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

The effects of the fungicide carbendazim (applied in the formulation Derosal) on enchytraeids were 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 study was performed. The tests were performed in Amsterdam (The Netherlands), Bangor (Wales, England), Coimbra (Portugal) and Flörsheim (Germany). Concerning the enchytraeid overall abundance and the number of species, differences between sampling points and differences between the TME tests and the respective field-validation studies were not found in the controls. Generally, a high variability of data which reduced the probability of determining statistically significant differences was determined. Effects of the model chemical carbendazim were determined for the overall abundance of enchytraeids and the number of enchytraeid species. The clearest dose-response relationship was found for the abundance of the genus Fridericia. The abundance of the genera Achaeta and Enchytraeus was not affected. Effects were most pronounced 8 and 16 weeks after application of the test chemical. The observed effects appeared not to differ between the TME tests and the respective field-validation studies. Due to the high variability of data NOEC-values could often not be determined. The EC50-values derived from the TME pre-test, TME ring-test and field-validation study indicate that the reproducibility (i.e. the variation between the partners) of the EC50-values was reasonable, although different soils were used at the different sites. The EC50-values for effects of carbendazim on enchytraeid abundance ranged between 0.5 and 28.4 kg a.i./ha (corresponding to 0.7-37.8 mg/kg), on the number of species between 7.2 and 87.4 kg a.i./ha (9.5-116.2 mg/kg) and on the abundance of Fridericia between 0.7 and 18.6 kg a.i./ha (0.9-24.7 mg/kg). Since one specific taxon has the potential to be more sensitive for a chemical stressor than other taxa, it is recommended to include investigations on the species level in the assessment of TME or field studies.