In August 2014, the water supply for the city of Toledo, Ohio, was poisoned. Officials issued an order to the half- million residents connected to the municipal water supply: Don’t drink, cook, or brush your teeth with the water. Do not use it to bathe your children, and don’t give it to your pets. Stores ran out of bottled water, and residents had to wait in long lines or travel to neighboring towns to find more. The culprit was a bright green plume of Microcystis, a cyanobacterium that thrives in warm water tainted with heavy loads of phosphorus and nitrogen. Every spring, rains wash a pulse of nutrients off fertilized fields and send it down the Maumee and Sandusky rivers and into western Lake Erie. Every summer, as water temperatures rise, Microcystis forms an iridescent mat over parts of the lake’s surface. In early August 2014, strong winds blew a lawn of cyanobacteria over Toledo’s water intake, which lies just outside the Maumee’s mouth. Tests showed that the city’s water contained dangerous levels of microcystin, a liver toxin produced by the bloom. The drinking water crisis was a dramatic signal of Lake Erie’s descent back into eutrophication. In the 1980s, after sewage plants in the watershed were upgraded and phosphate detergents banned, Lake Erie experienced a revival. Algal blooms faded, and populations of walleye rebounded. The lake grew a thriving tourist industry based on sport fishing. Then, in 1995, researchers recorded the lake’s first widespread bloom of Microcystis. Eruptions of Microcystis have since become a predictable event striking the western Lake Erie basin every summer. The most widespread and long- lasting blooms hit in 2011 and 2015, after intense spring rains dumped heavy loads of nutrients into the lake. Climate models forecast warmer summer temperatures and heavier spring rains for the Great Lakes region. Those conditions are a recipe for more and larger algal blooms, and are likely to favor Microcystis in particular. The regulatory efforts of the 1970s and 1980s made great progress in cleaning up discharges from industries and sewage treatment plants, but failed to address nonpoint source pollution flowing from farm fields and city streets.
Cyanobacterial harmful algal blooms are a biological disturbance to Western Lake Erie bacterial communities
