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

The effects of the fungicide carbendazim (applied in the formulation Derosal) on nematodes 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 study was performed. The tests were performed in Amsterdam (The Netherlands), Bangor (Wales, England), Coimbra (Portugal) and Flörsheim (Germany). Differences concerning nematode overall abundance, the number of nematode families, the trophical structure of the nematode cenosis and the maturity index (MI) were not found between the controls of TME tests and the respective field-validation studies. Effects caused by the chemical treatment, however, were observed on the number of nematode families, on the trophical structure of the nematode cenosis and on the maturity index (MI). Effects on the relative abundance of the omnivorous nematodes were most pronounced, whereas the overall nematode abundance was not affected. The observed effects appear not to differ between the TME tests and the respective field-validation studies. All measurement endpoints in both TMEs and field, showed rather large variations. Therefore, NOEC-values were often equal or higher than the highest treatment level and EC50-values were calculated only for the omnivorous nematodes. NOEC- and EC50-values derived from the TME ring-test and the field-validation study indicate that the reproducibility (i.e. the variation between the partners) was reasonable, although different soils from different sites were used. The EC50-values determined for the effect of carbendazim on the relative abundance of the omnivorous nematodes ranged between 0.93 and 7.24 kg a.i./ha (1.24-9.63 mg/kg). Due to the higher sensitivity of the relative abundance of the omnivorous nematodes compared to the other measurement endpoints it is recommended to use this parameter as the main endpoint.