Blue green algae can give local lakes a black eye. This pond scum can produce deadly toxins, harming people and their pets.
The DNR is warning boaters and swimmers about its effects across South Central Wisconsin.
Bridge Motel manager Jaye Gillett says, "most of the time you can see patches of it, traveling through water ... doesn't stay for very long."
But guests of the Bridge Motel near Lake Wisconsin come and go all season.
"We have groups come year after year ... some swim, some don't," Gillett says.
Some wonder what's that green substance floating on the lake's blue waters.
"I've had someone come to me and say what is that by the pier," she says.
Lake Researcher Dick Lathrop looks for algae, especially the blue green type.
"We had early last summer, in June, some ponds near Lake Kegonsa where a number of dogs developed seizure problems that we learned later were associated with this one particular algae," Lathrop says.
This season marks the third consecutive year DNR researchers will take samples from lakes statewide to learn more about toxic blue green algae.
"These are both neurotoxins that affect our nervous system as well as liver toxins," Lathrop says.
Today is windy and chilly on Lake Wisconsin ... not ideal conditions for blue green algae, but researchers hope their years-long study helps them better understand where and when this algae becomes toxic.
Lathrop says, "we're developing screening techniques. We can't determine certain species ... yeah, if you see it ... risk is higher, we should be alerting," he says.
Researchers also want to know whether runoff ponds might suffer more than bigger lakes.
Back in 2002, a boy died from exposure to toxins after jumping in a golf course pond.
Lathrop considers Lake Wisconsin a fertile area for algae, but the manager of the Bridge Motel says she has gone swimming in these waters for 15 years with little problem.
"I would be very interested to find out results to see how bad it is, because you know it's everywhere and what maybe causes it," Gillett says.
Because business depends on it ...
"I have a lot of fishermen so I would think if it's in water, it's gonna affect fish," Gillett says.
Experts remind people to use common sense. Keep people and pets away from blooms. Always shower after swimming.
Also, wash your pet if it comes into contact with blue green algae.