Effects of pulp mill effluent on benthic assemblages in mesocosms along the Saint John River, Canada

Abstract

We used mesocosms to examine the impact of different concentrations of pulp mill effluent (PME) on structural and functional endpoints of a benthic assemblage in the Saint John River (NB, Canada) during 1999 and 2000. Previous studies on this effluent's effects produced conflicting results, with field surveys suggesting a pattern of mild nutrient enrichment, while laboratory toxicity tests linked effluent exposure to moderate contaminant effects. Experimental treatments included three concentrations of sulfite pulp mill effluent (0, 5, 10% v/v PME). Endpoints for the assessment included algal biomass and taxonomic composition, benthic invertebrate abundance and composition, and insect emergence. Low concentrations of PME increased periphyton biomass and caused changes in community structure within the diatom-dominated community. Pulp mill effluent addition had little effect on several structural endpoints measured for benthic invertebrates, including abundance and taxonomic richness, but significantly changed community composition. For both periphyton and benthic invertebrates, community composition endpoints were more sensitive indicators of PME exposure. Insect emergence was a highly relevant functional endpoint. When benthic and emerged insects were combined, total abundance increased with PME addition. Results from two trophic levels, which provided multiple lines of evidence, indicated that the main impact of these PME concentrations is nutrient enrichment rather than effluent toxicity. Our findings also suggest that benthic invertebrate and periphyton assemblages, algal biomass production, and insect emergence are sensitive response measures. Future studies may confirm this observation. The consideration of both functional and structural endpoints at different trophic levels can greatly improve our understanding the effects of discharges to rivers. Such an understanding could not have been obtained using standard assessment techniques and illustrates the value of mesocosms and the benthic community assemblage approach in environmental assessment.

Impacts and prognosis of natural resource development on water and wetlands in Canada’s boreal zone

“…The release of pollutants and contaminants into surface waters can occur not only at the site of disturbance but can also be transported many kilometres downstream (Culp et al 2003;Muscatello et al 2008;Kelly et al 2010). Individual effects of headwater disturbances can potentially accumulate and affect downstream ecosystems and their services (Townsend et al 2008).…”

Northern Rivers Ecosystem Initiative: Nutrients and Dissolved Oxygen – Issues and Impacts

“…Weekly grab samples of reference water and the various treatment levels were collected and analyzed for nutrients and general water quality. Details of mesocosm methods can be found in Culp et al (2003Culp et al ( , 2004a.…”

“…In the second experiment, mesocosms were subjected to varying concentrations of P under conditions of N saturation (i.e., 135 μg L −1 N). Experiments were conducted in the mesocosm system described by Culp et al (2003Culp et al ( , 2004a. However, the substrate used in the dose-response experiments consisted of seven (4 cm 2 ) ceramic tiles, equally spread along the bottom of the stream.…”

Structural and functional responses of benthic invertebrates to imidacloprid in outdoor stream mesocosms

“…The use of controlled semi-field exposures, such as mesocosms, provides an opportunity to perform ecosystem-level research that can complement laboratory bioassays and, therefore, better predict effects of ecological relevant exposures of different types of anthropogenic substances to natural communities (Fairchild et al, 1992;Culp et al, 2003;Hickey and Golding, 2002;Van den Brink, 2006;Van den Brink et al, 2005). Mesocosms are smaller and less complex than natural ecosystems, yet they allow the use of relevant biological conditions (ambient abundance of natural biota), while maintaining the statistical power through replication of treatments and precise regulation of pesticide concentrations and other physico-chemical variables (Baird et al, 2001;Crane, 1997).…”