Water Resources Research Act Program

Details for Project ID 2016CO325B

Microbial community responses to metals contamination: mechanisms of metals exposure and bioaccumulation in a stream food web.

Institute: Colorado
Year Established: 2016 Start Date: 2016-03-01 End Date: 2017-02-28
Total Federal Funds: $5,000 Total Non-Federal Funds: $2,500

Principal Investigators: Will Clements, Brian Wolff

Project Summary: The upper Arkansas River (near Leadville, Colorado) has been heavily impacted by metal pollution due to historical mining. In 1983, the U.S. EPA added California Gulch to the National Priorities List (i.e. Superfund Site), due to heavy metals pollution from California Gulch that discharges into the Arkansas River. Metals pollution has caused a shift in aquatic macroinvertebrate community composition – a common method used to assess water quality – with a greater abundance of ‘metal-sensitive’ taxa (e.g. mayflies) at reference upstream sites to increased abundances of ‘metal-tolerant’ taxa (e.g. caddisflies) at polluted sites downstream of California Gulch. Despite improvements in water quality over the past fifteen years, the relative sensitively of the macroinvertebrate communities remain skewed between upstream and downstream sites. Given the increase in water quality downstream it is unclear why metal-sensitive invertebrates remain in low abundance downstream. The traditional approach for setting stream water quality guidelines has relied upon acute toxicity laboratory experiments assuming direct aqueous exposure (e.g. exposure to external gills) to aquatic macroinvertebrates. However, recent research suggests that dietary exposure may be equally as important. Interestingly, metal-sensitive macroinvertebrates commonly feed on benthic microbial biofilms while metal-tolerant taxa tend to feed on seston (organisms and non-living matter drifting in water column). Whereas this difference in dietary preference among metal-sensitive and metal-tolerant stream invertebrates is consistent to dietary metals exposure, the exact mechanism through which this affects stream macroinvertebrate fitness has yet to be evaluated. I seek to better understand how metal pollution affects stream microbial communities in order to understand the exact mechanism for how metals enter the aquatic food web. Because we are testing explicit physiological mechanisms, the results of this work will allow for more targeted remediation approaches that should be broadly applicable around the world.