The use of the multivariate Principal Response Curve (PRC) for community level analysis:: a case study on the effects of carbendazim on enchytraeids in Terrestrial Model Ecosystems (TME)

The effects of the fungicide carbendazim (formulation Derosal((R)) ) on enchytraeids were determined in Terrestrial Model Ecosystem (TME) tests. TMEs consisted of intact soil columns (diameter 17.5 cm; length 40 cm) taken from three grassland sites (Amsterdam (The Netherlands), Bangor (Wales, England) and Florsheim (Germany)) or an arable site (Coimbra (Portugal)). Results for each TME site were evaluated using the multivariate Principal Response Curve (PRC) method. The resulting No-Observable Effect Concentrations (NOECs) for the community were compared with the NOECs generated by univariate statistical methods. Furthermore, the EC(50)s (median effect concentrations) for the three taxa with the highest taxon weights determined by the PRC were compared with EC(50)s for the other endpoints. In eight out of 16 cases the PRC revealed the lowest NOEC for the enchytraeid species community. The lowest EC(50)s with the closest 95% confidence limits were calculated for the abundance of the three taxa with the highest taxon weights identified by the PRC. The EC(50)s ranging from 0.19-2.79 mg carbendazim/kg soil are similar to values from laboratory toxicity studies reported in the literature. Therefore, PRC is a useful instrument to analyse microcosm and mesocosm experiments; it allows for determination of NOECs for the species community (NOECcommunity), the evaluation of the taxa with the most pronounced treatment-related decrease in abundance and of the calculation of meaningful EC50 values for those. The resulting NOECcommunity and EC50 values offer a comprehensive tool for the risk assessment of chemicals at the ecosystem level.