ROLE OF SEASON IN AQUATIC HAZARD ASSESSMENT

This paper discusses the potential for time of year to influence the o utcome of aquatic hazard assessments. Exposure of fish to contaminants under winter conditions can cause them to develop Wi,ter Stress Syndr ome (WSS). Substantial mortality can result, potentially changing year -class strength and population structure of the affected species, and altering community-level ecological interactions. Aquatic contaminants should be evaluated in the context of seasonal metabolic changes that normally occur in test organisms. WSS could be an important, but as y et unquantified, cause of mortality in many circumstances. Wastewater discharges may pose a greater toxic threat to fish during winter than at other times of the year. A comprehensive protocol for aquatic hazar d assessment should include testing for WSS.