An NCCOS-funded research team, led by Mote Marine Laboratory and the University of Maryland Center for Environmental Science (UMCES), recently published three peer-reviewed studies that provide new insights into the factors driving the increasing frequency and severity of Florida red tide blooms caused by the toxic algae Karenia brevis. The findings link these trends to increasing water temperatures and the expanding human nutrient footprint in coastal waters along Florida’s West Coast. The results help explain why blooms have become more persistent, severe, and difficult to predict and manage, evidenced by events like the unprecedented 2017-2019 red tide, which caused an estimated $2.7 billion in losses.
Key findings show a clear decadal shift toward longer, more severe, and seasonally altered red tide events on the West Florida Shelf. Specifically, the research connects the trend of more intense, longer-lasting events to shifts in the El Niño-Southern Oscillation in the 1990s, which brought warmer water temperatures, increased rainfall, and more intense storms. These climate shifts, combined with population growth and increased riverine nitrogen inputs into coastal waters, help to prolong and intensify existing blooms. Furthermore, a dual nutritional strategy exhibited by Karenia brevis allows it to persist even during unfavorable environmental conditions, making its growth less dependent on encountering optimal conditions and further explaining the longevity of some blooms.
The research team, supported by the NCCOS Competitive Research Program, conclude that red tide is no longer an episodic event but is increasingly acting as a chronic, recurring stressor on southwest Florida coastal ecosystems. This ongoing pressure affects human health, well-being, and regional economies that rely on healthy coastal environments. Published findings are being shared broadly to inform NOAA and regional partners who deliver forecasts, support monitoring, and manage resources to reduce the costly impacts of Florida red tide on key sectors of the state’s economy.
Learn more about this research and find published findings on the NCCOS Ecology and Oceanography of Harmful Algal Bloom project page. NOAA is authorized to advance scientific understanding and assessment of HAB events through the Harmful Algal Bloom and Hypoxia Research and Control Act (33 U.S.C. §§ 4001 et seq.).
View the publications:
- A modeling investigation into the ecological role of mixotrophy in Karenia brevis blooms on the West Florida Shelf
- Climate shifts and anthropogenic footprints driving increased severity and duration of toxic Karenia brevis blooms in the Gulf of Mexico over the past ~50 years.
- More sustained, more severe blooms and shifting monthly patterns of the toxigenic dinoflagellate Karenia brevis on the West Florida Shelf.