Half Moon Lake's
(St.Paul Pioneer Press 8-13-11)
People are swimming, even snorkeling, in Half Moon Lake again.
Anglers report for the first time that they can see fish swimming several feet down in the lake.
Competitor, in the Eau Claire Triathlon have swum in the lake the past two years.
All this in a formerly green lake that by midsummer used to be so clogged with curly-leaf pondweed, an invasive aquatic weed, that even paddling a canoe was a chore in many areas.
Credit for the turnaround goes to a two-pronged effort. It started with three years of spring herbicide treatments of curly-leaf pondweed, followed this summer by a chemical treatment with alum to seal the nutrient phosphorus in the bottom sediments, said Phil Fieber, director of the city's Parks, Recreation and Forestry Department.
"Absolutely it's better, as the result of the herbicide that's knocked down most of the curly-leaf pondweed and the alum," Fieber said.
"We've had requests for triathlons out there," he said. "From talking with the anglers, they've noticed the difference. They can see fish. They can see the bottom — not everywhere, but more than they could in the past."
City and state Department of Natural Resources officials hoped that by eliminating most of the curly-leaf pond-weed, they would create space for native aquatic plants to return, and that seems to be happening, Fieber said.
The native plant elodea has had a growth spurt in parts of the lake, he said. It's growing so well that the city might have to bring back the weed cutter, Fieber said, but that's a better problem to have than the invasive plants that used to take over.
"It's better to have elodea in August and September, rather than curly-leaf pondweed all year long," he said.
The elodea is a better habitat for fish than the pondweed, Fieber said.
The herbicide treatments have been administered in the spring, timed to kill the early-growing pondweed before the native plants start growing, officials said.
Aaron Carlson, a research assistant with the U.S. Army Corps of Engineers who has been sampling the lake every other week with ecologist Bill James, agreed the increase in the clarity of the lake, was noticeable.
"It's definitely a lot clearer than it's been in years past," he said. "It almost looks like Lake Superior when you look into it."
Chlorophyll values, a measure of algae, are a lot lower now. Phosphorus levels in the water also have been lower.
Carlson said he and James haven’t done any statistical analysis of the measurements they've taken yet.