Narrator: This is Science Today. A red tide is a really dense accumulation of phytoplankton, which are microscopic algae that grow in the ocean. Peter Franks, a professor of biological oceanography at the University of California, San Diego's Scripps Institution of Oceanography, says red tides, which can sometimes be toxic, are actually well recorded in history.
Franks: The Koreans have a literature that records red tides back probably two thousand years or so. I think one of the best examples in Western literature is in the Bible - one of the plagues of Egypt was the rivers turned to blood and the people could not drink thereof and it's actually a perfect description of red tides.
Narrator: And one of the dominant red tide organisms on the East coast has the genus known as Alexandrium.
Franks: Which of course is Egyptian and it was originally isolated I believe, in the estuaries in Egypt, the Nile and other estuaries. And so it makes sense that they experienced red tides back then and they would have been pretty worried about the water quality when it turns that muddy brown color and probably was toxic as well.
Narrator: For Science Today, I'm Larissa Branin.