Cyanotoxin which is why they are usually green or blue. Cyanobacteria are found almost everywhere; in oceans, lakes and rivers as well as on land. They flourish in Arctic and Antarctic lakes, hotsprings and wastewater treatment plants. They even inhabit the fur of polar bears, to which they impart a greenish tinge. Cyanobacteria produce potent toxins, but they also produce helpful bioactive compounds, including substances with antitumour, antiviral, anticancer, antibiotic and antifungal activity, UV protectants and specific inhibitors of enzymes. Cyanotoxins are often implicated in what are commonly called "red tides" or "harmful algal blooms". Lakes and oceans contain many single-celled
Great Lakes is the largest lake that is entirely within one country. The Great Lakes began to form at the end of the last glacial period around 14,000 years ago, as retreating ice sheets exposed the basins they had carved into the land which then filled with meltwater. The lakes have been a major source for transportation, migration, trade, and fishing, serving as a habitat to a large number of aquatic species in a region with much biodiversity. The surrounding region is called the Great Lakes region, which includes the Great Lakes Megalopolis. Though the five lakes lie in separate basins, they