THE IMPACTS OF URBAN POLLUTION ON THE IMMUNE SYSTEM OF SPOTTAIL SHINERS (NOTROPIS HUDSONIUS) IN THE ST. LAWRENCE RIVER

摘要

The impacts of municipal sewage on the immune status of feral fish species are poorly understood. The purpose of this study was to determine the condition and phagocytosis indices of wild spottail shiners (Notropis hudsonius) collected at upstream and downstream sites (spanning 150 km distance) from a populated urban area in the Saint-Lawrence River (Montreal, Quebec, Canada). Shiners were collected, analyzed for fish weight/fork length, both resting and active phagocytosis activities in leukocytes. Samples of surface waters at the sampling site were also collected for fecal coliform counts. The results revealed that coliform levels followed a significant upstream-downstream correlation and fish collected at downstream sites had lower condition factor (g/cm). Resting and active phagocytosis activity was significantly positively correlated with fecal coliform levels suggesting that ambient bacterial levels stimulated phagocytosis activity. Normalization of both resting and active phagocytosis activity against fecal bacteria counts revealed an immunosuppressive effect in shiners collected downstream the city's municipal wastewater outflow. In conclusion, the immune system of spottail shiners is affected by urban pollution and reflects the cumulative contribution of exposure to bacteria and urban effluent contaminants.