Narrator: This is Science Today. Toxic algae, or harmful algal blooms, are caused by microscopic, toxin-producing phytoplankton, which enter the marine food web and may ultimately cause shellfish poisoning syndrome in humans. Mary Silver, a professor of ocean science at the University of California, Santa Cruz, studies environmental conditions that lead to toxin production and how these toxins make their way up the food chain to humans.
Silver: In most cases, there are very low levels of these in the water and they're not harmful at all, but as you approach some level, then there's enough cells to potentially cause a problem.
Narrator : Toxic algae is a naturally occurring phenomenon that's been part of the ocean's life cycle for thousands, if not millions, of years.
Silver: The concern is that we may be changing the environment in a way to increase their (toxic algae) abundance and that's of great concern and we need to know more about that as one of the ways humans are affecting the sea.
Narrator: Most states in the U.S. have monitoring systems to keep track of toxic algae levels. For Science Today, I'm Larissa Branin.