The objective of this study workplan is to determine the health of the planktonic community in the Eighteenmile Area of Concern (AOC) and to establish the status of the Use Impairment Indicator in the Eighteenmile Creek Remedial Action Plan (RAP). Results from this study will be compared to results of previously studied community structure data from control / reference sites: an undisturbed creek on the south shore of Lake Ontario (Yanty Creek), the open waters of Lake Ontario, and from Braddock Bay on Lake Ontario