RESEARCH ARTICLE Identification of realistic worst case aquatic macroinvertebrate species for prospective risk assessment using the trait concept André Gergs & Silke Classen & Udo Hommen & Thomas G. Preuss Received: 17 December 2010 / Accepted: 4 March 2011 / Published online: 29 March 2011 # Springer-Verlag 2011 Abstract Purpose Approaches in environmental risk assessment for pesticides are becoming more and more realistic. Thereby, risk assessment has to be protective in a way that no long- lasting (adverse) effects on populations will occur in the environment. Since this imperative includes species gener- ally showing high population vulnerability due to their life history traits, prospective risk assessment should be based on realistic worst cases. Based on life history traits, the purpose of the current study was to verify whether a worst case combination of low potential for intrinsic recovery and low ability for recolonisation can be found in the field. Methods Combinations of traits related to dispersal ability and reproduction of macroinvertebrates were investigated using monitoring data from edge of field water bodies in Germany. The relative distribution of traits was analyzed across different agricultural regions and across sites of different potential for exposure to pesticides. Species were sorted in a tiered approach in order to gain a list of realistic worst case species. Results Life history traits were found equally distributed across different regions. Thereby, dispersal ability and voltinism were not randomly combined. Within the data analysed, low dispersal ability was found to be exclusive to semivoltine taxa. Owing to their appearance in reference sites, poor dispersal ability and a long time reproduction, three species were considered potentially worst case. Conclusions The trait approach was found to be suitable in comparing trait distributions within different regions and in compiling a list of critical taxa for consideration in environmental risk assessment. Keywords Aquatic . Macroinvertebrate . Species . Trait 1 Introduction Approaches in environmental risk assessment for plant protection products are becoming more and more realistic, e.g. by the use of exposure scenarios covering different representative combinations of climate and soil conditions (FOCUS 2001) or by spatially explicit exposure modelling (Hendley et al. 2001; Seuntjens et al. 2008; Schulz et al. 2009; Hommen et al. 2010a). Thereby it has to be assured that these more realistic approaches are protective in terms of no long-lasting (adverse) effects on populations will occur in the environment (European Commission 2004). Since short-term effects on populations are accepted to some extent within the current risk assessment framework, population recovery has become an important concept (Brock et al. 2006). However, the extrapolation of recovery rates experimentally derived for different types of organisms to the field is still a matter of debate (Barnthouse 2004; Hommen et al. 2010b). In the field, the effects of pesticides on populations might not only depend on exposure and toxicity, but also on further factors such as life history characteristics, population structure, Responsible editor: Philippe Garrigues A. Gergs (*) : T. G. Preuss Institute for Environmental Research, RWTH Aachen University, Aachen, Germany e-mail: andre.gergs@bio5.rwth-aachen.de S. Classen Research Institute for Ecosystem Analysis and Assessment (gaiac), RWTH Aachen University, Aachen, Germany U. Hommen Fraunhofer Institute for Molecular Biology and Applied Ecology (IME), Schmallenberg, Germany Environ Sci Pollut Res (2011) 18:1316–1323 DOI 10.1007/s11356-011-0484-6