This slideshow requires JavaScript.

In August 2014, nearly half a million residents of Toledo, Ohio were told to avoid their water, which is supplied by Lake Erie. The lake had been suffering from a bloom of green slime, caused by the overgrowth of microscopic organisms commonly called blue-green algae, or cyanobacteria.

Pure Lake Erie is a site dedicated to supplying information about the problem with cyanobacteria in Lake Erie. This campaign hopes to warn people about the dangers, teach them about the basic biology, and provide information about how to reduce the problem.

For information about this years bloom, we recommend checking the NOAA’s HAB advisory forecasts

RM_Toxic Algae Infographic FIN


Lake Erie’s problem with cyanobacteria is not year round.  The water from the lake is normally quite clean and Toledo and the surrounding area enjoy excellent tap water derived from the lake.  The problem is that conditions during the hot summer months, especially after a wet spring, can occasionally promote the toxic blooms that lend the lake unwarranted ill fame.  Nutrient pollution in the lake from agriculture and other sources increases the likelihood of blooms growing large and dangerous.

Usually the blooms occur late in the summer, but the 2014 bloom started a month early, catching everyone off guard and then leading to the infamous water ban.[1]  The ban was in the beginning of August; by comparison the 2011 bloom (which was the worst on record) was in September and caused no ban on drinking water.[2]  When the blooms are anticipated, the water filtration facilities can get ready and administer the special treatments needed to keep the water safe.


The following video is by Quest/KQED. Quest is funded by a grant from the National Science Foundation.  Please visit science.kqed.org/quest for more information.