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.
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.