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

The effects of the fungicide carbendazim (applied in the formulation Derosal) on soil microarthropod communities was determined in three Terrestrial Model Ecosystem (TME) tests and a field-validation study for a period of 16 weeks after application. TMEs consisted of intact soil columns (diameter 17.5 cm: length 40 cm) taken from a grassland field. The TMEs for the two tests (pre-test and ring-test) in Amsterdam, The Netherlands, were taken from the same site where the field-validation study was performed, the third TME test (pre-test) was performed in Bangor, Wales. Collembola communities showed large variations in numbers and no effects of carbendazim on species diversity were seen. Mites were not determined to species but only to four main taxonomic groups (Astigmata, Cryptostigmata, Mesostigmata, Prostigmata). Mite numbers in both TME and field soils also showed rather large variations and it was difficult to find consistent effects of carbendazim treatment. Principal response curve (PRC) analysis was performed to further evaluate effects of carbendazim on Collembola and mites in the TME and field tests. This multivariate technique demonstrated significant effects of carbendazim on Collembola communities in one TME test and the field-validation study but not in the other two TME tests, while mite communities showed significant effects in two TME tests but not in the third TME test and the field-validation study. NOECs for the effect of carbendazim on Collembola and mite communities derived from these PRC analyses ranged from 0.36 to 87.5 kg a.i./ha.