During the 2012 drought, the hot, dry conditions caused blooms of blue-green algae (also known as cyanobacteria) in some water bodies. These blooms can produce a toxin known as microcystin, which has a World Health Organization (WHO) drinking water standard of 20 µg/L. They can also foul the taste and odor of drinking water. Elgin and Aurora reported serious issues with algae in the Fox River in 2012, making the water difficult to treat. Here’s what this stuff looks like:

(photo by Mike Bundren, Illinois EPA)

These blooms can also occur when there is no drought. In fact, wet conditions can cause them. Lake Erie has suffered from summertime algal blooms for the last decade or so, with the worst year being 2011, following the wettest spring on record. The reason for the blooms in Lake Erie is high levels of nutrients, especially phosphorous.

Lake Erie was horribly polluted in the 1960s, with phosphorous being one of the prime contaminants. Reductions in phosphate detergents in both the U.S. and Canada reduced phosphorous levels in the lake by two-thirds. However, levels have been increasing over the last 20 years. The main source is agriculture, namely, fertilizers. But phosphorous fertilizers have been used for a long time, so what’s changed?

Ironically, it appears that new management practices designed to prevent soil erosion might be the culprit. No-till farming means the fields are not plowed, and that seems to have led to more runoff of phosphorous following rain events. Once again, unintentional consequences. And it shows how interconnected ecosystems are, and how changes in land use or practices can have cascading effects that are difficult to predict. Fixing this problem is going to be difficult.