The Threat of Blue-Green Algae
Blue-green algae that can be potentially toxic is referred to as "cyanotoxins". Cyanotoxins are usually found in blooms that accumulate along shorelines and downwind bays. We call these blooms of toxic cyanobacteria Harmful Algal Blooms (HAB).
According to the Watershed Resources Working Group, a Seneca Nation technical advisory board, HABs were first recorded in Ohi:yo' in 1972 and today have increasingly been more severe and frequent.
Not all cyanobacteria is toxic.
https://www.pca.state.mn.us/water/blue-green-algae-and-harmful-algal-blooms (source)
http://epa.illinois.gov/topics/water-quality/monitoring/algal-bloom/index (source)