TRENDS IN CONCENTRATIONS AND EFFECTS OF PERSISTENT TOXIC CONTAMINANTSIN THE GREAT-LAKES - THEIR SIGNIFICANCE FOR INFERRING CAUSE-EFFECT RELATIONSHIPS AND VALIDATING MANAGEMENT ACTIONS

This paper summarizes a workshop on temporal trends in levels and effe cts of persistent toxic contaminants in the North American Great Lakes . Information on trends in contaminant levels is reasonably good for s ediments, fish, and birds, but is scanty or absent for other ecosystem components. Information on trends in effects has been reported for bi rds, but is scanty or absent for other groups of organisms. In princip le, information on differential trends in effects of contaminants coul d be used to validate or improve hypotheses about cause-effect relatio nships and to verify the effectiveness of management actions. However, little or no useful information on differential trends appears to be available. Use of trend data for these purposes will require collectio n of more derailed information and greater attention to conceptual for mulation of hypotheses.