A STANDARDIZED TRI-TROPHIC SMALL-SCALE SYSTEM (TriCosm) FOR THE ASSESSMENT OF STRESSOR INDUCED EFFECTS ON AQUATIC COMMUNITY DYNAMICS

Chemical impacts on the environment are routinely assessed in single-species tests. They are employed to measure direct effects on non-target organisms but indirect effects on ecological interactions can only be detected in multi-species tests. Micro- and mesocosms are more complex and environmentally realistic, yet, they are less frequently used for environmental risk assessment because resource demand is high while repeatability and statistical power are often low. Test systems fulfilling regulatory needs (i.e. standardization, repeatability and replication) and the assessment of impacts on species interactions and indirect effects are lacking. Here we describe the development of the TriCosm, a repeatable aquatic multi-species test with three trophic levels and increased statistical power. High repeatability of community dynamics of three interacting aquatic populations (algae, Ceriodaphnia, Hydra) was found with an average coefficient of variation of 19.5% and the ability to determine small effect sizes. The TriCosm combines benefits of both single-species tests (fulfillment of regulatory requirements) and complex multi-species tests (ecological relevance) and can be used, for instance at an intermediate tier in environmental risk assessment. Furthermore, comparatively quickly generated population and community toxicity data can be useful for the development and testing of mechanistic effect models. This article is protected by copyright. All rights reserved.