Algal blooms can kill fish and harm a lake’s ecosystem, but by reducing two nutrients together such as nitrogen and phosphorus – not just one or the other — water managers might limit the blooms in lakes and rivers, a new University of Florida study shows.
To come to this conclusion, UF Institute of Food and Agricultural Sciences researchers used an innovative method used in artificial intelligence. The method also will apply to bloom-control research in freshwater ecosystems around the world, UF/IFAS researchers say.
For years, scientists have argued about whether managing both nitrogen and phosphorus – versus managing strictly phosphorus or just nitrogen – would control harmful algal blooms.
For 25 years, Ed Phlips, a UF/IFAS professor in fisheries and aquatic sciences, has worked with scientists at the St. Johns River Water Management District to try to limit nutrients from entering Lake George and imperiling its ecosystem. Blooms in Lake George come from a group of algae that contain many species capable of producing toxins or otherwise disrupting ecosystems, such as creating low oxygen conditions, Phlips said.
“One of the central goals of the research has been identifying the factors that cause frequent harmful algal blooms in the lake, creating a range of challenges for the health and sustainability of key aquatic resources, including fish communities and water for human uses,” Phlips said.
Recently, Rafael Muñoz-Carpena, a UF/IFAS professor of agricultural and biological engineering, led a research team, with his doctoral student Natalie Nelson that reviewed 17 years of data collected by Phlips’ lab from the waters of Lake George, the second largest lake in Florida, behind Lake Okeechobee. Lake George lies in parts of Putnam, Lake, Marion and Volusia counties in central Florida.
Scientists used a new approach called Random Forests Analysis, which tests the sensitivity of bloom-forming species to several environmental conditions in the lake, Muñoz-Carpena said. Those include nutrient levels, water temperatures, light levels and densities of aquatic life that feed from the lake’s bottom.
Researchers found that the major bloom-forming algae in Lake George respond differently to levels of nitrogen and phosphorus, said Phlips.
“The results of this study have major implications for future potential directions in managing harmful algal blooms in Lake George,” Phlips said. “This shows that dual reductions in nitrogen and phosphorus levels may be required to effectively lower the potential for harmful algal blooms in Lake George.”
Algae are an important part of lake ecosystems and provide food for fish, shellfish and microscopic animals in the water, according to this UF/IFAS Extension document. However, intense blooms of harmful algae species also can impair important ecosystem functions and inhibit recreational uses of water, according to the report. Harmful algal blooms are stimulated by excessive levels of nutrients and by warm water.
The new study is published in the journal Environmental Science and Technology.
by Brad Buck, University of Florida Institute of Food and Agricultural Sciences