A community-based water group has raised concerns about dwindling mayfly numbers downstream of mining areas in the Elk Valley.
The latest report from the Elk River Watershed Regional Aquatic Effects Monitoring Program (RAEMP) shows populations of mayflies, and to a lesser degree stoneflies and caddisflies, have declined.
Of the 59 mine-exposed areas sampled in 2015, almost half (27 of 59) had proportions of these aquatic insects that were less the normal ranges for those species, according to the 2015-16 report.
The decline was attributed to “increasing gradients of mine-related influence on water quality and calcite”.
Elk River Alliance Interim Executive Director Allie Ferguson said this was concerning.
“Any decline in mayflies is important to monitor as mayflies are a particularly sensitive aquatic insect in a complex ecosystem that can tell us about the overall health of the watershed,” she said.
“We hope to see the results of causation studies as soon as possible, given the importance of mayflies to the ecology of the Elk River system, including as food for fish.”
An area of concern is the upper Fording River, where mayflies have declined over a distance of about 12km.
However, the species has been shown to recover in other areas including downstream from Greenhills Operations and upstream and downstream from Line Creek Operations.
Teck’s Manager of Social Responsibility Nic Milligan said a number of factors could be at play in Fording River.
“Factors may include both mining-related and natural factors, such as nitrate concentrations, temperature trends and annual variation in river flow,” he said.
“Further monitoring and assessment is being completed to investigate and confirm cause for the mayfly reduction.
“In addition, the RAEMP and numerous local aquatic effects monitoring programs, along with our chronic toxicity testing program and multiple supporting studies, will continue to be implemented to support understanding of aquatic health within the Elk River watershed, which includes mayflies.”
The Elk River Watershed RAEMP report was one of 13 technical reports published online by Teck Coal last month in an effort to increase its transparency.