The Impact of Low Dissolved Oxygen and Recovery Patterns of Benthos in Northern Rivers

Abstract

An ecological risk assessment for the Athabasca River was done. We did a review of literature pertaining to ecological risk assessment in the Athabasca River. The focus of the risk assessment was on the ecological impact of low dissolved oxygen (DO), because mainly ice-cover and pulp mill effluent discharges on the Athabasca River may potentially cause a low DO event. The ecological impact of low DO was assessed for the benthic invertebrate community, specifically the Orders Ephemeroptera, Plecoptera and Trichoptera (EPT), which are sensitive to low DO, and the Order Diptera. Based on the literature review, an ecological risk assessment involved: 1) using electroshocking to simulate low DO in the Athabasca River and determining recovery of benthic invertebrates following electroshocking and ice-out; 2) using a laboratory flume to determine the relationship between DO level and benthic invertebrate drift rate.