Ring-testing and field-validation of a terrestrial model ecosystem (TME)--an instrument for testing potentially harmful substances: effects of carbendazim on earthworms.

Abstract

The effects of the fungicide carbendazim (applied in the formulation Derosal) on earthworms (Lumbricidae) was determined in Terrestrial Model Ecosystem (TME) tests and field-validation studies. TMEs consisted of intact soil columns (diameter 17.5 cm; length 40 cm) taken from a grassland or, in one case, from an arable site. The TMEs were taken from the same site where the respective field-validation study was performed. The tests were performed in Amsterdam (The Netherlands), Bangor (Wales, UK), Coimbra (Portugal) and Flörsheim (Germany). The sites selected had an earthworm coenosis representative of the different land use types and regions. In addition, the differences between the coenosis found in the TMEs and the respective field sites were in general low. A high variability was found between the replicate samples, which reduces the probability of determining significant differences by the statistical evaluation of the data. Similar effects of the chemical treatment were observed on abundance as well as on biomass. Effects were most pronounced 16 weeks after application of the test chemical. The observed effects on earthworm abundance and biomass did not differ between the TME tests and the respective field-validation studies. Effects on earthworm diversity were difficult to assess since the number of individuals per species was low in general. However, the genus Lumbricus and in particular L. terrestris and L. rubellus seemed to be more affected by the chemical treatment than others. NOEC and EC50-values derived from the TME pre-test, the TME ring-test and the field-validation study indicate that the TMEs of the different partners delivered comparable results although different soils were used. Due to the high variability NOECs could often not be determined. The EC50-values for the effect of carbendazim on earthworm abundance ranged between 2.04 and 48.8 kg a.i./ha (2.71-65.2 mg/kg soil) and on earthworm biomass from 1.02 to 34.6 kg a.i./ha (1.36-46.0 mg/kg soil). These results indicate that the abundance and biomass of earthworms are suitable endpoints in ecotoxicological studies with TMEs.