MN lakes face blue-green problem

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photo credit: MPCA

By Matt Doll, Minnesota Environmental Partnership (@mattjdoll)

This week, Carver Lake, a popular beach destination in Woodbury that draws hundreds from throughout the East Metro in warm months, became the latest Minnesota lake to be temporarily closed this summer due to a blue-green algae outbreak. The same lake previously suffered from blue-green blooms in 2014 and 2017.

These outbreaks, which have become increasingly common in Minnesota and in the United States generally, can threaten human and animal health and aquatic ecosystems, especially in shallow lakes that suffer from nutrient runoff. We have solutions that can make the blooms rarer and less dangerous, but it will take a strong commitment – locally and large-scale – to improving water quality and climate mitigation.

A tiny, unpredictable culprit

Blue-green algae blooms are not actually algae at all, but photosynthesizing cyanobacteria. When these bacteria reproduce rapidly, they often create toxins that can harm humans, pets and wildlife. Symptoms of exposure can include skin effects, vomiting or diarrhea, and respiratory problems. Blue-green algae may also contribute to certain cancers, making avoiding exposure especially vital for humans. 

My dog loves water, so I keep her safely away from blue-green algae.

These toxins can be especially dangerous, even fatal, to swimming dogs. Fortunately, blue-green blooms are quite visible, and the MPCA offers some simple instructions on how to test for them. It’s important to let local health authorities know as soon as a bloom is detected. 

Why these blooms have become more common

The Environmental Working Group, an MEP partner organization, has tracked algal blooms across the country over the last few years. (EWG has produced an interactive map to provide data about the blooms since 2010.) And they’ve shown that these blooms are becoming more and more common due to the broad threats of climate change and nutrient pollution of our waters.

These nutrients primarily run off of farmland and lawns that have been treated with fertilizers, as well as from municipal storm water systems. It’s clear that the same problem afflicting the Gulf of Mexico and Minnesota’s groundwater is making our lakes less safe to swim and fish in.

Solutions to multiple problems

We know there are steps to turn the tide on blue-green algae blooms. Shifting to regenerative, less fertilizer-intensive agriculture is much-needed for many reasons, and will cut down on algal blooms. In urban areas, reducing or eliminating fertilizer use by municipalities and residents can help stave off these toxic events – and replacing areas of grass entirely with deep-rooted plants can help filter out nutrients and provide habitat for wildlife.

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