Several viewers want to know what exactly an algae bloom is. You may have seen green, gooey beaches on Lake Erie, but not know exactly what causes it.
The National Ocean Service says:
Ranging from microscopic, single-celled organisms to large seaweeds, algae are simple plants that form the base of food webs. Sometimes, however, their roles are much more sinister. A small percentage of algal species produce toxins that can kill fish, mammals, and birds, and may cause human illness. Other algae are nontoxic, but clog the gills of fish and invertebrates or smother corals and submerged aquatic vegetation. Others discolor water, form huge, smelly piles on beaches, or cause drinking water and fish to taste bad.