Not all algae is toxic to humans and animals, but the type of blue-green algae growing in Milwaukee's Veterans Park lagoon is. Earlier this month, the city’s health department issued an advisory against coming into contact with the lagoon’s water.
It's hard to know if scum you see on top of Wisconsin's lakes and streams is dangerous, unless you are like Todd Miller of the Zilber School of Public Health who has loads of experience and is able to test the water.
Miller’s research focuses on algal impacts on inland lakes and Lake Michigan. Normally, the lagoon wouldn’t fit his criteria. But, he says, he was eager to test a new sensor last year and the lagoon was convenient.
Miller said he was surprised to find the water tested at more than 1,000 ppb, or parts per billion, of algal toxin last October. He returned this summer - and although the levels were not sky high - they were far above EPA recommended limits.
The suggested recreational limit by the EPA is 4 ppb. And, Miller says the two measurements each came back at 72.
He found that the lagoon is home to a toxic blue-green algae called microcystis. The toxin in this algae - if ingested - can damage the liver and also the central nervous system.
Miller says you shouldn't drink the contaminated water and young children are particularly vulnerable since they weigh so little.
What's Causing This?
Miller's lab tests algae samples from around the globe – Ukraine to Guatemala.
“One thing we found in all of the lakes we sampled, the highest levels we get are from Wisconsin lakes. We think that’s from the intense agriculture that’s on our lakes," he explains.
A lead culprit, Miller says, is phosphorus, which is found in fertilizer spread on fields and manure that sometimes runs off into streams and lakes.
Though the Veterans Park lagoon is urban, water runs off an adjacent bluff and the roadway sends pollutants – including phosphorus - into it.
What Can Be Done?
Short of a comprehensive cleanup, Miller says this blue-green algae is not going away. “The algae will grow and when winter comes they sink. Some of them will die…but they do overwinter and then they’ll come back and seed the lagoon or the lake. By June, the rising temperature triggers buoyancy and metabolism in the cells and they float the the surface to get sunlight and begin to grow.”
Miller concludes, “And the cycle begins again.”
His lab is working to create models that predict when toxic blooms could occur.
“Most of our drinking water comes from surface water from lakes and rivers. And many are becoming capable of growing this bacteria, so I don’t see the problem going away any time soon.” Miller adds, “What we need are more protections for our water resources and better land management.”