Oceans and other bodies of water are filled with algae, a small number of which are toxic but often exist in such small concentrations that they pose little danger to people and marine life around them.

When those toxic aquatic organisms multiply, they can form what are known as harmful algal blooms, which have been reported in every coastal U.S. state.

Though there are dozens of potentially dangerous algae species, one known to make an appearance each year along Florida's Gulf Coast is called Karenia brevis, a microscopic organism with "whip-like appendages" called flagella it uses to swim.

When Karenia brevis algae multiply in large numbers, they can form blooms that turn the water a reddish-brown hue, giving the phenomenon the moniker "red tide."

Red tides have been documented along Florida's Gulf Coast as far back as the 1840s, state officials said.

Scientists can't predict when red tides will occur, but experts in Florida are researching prevention and mitigation measures to minimize their impact.

Karenia brevis produce what are known as brevotoxins, which can kill marine life and birds.

The red tide organism can also cause health problems in humans, such as skin irritation. Brevotoxins that have become airborne may cause those near the beach to develop a cough or congestion.

People who eat shellfish affected by brevotoxins can also come down with Neurotoxic Shellfish Poisoning, which can lead to gastrointestinal problems, tingling feelings in the mouth, the reversal of hot and cold sensations and other symptoms.