Organochlorine contaminants in mummichog (Fundulus heteroclitus) living downstream from a bleached-kraft pulp mill in the Miramichi Estuary, New Brunswick, Canada

Mummichog, a small-sized sentinel fish species, has been proposed for use i n environmental effects monitoring programs conducted by pulp mills that re lease their effluent in marine waters. In order to evaluate the suitability of mummichog as a sentinel species and to support the interpretation of bi ological effects data, tissue concentrations of polychlorinated dibenzo-p-d ioxins and dibenzofurans, (PCDD/Fs), chlorophenolic compounds (CPs), polych lorinated biphenyls (PCBs), and chlorinated pesticides were investigated in mummichog sampled in the Miramichi Estuary, which was receiving a bleached -kraft mill (BKM) effluent, and in a reference estuary, the Bouctouche Estu ary. Higher concentrations PCDD/Fs (up to 50 times), CPs (up to 60 times), DDT, and PCBs (up to 10 times) were found in mummichog sampled at the upstr eam site of the Miramichi Estuary. At this site, 2,3,7,8-tetrachlorodibenzo -p-dioxin toxic equivalent concentrations were slightly above the threshold for ethoxy resorufin O-deethylase induction. Multivariate analyses on cong ener profiles revealed that the contamination by PCDD/Fs and CPs originated both from the BKM and from a former wood-preservation plant and that PCDD/ Fs and CPs typical of the BKM were transported 40 km downstream from the mi ll. Patterns and levels of persistent contaminants differed between sites w ithin the Estuary, indicating that the fish did not mix during their growin g period. These findings support the use of mummichog in environmental effe cts monitoring programs, because this species bioaccumulates chlorinated co mpounds contained in BKM effluent and is sedentary. The cause-effect relati onship between exposure to the BKM effluent and the observed biological res ponses will have to be demonstrated by laboratory studies because of the pr esence of multiple sources of contamination.