REGIONAL- A local nonprofit has updated their water quality assessment of the White Iron chain of lakes, reporting mostly good news on overall lake health, some unsurprising bad news about sulfate, and one cautionary caveat regarding invasive species.
The White Iron Chain of Lakes Association — or WICOLA — evaluates water quality every five years for five interconnected lakes, including Birch, White Iron, Farm, Garden, and Fall. The group has been collecting water data since 1993. WICOLA issued its last water quality report in 2019 and the new report on June 17.
According to the latest report, “the water quality on our chain of lakes has remained stable since our last water quality report issued in April 2019.” Houston Engineering of Maple Grove, which prepared the report, reviewed the last ten years of trophic data for the five lakes and found no change in four of the lakes, while Fall Lake saw an improvement in its trophic state. The trophic state is a measure of the abundance of carbon, mostly algae, within a lake. Lakes with excessive trophic activity are characterized by green water due to algal growth, dense aquatic plants, a loss of deep oxygen, and in the worst cases, summertime fish die-offs.
Many lakes become naturally more trophic with time, a process called eutrophication. This is a slow process in nature. However, human activities like fertilizing lawns can greatly speed up the process of eutrophication by introducing excess phosphorus and other nutrients.
The improving water quality in Fall Lake is a good sign of the continuing progress from the clean-up of Shagawa Lake, which discharges into Fall Lake. Shagawa has long been the receiving water for Ely’s wastewater, which used to contain high amounts of phosphorus, and the lake is continuing to experience the effects of that discharge, although conditions continue to improve.
The latest report also included a review of historic trends in dissolved metals for the three of the lakes: Birch, Garden, and White Iron. For these lakes, all the dissolved metals analysis results were below the maximum allowed by Minnesota’s water quality standards.
The bad news
Sulfate, a byproduct of taconite processing, remains a point of concern in the lake chain, especially in Birch Lake, which is closest to the major sources of sulfate. In November 2023, the Minnesota Pollution Control Agency declared Birch Lake and its tributary, the Dunka River, as impaired.
Lakes and rivers with productive wild rice stands can only thrive when sulfate concentrations are less than 10 milligrams per liter. When sulfate concentrations exceed this amount, as they do in the Dunka River and the south half of Birch Lake, the state considers the affected surface water to be impaired.
Besides impact to wild rice, higher sulfate levels are also known to promote conditions favorable to the creation of methylmercury, a toxic form of mercury that readily bioaccumulates in fish tissue.
Like many other lakes in northern Minnesota, the five lakes covered in the WICOLA report already have advisories on the consumption of fish contaminated by methylmercury. While the source of the mercury is atmospheric pollution, increasing the sulfate concentrations in the lake water can lead to higher levels of methylmercury. For this reason, the report recommended that mercury levels should be tracked in the five lakes.
The fish consumption advisories for mercury for the five lakes in the White Iron chain are online through the Department of Natural Resources lake finder tool at dnr.state.mn.us/lakefind/index.html.
The caveat
“Aquatic invasive species are a looming threat” for the five lakes covered in the WICOLA report. The only invaders currently present are the spiny water flea in Fall Lake and the rusty crayfish in all the lakes. However, other invasive species remain a threat to the five lakes, including the curly-leaf pondweed, which is an unwelcome invader in other lakes regionally. The report also cautions that “The risk also remains high for zebra mussels.”  
Because of the invasive species threat, the water quality report made a strong recommendation for all lakeside residents and visitors to be vigilant in practicing “clean, drain, dry” practices for their watercraft.