Pollution-Induced Community Tolerance—A New Ecotoxicological Tool

Abstract

The authors hypothesize that pollution-induced community tolerance (PICT) is direct evidence that a community is disturbed by a pollutant and, furthermore, that the agent or agents causing the effects can be identified, because induced tolerance will be observed only for those compounds that have exerted selection pressure on the community. A similar concept has been formulated for population tolerance, but we suggest that the concept is more useful when applied at the community level. Our examination of some crucial points behind PICT, using arsenate and periphyton communities, demonstrates that (1) the tolerance increase can be determined in short-term photosynthesis experiments, (2) PICT correctly indicates changes in species composition and net production, and (3) the selection pressure of arsenate is specific—that is, a tolerance increase for one compound is not followed by co-tolerance to other compounds unless they are closely related chemically or in their mode of action. These results support the idea of using PICT as an ecotoxicological tool. If further corroborated, PICT can be applied in both laboratory and field studies. PICT might be used retrospecitively in the field to detect minor disturbances and to identify the causing agent. In a laboratory test system, PICT can be used to estimate the no-effect concentration for the community under study. The authors argue that test systems based on PICT will be sensitive and yield ecologically relevant information.