Characteristics of nearshore water quality of Lake Ontario coast under Credit Valley Conservation Jurisdiction, Ontario, Canada

Abstract

The 28.5 km Lake Ontario shoreline along Credit Valley Conservation’s jurisdiction is habitat for native flora and fauna, the source of drinking water for over two million residents, and the location of outfalls for Region of Peel’s two wastewater treatment plants. Some of the significant sources of pollutants to this region are urban tributaries and the Credit River. Instream, shoreside, and nearshore water quality of this region were characterized under this Lake Ontario Integrated Shoreline Strategy study. Eight Parameters of Concern (PoC); water temperature (WT), total suspended solids (TSS), total phosphorous (TP), orthophosphate (OP), nitrate-nitrogen (NO3-N), Escherichia coli (E. coli), specific conductivity (SC), and pH were studied from 2011 to 2013. Amongst all the PoCs TP was of concern since its instream (75th percentile range: 51.0 µg/L to 188 µg/L), shoreside (75th percentile range: 9.00 µg/L to 53.75 µg/L), and nearshore (75th percentile range: 9.75 µg/L to 19.00 µg/L) concentrations, exceeded their respective objectives of 30 µg/L and 10 µg/L. Other parameters in shoreside/nearshore samples met their respective provincial/federal objectives/guidelines; however, instream E. coli and specific conductivity levels were elevated, reflecting the effects of urbanization. The Lake water temperature moorings recorded lake stratification dynamics, including eight downwelling and five upwelling events during 2011 deployment period. These results provide baseline data for future climate change-related assessment studies.