哔咔漫画

Written by Sean Beckwith, PhD student

ST. PETERSBURG, FL 鈥� Red tides are extremely disruptive to the environment and to people living and working along the coast.  Tools exist to verify the presence of red tide and predict its movements, but continuation of these predictions depends on reliable support for deployment and maintenance of oceanographic instruments, for analysis of the data, and for fundamental research.

Critical areas farther off the west coast of Florida are rarely sampled for red tide, which means that we perpetually lack the predictive capability to alert us of incoming blooms and their severity.  Innovative methods and instruments may now give us the ability to detect red tide at its onset, to know the extent and severity of a bloom, and to quickly and accurately analyze water samples for the presence of the organism responsible for red tide.  Better understanding of the current and future state of red tides are realistic.  However, reductions in funding for scientific infrastructure have stymied efforts to monitor, predict, and assess these harmful blooms.  A resurgence of support for the scientific capabilities that have been developed specifically to respond to red tide would improve environmental management and societal tolerance of these harmful algal blooms.  As a supplier of innovation in this realm, the University of South Florida College of Marine Science (USF CMS) draws on its decades of experience, infrastructure, and products to answer the most pressing questions in its mission to create lasting, large-scale solutions that will mitigate future blooms. 

How does a red tide begin?

Red tides, a term given to blooms of a microscopic organism named Karenia brevis, originate in deeper waters offshore and manifest themselves in shallower waters as they become concentrated along the coast.  Ocean circulation patterns play a major role in the occurrence or absence of red tides as upwelling is created through prolonged interactions between the Gulf of Mexico Loop Current and Florida鈥檚 broad, shallow continental shelf.  Upwelling brings nutrients from deeper portions of the Gulf to the shelf waters.  In the case of red tide, it鈥檚 sort of a Goldilocks situation in that a lack of upwelling might not provide enough nutrients for K. brevis while too much upwelling allows faster growing organisms to outcompete K. brevis by feasting on the abundant nutrient supply. 

For a bloom to initiate, K. brevis requires the sanctuary conditions that deeper waters offshore provide:  ideal water chemistry and vertical space to avoid light stress at the surface.  However, once formed, a bloom of the organism tends to prevail, often to the point of excess.  Once ocean currents have transported a bloom to the shallow coastal waters, individuals find protection from light stress owing to higher concentrations of Color Dissolved Organic Matter (CDOM).  CDOM provides a bit of shading for K. brevis, analogous to how tea particles obscure the bottom of a cup of tea. 

What other factors contribute?

Terrestrial runoff carries nutrients from both natural and man-made sources to the coastal waters.  In an advanced state, a harmful algal bloom (HAB), such as red tide, does not show signs of being outcompeted by other, faster-growing organisms.  Instead, the bloom takes advantage of all the nutrients available, including land runoff and nutrients from decaying fish (specifically ammonium) that were victims of the bloom itself.  Peak conditions and the dissipation of blooms is currently being studied further. Tools are available to understand the impacts of offshore nutrient concentrations on blooms, as well as to predict the time to shore and severity of red tides.

What tools are available to understand and predict red tide?

Dr. Robert Weisberg, physical oceanographer at USF CMS, points out that monitoring potential blooms at offshore locations is presently the most important use of scientific funding because it is the only way to effectively predict red tide. 

 鈥淚t鈥檚 a combination of looking at larger scale circulation to see whether or not the West Florida Shelf is conducive or not to a major bloom, and, once we have a bloom, use observations to trace where that bloom may be heading,鈥� said Weisberg.

The most robust way to monitor a large area at multiple depths (and the cheapest) is with gliders.  Auto-controlled and torpedo-like, they glide effortlessly through the water column on battery power for up to a month.  Transmitting their data via satellite to researchers and engineers at the CMS Ocean Technology Group, they can provide a first-responder assessment of possible blooms.  Small boats, operated by the (FWC-FWRI), then carry to the most efficient locations to sample for the red tide organism, K brevis.  Models run by the at USF CMS use the sampling data from FWC to provide of the path of a bloom and its concentration at various locations. 

The research group also makes of red tide bloom based on a hypothesis that interactions of the Gulf of Mexico Loop Current with the shelf slope under certain conditions can reset the West Florida Shelf nutrient structure in ways that may prevent bloom development.  An altimetry derived offshore forcing index鈥攁 measure of how strongly the Gulf of Mexico Loop Current system interacts with the continental slope and induces upwelling on the shelf鈥攎ay serve as a seasonal predictor for major K. brevis blooms on the west Florida coast.

鈥淲e found that for 20 out of the past 25 years, in which we have concurrent data, we can actually predict the existence, or non-existence, of a major bloom simply on the basis of the ocean circulation,鈥� shared Weisberg. 

Overlaying the model simulated currents and alga concentration data, Dr. Chuanmin Hu鈥檚 at USF CMS produces a near real-time (IRIS).  From their website, anyone can access the satellite imagery files and click on links below the images to open multi-layer maps in Google Earth for all coastal regions of the eastern Gulf of Mexico (Louisiana to the Florida Keys).  Dr. Hu鈥檚 lab uses unique combinations of spectral bands from satellite data to monitor red tide from Earth鈥檚 orbit.  From this vantage point, and depending on cloud cover, the entire extent of a red tide bloom can be viewed in daily satellite imagery.

 鈥淭he advantage is the synoptic coverage.  We know the size.  For example, the current red tide as of yesterday is more than three times Tampa Bay in size,鈥� said Hu, referring to the size of the bloom about a week ago.  However, as of the writing of this article, the bloom is now estimated at four times the size of Tampa Bay. 

On the ground, Dr. John Paul, a microbiological oceanographer at USF CMS, detects the presence of K. brevis with an instrument that quantifies its RNA. 

鈥淲e use something called NASBA, which stands for Nucleic Acid Sequence Based Amplification,鈥� said Paul as he explained the method by which his device uses fluorescence to single out K. brevis.  鈥淭he time that the amplification occurs is inversely proportional to the concentration.鈥�

With extremely low error and simultaneous analysis of eight water samples, the (also known as the Red Tide Tricorder) can rapidly and accurately quantify K. brevis, with no crossover from non-target organisms.  This game changing tool is currently used in comparative analyses by FWC-FWRI and is readily available to state and federal agencies, the shellfish industry, and other end-users. 

Dana Nieuwkerk, a Ph.D. student working with Dr. Paul, added, 鈥淲hat鈥檚 really nice about this platform [referring to the portable Tricorder] is that you鈥檙e able to take the instrument in situ.  You can take the instrument on a boat and do testing and come back from a cruise with near real-time data, rather than having to go out and archive samples and bring them back to later analyze them鈥�It鈥檚 battery powered, so you can bring it to the beach and run samples right there.鈥�

How do red tides finally dissipate?

There are a few theories that explain the end of a red tide bloom; it is likely a combination of these ideas that provides the full answer.  Theories in the scientific community include 1) advection of a bloom to nutrient-depleted locations, which eliminates the organisms鈥� food source and reduces their population to levels that might be outcompeted, 2) hurricanes and winter swells that mix the water column, which disrupts and dilutes a bloom of K. brevis, and 3) a theory involving terminal cell response signals that cause individuals to limit their own production, perhaps as a mechanism of self-preservation.

A 鈥渃ure鈥� for red tide does not presently exist.  However, multiple tools for mitigation are available:  early detection and prediction of bloom movements, visualizations mapping the complete spatial extent of a bloom, and rapid analysis of water samples.  Karenia brevis is a very successful species by evolutionary criteria.  Blooms will continue to return on a regular basis, but as a society, there is much more to be done to better prepare our coasts for locals and visitors.