Often disregarded as "pond scum," algae get a bad rap. Indeed, they might be the most underappreciated of life forms. Algae are primary producers of organic matter at the base of the food chain and as such, life as we know it probably wouldn't exist without them.
While most algae are small — microscopic even — when they swarm they are among nature's grandest spectacles. To prove it, here's our list of some of the world's most wondrous, colorful, bizarre (and occasionally dangerous) algal blooms. (Text: Bryan Nelson)