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Improved NOAA Forecast for Red Tide in Florida

Coastal communities, public health managers benefit from better forecasts.

Red tide forecasts for Florida will now be even more accurate thanks to an improved method of forecasting that will allow NOAA scientists to see more clearly where the harmful algal blooms (HABs) that cause this phenomenon are located.  This will help local residents and visitors make better decisions about their recreational choices during a HAB event and aid public health managers who coordinate response efforts and mitigate the effects of red tide.

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illustration of redtide

Sometimes Tiny Algae Can Cause Big Problems

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.

What is a red tide?

A red tide, or harmful algal bloom, is 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. Karenia Brevis can cause severe respiratory irritation in people, produce large fish kills, and discolor water along the coast.

NOAA Improves HAB Forecasts

NOAA currently 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. Although the current algorithm used to analyze the satellite imagery performs well at detecting blooms, it cannot easily distinguish Karenia brevis from other types of algae. Currently, the processed satellite imagery only highlights areas of abnormally high chlorophyll (a pigment found in all algae, making it detectable in satellite imagery). Increases in chlorophyll could be due to a developing bloom of Karenia brevis, but could also be due to blooms of other species of algae that are not harmful.

NOAA's new satellite imagery product combines the current chlorophyll algorithm with two additional algorithms that are specific to the optical characteristics of Karenia brevis, essentially making it much easier for scientists to distinguish between the harmful algae and its otherwise tame relatives. Combining the three algorithms reduces the possibility of falsely highlighting a non-harmful bloom as Karenia brevis and refines the area that is highlighted, giving NOAA scientists a much better idea of the areas impacted by a bloom. This, in turn, improves NOAA's HAB forecasts. Although the new satellite imagery product is currently only being integrated into the Florida HAB forecasts, it will be evaluated for use in Texas and may lead to refinements to forecasts in that region in the future.

Putting the New Forecast into Action

The conditions report for red tide in Florida and Texas are available to the public and gives daily respiratory irritation forecasts by coastal region. NOAA also issues HAB bulletins that contain an analysis of ocean color satellite imagery, field observations, models, public health reports and buoy data. It also contains forecasts of potential Karenia brevis bloom transport, intensification and associated respiratory irritation based on the analysis of information from partners and data providers. These bulletins are primarily issued to public health managers, natural resource managers and scientists interested in HABs. 

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Did you know?

Less than one percent of algal blooms actually produce toxins. Not all algal blooms are harmful, some can actually be beneficial. Phytoplankton are found at the base of the marine food chain therefore all other life in the ocean relies on phytoplankton. Blooms can also be a good indicator of environmental change not only in the water, but also on land.

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