Indian River Lagoon Bloom Research
During 2011 and 2012, major harmful algal blooms (HABs) in the Indian River Lagoon (IRL) killed seagrass and raised concerns about detrimental effects on fish and wildlife that depend on this habitat. The 2011 “green tide” was mostly attributed to a chlorophyte, a type of green microalgae, and the 2012 “brown tide” was dominated by the pelagophyte Aureoumbra lagunensis. These blooms marked a dramatic shift in the size of algae typically responsible for blooms in the IRL. These microalgae were tiny: less than 6 micrometers in diameter or 10-100 times smaller than the diatom and dinoflagellate species that bloomed in the past! Their size makes these microalgae difficult to identify with light microscopy, the established method for identifying most microalgae. This shift in the composition of blooms triggered scientists to consider new tools that can identify and count these species accurately and rapidly. In a project funded by the Indian River Lagoon National Estuary Program, FWC scientists are working with partners from the University of Florida (UF) and the St. Johns River Water Management District (SJRWMD) to evaluate existing analytical techniques and develop new tools that may enhance detection and quantification of future blooms.
This project explores molecular and flow cytometric methods – powerful tools for distinguishing microalgae that can be tailored to target particular organisms or communities of interest. Molecular identification usually targets unique genetic sequences (DNA or RNA), often with fluorescent tags designed to stick only to cells that possess those sequences. These unique sequences also can be used in polymerase chain reactions, or PCR, which amplifies small amounts of genetic material and can quantify the occurrence of target species in a sample. Flow cytometry is a laser-based technology that counts, measures, characterizes, and sorts cells in a stream of fluid. Sticking fluorescent tags to targeted cells enhances the specificity of flow cytometry. The molecular and flow cytometric tools being developed as part of this project will identify and count targeted algae.
This project is divided into distinct phases: (1) method design, (2) method testing or “validation”, and (3) method comparison.
Since the start of the project in 2014, we have designed methods that target the species responsible for the green and brown tides. We also have evaluated previously-developed methods to detect Aureoumbra. To test the accuracy of the methods, we assess their sensitivity and ability to detect key species by testing algae from cultures of single species grown in the lab. Lab testing also has informed our methods for collecting field samples. Even something as simple as collecting water samples requires extensive planning because molecular and flow cytometric tools require water samples to be collected and stored in special ways. For example, some of the techniques require the water to be filtered and frozen within minutes. SJRWMD and UF are key partners in this ongoing work because they provide valuable logistical support. Every two weeks, SJRWMD and UF crews tag-team to collect algal samples needed by the FWC scientists. UF also provides live cultures and validation of results based on microscopy.
Although this project is ongoing, we already have gained a deeper understanding of the 2011 and 2012 blooms, including identification of specific organisms forming the blooms. In turn, this understanding has helped us develop and modify our tools. With continued development of these techniques, agencies will be able to process samples more quickly and accurately than they have in the past. Such rapid turn around may help managers as they try to cope with algal blooms.