Termination of the 2018 Florida red tide event: A tracer model perspective. (5th August 2022)

• Record Type: Journal Article
• Authors: Liu, Yonggang; Weisberg, Robert H.; Zheng, Lianyuan; Heil, Cynthia A.; Hubbard, Katherine A.
• Is Part Of: Estuarine, coastal and shelf science. Volume 272(2022)
• Publication Date: 2022-08-05
• Subjects: Red tide -- West Florida shelf -- Tracer model -- Coastal upwelling -- Harmful algal bloom -- Bloom termination; Estuarine oceanography -- Periodicals; Coasts -- Periodicals; Estuarine biology -- Periodicals; Seashore biology -- Periodicals; Coasts; Estuarine biology; Estuarine oceanography; Seashore biology; Periodicals; 551.461805
• DOI: 10.1016/j.ecss.2022.107901
• Languages: English
• ISSNs: 0272-7714

Abstract

Abstract: The 2018 Karenia brevis harmful algal bloom experienced along the west coast of Florida was the worst red tide occurrence there since 2005. Cell concentrations peaked in early fall of 2018, lessened in winter, and disappeared early in 2019. Here we examine the termination of this red tide event by using hindcast simulations of the West Florida Coastal Ocean Model, a numerical ocean circulation model that downscales from the deep Gulf of Mexico, across the continental shelf and into the estuaries. The underlying hypothesis is that without an offshore source of K. brevis cells, a nearshore bloom may quickly dissipate under the influence of a persistent upwelling circulation. To test this hypothesis, we used a passive tracer (without consideration of biological growth or decay) in the model to virtually indicate K. brevis cells. The tracer, inputted along the central West Florida coast where highest bloom concentrations were observed, was subsequently transported southward along the coast and offshore, significantly reducing the tracer concentrations over the three-month-long experimental duration, as was observed for the actual K. brevis cell concentrations. Whereas modeled tracer concentrations decreased over most of the West Florida coast, relatively higher concentrations remained just south of Sanibel Island, trapped there by the sharp bend in the coastline. Longer residence time for this area has important K. brevis implications. Lake Okeechobee nutrient flux through the Caloosahatchee River was thought to contribute to red tide in this region, and while these inputs may be a factor, a persistent upwelling circulation may also play a contributing role. Highlights: The termination of the 2018 Florida Karenia brevis red tide event was simulated with a passive tracer model. Without offshore source of K. brevis cells, a nearshore bloom may quickly dissipate due to persistent upwelling circulation. Due to the coastline geometry, upwelling circulation may trap K. brevis cells in the coastline nook south of Sanibel Island.