assessment are available conceptually and in research but also increasingly find their way into practical monitoring. Substantial progress in the development, evaluation and demonstration of these tools, for example, in the SOLUTIONS project enhanced their acceptability. Further advancement, integration and demonstration, extensive data exchange and closure of remaining knowledge gaps are suggested as high priority research needs for the next future to bridge the gap between insufficient ecological status and cost-efficient abatement measures.

Species Diversity Hinders Adaptation to Toxicants

Environmental toxicants such as pesticides exert strong selection pressure on many species. While the resulting development of pesticide resistance in agricultural pest species is well-known, reports on the extent of adaptation in exposed nontarget species are contradictory. These contradictory reports highlight a continuing challenge in understanding the relevant ecological mechanisms that facilitate or hinder adaptation to toxicants in the field. Here we show that species diversity hinders the adaptation to toxicants. In agricultural streams with low diversity, we observed an up to 8-fold increase in insecticide tolerance in a total of 17 macroinvertebrate species that was not observed in more diverse communities under similar contamination. High species diversity occurred independently from adjacent nonpolluted refuge areas. Therefore, the low level of adaptation in diverse streams cannot be explained by an increased recolonization of sensitive individuals from refuge areas. Instead, high intraspecific competition may facilitate the selection for increased tolerance in low-diverse communities. In diverse communities, by contrast, species interactions may reduce intraspecific competition and, thus, the potential for developing toxicant resistance. We suggest that this mechanism may be the general case in adaptation to environmental stressors. Additionally, we conclude that the current framework for risk assessment of pesticides is not protective against selection for tolerant organisms and the associated risk of genetic erosion.

Realistic pesticide exposure through water and food amplifies long-term effects in a Limnephilid caddisfly

Pesticides are increasingly recognized as relevant stressors in stream ecosystems. Stream biota is exposed to pesticides with low water solubility, e.g. pyrethroid insecticides, via water, habitat, and food. However, long-term effects of simultaneous exposure pathways are unknown. In this context, we conducted a microcosm experiment with the caddisfly Anabolia nervosa exposing the larvae to the pyrethroid insecticide esfenvalerate (EFV) at 0.1 and 1.0μgL^-1 via (i) water, (ii) food or a (iii) combination of water and food. Combined exposure through water and food significantly reduced emergence by 60% and significantly postponed emergence timing at the highest EFV level, whereas none of the single-phase exposures showed significant effects. Moreover, our study revealed that successfully emerged females from the highest biphasic treatment level were characterised by altered composition of storage lipids indicative of reduced energy reserves. Consequently, a realistic test scenario that represents simultaneous exposure of organisms and their food may reveal substantially increased long term effects of pyrethroids when compared with current ecological risk assessment applying only single phase exposure. We recommend that relevant concurrent exposure routes of pesticides should be considered in order to derive realistic regulatory acceptable concentrations of pesticides.

Population modeling for pesticide risk assessment of threatened species-A case study of a terrestrial plant, Boltonia decurrens

Although population models are recognized as necessary tools in the ecological risk assessment of pesticides, particularly for species listed under the Endangered Species Act, their application in this context is currently limited to very few cases. The authors developed a detailed, individual-based population model for a threatened plant species, the decurrent false aster (Boltonia decurrens), for application in pesticide risk assessment. Floods and competition with other plant species are known factors that drive the species' population dynamics and were included in the model approach. The authors use the model to compare the population-level effects of 5 toxicity surrogates applied to B. decurrens under varying environmental conditions. The model results suggest that the environmental conditions under which herbicide applications occur may have a higher impact on populations than organism-level sensitivities to an herbicide within a realistic range. Indirect effects may be as important as the direct effects of herbicide applications by shifting competition strength if competing species have different sensitivities to the herbicide. The model approach provides a case study for population-level risk assessments of listed species. Population-level effects of herbicides can be assessed in a realistic and species-specific context, and uncertainties can be addressed explicitly. The authors discuss how their approach can inform the future development and application of modeling for population-level risk assessments of listed species, and ecological risk assessment in general. Environ Toxicol Chem 2017;36:480-491. © 2016 SETAC.

Scientific Opinion addressing the state of the science on risk assessment of plant protection products for in-soil organisms

Following a request from EFSA, the Panel on Plant Protection Products and their Residues developed an opinion on the science behind the risk assessment of plant protection products for in-soil organisms. The current risk assessment scheme is reviewed, taking into account new regulatory frameworks and scientific developments. Proposals are made for specific protection goals for in-soil organisms being key drivers for relevant ecosystem services in agricultural landscapes such as nutrient cycling, soil structure, pest control and biodiversity. Considering the time-scales and biological processes related to the dispersal of the majority of in-soil organisms compared to terrestrial non-target arthropods living above soil, the Panel proposes that in-soil environmental risk assessments are made at in- and off-field scale considering field boundary levels. A new testing strategy which takes into account the relevant exposure routes for in-soil organisms and the potential direct and indirect effects is proposed. In order to address species recovery and long-term impacts of PPPs, the use of population models is also proposed.

Do drivers of biodiversity change differ in importance across marine and terrestrial systems - Or is it just different research communities' perspectives?

Cross-system studies on the response of different ecosystems to global change will support our understanding of ecological changes. Synoptic views on the planet's two main realms, the marine and terrestrial, however, are rare, owing to the development of rather disparate research communities. We combined questionnaires and a literature review to investigate how the importance of anthropogenic drivers of biodiversity change differs among marine and terrestrial systems and whether differences perceived by marine vs. terrestrial researchers are reflected by the scientific literature. This included asking marine and terrestrial researchers to rate the relevance of different drivers of global change for either marine or terrestrial biodiversity. Land use and the associated loss of natural habitats were rated as most important in the terrestrial realm, while the exploitation of the sea by fishing was rated as most important in the marine realm. The relevance of chemicals, climate change and the increasing atmospheric concentration of CO₂ were rated differently for marine and terrestrial biodiversity respectively. Yet, our literature review provided less evidence for such differences leading to the conclusion that while the history of the use of land and sea differs, impacts of global change are likely to become increasingly similar.

The pros and cons of ecological risk assessment based on data from different levels of biological organization

Ecological risk assessment (ERA) is the process used to evaluate the safety of manufactured chemicals to the environment. Here we review the pros and cons of ERA across levels of biological organization, including suborganismal (e.g., biomarkers), individual, population, community, ecosystem and landscapes levels. Our review revealed that level of biological organization is often related negatively with ease at assessing cause-effect relationships, ease of high-throughput screening of large numbers of chemicals (it is especially easier for suborganismal endpoints), and uncertainty of the ERA because low levels of biological organization tend to have a large distance between their measurement (what is quantified) and assessment endpoints (what is to be protected). In contrast, level of biological organization is often related positively with sensitivity to important negative and positive feedbacks and context dependencies within biological systems, and ease at capturing recovery from adverse contaminant effects. Some endpoints did not show obvious trends across levels of biological organization, such as the use of vertebrate animals in chemical testing and ease at screening large numbers of species, and other factors lacked sufficient data across levels of biological organization, such as repeatability, variability, cost per study and cost per species of effects assessment, the latter of which might be a more defensible way to compare costs of ERAs than cost per study. To compensate for weaknesses of ERA at any particular level of biological organization, we also review mathematical modeling approaches commonly used to extrapolate effects across levels of organization. Finally, we provide recommendations for next generation ERA, submitting that if there is an ideal level of biological organization to conduct ERA, it will only emerge if ERA is approached simultaneously from the bottom of biological organization up as well as from the top down, all while employing mathematical modeling approaches where possible to enhance ERA. Because top-down ERA is unconventional, we also offer some suggestions for how it might be implemented efficaciously. We hope this review helps researchers in the field of ERA fill key information gaps and helps risk assessors identify the best levels of biological organization to conduct ERAs with differing goals.

Predicting the synergy of multiple stress effects

Toxicants and other, non-chemical environmental stressors contribute to the global biodiversity crisis. Examples include the loss of bees and the reduction of aquatic biodiversity. Although non-compliance with regulations might be contributing, the widespread existence of these impacts suggests that for example the current approach of pesticide risk assessment fails to protect biodiversity when multiple stressors concurrently affect organisms. To quantify such multiple stress effects, we analysed all applicable aquatic studies and found that the presence of environmental stressors increases individual sensitivity to toxicants (pesticides, trace metals) by a factor of up to 100. To predict this dependence, we developed the “Stress Addition Model” (SAM). With the SAM, we assume that each individual has a general stress capacity towards all types of specific stress that should not be exhausted. Experimental stress levels are transferred into general stress levels of the SAM using the stress-related mortality as a common link. These general stress levels of independent stressors are additive, with the sum determining the total stress exerted on a population. With this approach, we provide a tool that quantitatively predicts the highly synergistic direct effects of independent stressor combinations.

Multiple exposure routes of a pesticide exacerbate effects on a grazing mayfly

Hydrophobic pesticides such as pyrethroid insecticides tend to occur in their soluble form mainly as transient pulses in streams. In addition, they are regularly detected in significant quantities adsorbed to stream sediments and other organic in-stream structures. Consequently, stream biota is likely subjected to pesticide exposure via multiple routes. In this study we aimed at investigating the influence of exposure routes for the pyrethroid insecticide lambda-cyhalothrin on the grazing mayfly Heptagenia sulphurea. Therefore, H. sulphurea was exposed to lambda-cyhalothrin via single- (water or biofilm) or biphasic exposure (water and biofilm) at environmentally realistic concentrations (0, 0.1, 1μgL(-1)) and exposure duration (2h) in a full factorial design (n=5). Mortality, moulting frequency, and biofilm accrual (proxy for feeding rate) were recorded subsequent to a 7 d post exposure period. Mortality significantly increased and moulting frequency significantly decreased with increasing concentrations of lambda-cyhalothrin in the water phase whereas exposure via biofilm prompted no significant effects on these endpoints (α=0.05). Effect predictions systematically underestimated and overestimated effects for mortality and moulting frequency, respectively. Similarly, mayfly feeding rate was significantly reduced by water phase exposure whereas pre-exposed biofilm did not significantly affect this variable. However, we found a significant but non-systematic interaction between water phase and biofilm exposure on mayfly feeding rate. Our results show that exposure to the same pesticide via multiple exposure routes may increase the magnitude of effects beyond the level predicted from single phase exposures which has clear implications for the aquatic risk assessment of hydrophobic pesticides. However, our results additionally reveal that interactions between pesticide exposure routes may vary between selected dependent variables. We emphasize that unravelling the underlying mechanisms causing these discrepancies in interactive effects between exposure routes is a major aspect that should receive further attention in future research.

Trait modality distribution of aquatic macrofauna communities as explained by pesticides and water chemistry

Analyzing functional species' characteristics (species traits) that represent physiological, life history and morphological characteristics of species help understanding the impacts of various stressors on aquatic communities at field conditions. This research aimed to study the combined effects of pesticides and other environmental factors (temperature, dissolved oxygen, dissolved organic carbon, floating macrophytes cover, phosphate, nitrite, and nitrate) on the trait modality distribution of aquatic macrofauna communities. To this purpose, a field inventory was performed in a flower bulb growing area of the Netherlands with significant variation in pesticides pressures. Macrofauna community composition, water chemistry parameters and pesticide concentrations in ditches next to flower bulb fields were determined. Trait modalities of nine traits (feeding mode, respiration mode, locomotion type, resistance form, reproduction mode, life stage, voltinism, saprobity, maximum body size) likely to indicate pesticides impacts were analyzed. According to a redundancy analysis, phosphate -and not pesticides- constituted the main factor structuring the trait modality distribution of aquatic macrofauna. The functional composition could be ascribed for 2-4 % to pesticides, and for 3-11 % to phosphate. The lack of trait responses to pesticides may indicate that species may have used alternative strategies to adapt to ambient pesticides stress. Biomass of animals exhibiting trait modalities related to feeding by predation and grazing, presence of diapause form or dormancy, reproduction by free clutches and ovoviviparity, life stage of larvae and pupa, was negatively correlated to the concentration of phosphate. Hence, despite the high pesticide pollution in the area, variation in nutrient-related stressors seems to be the dominant driver of the functional composition of aquatic macrofauna assembly in agricultural ditches.

Rapid evolution of increased vulnerability to an insecticide at the expansion front in a poleward-moving damselfly

Many species are too slow to track their poleward-moving climate niche under global warming. Pesticide exposure may contribute to this by reducing population growth and impairing flight ability. Moreover, edge populations at the moving range front may be more vulnerable to pesticides because of the rapid evolution of traits to enhance their rate of spread that shunt energy away from detoxification and repair. We exposed replicated edge and core populations of the poleward-moving damselfly Coenagrion scitulum to the pesticide esfenvalerate at low and high densities. Exposure to esfenvalerate had strong negative effects on survival, growth rate, and development time in the larval stage and negatively affected flight-related adult traits (mass at emergence, flight muscle mass, and fat content) across metamorphosis. Pesticide effects did not differ between edge and core populations, except that at the high concentration the pesticide-induced mortality was 17% stronger in edge populations. Pesticide exposure may therefore slow down the range expansion by lowering population growth rates, especially because edge populations suffered a higher mortality, and by negatively affecting dispersal ability by impairing flight-related traits. These results emphasize the need for direct conservation efforts toward leading-edge populations for facilitating future range shifts under global warming.

Modeling Macroinvertebrate Community Dynamics in Stream Mesocosms Contaminated with a Pesticide

Modeling community dynamics of aquatic invertebrates is an important but challenging task, in particular in ecotoxicological risk assessment. Systematic parameter estimation and rigorous assessment of model uncertainty are often lacking in such applications. We applied the mechanistic food web model Streambugs to investigate the temporal development of the macroinvertebrate community in an ecotoxicological mesocosm experiment with pulsed contaminations with the insecticide thiacloprid. We used Bayesian inference to estimate parameters and their uncertainty. Approx. 85% of all experimental observations lie within the 90% uncertainty intervals indicating reasonably good fits of the calibrated model. However, a validation with independent data was not possible due to lacking data. Investigation of vital rates and limiting factors in the model yielded insights into recovery dynamics. Inclusion of the emergence process and sub-lethal effects turned out to be potentially relevant model extensions. Measurements of food source dynamics, individual body size (classes), and additional knowledge on sub-lethal effects would support more accurate modeling. This application of a process-based, ecotoxicological community model with uncertainty assessment by Bayesian inference increased our process understanding of toxicant effects in macroinvertebrate communities and helped identifying potential improvements in model structure and experimental design.

Shared effects of organic microcontaminants and environmental stressors on biofilms and invertebrates in impaired rivers

Land use type, physical and chemical stressors, and organic microcontaminants were investigated for their effects on the biological communities (biofilms and invertebrates) in several Mediterranean rivers. The diversity of invertebrates, and the scores of the first principal component of a PCA performed with the diatom communities were the best descriptors of the distribution patterns of the biological communities against the river stressors. These two metrics decreased according to the progressive site impairment (associated to higher area of agricultural and urban-industrial, high water conductivity, higher dissolved organic carbon and dissolved inorganic nitrogen concentrations, and higher concentration of organic microcontaminants, particularly pharmaceutical and industrial compounds). The variance partition analyses (RDAs) attributed the major share (10%) of the biological communities' response to the environmental stressors (nutrients, altered discharge, dissolved organic matter), followed by the land use occupation (6%) and of the organic microcontaminants (2%). However, the variance shared by the three groups of descriptors was very high (41%), indicating that their simultaneous occurrence determined most of the variation in the biological communities.

Ecotoxicological risk assessment of chemical pollution in four Iberian river basins and its relationship with the aquatic macroinvertebrate community status

Ecotoxicological risk assessment of chemical pollution in four Iberian river basins (Llobregat, Ebro, Júcar and Guadalquivir) was performed. The data set included more than 200 emerging and priority compounds measured at 77 sampling sites along four river basins studied. The toxic units (TU) approach was used to assess the risk of individual compounds and the concentration addition model (CA) to assess the site specific risk. Link between chemical pollution and aquatic macroinvertebrate communities in situ was examined by using four biological indexes; SPEAR ("Species at Risk Index") as the indicator of decline of sensitive species in relation to general organic (SPEARorganic) and pesticides (SPEARpesticides) pollution; and Shannon and Margalef biodiversity indexes. The results of the study suggested that organic chemicals posed the risk of acute effects at 42% of the sampling sites and the risk of chronic effects at all the sites. Metals posed the acute risk at 44% of the sites. The main drivers of the risk were mainly pesticides and metals. However, several emerging contaminants (e.g. the antidepressant drug sertraline and the disinfectant triclosan) were contributing to the chronic effects risk. When risk associated with metals and organic chemicals was compared, the latter dominated in 2010, mainly due to the presence of highly toxic pesticides, while metals did in 2011. Compounds that are not regulated on the European level were posing the risk of chronic effects at 23% of the sites. The decline of sensitive macroinvertebrate taxa expressed in terms of SPEAR index was correlated with the increase of toxic stress related to organic compounds Biodiversity indexes were negatively correlated with the metals and the urban land use type in the catchment.

Additivity and Interactions in Ecotoxicity of Pollutant Mixtures: Some Patterns, Conclusions, and Open Questions

Understanding the effects of exposure to chemical mixtures is a common goal of pharmacology and ecotoxicology. In risk assessment-oriented ecotoxicology, defining the scope of application of additivity models has received utmost attention in the last 20 years, since they potentially allow one to predict the effect of any chemical mixture relying on individual chemical information only. The gold standard for additivity in ecotoxicology has demonstrated to be Loewe additivity which originated the so-called Concentration Addition (CA) additivity model. In pharmacology, the search for interactions or deviations from additivity (synergism and antagonism) has similarly captured the attention of researchers over the last 20 years and has resulted in the definition and application of the Combination Index (CI) Theorem. CI is based on Loewe additivity, but focused on the identification and quantification of synergism and antagonism. Despite additive models demonstrating a surprisingly good predictive power in chemical mixture risk assessment, concerns still exist due to the occurrence of unpredictable synergism or antagonism in certain experimental situations. In the present work, we summarize the parallel history of development of CA, IA, and CI models. We also summarize the applicability of these concepts in ecotoxicology and how their information may be integrated, as well as the possibility of prediction of synergism. Inside the box, the main question remaining is whether it is worthy to consider departures from additivity in mixture risk assessment and how to predict interactions among certain mixture components. Outside the box, the main question is whether the results observed under the experimental constraints imposed by fractional approaches are a de fide reflection of what it would be expected from chemical mixtures in real world circumstances.

Toxicological evaluation of ametryn effects in Wistar rats

São Paulo state, Brazil, is one of the main areas of sugar cane planting in the world. Extensive use of ametryn, a triazine herbicide, in sugar cane agriculture and the properties of this herbicide suggest it could be present in the environment as a potential contaminant of soil, surface water, groundwater, and river sediment. In order to clarify the mechanism through which ametryn could be toxic, an in vivo study with Wistar rats was conducted using hematological, biochemical, molecular, morphological and genotoxic approaches. For this purpose, two sub-lethal ametryn concentrations (15 mg and 30 mg/kg/day) were administered to 42 rats divided into three groups (n=12) by gavage during 56 days, whereupon blood, liver and bone marrow were collected. The results showed ametryn genotoxic activity by in vivo micronuclei testing. This event probably occurred as consequence of oxidative stress induction demonstrated by GSTM1 transcript levels increase (indicating complexation between ametryn and/or metabolites with GSH) and by SOD activity decrease. Also, Mn-SOD transcripts were increased, probably avoiding mtDNA damage caused by EROS. These mechanisms displayed hepatic stellate cell (HSCs) activation because two major biomarkers were regulated, connexin and cadherin. N-cad transcripts were increased on both exposed groups while E-cad decreased in the T1 group, indicating epithelial-to-mesenchymal transition. In addition, Cx43 transcripts were decreased suggesting an increase in collagen content. Volumetric proportion of sinusoids was significantly decreased in T1 group and no significant alteration in hepatocyte volume was observed, indicating an increase in the space of Disse, due to fibrosis. Hepatocyte nuclei showed significant decrease in diameter and volume. Few hematological alterations were found. We emphasize the importance of other approaches, such as cell death and proliferation assays, so that ametryn toxicity can better be understood.