Cyanobacteria, formerly known as blue-green algae, is contaminating Clear Lake, in Lake County, California. The microorganisms are capable of rapid population growth under ideal conditions, resulting in a "bloom."
The microscopic beings thrive in conditions of high nutrition and abundent sunlight. These blooms can discolor water, and lead to buildup of slime and scum, which can collect on shorelines. Such events can play havoc with public beaches in need of revenue from tourists.