Phagocytic response of macrophages from the pronephros of American plaice (Hipoglossoides platessoides) exposed to contaminated sediments from Baie des Anglais, Quebec

Sediments of Baie des Anglais on the St. Lawrence estuary have a history of environmental contamination, but little information exists regarding their toxicity. The purpose of the present study was to determine the effects of contaminated Baie des Anglais sediments on American plaice (Hippoglossoide s platessoides) immune function. Three sites in Baie des Anglais were selec ted which vary in proximity to local industries and in their sediment conta minant load. Sites 1 and 2 (within the bay) are the closest to shore and mo st heavily contaminated while sediments at Site 3, which is outside the bay , are the least contaminated. In the first experiment, American plaice were placed in cages at each site for three weeks and immune function was asses sed by measuring the phagocytic activity of pronephric macrophages. At the time of sampling, plaice displayed pronephros cell immune response disturba nces indicating that Site 1 and 2 were most toxic and Site 3 the least toxi c. The results obtained for phagocytosis revealed that contaminants present in the sediments are bioavailable to fish, which came in contact with them and significantly affected their immune system. In the second experiment, sediments from the most toxic site, Site 1, were collected for a laboratory controlled experiment in which plaice were exposed for up to 3 months to t hese contaminated marine sediments, while the control group was exposed to relatively uncontaminated beach sand. At the end of the exposure period, pl aice were transferred from contaminated sediment to beach sand and sampled one month later in order to determine if immune function had returned to co ntrol levels. The total number of macrophages decreased following three mon ths of exposure, while the active macrophages had already decreased after t he first month of exposure. Following the rehabilitation period a significa nt trend toward normal response was noted. Sediments from Baie des Anglais contain primarily less highly chlorinated PCBs and lower concentrations of the intermediate and highly chlorinated PCBs. The total concentration of PC Bs (sum of 20 congeners) in the contaminated sediments was 1500 ng/g while in the beach sand, the levels were 13.6 ng/g dry weight. Only the low chlor inated PCB congeners were efficiently transferred from the sediments to the plaice liver. Together, these results suggest that the effect of chemical exposure on the phagocytosis of plaice macrophages may be reversible if the fish are returned to a non-contaminated habitat. (C) 2001 Elsevier Science Ltd. All rights reserved.