While cyanotoxins released from cyanobacteria (blue-green algae) blooms has been a problem for beachgoers for several years now, the recent contamination of Toledo’s drinking water with cyanotoxin has brought this issue to the national news. Many people seem to blame fertilizer run-off from farms for Lake Erie’s toxic blooms, but the causes for cyanobacteria blooms are likely far more complex. Agriculture can lead to increased nutrient levels in lakes, but urban regions also contribute nutrients. Poorly treated wastewater in cities can fertilize a lake and even contaminate drinking water with other microbes – here in Wisconsin, Milwaukee suffered an outbreak of Cryptosporidium that was traced back to sewage released into Lake Michigan. Some blame artificially high water temperatures from nuclear power plants. Additionally, ecological factors in Lake Erie itself may have contributed to the cyanobacteria blooms. Research shows that the invasive zebra mussels that have spread across the Great Lakes prefer not to eat cyanobacteria, but do eat their competitors. There are also several new potential sources of nutrients in the Great Lakes region, such as fish farming. And while drinking water treatment is pretty good at preventing the bacteria themselves from entering water systems, their toxin is much more difficult to remove. Overall, this is an important issue that will require scientists from multiple disciplines to solve!