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National Assessment of Pulp and Paper Environmental Effects Monitoring Data

5.0 Overall Conclusions

The Canadian pulp and paper industry has invested billions of dollars towards research and technology aimed at reducing its emissions and improving the quality of their effluent. Today, most pulp and paper mills in Canada are equipped with at least primary and secondary treatment systems. Although mills have been successful in dramatically reducing the toxicity of their effluents, EEM data show that impacts continue in the aquatic environment.

On a national scale, the benthic invertebrate community surveys most commonly revealed a eutrophication response pattern as a result of exposure to pulp mill effluent. This nutrient enrichment effect, which was usually mild to moderate (but sometimes pronounced), was likely due to the phosphorus, nitrogen, and organic content of the effluent. EEM studies showed that study design and habitat type had some influence on the results. For example, riverine habitats showed mild eutrophication, marine/estuarine habitats showed signs of toxic or smothering effects, and lakes showed more intermediate responses.

Effects were also observed on fish downstream of pulp mill effluent, with the overall response pattern being one of combined metabolic disruption and nutrient enrichment. The national trend for fish was towards a decrease in gonad weight and an increase in liver weight, condition factor, and weight at age. Other response patterns were also observed, however, including ones expected under conditions of food limitation.

The integration of the results from the benthic invertebrate community and fish population surveys showed good agreement. That is, the combined metabolic disruption/nutrient enrichment observed in fish reflected the eutrophication results seen in benthos. The results also showed that a predominantly nutrient enrichment effect in fish (without measurable metabolic disruption) may not be detected until the benthos reach a state of pronounced eutrophication. This integration also showed that these two main components of the EEM field survey complement each other by revealing different aspects of the effects associated with effluent exposure.

The national EEM data assessment has revealed some important response patterns in the aquatic environments around pulp and paper mills. Although effluent quality has vastly improved since the 1992 Pulp and Paper Effluent Regulations were promulgated, mills continue to have an impact on fish and their habitat (as measured by the benthic invertebrate community survey). More monitoring is needed to assess the spatial extent and ecological importance of the observed effects, and Environment Canada will continue to work with industry and other stakeholders to better understand their importance. As well, the results of the national assessment verified that each of the endpoints being used in the EEM Program provide ecological relevant and useful monitoring information. These results are an excellent starting point and underline the importance of continued EEM.