Artificial multi-species test system that simulates major characteristics of the natural environment for
the purposes of ecotoxicological effects and risk assessment; such systems are normally terrestrial or
aquatic and may contain plants, animals (vertebrates and invertebrates), and microorganisms.
Note:       The terms mesocosm and macrocosm are used to refer to larger and more complex sys-
tems than microcosms, but the distinction is often not clearly defined.