Contaminant-Adaptation and Community Tolerance in Ecological Risk Assessment: Introduction

Contaminant tolerance, either at the level of the community or an adaptation within populations, has important implications to the risk assessment field. Such tolerance has alternatively been described as a nuisance variable, complicating the extrapolation of toxicity data to field conditions, or as a ‘good weather indicator’, suggesting environmental resilience to a contaminant. These and other issues are explored in this set of invited papers, in which experienced workers from the field of contaminant tolerance have been invited to comment on the relationship between tolerance and the analysis of environmental risk. In addition, recent decades have seen the use of tolerance as a tool for assessing contaminant stress, particularly when establishing causality between specific contaminant exposure and significant ecological impact. The paradigm suggests that an increased tolerance to a contaminant is powerful causal evidence that this contaminant has exerted significant stress. Review, commentary and original data contributions within this Debate and Commentary section explore both the complicating and advantageous aspects of tolerance in risk assessment. The papers conclude that complications associated with tolerance demand careful consideration during risk assessments, and that while population adaptation does not appear to be a promising tool, community-level resistance might be a powerful instrument in ecological risk assessment.