Use and abuse of heavy metal bioassays in environmental monitoring

Animals, plants and fungi, through their highly specific demands on environmental resources, can be usefully employed to monitor pollution, provided it is appreciated that their response to various concentrations of pollutants will vary both inter- and intra-specifically. Bioindicators are selected for their ability to respond specifically to a rise (or more rarely to a fall) in concentration of a particular pollutant and/or to accumulate one or more particular elements, subsequently measured by chemical analysis. Species are hierarchical in their susceptibility to a defined pollution burden, but several contaminants may be acting independently, synergistically or collectively with the elements bioassayed. Bioassays have often been ineffectual in environmental monitoring due to difficulties in communication, taxonomy, performance indicators, time-scale, consistency of habitat and standardization of techniques and expression of results. All these problems will be considered, with examples drawn from a wide variety of organisms in different contexts.