Red Tide

About Red Tide

This app shows a map with recent red tide (harmful algal bloom) measurements for Florida coastal areas.

No registration or login required.

Data source: NOAA National Coastal Data Development Center

The current version of this app covers the state of Florida only.


RED TIDE BACKGROUND INFORMATION
Source: Florida Fish and Wildlife Conservation Commission website

What is a red tide?

A red tide, or harmful algal bloom, is a higher-than-normal concentration of a microscopic alga (plantlike organism). In Florida and the Gulf of Mexico, the species that causes most red tides is Karenia brevis, often abbreviated as K. brevis.

Are red tides red?

At high enough concentrations, red tide can discolor water a red or brown hue. Blooms caused by other algal species can appear red, brown, green or even purple. The water can also remain its normal color during a bloom.

Is red tide a new phenomenon?

No, red tides were documented in the southern Gulf of Mexico as far back as the 1700s and along Florida's Gulf coast in the 1840s. Fish kills near Tampa Bay were even mentioned in the records of Spanish explorers.

How long do red tides last?

Red tides can last as little as a few weeks or longer than a year. They can even subside and then reoccur. The duration of a bloom in nearshore Florida waters depends on physical and biological conditions that influence its growth and persistence, including sunlight, nutrients and salinity, as well as the speed and direction of wind and water currents.

Is red tide in Florida found in estuaries, bays or freshwater systems?

Red tide in Florida can be found in bays and estuaries but not in freshwater systems such as lakes and rivers. Because Karenia brevis cannot tolerate low-salinity waters for very long, blooms usually remain in salty coastal waters and do not penetrate upper reaches of estuaries. However, other harmful algae, including cyanobacteria (blue-green algae), typically bloom in freshwater lakes and rivers.

Why are red tides harmful?

Many red tides produce toxic chemicals that can affect both marine organisms and humans. The red tide organism in Florida, Karenia brevis, produces brevetoxins that can affect the central nervous system of fish and other vertebrates, causing these animals to die. Wave action can break open K. brevis cells and release these toxins into the air, leading to respiratory irritation. For people with severe or chronic respiratory conditions, such as emphysema or asthma, red tide can cause serious illness. The red tide toxins can also accumulate in molluscan filter-feeders such as oysters and clams, which can lead to Neurotoxic Shellfish Poisoning in people who consume contaminated shellfish.

HEALTH AND SAFETY ISSUES

Will I experience respiratory irritation during a red tide in Florida?

Some people experience respiratory irritation (coughing, sneezing, tearing and an itchy throat) when the red tide organism, Karenia brevis, is present and winds blow onshore. Offshore winds usually keep respiratory effects experienced by those on the shore to a minimum. The Florida Department of Health advises people with severe or chronic respiratory conditions, such as emphysema or asthma, to avoid red tide areas.

Is it safe to swim during a red tide in Florida?

Swimming is safe for most people. However, the red tide can cause some people to suffer skin irritation and burning eyes. People with respiratory illness may also experience respiratory irritation in the water. Use common sense. If you are particularly susceptible to irritation from plant products, avoid an area with a red tide bloom. If you experience irritation, get out of the water and thoroughly wash off. Do not swim among dead fish because they can be associated with harmful bacteria.