Tailings from Oil Sands Creating Toxic Wetlands for Wood Frogs

Tailings from Oil Sands Creating Toxic Wetlands for Wood Frogs

In a recent study published in Toxicological & Environmental Chemistry in September 2010, contained data which branches the connection between the age of wetlands and toxicity level of oil sands process-affected material (OSPM) in which wetlands were reclaimed with. The study was carried out using the test subjects to determine the reasoning behind the reduction of OSPM levels of toxicity over time, testing the conditions of various reclaimed and control/reference sites. The subjects used in the test were wood frogs (Rana sylvatica), native to the area, and are anticipated to live in such wetlands containing tailing materials. The uses of amphibians are very useful tools in determining changes in toxicity of aquatic environments, over a small period of time (Harris et al. 2001).

The oil sands refining process produces not only crude oil, but also sand and most importantly water containing suspended fine particles making up OSMP, that contain such toxic materials (not limited to aquatic life) as; naphthenic acids (NAs) and polycyclic aromatic hydrocarbons (PAHs) which can increase pH and salinity levels in aquatic environments. The OSMP, which are produced in the extraction process, are called tailings, and are held in large tailing ponds until operation of these mine sites end, in which reclamation methods must be put in place. The reclamation method used is “wet landscape”, this involves the use of the tailing materials to create new wetlands, in efforts to try and imitate the ecological role of naturally occurring wetlands.

The study conducted used a variety of wetland sites located 40 km north of Fort McMurray, Alberta, on mining sites used for oil sand extraction. A total of 14 different wetlands were used in the experiment, containing four separate categories of wetland site classification; young reference or old reference wetlands (controls), and young reclaimed or old reclaimed wetland sites. Old tailing-affected wetlands (old reclaimed) are at least seven years or older, while young reclaimed wetland sites are equal to or less than seven years old. The “reference” wetlands used have never received tailing materials directly or indirectly. The subjects were fed fresh boiled lettuce every two days, along with air temperature and water temperature readings during these times. Four caged enclosures were set in each wetland; every enclosure was stocked with 50 tadpole larvae. The developmental progress of the tadpoles was studied closely until the metamorphic climax (fore-limb development) was reached. The metamorphic climax was compared to Gosner stage 42 (Gosner scale is used to describe the progress of maturity based on anatomical features). The study continued for 52 to 75 days, depending on the percentage of tadpoles that reached metamorphic climax (75%).

The data presented in the results form the study show that the survival rate of tadpoles was generally low in young wetlands containing OSPM (young reclamation wetlands). Over generations of amphibians, this direct exposure to oil sands process-affected material in tailings, like toxic compounds such as NAs and PAHs, could put amphibian populations in danger. The reclaimed wetland areas constructed by oil sand companies, on oil sands mine sights are not immediately inhabitable for amphibians like the wood frog. The results shown by the study indicates that poor survival rates existed in young reclaimed wetlands. Young reclaimed wetlands had a 41.5%, 62.6% and 54.7% higher mortality rate of tadpoles than that of old reclaimed, young reference and old reference wetlands. Survival rates in old reclaimed wetlands suggest that maturing time for young OSMP wetlands to be inhabitable is seven years. Toxicity levels decrease of the seven years, enough to have old wetlands with toxic levels comparable to that of the reference wetlands. Old reclaimed wetlands contained a noticeable lower toxicity that that of young reclaimed wetland sites. The reduced toxic levels in old reclaimed wetlands sites is caused by the breakdown of some NAs and PAHs by microbes, but this process takes at least seven to 15 years for the toxic level to plateau to an inhabitable level for amphibians like the wood frog. The oil sands tailing materials used to create the manmade wetlands have an effect on the survival and growth of an amphibian like the wood frog. The results proved evidence that amphibian life can be sustained in wetlands containing OSMP (tailing materials), only if the wetland is seven years or older, but if the wetland is too young, amphibian life cannot sustain a functional population, with such a high mortality rate.

Hersikron, H.D., Ciborowski, J., Smits, J. 2010. The effects of oil sands wetlands on wood frogs (Rana sylvatica). Toxicological & Environmental Chemistry, 92(8): 1513-1527.