Public health officials have their hands full keeping your clam chowder and raw oysters safe. That's due, in part, to red tides.

Red tides happen nearly every year as coastal waters warm, killing fish and poisoning shellfish along U.S. coasts. They're not actually tides - they're huge blooms of naturally-occurring toxic algae.

If people eat shellfish infected with these algae they can become sick with what's called paralytic shellfish poisoning.

But scientists with the National Oceanic and Atmospheric Administration are working to prevent outbreaks by tracking when and where red tides will happen next.

via Battling 'Red Tide,' Scientists Map Toxic Algae To Prevent Shellfish Poisoning : The Salt : NPR.