Red Tide Event Response

The Harmful Algal Blooms (HAB) group at the Fish and Wildlife Research Institute will be the first to tell you that it takes a team to track and study red tides in Florida waters. 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, the Florida red tide organism often abbreviated as K. brevis. HAB researchers combine field sampling, satellite imagery, and modeling to obtain a comprehensive picture of bloom progression, as well as mitigate the negative effects of blooms by providing timely information to stakeholders and the public.

Researchers in the HAB group, working closely with numerous partners, use a diverse set of tools and technologies to understand the factors that contribute to bloom development and demise. One key partner in red tide monitoring is Mote Marine Laboratory. Joint FWRI-Mote field operations allow for comprehensive sampling that includes both ship-based efforts and remote data collection via gliders. Another partner that plays a vital role in monitoring is the University of South Florida. USF’s Optical Oceanography Laboratory processes data collected by NOAA and NASA satellites through mathematical algorithms to generate images of blooms, which allow FWRI researchers to detect offshore blooms, assess the spatial extent of inshore blooms and focus response efforts in the field. USF’s Coastal Ocean Monitoring and Prediction program also provides valuable information on subsurface blooms through glider deployments. Finally, the Collaboration for Prediction of Red Tides – a collaboration between FWRI scientists and USF scientists – provides three-day bloom forecasts researchers use to track and predict where ongoing blooms are heading.


FWC researchers Eric Muhlbach, Kate Hubbard and Sheila O’Dea collecting water samples.


In the summer of 2014, one particular red tide called FWRI and its partners into action. It was a large bloom approximately 80 miles long and 50 miles wide located 40 to 90 miles offshore between Dixie and Pasco counties. On July 9, the FWC’s Fish Kill Hotline received reports from recreational anglers of dead benthic reef fish species. These reports were the first indication of an offshore HAB. With the help of FWC law enforcement and Fish and Wildlife Health scientists, the HAB group confirmed the bloom was caused by K. brevis. The team led subsequent event response efforts to track and study the bloom. In addition to leading day trips to sample bloom patches, the group orchestrated and crewed three major research cruises aboard the R/V Bellows: one in early August, one in late August and one in mid-September of 2014. Each cruise lasted approximately three days and tracked the development of the bloom and associated physical, chemical, and biological factors through space and time. This sampling was particularly important because it provided subsurface data on HAB species. Satellite data and surface sampling only provide information on the surface expression of the bloom, which for K. brevis is just the tip of the iceberg.

Through the research cruises, scientists documented an inshore-offshore gradient in the HAB populations, with potentially toxic diatoms in the genus Pseudo-nitzschia. Researchers also found an overall shift to Pesudo-nitzschia through time. This shift, as well as the inshore-offshore gradient, was attributed to a change in the upwelling regime. Upwelling is a process in which deep, cold, nutrient-rich water rises toward the surface. The shift highlights the importance of physical factors like upwelling in dictating where and when red tides will occur. The comprehensive sampling led by FWRI resulted in 3D pictures of both HABs, as well as the physical and chemical environments. This information is being used to address specific hypotheses related to bloom drivers. Researchers were also able to test new markers during the bloom period, which are now in final stages of development.

This article appeared in the 2015-2016 FWRI Programs Document