Crimson tide or red tide, caused by plankton.

Trichodesmium erythraeum caused blooms in red sea

In the ocean, microscopic forms of algae, known as dinoflagellates , can "bloom" into dense patches near the surface, often referred to as "red...

“And the river will run red with blood”. Red tide in Florida seems pretty biblical to me!

Researchers have found that human activity helps power and provides fuel for naturally occurring Red Tide events.

Red tide - algal bloom (large concentrations of aquatic microorganisms) are events in which estuarine, marine, or fresh water algae accumulate rapidly in the water column, resulting in coloration of the surface water. It is usually found in coastal areas

Photo about Many dead fishes have been washed up to a beach during an algal bloom. People, building and ocean in the background. Image of beach, negative, algae - 11760936

This red tide collection includes activities, assignments, and reading materials created specifically for educators. web site. Investigating the Ocean Algal Blooms. This NOAA computer-based activity is designed to ...