The slimy algae topping Florida's waterways are more than just unsightly. They are often toxic to humans, animals and the environment.
To mitigate those risks, University of Florida researchers are collaborating with North Carolina State University and University of South Florida scientists on a next-day prediction model to warn and inform water managers about harmful algal blooms.
The research is funded by two U.S. Army Corps of Engineers grants for two phases, totaling $4.4 million. The project is led by David Kaplan, Ph.D., a professor with the Engineering School of Sustainable Infrastructure and Environment in the Herbert Wertheim College of Engineering and director of the Howard T. Odum Center for Wetlands, and Mauricio Arias, Ph.D., an associate professor at USF.
In a paper published recently in the Journal of Environmental Management, Kaplan, UF assistant professor Elise Morrison, Ph.D., and NCSU's Maria Menchu Maldonado, Ph.D., chronicled their work with harmful algal blooms in the Caloosahatchee River and Estuary, the environmentally sensitive link between Lake Okeechobee and Florida's southwestern coast. Maldonado performed the work under the guidance of NCSU collaborator Natalie Nelson.
In a collaboration between multiple colleges, organizations, departments and universities, the paper's other authors are Eric Milbrandt of the Sanibel-Captiva Conservation Foundation, Edward Phlips of UF and Natalie G. Nelson of NCSU. The project's facilitators include Darlene Velez, research coordinator with the UF Water Institute, and Lisa Krimsky, Ph.D., a water resources regional specialized agent with IFAS.
Using water samples and computer algorithms, the team developed prediction models based on two water sources feeding the river: Lake Okeechobee and the river's watershed – the water run-off from the surrounding land. The models determine levels of chlorophyll-a, which is a pigment in algae that is indicative of algal bloom conditions.
"For watershed-dominated conditions, the model was able to predict 49% of the variation in next-day chlorophyll-a, which isn't bad, but for lake-dominated conditions, the model was much better, explaining 78% of the variation in next-day chlorophyll-a in the water," Kaplan noted.
Unlike traditional forecasting models for algal blooms, which are often complex and require much computing power, these models are designed to be practical for daily decision-making, particularly for the Southwest Florida Water Management District (SWFWMD), which has made improving the health of the Caloosahatchee Estuary a state priority.
Ultimately, researchers want to develop an algae-prediction system and tools for water managers to reduce risks in all freshwater bodies.
"Definitely, this model could be expanded with the use of more data," said Maldonado. "The same procedure could be applied in other lakes that are highly managed. And this could be done around the world."
Algal blooms in Florida's lakes, rivers and estuaries have caused significant environmental and economic damage in recent years, UF researchers contend. Blooms are becoming more frequent and longer lasting.
The initial project – called Coupling Lake, Estuarine, and Watershed Models for the Caloosahatchee River and Estuary (CLEW) – designed data- and model-driven guidance for Lake Okeechobee water releases.
"The overall motivation is that Lake Okeechobee is a challenging natural resource to manage, particularly deciding when and how much water to discharge from the lake to either estuary," Kaplan said. "There are many competing needs surrounding management of the lake, which has only so much volume. We don't want to cause flooding or other ecological harm."
The follow-up project is UF's collaboration with USF to develop tools for end users, meaning agencies and managers to make better decisions. The team wants to deliver a system where water managers press the button to get the one-day risk forecast.
The study was organized to predict whether the algae-toxin risk is low, medium or high.
"In this case, there is a threshold of algal organisms that is considered harmful," Maldonado said. "Those waters carry phytoplankton species, a microscopic algae that produce toxins. They can be dangerous to swim in, and they can be harmful to the environment. It can be a liver toxin."
Beginning in the late 19th century, the Caloosahatchee River and its watershed underwent extensive modifications that significantly altered the hydrology of the region, according to SWFWMD. The once-shallow river was deepened and widened into a regulated waterway that was connected to Lake Okeechobee and the Kissimmee Chain of Lakes for navigation, water supply and flood control purposes.
"Water quality is a challenge in Lake Okeechobee, including sometimes pretty bad harmful algal blooms," Kaplan said. "And then, of course, the downstream recipients of whatever water is discharged are very sensitive to the amount of water they're getting and what's in it. They'd prefer it to be only the right amount at only the right times with the best quality."
