NEW EVIDENCE SELENIUM CONCENTRATIONS ARE INCREASING IN LAKE KOOCANUSA'S RESIDENT FISH

The mobilization of selenium (Se) released from expansive coal mines in the Elk Valley of southeastern B.C. have resulted in elevated concentrations in fish in downstream lotic systems. Lentic systems are not present in the basin until the Elk River flow through Elko dam and enters Lake Koocanusa, just north of the B.C.-Montana border, making the reservoir a likely source for Se loading. Lake Koocanusa is considered to be sensitive to Se accumulation because physicochemical conditions exist for inorganic Se to be converted into toxic organic Se and accumulate in biota.

Described as the “paradox of Se” in fish, Se is nutritionally required in small quantities, yet becomes highly toxic in slightly greater amounts. The most sensitive biological end point are eggs, where newly hatched larval fish can experience teratogenic deformities and death, while adult fish still appear healthy. This atypical relationship could move a fish population from un-impacted to complete reproductive failure with only a small increase in Se loading.

In 2008, concerns over further coal development in B.C. prompted Montana Fish, Wildlife & Parks (FWP) to collect fish from the Flathead and Kootenay basins and analyze fish muscle, egg, and liver tissues for Se concentrations. While an accord between Montana and B.C. in 2010 prohibited coal mining and exploration in the North Fork of the Flathead River Basin, the Kootenay continued to see rapid coal mine expansions. In 2013, FWP repeated the fish tissue Se analysis done on Lake Koocanusa to evaluate if Se concentrations had increased. In all 6 species analyzed, Se concentrations in muscle tissues significantly increased (21-70%) between 2008 and 2013. Burbot muscle plug (non-lethal) samples were also collected from fish in Lake Koocanusa during the early spring of 2012 and 2013 and compared to Moyie Lake, a reference lake in B.C. considered to be un-impacted from coal mining. Burbot collected from Lake Koocanusa had on average 2.9 times higher Se concentration than reference fish from Moyie lake. While mean tissue concentrations are still below threshold levels, it appears Se loading is occurring in Lake Koocanusa and accumulating in resident fish tissues.