Effect of a Pulp and Paper Mill Effluent on the Productivity of Periphyton and Phytoplankton

The short-term effect of a kraft mill effluent on the productivity of periphyton and phytoplankton in Nipigon Bay was examined. Addition of raw effluent at concentrations of 10−2 and higher consistently reduced photosynthesis of both periphyton and phytoplankton. Significant reductions were occasionally observed at effluent concentrations as low as 10−4. At high effluent concentrations pH change produced a major portion of the depression. Laboratory experiments with four compounds identified from the effluent showed dehydroabietic acid to be slightly toxic.