USE AND ABUSE OF HEAVY-METAL BIOASSAYS IN ENVIRONMENTAL MONITORING

Animals, plants and fungi, through their highly specific demands on en vironmental resources, can be usefully employed to monitor pollution, provided it is appreciated that their response to various concentratio ns of pollutants will vary both inter- and intra-specifically. Bioindi cators are selected for their ability to respond specifically to a ris e (or more rarely to a fall) in concentration of a particular pollutan t and/or to accumulate one or more particular elements, subsequently m easured by chemical analysis. Species are hierarchical in their suscep tibility to a defined pollution burden, but several contaminants may b e acting independently, synergistically or collectively with the eleme nts bioassayed. Bioassays have often been ineffectual in environmental monitoring due to difficulties in communication, taxonomy, performanc e indicators, time-scale, consistency of habitat and standardization o f techniques and expression of results. All these problems will be con sidered, with examples drawn from a wide variety of organisms in diffe rent contexts.