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
Alexander the Great in the Quran a barrier and a forbidding partition. (Quran 25:53) This has been compared to the ancient Akkadian myth of the "Abzu", the name for a fresh water underground sea that was given a religious quality in Sumerian and Akkadian mythology. Lakes, springs, rivers, wells, and other sources of fresh water were thought to draw their water from the "Abzu" underground sea, while the Ocean that surrounded the world was a saltwater sea. This underground sea is called Tehom in the Hebrew Bible. For example, Genesis 49:25 says, "blessings of the heavens above, and Tehom lying beneath". Wensinck explains, "Thus it appears