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Growth responses of periphyton and chironomids exposed to biologically treated bleached-kraft pulp mill effluent

Dube, M.G., Culp, J.M.
Environmental toxicology and chemistry 1996 v.15 no.11 pp. 2019-2027
Chironomidae, biofilm, biomass, carbon, chlorophyll, grazing, growth retardation, insects, monitoring, periphyton, phenolic compounds, phosphorus, pulp, pulp and paper mill effluents, resin acids, rivers, streams, wood extractives, British Columbia
Experiments were conducted in artificial streams to determine the effects of increasing concentrations of bleached-kraft pulp mill effluent (BKME) on periphyton and chironomid (Chironomidae) growth in the Thompson River, British Columbia, Canada. Periphyton growth, as determined by increases in chlorophyll a, was significantly stimulated at all effluent concentrations tested (0.25, 0.5, 1.0, 5.0, and 10.0%). Chironomid growth (total biomass and individual weight) was also significantly stimulated at low effluent concentrations (less than or equal to 1.0%). At higher concentrations (5.0 and 10.0%), chironomid growth was inhibited relative to the 1.0% treatment streams but was greater than in the controls. Increases in growth were attributed to the effects of nutrient and organic enrichment from BKME. The effluent contained high concentrations of phosphorus and appears to be an important source of carbon for benthic insects grazing on the biofilm. In high-concentration effluent streams, chironomid growth decreased despite low levels of typical pulp mill contaminants (chlorinated phenolics, resin acids, and adsorbable organic halide). This suggests that other compounds in the effluent, such as wood extractives, may be inhibiting chironomid growth. These results support findings of field monitoring studies conducted in the Thompson River, in which changes in periphyton and chironomid abundance occurred downstream of a bleached-kraft pulp mill.