Chippewa County, Minn., resident looks to solve mystery of Carlton Lake

MONTEVIDEO -- Carlton Lake was his favorite swimming hole as a kid, became his prime duck hunting spot as an adult, and since 1984, it's been his home.

Finding a cause
Vernon Jahns, 88, grew up near Carlton Lake. He and his wife, Audrey, acquired the property surrounding the lake and built their home on its shores in 1984. The couple has never seen a white coating on the granite outcrops that surround the lake as has occurred this year, leading them to find a cause. Tribune photo by Tom Cherveny

MONTEVIDEO -- Carlton Lake was his favorite swimming hole as a kid, became his prime duck hunting spot as an adult, and since 1984, it's been his home.

As Vernon Jahns celebrated his 88th birthday last week, it's also become a mystery he wants to solve.

In all these years, he's never before seen the bright white coating visible now on the granite rocks and outcrops that surround much of the 40-acre lake. Like a ring around a bathtub, the white coating is evidence of the rapid drop in lake level following months of flood conditions.

Similar rings can be seen around other water bodies as they evaporate and minerals dissolved in the waters are left behind. But the ring around this lake is much more prominent and distinctive than anything that Vernon and his wife, Audrey, have ever witnessed here.

Is it entirely the result of this year's weather extremes, an as-of-yet-unknown source of contamination, or a combination of pollutants delivered by floodwaters in the spring?


"I have no idea,'' said Vernon Jahns and he and his wife discussed the white ring.

They were able to have the white coating tested at a laboratory and learned a few things. Spill a little hydrochloric acid on it, and it fizzes. That is evidence that the coating contains calcium carbonate, which occurs normally in our waters. A chemical analysis showed very small amounts of calcium, magnesium, manganese, sulfur and carbon.

Put the coating under a microscope, and it looks like a "bowl of rigate pasta.'' The "pasta'' is actually diatoms, the "skeletons" of dead algae. It is apparent the lake had a significant algae bloom, the result of excessive nutrients.

It remains a problem: The Jahns were watching a large, green slick of algae floating about the lake this week. It's something they had never seen this late in the year.

With a depth of 37 feet, the lake is not normally prone to the kinds of algae blooms more often seen in shallow waters, they said.

As happened in 1997 and 2001, the Jahns said the lake was flooded this spring by the Minnesota River. This year the lake waters remained high longer than they had ever seen before.

This year's above-normal precipitation levels and flooding may have carried sediment into the lake, adding phosphorus to feed an algae bloom.

The Jahns said they have seen a steady degradation of water quality in the lake through their years living on it. Vernon said he once used to host Montevideo's annual community hunt on the lake. U.S. Rep. Collin Peterson was among those who regularly enjoyed the opportunity to hunt waterfowl on its shores.


Today, the lake is anything but a duck hunting mecca, according to Vernon.

The congressman was among a number of elected and state officials who answered the Jahns request to look at the white ring around the lake while the officials were in town Oct. 15 for the Governor's Pheasant Opener. None could make any promises of action, but the Jahns said they will continue to make known their concerns about what they are seeing.

Said Audrey: "It's not right to let something this beautiful be destroyed.''

What To Read Next
Get Local