ABSTRACT
Freshwater microcosms and mesocosms are frequently used as research tools in aquatic ecotoxicology. They are bounded systems that are constructed articially with samples from, or portions of, natural freshwater ecosystems or that consist of enclosed parts of natural freshwaters. Although these model ecosystems usually are characterized by a reduction in size and complexity when compared with natural ecosystems, they have to include an assemblage of organisms representing several trophic levels, and this assemblage should be in “dynamic equilibrium” with its ambient environment (see, e.g., Brock et al. 1995; Caquet et al. 2000). The terms “microcosm” and “mesocosm” are used more or less interchangeably when referring to model ecosystems. Following the denitions proposed by Crossland et al. (1993), microcosms are experimental systems containing less than 15 m3 water volume or
8.1 General Introduction ..................................................................................... 101 8.2 Role of Micro-and Mesocosms in Pesticide Risk Assessment .................... 103 8.3 Selecting Dosing Regimes in Micro/Mesocosm Experiments ..................... 105 8.4 Threshold Concentrations for Effects in Micro/Mesocosm Experiments
and Linking Exposure and Effects in the Risk Assessment ......................... 106 8.5 Factors that Affect Recovery of Sensitive Populations
in Micro/Mesocosm Experiments ................................................................ 112 8.6 Can NOEAECs Derived from Aquatic Micro/Mesocosm Experiments
Be Extrapolated in Space and Time? ............................................................ 114 8.7 Linking Exposure and Effects When Recovery Is Taken into Account ....... 115
experimental streams less than 15 m in length, while mesocosms are larger. However, in Europe, indoor experimental ecosystems are often referred to as microcosms and outdoor experimental ecosystems as mesocosms.
