CIMP 161_Cumulative Impacts Monitoring of Aquatic Ecosystem Health of Yellowknife Bay, Great Slave Lake, NWT

Yellowknife Bay on Great Slave Lake is a water body of cultural, subsistence and recreational importance for the Yellowknives Dene First Nation and residents of Yellowknife. The ecosystem health of Yellowknife Bay has been impacted by historical mining releases of arsenic and metals, and contaminant loading to the bay from the closed Giant Mine continues today. Arsenic and metals were dispersed to the bay through atmospheric deposition of ore roaster emissions, as well as effluent and tailings releases at Giant Mine. Over several decades, considerable study has been conducted on arsenic and metal pollution in near- and far-field receiving environments of Yellowknife Bay. This three-year project aimed to enhance previous studies and investigate data gaps in order to obtain a more complete picture of the current environmental conditions in the bay. Multiple environmental components including water, sediment and the aquatic food chain were sampled to measure current levels of arsenic and metals, and to better understand the processes controlling their environmental fate. Project findings have been presented in several reports outlined below, and additional reports are being prepared to summarize the datasets. This project generated significant new information that will inform the management, assessment and use of the Yellowknife Bay ecosystem.