Event Title

Impacts of run-of-river hydropower on food web structure and mercury bioaccumulation in American dippers of coastal British Columbia

Presentation Abstract

Run-of-river (RoR) dams are an increasingly common alternate energy source on mountain streams. Despite reductions in dam size and greenhouse gas emissions compared to conventional impoundments, RoR hydro may have ecotoxicological impacts through disruption of the natural flow regime. The American Dipper (Cinclus mexicanus) is a high trophic level river bird that occupies mountain streams suitable for RoR dams year-round and are known indicators of stream health; thus, they are an ideal species to study potential impacts of run-of-river hydropower. The objectives of this study are to 1) characterize the food web upstream and downstream of regulated and unregulated streams using stable isotopes (δ13C, δ15N, δ34S); 2) evaluate the methylmercury biomagnification potential upstream and downstream of regulated streams and compare dipper methylmercury levels between regulated and unregulated streams; and 3) determine if in-stream and riparian habitat features important for river birds are altered by run-of-river dams. Food webs were sampled at regulated and unregulated streams using a paired design a) upstream and downstream of 7 regulated and 7 unregulated streams and b) between regulated and unregulated streams. Surveys have found dippers congregating immediately upstream and downstream of several RoR dams in coastal BC, particularly during autumn. This has led to the hypothesis that reduced flow associated with these small dams creates a novel habitat in which dippers may forage more efficiently. Analyses of the blood and invertebrate samples from 14 streams has revealed isotopic changes on regulated streams, specifically 34S-depleted dipper blood, suggesting microbial activity associated with the headponds. We are assessing whether this modified habitat reflects higher levels of methylmercury than upstream of the dam or nearby unregulated streams. This study is an opportunity to examine the effects of reduced and stabilized flow on lotic food webs and improve our understanding of methylmercury biomagnification in mountain streams.

Session Title

General contaminant toxicology in aquatic and terrestrial species

Conference Track

Fate and Effects of Pollutants

Conference Name

Salish Sea Ecosystem Conference (2016 : Vancouver, B.C.)

Document Type

Event

Location

2016SSEC

Type of Presentation

Oral

Contributing Repository

Digital content made available by University Archives, Heritage Resources, Western Libraries, Western Washington University.

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Type

Text

Language

English

Format

application/pdf

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Impacts of run-of-river hydropower on food web structure and mercury bioaccumulation in American dippers of coastal British Columbia

2016SSEC

Run-of-river (RoR) dams are an increasingly common alternate energy source on mountain streams. Despite reductions in dam size and greenhouse gas emissions compared to conventional impoundments, RoR hydro may have ecotoxicological impacts through disruption of the natural flow regime. The American Dipper (Cinclus mexicanus) is a high trophic level river bird that occupies mountain streams suitable for RoR dams year-round and are known indicators of stream health; thus, they are an ideal species to study potential impacts of run-of-river hydropower. The objectives of this study are to 1) characterize the food web upstream and downstream of regulated and unregulated streams using stable isotopes (δ13C, δ15N, δ34S); 2) evaluate the methylmercury biomagnification potential upstream and downstream of regulated streams and compare dipper methylmercury levels between regulated and unregulated streams; and 3) determine if in-stream and riparian habitat features important for river birds are altered by run-of-river dams. Food webs were sampled at regulated and unregulated streams using a paired design a) upstream and downstream of 7 regulated and 7 unregulated streams and b) between regulated and unregulated streams. Surveys have found dippers congregating immediately upstream and downstream of several RoR dams in coastal BC, particularly during autumn. This has led to the hypothesis that reduced flow associated with these small dams creates a novel habitat in which dippers may forage more efficiently. Analyses of the blood and invertebrate samples from 14 streams has revealed isotopic changes on regulated streams, specifically 34S-depleted dipper blood, suggesting microbial activity associated with the headponds. We are assessing whether this modified habitat reflects higher levels of methylmercury than upstream of the dam or nearby unregulated streams. This study is an opportunity to examine the effects of reduced and stabilized flow on lotic food webs and improve our understanding of methylmercury biomagnification in mountain streams.