Multiple stressors affecting river food webs

Investigating impacts of run-of-river hydropower on American dippers and the river food webs of coastal British Columbia

Run-of-river dams, a form of small-scale hydro known synonymously as river diversions, are an increasingly common alternate energy source. Despite reductions in dam size and greenhouse gas emissions compared to conventional impoundments, run-of-river hydro may have ecological impacts through disruption of the natural flow regime and associated infrastructure. The American Dipper (Cinclus mexicanus) is a high trophic level river bird whose habitat overlaps with the placement of run-of-river dams on coastal mountain streams of British Columbia. Dippers are also known indicators of stream health; thus, they are an ideal species to study potential impacts of run-of-river hydropower. This study is an opportunity to examine the effects of reduced and stabilized flow on lotic food webs and improve our understanding of mercury biomagnification in rivers with impoundments. We hope this research will also allow us to apply novel biomonitoring techniques to improve sustainable energy development. This involves the application of stable isotopes to measure changes in the food web associated with altered flow.

The objectives of this study are to:

1) identify American Dipper habitat use upstream and downstream of regulated and unregulated streams in southwest BC;

2) characterize the food web at these sites using stable isotope analysis of dippers and their prey;

3) evaluate the mercury biomagnification potential at these sites through mercury analysis of blood and feathers in dippers.