A major challenge facing Canada’s oil sands industry is returning post-mining landscapes to equivalent land capability. Especially problematic are the fluid tailings (FT) produced during bitumen extraction, since these contain several chemicals of ecological concern. The long-term land closure plans of all oil sands mining operators include reclaiming fluid tailings in pit lakes. Pit lakes are reservoirs constructed within the boundaries of a former mine pit. In the oil sands industry they can serve the dual purpose of containing FT in their sediments and eliminating mined landscape depressions. Oil sands pit lakes should sequester FT and bioremediate the water layer over time, and eventually become integrated into local watersheds. Although pit lakes are common in other mining industries, they are still not a government approved reclamation strategy for the oil sands industry. Over thirty pit lakes are in the planning stages, but their approval will depend on pilot studies.  Understanding the development of pit lakes is critical to determining if they are a viable long-term tailings management and remediation strategy in the oil sands region.

Assessing reclaimed pit lakes will require methods for measuring the chemical, physical, economic or biological status of the pit lake compared to minimally disturbed reference lakes. Traditional biological methods for ecosystem assessment rely mostly on the detection of large plant and animal species that are sensitive to pollution stress. However, food webs in lakes are based on algae rather than plants. Other measurements of ecosystem status must be developed. In this study we will assess food webs of bacteria, algae, and small multicellular zooplankton using DNA-based “omic” methods. The communities in an oil sands pit lake will be compared to natural boreal lakes, to identify indicator species and functional genes that can be used to assess and future pit lakes in the Alberta oil sands region.