Developing Triggers for Environmental Effects Monitoring Programs for Trout-Perch in the Lower Athabasca River (Canada)

Baseline variations in trout-perch energy use (growth, gonad size) and energy storage (condition, liver size) were characterized between 2009 and 2015 in 8 reaches of the Athabasca River (AB, Canada), including 2 reaches upstream of the city of Fort McMurray (AB, Canada) and 6 reaches downstream of Fort McMurray among existing oil sands operations. Generalized linear models, used to account for background variation, indicated that fork length, gonad size, and liver size decreased, whereas body weight increased, in relation to river discharge, for both male and female trout-perch. Air temperature was positively correlated with liver size and negatively correlated with gonad size and body weight for females, but only positively correlated with gonad weight for males. These linear models explained approximately 20 to 25% of the variation in adjusted body size, and upward of 80% of the variation in adjusted body weight, liver weight, and gonad weight. Residuals from linear models were used to estimate normal ranges of variation for each of the fish population performance measures. Combined, the models and normal ranges can be used to assess subsequent monitoring data, providing potential triggers for follow-up monitoring activities. Environ Toxicol Chem 2019;38:0-0. Environ Toxicol Chem 2019;38:1890-1901. © 2019 SETAC.

Bioaccumulation of Tl in otoliths of Trout-perch (Percopsis omiscomaycus) from the Athabasca River, upstream and downstream of bitumen mining and upgrading

It has been suggested that open pit mining and upgrading of bitumen in northern Alberta releases Tl and other potentially toxic elements to the Athabasca River and its watershed. We examined Tl and other trace elements in otoliths of Trout-perch (Percopsis omiscomaycus), a non-migratory fish species, collected along the Athabasca River. Otoliths were analyzed using ICP-QMS, following acid digestion, in the metal-free, ultraclean SWAMP laboratory. Compared to their average abundance in the dissolved (<0.45 μm) fraction of Athabasca River, Tl showed the greatest enrichment in otoliths of any of the trace elements, with enrichments decreasing in the order Tl, Sr, Mn, Zn, Ba, Th, Ni, Rb, Fe, Al, Cr, Ni, Cu, Pb, Co, Li, Y, V, and Mo. Normalizing Tl in the otoliths to the concentrations of lithophile elements such as Li, Rb, Al or Y in the same tissue reveals average enrichments of 177, 22, 19 and 190 times, respectively, relative to the corresponding ratios in the water. None of the element concentrations (Tl, Li, Rb, Al, Y) or ratios were significantly greater downstream of industry compared to upstream. This natural bioaccumulation of Tl most likely reflects the similarity in geochemical and biological properties of Tl⁺ and K⁺. SUMMARY OF MAIN FINDINGS: Thallium is enriched in fish otoliths, relative to the chemical composition of the river, to the same degree both upstream and downstream of industry.