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NOAA Harmful Algal Bloom Operational Forecast System (HAB-OFS)

Frequently Asked Questions about the HAB Conditions Report


Additional Information

What is the NOAA Harmful Algal Bloom (HAB) Forecast System?

The HAB Forecast System develops predictions of the transport and potential development of harmful algae conditions that may impact the coastal areas of the Gulf of Mexico. The system focuses on the most common harmful algae in the Gulf of Mexico, which is the microscopic algal species Karenia brevis, commonly known as red tide.

To create a forecast, analysts gather data from various ocean observing systems, including images from commercial and government satellites, meteorological data from buoy and land-based stations, and field data collected by state and university monitoring programs. The analysts then compile and interpret this information to determine the current and future location and intensity of a HAB, as well as the potential impacts on humans, marine mammals, and fish. This information is provided to natural resource managers in the HAB Bulletin. General information regarding bloom locations and expected impacts is available as a Conditions Report to the public on the HAB Forecast System Web site. This project is ongoing and will be updated and improved as new information and research becomes available.

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How often are Condition Reports issued?

If Karenia brevis red tide is reported and verified in the Gulf of Mexico, reports are issued twice a week; otherwise, information is updated weekly.

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What data are used in HAB monitoring and forecasting?

The data sources used in this effort routinely include images of ocean color from satellites, wind direction and speed from coastal and offshore buoys, field observations of bloom location and intensity provided by state agencies, and marine weather forecasts from the National Weather Service. Data and models from the research community are frequently consulted. All these data sets are needed to evaluate a red tide. Descriptions of many of the data sets used in the development of this product are provided in HAB bulletin guide. (Adobe Reader is required to read the PDF document.)

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What's the difference between a red tide and a harmful algal bloom?

The rapid proliferation of toxic or nuisance algae is called a harmful algal bloom (HAB). HABs may discolor the water when algae concentrations are very high. For this reason, HABs are sometimes referred to as "red tide"; however, this term is actually a misnomer because there are many types of HABs that do not color the water red. In the Gulf of Mexico, the microscopic algae Karenia brevis is frequently responsible for HABs, and it is often referred to as the red tide organism.

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What are the impacts of red tides?

In the Gulf of Mexico, one of the most common HABs is the phytoplankton species Karenia brevis. Commonly known as red tide, this organism produces a toxin that can cause respiratory irritation in humans, contaminate some shellfish, and affect the central nervous system of fish – potentially causing fish kills.

When Karenia brevis cells near the ocean surface are broken up by surf at the shore or by breaking waves offshore, the toxin is released into the air and known as aerosol. Winds blowing onshore can bring the aerosol onto the beach, potentially causing eye and respiratory irritation (coughing, sneezing, tearing, and itching) to beachgoers. Onshore wind and currents can also transport fish killed by exposure to the toxin onto the beach. Respiratory irritation in humans is significantly reduced when the winds are blowing offshore. Any effects usually decline when a person is no longer exposed, and wearing a particle mask can reduce irritation for some people. People with severe or persistent respiratory conditions (such as chronic lung disease or asthma) may experience stronger adverse reactions.

State authorities monitor the levels of Karenia brevis and when cell concentrations reach a predetermined level, are required to put a shellfish ban in effect stating that it is not safe to harvest mollusks (e.g., clams and oysters) and gastropods that feed on bivalves (e.g., whelks). These notices are available from the Florida Department of Agriculture and Consumer Services ( http://www.floridaaquaculture.com). For more information regarding red tides and their impacts in the Gulf, refer to the Red Tide Alliance (http://www.redtideonline.com) and the Florida Department of Health Aquatic Toxins Web site ( http://www.myfloridaeh.com) and the references listed below.

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Can I swim during a red tide?

Although some people can experience skin irritation and burning eyes, swimming during a red tide is safe for most people. However, never swim among dead fish because they can be associated with harmful bacteria. For more information about being in and around a red tide, visit the Florida Fish and Wildlife Research Institute's (FWRI) red tide Web site.

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Is it okay to eat seafood during a red tide?

Commercial seafood from local restaurants and seafood markets must be harvested from waters where there is no red tide, so the food is safe to eat.

According to the Texas Department of State Health Services, it is usually okay to eat fish, crabs, and shrimp during a red tide bloom because the toxin is not absorbed into the fleshy tissues of these animals. This advice is based on the assumption that only the "edible" portions are being consumed (the fillet or muscle).

Oysters and other shellfish, such as clams, mussels, whelks, and scallops, can accumulate red tide toxins in their tissues. People that eat oysters or other shellfish containing red tide toxins (brevetoxins) may become seriously ill with neurotoxic shellfish poisoning (NSP). Once a red tide appears to be over, toxins can remain in the oysters for weeks or months. Toxins are heat resistant, so cooking infected shellfish will not remove or deactivate the toxins.

State authorities monitor the levels of Karenia brevis and, when cell concentrations reach a predetermined level, are required to put a shellfish ban in effect stating that it is not safe to harvest mollusks (e.g., clams and oysters) and gastropods that feed on bivalves (e.g., whelks). These notices are available from the Florida Department of Agriculture and Consumer Services (http://www.floridaaquaculture.com). For more information on red tides and their impacts in the Gulf, refer to the Red Tide Alliance and the references listed below.

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What impacts are reported on by the HAB Forecast System?

Impacts addressed in the Condition Report refer to the impacts on humans caused by the toxic aerosol and the potential transport of dead fish to the coast. For shellfish closures, refer to the Florida Department of Agriculture and Consumer Services Division of Aquaculture.

The impact levels are based on studies reported in the scientific literature (see Kirkpatrick and others 2004, referenced below). The criteria used are the direction and strength of the nearshore winds and the intensity of the red tide, which is determined by the concentration of Karenia brevis cells in the water.

Studies (e.g. Kirkpatrick and others, 2004, referenced below) have shown that onshore winds and breaking surf result in the release of toxins as aerosols. Wind speeds of greater than 7 miles per hour or 3 meters per second are an approximate threshold for the onset of breaking waves. When winds of this speed or greater are onshore, toxic aerosols may be present at the beach. Present wind conditions and wind forecasts are provided by the NOAA National Weather Service's National Data Buoy Center and models run by the National Weather Service's National Centers for Environmental Prediction.

Cell concentration categories used to determine red tide impacts are defined by the Florida Fish and Wildlife Research Institute and have been reported in several peer-reviewed journal articles (see below). In general, higher cell concentrations can produce more aerosols and potentially create a more serious impact.

For this Web site, the impact levels are defined as follows:

Impact Level Criteria Expected Impact1
None No Karenia brevis present None
Very Low Onshore winds < 7 mph and very low concentrations of Karenia brevis • Impacts at the beach are unlikely. People with severe or chronic respiratory conditions may be more sensitive.
• Possible shellfish harvesting closures.
• Presence of dead fish due to red tide is unlikely.
Low Onshore winds > 7 mph and low concentrations of Karenia brevis • Most people at the beach will not notice any symptoms. People with severe or chronic respiratory conditions may be more sensitive.
• Shellfish harvesting closures are likely.
• Presence of dead fish due to red tide is unlikely.
Moderate Onshore winds > 7 mph and medium concentrations of Karenia brevis • People at the beach may notice mild symptoms. People with severe or chronic respiratory conditions may be more sensitive.
• Presence of dead fish due to red tide is possible.2
High Onshore winds > 7 mph and high concentrations of Karenia brevis • Most people at the beach may notice adverse respiratory symptoms. People with severe or chronic respiratory conditions likely will be affected.
• Shellfish harvesting closures.
• Discoloration of water possible.
• Presence of dead fish due to red tide is possible.2
  1. See Kirkpatrick and others, 2004, referenced below. Health studies associated with Karenia brevis are also available from the Centers for Disease Control and Prevention (CDC) at http://www.cdc.gov/hab/redtide/.
  2. The public information on red tide conditions includes information on the impacts of confirmed fish kills caused by red tides during recent days. Since there are many factors that can cause fish kills, the Conditions Report does not attempt to predict the potential for dead fish to reach the beach. For more information on the effect of red tides on various marine animals, refer to Landsberg and others (2002) referenced below and the Florida Fish and Wildlife Research Institute Web site at http://research.myfwc.com/.

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How much of the coast is affected during a red tide?

Not all areas of the coast are equally affected during a red tide. HABs are generally isolated patches that are transported by winds and currents. They often concentrate around wind- or tide-protected areas like man-made jetties (Texas Parks and Wildlife: http://www.tpwd.state.tx.us/landwater/water/environconcerns/hab/redtide/faq.phtml).

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Florida county map

Image of FL counties

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Hot lines for more local information

Florida

Florida Department of Health aquatic toxins hotline: (888) 232-8635
Collier County Red Tide Hotline: (239) 732-2591
Manatee County Red Tide Alert Line: (941) 745-3779
Fish and Wildlife Research Institute (FWRI) fish kill hotline: (800) 636-0511
Florida Department of Health, Environmental Health, Environmental Epidemiology, Tallahassee: (850) 245-4299

Texas

Texas red tide phone information: (800) 792-1112, select "fishing" and then "red tide"
Texas Parks and Wildlife Kills and Spills Team: (512) 912-7055.

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Reference Literature

Kirkpatrick, B., L.E. Fleming, D. Squicciarini, L.C. Backer, R. Clark, W. Abraham, J. Benson, Y.S. Cheng, D. Johnson, R. Pierce, J. Zaias, G.D. Bossart, and D.G. Baden. 2004. "Literature Review of Florida Red Tide: Implications for Human Health Effects." Harmful Algae. Volume 3. Pages 99 to 115.

Kusek, K.M., G. Vargo, and K. Steidinger. 1999. "Gymnodinium Breve in the Field, in the Lab, and in the Newspaper - A Scientific and Journalistic Analysis of Florida Red Tides." Contributions in Marine Science. Volume 34. 229 pages.

Lansberg, J.H. 2002. "The Effects of Harmful Algal Blooms on Aquatic Organisms." Reviews in Fisheries Science. Volume 10, Number 2. Pages 113 to 390.

Steidinger, K.A., G.A. Vargo, P.A. Tester, and C.R. Tomas. 1998. "Bloom Dynamics and Physiology of Gymnodinium breve with Emphasis on the Gulf of Mexico." In Physiological Ecology of Harmful Algal Blooms. Editors D.M Anderson, A.D. Cembella, and G.M. Hallegraeff.

Stumpf, R.P., M.E. Culver, P.A. Tester, M. Tomlinson, G.J. Kirkpatrick, B.A. Pederson, E. Truby, V. Ransibrahmanukul, and M. Soracco. 2003. "Monitoring Karenia brevis Blooms in the Gulf of Mexico Using Satellite Ocean Color Imagery and Other Data." Harmful Algae. Volume 2. Pages 147 to 160.

Tomlinson, M.C., R.P. Stumpf, V. Ransibrahmanakul, E.W. Truby, G.J. Kirkpatrick, B.A. Pederson, G.A. Vargo, and C.A. Heil. 2004. "Evaluation of the Use of SeaWiFS Imagery for Detecting Karenia brevis Harmful Algal Blooms in the Eastern Gulf of Mexico." Remote Sensing of Environment. Volume 91. Pages 293 to 303.

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Revised: 10/15/2013
NOAA / National Ocean Service
Web site owner: Center for Operational Oceanographic Products and Services