The Athabasca oil sands deposit is the largest reservoir of crude bitumen in the world. Recently, the soaring demand for oil and the availability of modern bitumen extraction technology has heightened exploitation of this reservoir and the potential unintended consequences of pollution in the Athabasca River. The main objective of the present study was to evaluate the potential impacts of oil sands mining on neighboring aquatic microbial community structure.
The Athabasca River stretches 1,231 kilometres from the Athabasca Glacier in west-central Alberta to Lake Athabasca in Northeastern Alberta. Annual mean discharge downstream of Fort McMurray is 619 cubic metres per second with a maximum of 1,010 cubic meters per second (http://www.ec.gc.ca/eau-water/, station 07DA001, accessed October 12, 2011). The direction of the flow near Fort McMurray is from the south to the north. A single large 10kg sample was taken from each of the following sites (17 samples): five sampling sites were chosen on the Athabasca River: a reference site near Fort McMurray, upstream of the oil sands mining activities (AR); near the Northland Sawmill, close to mining activities (NSM); near Suncor mining activities (DSU); near the mouth of the Muskeg River, downstream of the mining activities (MSK); and finally near the mouth of the Ells River, about 25 km downstream of the mining activities (AER). Nine other sampling sites were chosen in three of the Athabasca tributaries: upper (EU), mid (EM) and lower (EL) Ells River (slightly affected by mining activities) upper (FU), mid (FM) and lower (FL) Firebag Creek (not affected by mining activities); upper (SU), mid (SM), and lower (SL): Steepbank Creek (strongly affected by mining activities). Three samples were taken from oil sands tailings ponds: samples SY1A was taken from the Mildred Lake settling basin at about the mid-point adjacent to the east shore, SY1B was taken parallel to the east shore but further south in the basin. Less...