What are the green globs that are sometimes seen floating in or even taking over Florida’s natural springs and waterways? Those would be algae blooms and, turns out, snail grazers have a role to play.
For 20 years, waterway nitrate levels have been a primary source of blame for the overpopulation of algae blooms in Florida’s natural springs. But these blooms aren’t necessarily the only cause. That’s what three researchers from the University of Florida’s Institute of Food and Agricultural Sciences (UF/IFAS), Dina Liebowitz, Paul Donsky, and Matt Cohen, along with their co-authors, explain in a recently published study.
“Nitrogen can cause problems in all sorts of environments and needs to be managed,” explains Liebowitz, “but the evidence that it’s the primary cause of the algae blooms in the springs is unclear.”
Liebowitz says that a declining population of grazers, particularly freshwater snails called Elimia, and a decline in dissolved oxygen levels could be part of what’s driving the changes. “We had done surveys across eight springs, repeated over a year that showed a strong negative relationship between the snails and filamentous algae blooms, meaning that there were generally low algae amounts in areas with high snail populations,” Liebowitz explained. “The next step was to explore that relationship more deeply.”
Photo Credit: Chris Lukhaup
She explains that in an environment with small amounts of algae and good oxygen levels, if left to their own devices, strong snail communities will help to keep a healthy and balanced ecosystem. But that’s where environmental complexity comes in.
To keep the all-you-can-eat algae buffet at a manageable level and not explode to bloom status, factors like the Elimia snail population and the condition of dissolved oxygen need more consideration in the management conversation.
Depleted dissolved oxygen supplies can make the snails lose vigor for foraging activity and, even though there’s still plenty of algae to be eaten, their survivability plummets, or they can slink off somewhere else.
Donsky explains this can initiate a nasty feedback loop: oxygen depletion drives snails away, more algae blooms, and underwater vegetation dies and changes the habitat. Then, even if oxygen goes back up and snails try to come home, there’s too much algae for them to tackle, and the green goo cycle continues.
The research team looked at two different rounds of three experimental treatments across four sites within the Florida spring-fed Ichetucknee River in north central Florida.
They found that the overall success of snail control of algae blooms depends on three things: the amount of algae initially present, the size of the snail population, and the levels of dissolved oxygen.
“When you have these balanced ecosystems and the snails are doing what they do, they’re little janitors,” said Liebowitz. “They keep the springs beautiful for us, they provide an ecosystem service, and we don’t have to do anything.”
“Ecosystem restoration isn’t easy, but there’s exciting new research to help lead the way,” Liebowitz said. “It’s important to keep learning about these incredible systems and what we can do to help them thrive.”
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ABOUT UF/IFAS
The mission of the University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) is to develop knowledge relevant to agricultural, human and natural resources and to make that knowledge available to sustain and enhance the quality of human life. With more than a dozen research facilities, 67 county Extension offices, and award-winning students and faculty in the UF College of Agricultural and Life Sciences, UF/IFAS brings science-based solutions to the state’s agricultural and natural resources industries, and all Florida residents.
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