COEUR D'ALENE, Idaho (AP) — Declining levels of oxygen in Lake Coeur d'Alene in northern Idaho are raising concerns that toxic heavy metals buried in its bottom will get free and become suspended in the water column, scientists say.
"Deep down here at the bottom of the lake, the oxygen levels are decreasing," said Craig Cooper, a lake scientist for the Idaho Department of Environmental Quality. "The changes we're seeing are subtle and slow, but they are real."
Scientists say oxygen acts as a cap on the toxic metals contained in 75 million tons of sediment polluted with lead and other heavy metals washed downstream from more than a century of mining in Idaho's Silver Valley.
Cooper spoke Tuesday about Lake Coeur d'Alene's water quality at a conference called Our Gem Symposium, the Spokesman-Review reported.
"Oxygen levels are going in a direction we don't want to see them go," he said.
He said monitoring sites show the trend of lower oxygen is most pronounced in the north and middle parts of the lake. Also, oxygen levels are lowest during the summer and fall when organisms are growing and using oxygen.
Phil Cernera, director of the Coeur d'Alene Tribe's lake department, said the monitoring should be a wakeup call.
"Nobody thinks this will happen in our lifetime, but it could," he said.
On another front, a recent University of Idaho study looking at property values found that resale values were $27,000 higher in areas where people could see 16 feet deep into the lake. In areas where invasive milfoil was present, property values declined by an average of $65,000.
"If we don't take care of the lake, there will be a direct effect on property values and our ability to enjoy the lake," said Mark Solomon, interim director of the Idaho Water Resources Research Institute. "It's not a disconnected issue."
Officials are working to quantify how nutrients get in the lake, with possibilities including erosion, septic tanks, runoff from residential developments and manure from livestock.
Results should be out later this year, Cooper said, while noting that anything involving land use regulations could face opposition.
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Information from: The Spokesman-Review
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