Soil microarthropod community testing: A new approach to increase the ecological relevance of effect data for pesticide risk assessment (original) (raw)
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Environmental Toxicology and Chemistry, 2006
Species sensitivity distributions (SSD) and 5% hazardous concentrations (HC5) are distribution-based approaches for assessing environmental risks of pollutants. These methods have potential for application in pesticide risk assessments, but their applicability for assessing pesticide risks to soil invertebrate communities has not been evaluated. Using data obtained in a systematic review, the present study investigates the relevance of SSD and HC5 for predicting pesticide risks to soil invertebrates. Altogether, 1,950 laboratory toxicity data were obtained, representing 250 pesticides and 67 invertebrate taxa. The majority (96%) of pesticides have toxicity data for fewer than five species. Based on a minimum of five species, the best available endpoint data (acute mortality median lethal concentration) enabled SSD and HC5 to be calculated for 11 pesticides (atrazine, carbendazim, chlorpyrifos, copper compounds, diazinon, dimethoate, ␥-hexachlorocyclohexane, lambda-cyhalothrin, parathion, pentachlorophenol, and propoxur). Arthropods and oligochaetes exhibit pronounced differences in their sensitivity to most of these pesticides. The standard test earthworm species, Eisenia fetida sensu lato, is the species that is least sensitive to insecticides based on acute mortality, whereas the standard Collembola test species, Folsomia candida, is among the most sensitive species for a broad range of toxic modes of action (biocide, fungicide, herbicide, and insecticide). These findings suggest that soil arthropods should be tested routinely in regulatory risk assessments. In addition, the data indicate that the uncertainty factor for earthworm acute mortality tests (i.e., 10) does not fully cover the range of earthworm species sensitivities and that acute mortality tests would not provide the most sensitive risk estimate for earthworms in the majority (95%) of cases.
Currently, earthworm field tests and litter-bag studies are regularly required as part of the environmental risk assessment of pesticides in soil. These tests give almost no indication if there is any structural impact, i.e. on the biodiversity of the soil organism community. Therefore, a design is presented here for such a structural study, which follows basically the design of litter bag studies. Our proposal is based on practical experience made in Southern Germany in 2007 / 2008. A new pesticide was tested, framed by a control (water) and a mix of two reference substances (the fungicide Benomyl and the insecticide Chlorpyrifos(ethyl)) of known effect, the latter in order to confirm the sensitivity of the studied soil organisms. For confidentiality reasons, the identity of the test substance cannot be given here. Six replicates were used per treatment (plot size: 7 m x 3 m). The study was performed on grassland and test chemical and reference substance were applied without soil incorporation. Grassland was chosen because diversity and abundance of enchytraeids, mites and nematodes (and soil mesofauna in general) is usually very low in agricultural soil. The duration of the study was one year and sampling was performed –2, 32, 89, 187 and 372 DAT (days after treatment). The taxonomic groups assessed were enchytraeids, soil-inhabiting mites, collembolans, and nematodes, but collembolans will not be covered in this contribution. All groups except nematodes were sampled using ISO standard methods. Specimens were sampled with soil corers (diameter and depth: 5 cm each). The enchytraeids were identified to the species level, but assessment is based on the genus level. Among mites only the oribatids were identified to species level, the rest to higher groups. The nematodes were only assessed quantitatively. The variance of the samples collected was small enough to detect a change in the taxonomic structure of the soil organism community. In this contribution results from the control, test substance and reference plots are presented. In comparison to the control, the number of enchytraeids on the reference plots was reduced by 60 % at individual sampling dates, thus validating the test design. Mites were not affected at all. The number of nematodes decreased by 48 % at most. The test substance itself showed no significant effect at all, except an unexplained reduction of enchytraeids at the 4th sampling date. Genera of enchytraeids behaved slightly differently, suggesting that in future studies the species level should be addressed. Referring to the experiences made in this study it is concluded that the use of soil mesofauna groups in field studies is a practical and promising tool in the environmental risk assessment of pesticides.
Environmental Toxicology and Chemistry, 2006
To assess the impact of pesticides on aquatic organisms under realistic worst-case conditions, a macroinvertebrate community of small ditches was sampled at 40 sites of the orchard region Altes Land near Hamburg, Germany. To differentiate between pesticide impact and other variables, the ditches selected for sampling were located at different distances along grassland, unused apple orchards, and orchards managed with integrated and/or organic crop protection methods. Samples of macroinvertebrates were taken on five dates over two years. In addition to biological data, water chemistry and structural parameters were measured. For each sampling site, a potential for exposure was calculated on the basis of the distance of the ditch to the nearest row of trees and the depth and width of the ditch. The neighborhood to either grassland or orchards turned out to have a larger impact on the macroinvertebrate community than the potential for exposure. Therefore, grassland sites were omitted from further evaluation. Remaining sites were grouped into low exposure (sites at unused orchards), medium exposure (distance of 3-5 m [track] between trees and ditch), and high exposure (trees close to the ditch, mean distance Յ 1.5 m). Principal response curves showed differences in community structure between the three exposure groups over time. Whereas for sites from the high exposure group significant differences from low exposure was observed in all seasons, significant differences between low and medium were observed only occasionally. Effects were less pronounced in samples taken at springtime before the starting pesticide applications, suggesting some community recovery. Species richness was negatively correlated to exposure potential. Isopoda, Eulamellibranchiata, and insects, especially Ephemeroptera, showed a high negative correlation with the potential for pesticide exposure, suggesting that these taxa are sensitive to the pesticide use in the orchards.
Ecotoxicology, 2013
The EU plant protection regulation 1107/2009/ EC defines the requirements for active ingredients to be approved, specifically including the assessment of effects on biodiversity and ecosystems. According to that, semi-field methods are expected to be more important in the near future. Therefore, a higher-tier experiment suitable to assess the risk for soil organisms was conducted to further develop the TME (terrestrial model ecosystems) methodology in a doseresponse design with the persistent insecticidal model compound lindane (gamma-HCH). The effects of lindane on soil communities such as collembolans, oribatid mites, nematodes, soil fungi and plant biomass were determined in 42 TME. Intact TME-soil cores (diameter 300 mm, height 400 mm) from undisturbed grassland were stored outdoor under natural climatic conditions. Lindane was applied in five concentrations between 0.032 mg active ingredients (ai)/kg dry soil and 3.2 mg ai/kg dry weight soil, six-fold replicated each. Twelve TME served as untreated controls. Abundance and community structures of oribatids, collembolans, enchytraeids, nematodes and fungi were recorded. Oribatid mites' community responded 3 months after treatment, although they were not significantly affected by the overall treatment regimen. Collembolans in total and species-specific abundance as well as the community endpoints (principal response curves, diversity measures) were adversely affected by moderate dosages of lindane. Effects were transient between 3 and 5 months after treatment with a recovery within 1 year. No significant effects could be detected for enchytraeids, nematodes and fungi. The study design and the obtained results allow for calculations of no observed effect concentrations below the highest treatment level for populations and for soil communities as defined entities, as well as effective concentrations. The paper discusses the limits of effect detection in the light of achievable coefficients of variation and by means of minimum detectable differences. Outdoor TME are useful to analyze and assess functional and structural endpoints in soil organisms' communities and their possible recovery after pesticide treatment within 1 year.
2014
A soil multi-species, SMS, experimental test system consisting of the natural microbial community, five collembolan species and a predatory mite along with either Enchytraeus crypticus or the earthworm Eisenia fetida were exposed to a-cypermethrin. A comparison of the performance of these two types of SMSs is given to aid the development of a standard test system. E. fetida had a positive effect on the majority of the species, reducing the negative insecticide effect. E. fetida affected the species sensitivity and decreased the degradation of the insecticide due to the organic matter incorporation of earthworm food. After 8 weeks, the EC50 was 0.76 mg kg À1 for enchytraeids and ranged between 2.7 and 18.9 mg kg À1 for collembolans, more sensitive than previously observed with single species. Changes observed in the community structure and function illustrates the strength of a multi-species test system as an ecotoxicological tool compared to single species tests.
Environmental Toxicology and Chemistry, 1997
We used a refined microcosm technique to investigate the toxicity of copper, cadmium, malathion, and the polychlorinated biphenyl, Aroclor 1254, to trophic groups of soil nematodes and to the microarthropod community. Comparisons of changes in nematode abundance in control soils through time indicated that day 7 was the most appropriate time to sample the microcosms after chemical application. Nematode abundance was reduced after exposure to copper at 100 g/g, with fungivore, bacterivore, and omnivore-predator nematodes being the most sensitive groups. Cadmium did not affect the nematode or microarthropod communities. Microarthropods were far more sensitive to malathion than were nematodes, and total microarthropod abundance was lower than controls at 400 g/g. Prostigmatid mites and ''other'' arthropods were the most affected groups. Aroclor 1254 also had a greater negative impact on microarthropods than on nematodes. Total microarthropod abundance declined at 2,500 g/g, with prostigmatid and oribatid mites exhibiting the highest susceptibility. Strong differential sensitivity between nematode and microarthropod communities indicates that both groups should be examined to fully evaluate the biological impact of chemicals on soils. We conclude that microcosms with field-collected soil microfaunal communities offer high resolution of the ecotoxicologic effects of chemicals in complex soil systems.