ORGANOCHLORINE CONTAMINANT CONCENTRATIONS IN CADDISFLY ADULTS (TRICHOPTERA) COLLECTED FROM GREAT-LAKES CONNECTING CHANNELS

Pennsylvania-style light traps were used to capture adult Trichoptera from the St. Marys, St. Clair, Detroit and Niagara rivers, Canada. Ade quate biomass was acquired in single, 2-h collections to permit tripli cate gas chromatographic analyses of 1-4 g samples for 36 organochlori ne contaminants. Contaminant levels varied unpredictably but relativel y little among samples taken at monthly intervals over the summer. Sam ples collected simultaneously from the two sides of the Detroit R. ref lected local sediment contaminant patterns, suggesting limited dispers al by adults. Genus-specific differences in contaminant concentrations within the Hydropsychidae and Leptoceridae probably reflect differenc es in larval habitats and manner of feeding. Contaminant concentration s and relative composition paralleled published reports of contaminant s in sediments from collection locations. St. Marys R. caddisflies con tained contaminant levels indistinguishable from samples collected at reference sites. St. Clair R. samples contained high levels of compoun ds associated with petrochemical industries located in the river's ups tream reaches. High levels of polychlorinated biphenyls (PCBs) and mos t other contaminants in Detroit R. samples reflected industrial loadin gs near Detroit, Michigan. Niagara R. samples contained elevated conce ntrations of PCBs and pesticides. Cluster analysis grouped samples int o five clusters each with unique contaminant composition. These also c orresponded to geographic origin: St. Marys, St. Clair, Detroit and up per and lower Niagara rivers. The relative ease of collection and cons istent results obtained render adult Trichoptera potentially valuable candidates for surveys of aquatic contamination over a broad range of geographical and ecological conditions.