Benthic community populations near two adjacent northern pulpmill discharges

Benthic invertebrate communities were investigated as part of the federal Environmental Effects Monitoring programs conducted as required by the amended Pulp and Paper Effluent Regulations (PPER) of the federal Fisheries Act. A Refiner Mechanical (RMP) and larger Kraft pulpmill, both situated on a northern, BC reservoir, discharge secondary-treated effluent within 5 km of each other. Efforts to independently distinguish potential effects associated with these individual discharges were complicated by the proximity of the diffusers, their location within a complex ecological region of a reservoir, and the presence of temporal and spatial confounding influences. A comprehensive examination of the benthic community structure involved the combined assessment of several endpoints (total population numbers, relative proportion of taxonomic groups, and species richness). A tiered, spatial approach, based on a reservoir ecological model (Thornton et al., 1981), was adapted to assess and distinguish community structures and reservoir- and mill-related influences. Results suggested that effects associated with the two different mills could be distinguished based on subtle and distinct differences in benthic community profiles.