One of the most well-known harmful algal blooms (HABs) is the Florida "red tide" caused by Karenia brevis, a type of algae that produces potent neurotoxins. The toxins can be suspended in the air near beaches and cause human respiratory illness. They can also accumulate in shellfish and cause Neurotoxic Shellfish Poisoning in humans, so affected states closely monitor shellfish and may close harvesting for a period of time to protect public health. Blooms also discolor the water and cause widespread mortality of fish, turtles, birds, and marine mammals. While these events are most frequent in coastal regions of southwest Florida, they occur to a lesser extent throughout the Gulf region.

The Gulf of Mexico experiences a variety of other HABs. Shellfish harvesting closures have occurred in Texas due to blooms of Dinophysis, which can produce toxins causing Diarrhetic Shellfish Poisoning. In Florida, closures have occurred due to an organism called Pseudo-nitzschia, which can produce toxins causing Amnesic Shellfish Poisoning. In addition, recreational harvesting of puffer fish is banned in some estuaries in Florida because of the threat of saxitoxins produced by an organism called Pyrodinium. Lastly, Ciguatera Fish Poisoning can be an issue in South Florida and off of Texas, due to toxins produced by Gambierdiscus, a type of organism associated with macroalgae on coral reefs.

NOAA issues forecasts to monitor bloom conditions and the potential for impacts. The forecasts help people make informed choices about where and when to visit areas that may be temporarily affected by a bloom.

NOAA Resources

Gulf of Mexico Harmful Algal Bloom Forecast
In the Gulf of Mexico, some harmful algal blooms are caused by the microscopic algae species Karenia brevis, commonly called red tide. These algal blooms can cause respiratory illness and eye irritation in humans. It can also kill marine life, and lead to shellfish closures. Blooms are often patchy, so impacts vary by beach and throughout the day. NOAA's National Centers for Coastal Ocean Science monitors conditions daily and issues regular forecasts for red tide blooms in the Gulf of Mexico and East Coast of Florida. This website offers forecasts and up-to-date conditions.

Harmful Algal Bloom Monitoring System
NOAA's National Centers for Coastal Ocean Science developed this site to routinely deliver near real-time products for use in locating, monitoring, and quantifying algal blooms in coastal and lake regions of the U.S. This application delivers a suite of bloom detection products in the form of geographic based images.

NOAA Awards $18.9M for Harmful Algal Bloom Research, Monitoring
NOAA is announcing $18.9 million in funding for harmful algal bloom (HAB) research projects and monitoring activities throughout U.S. coastal and Great Lakes waters.

Harmful Algal Bloom Observing System (HABSOS)
HABSOS is a data collection and distribution system for harmful algal bloom (HAB) information in the Gulf of Mexico. The goal of HABSOS is to provide environmental managers, scientists, and the public with a data driven resource for HAB events.

Red Tide Respiratory Forecast
The Red Tide Respiratory Forecast is a beach-level risk forecast activated during red tide conditions that tells beachgoers what red tide impacts are expected to be at individual beaches at different times of the day. Initially developed and tested in Pinellas County, Florida, the forecast was expanded to Lee County in 2018. Today, it includes more than 20 Gulf Coast beaches and is hosted by the Gulf of Mexico Coastal Ocean Observing System (GCOOS).

Frequently Asked Questions
Frequently asked questions about Gulf of Mexico harmful algal bloom

State Resources

Florida

Algal Bloom Monitoring and Support
Consolidated site from Florida Department of Environmental Protection for all Florida algal bloom resources.

Fish and Wildlife Research Institute Red Tide Resources
Red tide status, frequently asked questions, tools for tracking red tides, and general information from Florida Fish and Wildlife Conservation Commission.

Aquatic Toxins: Poison Control Center
Resources on aquatic toxins, to include Florida red tide, from Florida's Poison Control Center.

Visitbeaches.org
Mote Marine Laboratory’s beach conditions report and red tide information.

Frequently asked questions from Florida Sea Grant.

Texas

Harmful Algal Bloom Resources
Harmful algal bloom resources and frequently asked questions from Texas Parks & Wildlife.

Texas Red Tide Status
Current status of red tide occurrence from Texas Parks & Wildlife.

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General Information About Red Tides in Florida and Texas

What is red tide?

Harmful algal blooms occur nearly every summer along the nation's coasts. Often, the blooms turn the water a deep red. While many people call all such events "red tides," scientists prefer the term harmful algal bloom or HAB. A red tide or HAB results from the rapid growth of microscopic algae. Some produce toxins that have harmful effects on people, fish, marine mammals, and birds.  In Florida and Texas, this is primarily caused by the harmful algae species Karenia brevis. Red tide can result in varying levels of eye and respiratory irritation for people, which may be more severe for those with preexisting respiratory conditions (such as asthma). The blooms can also cause large fish kills and discolored water along the coast.

How Does the NOAA Forecast Work?

NOAA uses a combination of satellite imagery and water samples of the algae species Karenia brevis, collected from the field by local partners, to forecast the location and intensity of red tide events.  Satellite imagery is a key tool for detecting blooms before they reach the coast, verifying bloom movement and forecasting potential respiratory irritation.

Putting the Forecast into Action

The conditions reports for red tide in Florida and Texas are available to the public and give the daily level of respiratory irritation forecasts by coastal region. NOAA also issues HAB bulletins that contain analyses of ocean color satellite imagery, field observations, models, public health reports, and buoy data. The bulletins also contain forecasts of potential Karenia brevis bloom transport, intensification, and associated respiratory irritation based on the analysis of information from partners and data providers. The bulletins are primarily issued to public health managers, natural resource managers, and scientists interested in HABs.  A week after the the bulletin is issued, it is posted to the Bulletin Archive where the public can access it. 

Infographic Transcripts: Red Tide