Wednesday, September 30, 2009

Lake Winga's underwater wonderland is tinged with gold now, and it's more visible

Wingra's Gold-tinged Underwater Wonderland Is More Visible Now
Autumn color comes to the bottom of Lake Wingra as well as to the trees around it, and you can see it better this year. All summer long, it seemed that the water in Lake Wingra was clearer than in the past. You could see the bottom to a greater depth, where there just used to be impenetrable murk. At first, I wondered if it were an illusion, but it turned out it's not.

It's because of a carp management program. This experimental attempt to improve water quality in the lake, sponsored by Friends of Lake Wingra, has been strikingly successful, according to a story in the Wisconsin State Journal a few weeks ago that Chris Gruhl pointed out to me.
Limnologists with UW-Madison say recent tests have shown that Lake Wingra is cleaner than it has been during the past 12 years or more.

But it doesn't take a scientist to see the difference. All you have to do is stand hip-deep in the lake and look through the clear water to the sandy bottom where native aquatic plants make it look like you're wading around in an aquarium. The reason for this turnaround? Carp. Or, more precisely, the lack of carp.

Limnologist Dick Lathrop said the removal of more than half of the carp in the lake over the last two winters has resulted in less silt being churned up by the muck-loving fish. Not only is the water clearer, according to Lathrop, but native plants are doing better and outbreaks of blue-green algae have been minimal. The popular beach on the lake has not been closed once this year due to water quality.
So, why do the carp have such a big effect on the water quality in the lake? It's because when there are too many of them, they stir up the bottom. More of the sediment is suspended in the water, carrying nutrients with it for algae blooms and invasive species to feed on. The nutrients, of course, come from storm water runoff into the lake, which Friends of Lake Wingra has been trying to reduce. Which is why they got involved with the carp project in the first place.

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