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A review of the use of invertebrate communities in lotic microcosms and mesocosms to assess the toxicity of chemicals

Project Abstract
By Tom F. Cuffney

Abstract

Lotic microcosm and mesocosm model systems are being used for chemical toxicity tests with increasing frequency because they provide more environmental realism than single-species toxicity tests. These systems commonly include more of the physical, chemical, and biological complexity inherent in the natural environment. These model systems allow experimentation with complex biological communities without the problems of indefinite system boundaries, uncontrolled fluctuations in environmental conditions, and unmanageable size encountered in "real" ecosystems. Furthermore, model systems offer the advantages of containment, replicability, and experimental control not possible in natural systems. They have been successfully used to assess the effects of metals, acidification, pesticides, chlorine, p-Cresol and several other organic compounds on benthic invertebrate communities. Endpoints such as diversity, evenness, density, biomass, production, fecundity, drift, and leaf decomposition and invertebrate collection methods including artificial substrates, corers, emergence traps, hand netting, drift nets, macrophytes, and litter bags are similar to those used in natural systems though scaled down to the size of the model system.

Important issues related to using lotic microcosms and mesocosms in toxicity assessments include: (1) the need to establish and maintain realistic communities for experimentation; (2) need to establish replicate streams; (3) variability that increases directly with realism; (4) problems associated with down scaling of physical systems; and (5) the cost of construction and operation. Despite such problems these model systems offer an important link in the extrapolation of laboratory toxicity tests to community level effects in the environment. Such links are particularly important with the advent of policies to control toxic chemicals based on water quality and the emerging emphases on biological criteria and bioassessments in controlling environmental pollution.