The toxicity of oil sands tailings was examined with respect to wet landscape reclamation for two benthic invertebrates. Exposure of the leech Nephelopsis obscura to mature fine tails (MFT) covered with clean water resulted in complete mortality within 2 weeks. Exposure to MFT separated from overlying water by a 2 cm layer of clean sediment had no effect on survival and minimal effects on the energy budget, with a decrease in ammonia production which compensated for energetic losses. Reproduction was reduced compared to controls, likely due to differences in behavior. Preference-avoidance testing showed that N. obscura avoids consolidated tailings (CT) water. Exposure of the oligochaete Tubifex tubifex to fresh and sparged (vigorously aerated) MFT covered with clean water resulted in complete mortality within 1 week. Survival and individual growth in fresh and sparged CT was equivalent to controls. Reproduction and population growth were delayed by 4-6 weeks compared to controls.