ABSTRACT
The high degree of spatial heterogeneity and the challenge of obtaining true replicates make it difficult to predict or to quantify the impacts of complex effluents on riverine biota. We have developed an experimental stream system that simulates the riverine environment for the purpose of assessing the impacts of effluent discharges on large rivers. This transportable outdoor system is established beside the study river, providing ambient water temperature and light regimes. The system is comprised of 16 circular 0.9 m2 streams, allowing for adequate replication. Current velocity is provided by an inexpensive belt-driven propeller that can produce mid-water velocities exceeding 20 cm sec−1. The system is partially recirculating and the water depth and hydraulic residence times are easily adjusted. By increasing water residence time within the streams, the volume of toxic effluents or contaminants required during an experiment can be minimized. We have used this system to investigate the nutrient and contaminant effects of treated effluents from kraft pulp mills on complex food webs in the Athabasca River, Alberta, Canada. Multiple trophic-level effects are examined by seeding the tanks with natural substrata and biota (i.e., biofilm, invertebrates, fish) from the river.
