Title

How stream biomonitors reveal past, present and future metal trends in the CF River, MT

Abstract

Bioaccumulation studies of a resident aquatic organism can provide a direct indicator of bioavailable metal in mine-impacted rivers. This approach is supported by concurrently evaluating bed sediment metal concentrations and water quality data. We examine the effectiveness of mine waste remediation in the Clark Fork River using a resident biomonitor (Hydropsyche spp., O: Trichoptera) and streambed sediment. Over a 19-year period, Cu concentrations declined in both indicators at the two most upstream stations, a pattern coincident with remediation events. Sediment Cu declined at most stations along the 200 km study reach. However, Cu concentrations in Hydropsyche in the middle (85 km) and lower (190 km) reaches were significantly influenced by total annual discharge, masking the impact of remediation on bioaccumulation, at least to date.

A biodynamic model was used to make predictive assessments of Cu bioaccumulation under varying metal exposures. We experimentally-derived physiological constants and used site-specific geochemical field conditions to predict Cu bioaccumulation in Hydropsyche (Hydropsyche is a useful proxy for metal exposure in sensitive species). Hydropsyche has a fast Cu uptake and loss rate. However, dietary Cu influx is ~3-fold higher than dissolved influx, suggesting that Cu uptake from food prevails in nature for that species. Bioaccumulation data from the Clark Fork was used to validate this model. The model under-predicted Cu concentrations in Hydropsyche by ~70% when only dissolved Cu concentrations are considered. However, predicted concentrations fall within range of observed values when dietary influx is incorporated into the model. Ongoing field monitoring coupled with biodynamic modeling is a unique approach that strengthens our predictive capabilities as metal exposure conditions change.

This topic was presented as both a talk and as a poster.

Start Date

5-3-2010 12:00 PM

End Date

5-3-2010 2:00 PM

Document Type

Poster

 
Mar 5th, 12:00 PM Mar 5th, 2:00 PM

How stream biomonitors reveal past, present and future metal trends in the CF River, MT

Bioaccumulation studies of a resident aquatic organism can provide a direct indicator of bioavailable metal in mine-impacted rivers. This approach is supported by concurrently evaluating bed sediment metal concentrations and water quality data. We examine the effectiveness of mine waste remediation in the Clark Fork River using a resident biomonitor (Hydropsyche spp., O: Trichoptera) and streambed sediment. Over a 19-year period, Cu concentrations declined in both indicators at the two most upstream stations, a pattern coincident with remediation events. Sediment Cu declined at most stations along the 200 km study reach. However, Cu concentrations in Hydropsyche in the middle (85 km) and lower (190 km) reaches were significantly influenced by total annual discharge, masking the impact of remediation on bioaccumulation, at least to date.

A biodynamic model was used to make predictive assessments of Cu bioaccumulation under varying metal exposures. We experimentally-derived physiological constants and used site-specific geochemical field conditions to predict Cu bioaccumulation in Hydropsyche (Hydropsyche is a useful proxy for metal exposure in sensitive species). Hydropsyche has a fast Cu uptake and loss rate. However, dietary Cu influx is ~3-fold higher than dissolved influx, suggesting that Cu uptake from food prevails in nature for that species. Bioaccumulation data from the Clark Fork was used to validate this model. The model under-predicted Cu concentrations in Hydropsyche by ~70% when only dissolved Cu concentrations are considered. However, predicted concentrations fall within range of observed values when dietary influx is incorporated into the model. Ongoing field monitoring coupled with biodynamic modeling is a unique approach that strengthens our predictive capabilities as metal exposure conditions change.

This topic was presented as both a talk and as a poster.