June 26, 2008
Something’s Missing From Twin Cities Lakes This Year
By Nick Ferraro, Pioneer Press, St. Paul, Minn.
Jun. 26--A welcome surprise jumped out at Dave Haak as he sat near the shoreline at Lily Lake one sunny afternoon late last week -- and it wasn't a giant sunfish.
Thanks to the later-than-normal ice-out and cool spring temperatures, summer enthusiasts eager to take a dip or drop a line are likely to see less of the annoying weeds and murky water at their favorite Twin Cities lakes, water researchers say.
Those cool, cloudy spring days helped keep weeds and algae -- which thrive in warm, shallow, nutrient-rich lakes -- at bay, said Steve Heiskary, a scientist for the Minnesota Pollution Control Agency.
"For lakes users and swimmers, it's the blue-green algae that people respond to, because the blue-greens tend to accumulate near the surface of the water," Heiskary said.
Unusually dry and warm weather in spring 2007 allowed algae blooms to show up earlier than normal in many lakes in the area and across Minnesota. The blooms became more abundant as summer wore on.
Most of the algae blooms were harmless, but the blue-green type produced toxins that led to slimy, smelly weeds at the surface, as well as four known dog deaths after the animals ingested lake water.
"Last summer was difficult, especially early in the season," Heiskary said. "It took us by
But favorable weather this year doesn't guarantee a summer free of the nuisance algae blooms, especially in the smaller lakes, Heiskary cautioned. This spring's heavy rainfall likely caused excessive water runoff, which can carry nitrogen and phosphorous -- key nutrients that make algae flourish, he said.
"With all this runoff, I would suspect that as things start to warm up and we get a lot of sun, we're going to see some water-quality problems and blue-green blooms in the lakes," he said.
So far, algae growth has been slow in favorite metro lakes, including in Dakota and Washington counties. Take, for instance, Lily Lake, Haak's favorite summer spot, where a June 16 reading showed the water clarity depth at 6 1/2 feet -- more than twice the depth at this time last year.
"The water levels really bounced back from the precipitation, so I don't think algae has been as bad as last year" across the county, said Travis Thiel, a water resource specialist for Washington Conservation District. "But time will tell once we get a little more into summer."
Johnny Forrest, natural resources coordinator for Dakota County parks and recreation, said popular Schulze Lake in Eagan's Lebanon Hills Regional Park should remain free of excessive algae blooms.
He said the main reasons are the natural vegetation in the upstream watershed and newly planted prairie vegetation -- all of which capture the soil and nutrients such as phosphorous and nitrogen.
Schulze Lake Beach also has a treatment train of upstream lakes that filter and improve water quality as water moves downstream from lake to lake, Forrest said.
Algae and weed growth is also down at St. Paul's popular Lake Phalen, said Lynn Waldorf, the city's aquatics supervisor. "They're just starting to spring up now," she said.
But swimmers might want to enter the water slowly. Cooler temperatures, of course, mean cooler lakes.
"That would be the one downside to the cooler spring," said Dave Wright, unit supervisor for the Department of Natural Resources' division of ecological resources.
"I would guess that for the people that are out swimming, it won't be nearly nice as it was last year. The water probably looks inviting, until you put your foot in."
Until last week, the water temperature at Lake Phalen had averaged 60 to 63 degrees, keeping many swimmers away, Waldorf said.
"We just recently got up to 70 degrees," she said. "Summer for us really started with the first 80-degree day -- that's when we got busy at all our sites. The water has been too chilly for some."
Haak, the Stillwater granddad, agrees and opted not to take a dip in Lily Lake last week.
"I haven't been in yet," he said. "It's too cold for an old guy like me. Maybe in another month."
Nick Ferraro can be reached at 651-228-2173.
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Copyright (c) 2008, Pioneer Press, St. Paul, Minn.
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