A toxic summer and an uncertain future

Blue-green algae on Peltier Lake, near Lino Lakes, MN, in July 2017. Dan Kraker | MPR News

2019 was the summer of toxic algae.

Blooms of single-celled cyanobacteria, or blue-green algae, consumed lakes across the US. Beaches closed, and opportunities for fishing and boating were cancelled. Blue-green algae “stole New Jersey’s summer,” wrote Michele Byers.

So, what caused this summertime grinch? And are toxic algae blooms here to stay?

Blue-green algae grow naturally in lakes, usually in sparse numbers. But adding two ingredients to a lake—nutrients and heat—can spark an explosion of blue-green algae. High temperatures and heavy rains, which flush nutrients from farms and cities into waterways, likely spurred this summer’s infestation. And the results were devastating.

When their population spikes, blue-green algae secrete toxins deadly to dogs and harmful to people. That’s when the caution tape comes out. This summer has seen closures of lake and coastal beaches in all corners of the country. And the issue spreads beyond swimming—shellfish can accumulate algal toxins and turn poisonous. Algae blooms wreak $82 million in damages to the seafood and tourism industries each year, according to NOAA.

Experts say the problem won’t solve itself. In fact, climate change models suggest it’s getting worse. While there’s no silver-bullet solution, water managers have explored a range of algae-fighting tactics.

Minnesota banned the use of phosphorus in lawn fertilizer in the early 2000s, a move since emulated by 10 other states. Hundreds of localities have adopted stormwater utilities, which can charge property owners for generating nutrient-rich water runoff. And lake managers have suppressed and removed algae directly from waterways.

It’s not clear which combination of solutions works best, and the winning formula likely differs from place to place. What is clear is that toxic algae blooms aren’t going away. Proactive research and testing of possible fixes will be key to saving future summers from toxic algae.

You can find a nationwide map of toxic algae blooms from the Environmental Working Group here. And be sure to check out their video on how to tell if an algae bloom is toxic.