Mikhail A. Beketov

Pesticides reduce regional biodiversity of stream invertebrates

The biodiversity crisis is one of the greatest challenges facing humanity, but our understanding of the drivers remains limited. Thus, after decades of studies and regulation efforts, it remains unknown whether to what degree and at what concentrations modern agricultural pesticides cause regional-scale species losses. We analyzed the effects of pesticides on the regional taxa richness of stream invertebrates in Europe (Germany and France) and Australia (southern Victoria). Pesticides caused statistically significant effects on both the species and family richness in both regions, with losses in taxa up to 42% of the recorded taxonomic pools. Furthermore, the effects in Europe were detected at concentrations that current legislation considers environmentally protective. Thus, the current ecological risk assessment of pesticides falls short of protecting biodiversity, and new approaches linking ecology and ecotoxicology are needed.

Thresholds for the Effects of Pesticides on Invertebrate Communities and Leaf Breakdown in Stream Ecosystems

We compiled data from eight field studies conducted between 1998 and 2010 in Europe, Siberia, and Australia to derive thresholds for the effects of pesticides on macroinvertebrate communities and the ecosystem function leaf breakdown. Dose-response models for the relationship of pesticide toxicity with the abundance of sensitive macroinvertebrate taxa showed significant differences to reference sites at 1/1000 to 1/10,000 of the median acute effect concentration (EC50) for Daphnia magna, depending on the model specification and whether forested upstream sections were present. Hence, the analysis revealed effects well below the threshold of 1/100 of the EC50 for D. magna incorporated in the European Union Uniform Principles (UP) for registration of single pesticides. Moreover, the abundances of sensitive macroinvertebrates in the communities were reduced by 27% to 61% at concentrations related to 1/100 of the EC50 for D. magna. The invertebrate leaf breakdown rate was positively linearly related to the abundance of pesticide-sensitive macroinvertebrate species in the communities, though only for two of the three countries examined. We argue that the low effect thresholds observed were not mainly because of an underestimation of field exposure or confounding factors. From the results gathered we derive that the UP threshold for single pesticides based on D. magna is not protective for field communities subject to multiple stressors, pesticide mixtures, and repeated exposures and that risk mitigation measures, such as forested landscape patches, can alleviate effects of pesticides.

ACUTE AND DELAYED EFFECTS OF THE NEONICOTINOID INSECTICIDE THIACLOPRID ON SEVEN FRESHWATER ARTHROPODS

Ecotoxicological risk assessment of contaminants often is based on toxicity tests with continuous-exposure profiles. However, input of many contaminants (e.g., insecticides) to surface waters typically occurs in pulses rather than continuously. Neonicotinoids are a new group of insecticides, and little is known about their toxicity to nontarget freshwater organisms and potential effects on freshwater ecosystems. The aim of the present research was to assess effects of short-term (24-h) exposure to the neonicotinoid insecticide thiacloprid, including a postexposure observation period. A comparison of several freshwater insect and crustacean species showed an increase of sensitivity by three orders of magnitude in the following order: Daphnia magna < Asellus aquaticus = Gammarus pulex < Simpetrum striolatum < Culex pipiens = Notidobia ciliaris = Simulium latigonium, with median lethal concentrations (LC50s) of 4,400, 153, 190, 31.2, 6.78, 5.47, and 5.76 mug/L, respectively (postexposure observation 11-30 d). Thiacloprid caused delayed lethal and sublethal effects, which were observed after 4 to 12 d following exposure. Reduction in LC50s found when postexposure observation was extended from 1 d to a longer period (11-30 d) was up to >50-fold. Hence, delayed effects occurring after short-term exposure should be considered in risk assessment. The 5% hazardous concentration (HC5) of thiacloprid obtained in the present study (0.72 microg/L) is more than one order of magnitude below the currently predicted worst-case environmental concentrations in surface water. Concerning the selection of test organisms, we observed that the widely employed test organism D. magna is least sensitive among the arthropods tested and that, for neonicotinoid insecticides, an insect like the mosquito C. pipiens would be more suitable for predicting effects on sensitive species.

Potential of 11 Pesticides to Initiate Downstream Drift of Stream Macroinvertebrates

Downstream drift of lotic macroinvertebrates induced by toxicants is a well-known ecologically relevant phenomenon. However, little is known about which toxicants can initiate drift, and potential drift-initiating effects of contaminants are not taken into account in ecotoxicological risk assessment. The aim of the present study was to evaluate potential drift-initiating action of 11 pesticides having different target groups and modes of action. Sublethal concentrations of the pesticides were tested in stream microcosms with amphipods (Gammarus pulex), blackfly larvae (Simulium latigonium), and mayfly larvae (Baetis rhodani). The results show that 6 out of 11 pesticides tested can initiate drift of macroinvertebrates at sublethal concentrations 7–22 times lower than acute LC50s (thiacloprid, imidacloprid, acetamiprid, iprodione, fenvalerate, and indoxacarb). All the toxicants that exhibited drift-initiating action are neurotoxic insecticides belonging to the groups of pyrethroids and neonicotinoids except the fungicide iprodione. The pesticides that did not initiate drift are fungicides (cyprodinil, prochloraz, and azoxystrobin), a juvenile-hormone mimic (fenoxycarb), and a pyrazole insecticide (tebufenpyrad) affecting cell energy production. Remarkably, for all the drift-initiating toxicants, drift of the tested animals was detected within 2 h after contamination. This shows that macroinvertebrate drift can be induced even by short-term pulse exposures to neurotoxic insecticides, at field-relevant concentrations. The present results imply that the possibility of drift-initiating effects of pesticides should be considered within the risk assessment framework for pesticides, as all neurotoxic substances that were investigated did initiate drift at sublethal concentrations.

Acute contamination with esfenvalerate and food limitation: Chronic effects on the mayfly, Cloeon dipterum

Results of environmental risk assessments based merely on toxic effects of contaminants at the individual level, without consideration of population-level effects, may be questionable. The aim of the present study was to investigate how limited food resources, resulting in intraspecific competition, could interact with the chronic effect of short-term contamination with the insecticide esfenvalerate. Larvae of the mayfly, Cloeon dipterum, were exposed to esfenvalerate (0.001-100 microg/L) for 1 h and then transferred to indoor microcosms containing insecticide-free water, where they were maintained at various food levels until emergence. The results showed that short-term exposure to 10 or 100 microg/L resulted in acute mortality. Chronic effects on survival occurred at concentrations up to three orders of magnitude lower than that causing the acute effect (0.01 microg/L). Food limitation increased effects on organisms during medium-term observation (8-15 d), but assessment of long-term survival rates suggested that the chronic effects of low insecticide concentrations could be compensated for, at least regarding some endpoints. The authors assume that in limited-food conditions, lethal and sublethal effects reduced competition between individuals, resulting in significantly increased final survival.

SPEAR indicates pesticide effects in streams - Comparative use of species- and family-level biomonitoring data

To detect effects of pesticides on non-target freshwater organisms the Species at risk (SPEAR(pesticides)) bioindicator based on biological traits was previously developed and successfully validated over different biogeographical regions of Europe using species-level data on stream invertebrates. Since many freshwater biomonitoring programmes have family-level taxonomic resolution we tested the applicability of SPEAR(pesticides) with family-level biomonitoring data to indicate pesticide effects in streams (i.e. insecticide toxicity of pesticides). The study showed that the explanatory power of the family-level SPEAR(fm)(pesticides) is not significantly lower than the species-level index. The results suggest that the family-level SPEAR(fm)(pesticides) is a sensitive, cost-effective, and potentially European-wide bioindicator of pesticide contamination in flowing waters. Class boundaries for SPEAR(pesticides) according to EU Water Framework Directive are defined to contribute to the assessment of ecological status of water bodies.

Predation risk perception and food scarcity induce alterations of life‐cycle traits of the mosquito Culex pipiens

Abstract 1. Predators may affect prey populations by direct consumption, and by inducing defensive reactions of prey to the predation risk. Food scarcity frequently has effects on the inducible defences of prey, but no consistent pattern of food–predation risk interaction is known.

The influence of predation on the chronic response of Artemia sp. populations to a toxicant.

Summary 1 Environmental risk assessment of contaminants is conventionally based on toxic effects assessed in organism‐level test systems. We suggest that, for the prediction of toxicant effects, population‐ and community‐level effects should be considered. The aim of this study was to investigate how predation could alter a prey populations response to a toxicant to reveal effects at population and community levels.2 Populations of the brine shrimp Artemia sp. were maintained in the laboratory with and without simulated predation. Individuals were exposed for 1 h to the pyrethroid insecticide esfenvalerate (0, 0·01, 0·04 and 0·08 µg L−1) and subsequently observed for 6 weeks.3 Unpredated exposed populations showed a reduced population density compared with the control. However, even at the highest concentration of insecticide, populations were sustained until the end of the experiment. The lower density in the exposed populations led to reduced competition and subsequently to enhanced development of surviving individuals and an increased proportion of young individuals. In contrast, the combination of predation and short‐term toxicant exposure at concentrations of 0·04 and 0·08 µg L−1 produced extinction of the populations after 39 and 32 days of exposure, respectively.4 Synthesis and applications. The response of populations of brine shrimp to toxicants at the community level may be stronger when predation is present than the response of populations without predation pressure, as the regulation capacity of the population (measured as an increased production of offspring at reduced population densities) is exhausted when predation is present. Future ecotoxicological risk assessment schemes should consider relevant community characteristics such as predation as part of an environmental risk assessment.

Different sensitivity of mayflies (Insecta, Ephemeroptera) to ammonia, nitrite and nitrate: linkage between experimental and observational data

Complex toxic effects of ammonia, nitrite and nitrate to aquatic animals are not well investigated. In rivers of southwestern Siberia, Russia, elevated ammonia and nitrite concentrations corresponded to significant reduction in species diversity of mayflies. The objectives of the study were to evaluate the sensitivity of six mayfly species to the mixture of ammonia, nitrite and nitrate in acute laboratory tests and to compare the sensitivity found with results of the first river bioassessment in the region considered and with species saprobic indexes. The rank of the species sensitivity was: Baetis vernus < Potamanthus luteus < B. fuscatus=Cloeon bifidum < Ephemerella lenoki < Heptagenia sulphurea (p < 0.05). The experiments revealed variation in sensitivity among the species by a factor of 7.5. Comparison of the tests results and the available field data shows that species which exhibit higher tolerance in the tests inhabit comparatively greater amount of sites include contaminated places. Final conclusion is addressed in comparison of the results found with more spatially and temporally extensive observations. Saprobic indexes of the species and their acute tolerances (LC50s) tend to be positively correlated (r=0.93, p=0.02).

How to Characterize Chemical Exposure to Predict Ecologic Effects on Aquatic Communities

Reliable characterization of exposure is indispensable for ecological risk assessment of chemicals. To deal with mixtures, several approaches have been developed, but their relevance for predicting ecological effects on communities in the field has not been elucidated. In the present study, we compared nine metrics designed for estimating the total toxicity of mixtures regarding their relationship with an effect metric for stream macroinvertebrates. This was done using monitoring data of biota and organic chemicals, mainly pesticides, from five studies comprising 102 streams in several regions of Europe and South-East Australia. Mixtures of less than 10 pesticides per water sample were most common for concurrent exposure. Exposure metrics based on the 5% fraction of a species sensitivity distribution performed best, closely followed by metrics based on the most sensitive species and Daphnia magna as benchmark. Considering only the compound with the highest toxicity and ignoring mixture toxicity was sufficient to estimate toxicity in predominantly agricultural regions with pesticide exposure. The multisubstance Potentially Affected Fraction (msPAF) that combines concentration and response addition was advantageous in the study where further organic toxicants occurred. We give recommendations on exposure metric selection depending on data availability and the involved compounds.