Effects of eroding oil sand and periodic flooding on benthic macroinvertebrate communities in a brown-water stream in Northeastern Alberta, Canada

The portion of the Steepbank River which cuts through the Athabasca oil sands deposit supported a less diverse benthic invertebrate community than did upstream areas. The variety and relative abundance of Plecoptera and Trichoptera were consistently lower in the area of oil sand exposure. As a substrate for benthic invertebrates, oil sand appears to be analogous to bedrock, supporting about 60% as many animals per unit area as adjacent rubble substrates. Burrowing and negatively phototropic organisms were significantly less abundant on oil sand than on rubble. When high discharge of the Athabasca River flooded a riffle to form a pool near the mouth of the Steepbank, rheophilic forms, such as Baetis and Simulium, were largely eliminated from the riffle and benthic standing stocks were reduced by about 50%. The invertebrate community recovered quickly after riffle conditions returned.