Category Archives: Harmful Algal Bloom Research

Employing New Technology to Indirectly Monitor Karenia Brevis

By Matt Garrett and Kelsey Marvin

Over 14,000 water samples were processed during the Karenia brevis bloom that began in November 2017 and ended in February 2019. Each of these samples represents a single moment in space and time, and both routine and event response sampling play a critical role in tracking blooms. Marine and estuarine environments –and blooms of K. brevis – are dynamic and can change rapidly over space and time. To help bridge gaps between sampling events, the HAB Group has been working to adapt a new passive sampling technology to monitor for brevetoxins produced by K. brevis in the Gulf of Mexico called Solid Phase Adsorption Toxin Tracking, or SPATT. SPATT uses tiny resin beads that passively adsorb free brevetoxins in the water. These beads are sealed in small mesh bags and can be deployed in various locations (on fishing piers, docks, buoy lines) for upwards to a month at a time, and once the bags are recovered, toxins can then be extracted and measured. Since this method only measures toxin exposure over time, it cannot be used to infer actual cell concentrations, like those provided on our weekly maps.  Instead, scientists can infer K. brevis’ presence and general concentration at a particular location and depth during the deployment period.

SPATT bags, which are nylon mesh bags filled with resin, are attached to a bouyed line at different depths, along with a temperature and light sensor attached at each depth. The SPATT bag on the left is seen just prior to deployment, while the image on the right is a bag harvested after one month.

Using SPATT bag analyses to detect toxins offshore and/or at depth is of particular interest, since sub-surface samples are beyond the reach of remote sensing, and most samples are taken within 0.5 m of the surface and/or in nearshore coastal and estuarine systems. Analyses of recently deployed SPATT bags have shown higher concentrations at depth, both when compared to concentrations at the surface and in previous months. These types of measurements are increasingly critical, as evidence points to bloom formation occurring at depth in the offshore environment. Information about bloom conditions at depth is particularly important to have for use in predictive models of bloom development and transport to the nearshore coast, where a bloom can become a severe red tide event.

Use of this technology in the lab and field has been very promising! In the future, the HAB Group hopes to be able to deploy SPATT bags in multiple locations spanning nearshore to offshore so that they can serve as an early warning sentinel system for K. brevis blooms. SPATT technology is currently used in other parts of the U.S. to monitor different marine and freshwater toxins, and FWRI HAB researchers also plan to determine how this method could be used to measure and track the multiple toxins produced by other HAB species in Florida waters.

New bouyed SPATT line prepped for deployment on 4/1/19.

A Tale of Two Teams: Coordinated Harmful Algal Bloom and Fish Kill Event Response

by Matt Garrett and Adam Richardson

dead fish on beach

In 2015-2016, a bloom of the red tide alga Karenia brevis and associated fish kills occurred in Northwest and Southwest Florida. Coastal blooms in both areas were first observed in September 2015. Although the Northwest bloom ended in January, the Southwest bloom endured until April 2016. Throughout this period, the bloom location and intensity, and associated local impacts including fish kills and reports of respiratory irritation, varied spatially from Pinellas to Monroe County. The extensive monitoring and response efforts required to track a bloom and its impacts of this spatial and temporal extent involved help from various groups within FWRI and other partners across the state, including an extensive volunteer monitoring network. Two events in particular involved careful coordination of FWRI’s Harmful Algal Bloom (HAB) and Fish and Wildlife Health (FWH) groups.

The first event occurred in late February, when extensive fish kills of marine species along the coastline of the Western Everglades were reported, several involving red drum, mullet, mangrove snapper, and snook. This raised concerns that a more extensive bloom of K. brevis, which had been previously observed at “medium” concentrations ranging from 105,500 – 473,000 cells per liter offshore of Pavilion Key (Monroe County), was causing the fish kills. Given the remote location of the reported fish kills, and the need for a rapid response to inform both management and stakeholders, scientists from the FWH and HAB groups designed a response plan utilizing two vessels to simultaneously sample both nearshore and offshore waters in the area impacted by fish kills. Staff obtained water quality data, water samples for phytoplankton, toxin, and eDNA analyses, deceased or moribund fish, seagrass samples, and sediments. Without the cooperation and rapid mobilization of the two groups, and the help of the Everglades National Park, timely samples from such a large area would not have been collected and analyzed. Although the bloom likely had a more northern origin, it is not clear what caused the fish kill. It is possible that a larger-scale bloom advected out of the system and was not detected at the time of sampling. It is also possible that either fish and/or cells may have been entrained or mixed within less saline waters, which can be detrimental to both marine fish and marine phytoplankton. For K. brevis, an influx of fresh water could contribute to cell lysis and subsequent release of intracellular toxins into surrounding water.

A second event occurred in early April, when FWC’s Fish Kill Hotline received numerous reports of a fish kill concentrated in Pinellas County, from the southern end of Madeira Beach to Indian Rocks Beach. Once again, FWH and HAB staff investigated. FWH staff conducted a beach survey, and experienced respiratory irritation in certain areas. Beachgoers were also impacted and FWH staff were approached several times with questions; they used this as an opportunity to obtain further information about the fish kill. Low densities of a variety of dead fish in early to late stages of decomposition, including hardhead catfish, spadefish, burrfish, toadfish, and grunts, were spread along the shore. Water samples from the shoreline confirmed “high” concentrations of K. brevis, ranging from 1.1 to 1.6 million cells per liter. HAB staff sampled coastal and offshore waters and in the fish kill area and further south, “medium” concentrations of K. brevis occurred in coastal waters. Cells were not observed further offshore. An autonomous glider was subsequently deployed offshore of Pinellas County through FWC and Mote Marine Laboratory’s Cooperative Red Tide program. The glider measures physical and biological parameters at different depths and its sampling track was programmed to facilitate continued surface and subsurface bloom tracking. Again, the collaborative efforts between FWH and HAB staff led to more comprehensive and spatially extensive sampling, and timely dissemination of information to stakeholders, and provided relevant contextual data to inform further response efforts at the time of the events, as well as our understanding of how these specific events occurred to improve monitoring and event response efforts.

HAB Research and Sampling


by Kate Hubbard

woman on dock holding equipmentRecently, FWC HAB staff went out on the Research Vessel F. G. Walton Smith out of the University of Miami to collect samples for genetic and microscopic analysis as part of collaborative research efforts to monitor biodiversity in the Florida Keys National Marine Sanctuary. Samples are collected every other month, and most recently on the March 2016 cruise, samples of opportunity were collected to help determine the distribution of the red tide organism, Karenia brevis, in the nearshore and offshore waters surrounding Monroe County. Samples are collected using a rosette of Niskin bottles, which can be closed at targeted depths.



HAB Researchers Continue to Track Red Tides in FL

by Alina Corcoran


fish kill

aerial view of red tide bloom
Fish kill in St. Joe Bay during September (top, image courtesy of A. Reich) and aerial image of K. brevis bloom off Venice during December (bottom, image courtesy of T. Reinhart).

In September, a Florida resident reported that she and her family experienced respiratory irritation in Northwest Florida at Bid-A-Wee Beach in Panama City. At the same time, FWC’s Harmful Algal Bloom (HAB) group confirmed that bloom concentrations of Karenia brevis were present in water samples collected by the Florida Department of Agriculture and Consumer Services (FDACS) and volunteers for the HAB program from Gulf and Franklin counties. Sampling efforts, along with reports of respiratory irritation and fish mortalities throughout October, demonstrated the persistence of K. brevis blooms in this area, with expansion of the bloom west towards Okaloosa and Walton counties by the end of October. In early November, the FWC Fish Kill Hotline received reports of fish and crab mortalities in Manatee and Charlotte counties in
Southwest Florida, which were quickly linked to red tide — confirming the presence of co-occurring blooms in both Northwest and Southwest Florida.

Since late September, the HAB group has been tracking these blooms through sample analysis as well as imagery supplied by USF’s Optical Oceanography Laboratory.  Multiple FWC partners, including staff in the Fisheries Independent Monitoring, Fisheries Dependent Monitoring, Mollusc, and Fish and Wildlife Health groups, have contributed to sampling efforts. Sample analysis has also ramped up, thanks to teamwork by multiple HAB staff! FWC HAB staff have continued to work with USF researchers to generate short term forecasts of bloom movement via the Collaboration for Prediction of Red Tides.

Sampling this year — markedly skewed towards inshore waters — has revealed persistent blooms in bays and estuaries including Pensacola Bay, St. Andrews Bay, St. Joe’s Bay, Tampa Bay, Sarasota Bay, and Charlotte Harbor. Tidal cycles have pushed K. brevis into Tampa Bay past the Skyway Bridge, where staff recently confirmed concentrations greater than 3 million cells L-1. The blooms in both regions have resulted in numerous fish kills, extensive respiratory irritation, and multiple closures of shellfish harvesting areas.
The FWC HAB group publishes a midweek red tide update each Wednesday and a full report each Friday by 5pm on the FWC website at:

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