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Examining How Red Tide Impacts Loggerhead Hatchlings
A collaborative four-year study led by SCCF showed that red tide events are having a significant impact on both adult and hatchling sea turtles in the Gulf.
“In addition to confirming that the transfer of red tide toxins occurs from female to hatchling through the egg yolk, we established alarmingly high concentrations of toxins in many hatchling livers and found that nests with higher toxin loads had lower hatch success,” said SCCF Coastal Wildlife Director and Sea Turtle Program Coordinator Kelly Sloan, the principal investigator on the project. “Our results provide evidence that even in the absence of active blooms, red tide events act as physiological stressors with lasting impacts on the health and reproductive success of sea turtles.”
The physiological impacts of red tide toxins (called brevetoxins) on hatchlings are currently unknown, but the study’s results indicated impacts to adult loggerhead immune function and overall health.
Following up on this study, SCCF started a project to examine how brevetoxins are impacting hatchling fitness, health, and survival.
Sampled hatchlings underwent several trials testing locomotor performance, including how long it took them to turn themselves back over after being inverted.
“A hatchling’s ability to quickly right itself is vital in rapidly moving through coastal waters and evading predators, so this test of locomotor performance is commonly used as a proxy for survival,” Sloan said. “After the fitness tests, we collected a small blood sample for brevetoxin and health analysis.”
Several additional nesting beaches along Florida’s Gulf coast have agreed to collaborate with SCCF and provide hatchling samples in an effort to determine brevetoxin exposure in other geographic regions.
“We are hopeful that our results will help fill a data gap on how red tide affects hatchling sea turtles. The results can be considered when evaluating the overall health of sea turtles in the Gulf,” Sloan said.
This project was generously funded by Linda and Nick Linsmayer and the AWC Family Foundation.
About Red Tide
Red tide blooms are caused by large concentrations of Karenia brevis, a single-celled organism belonging to a group of algae called dinoflagellates. Blooms develop offshore and are brought inshore by currents and winds, usually in bottom waters. The neurotoxins (brevetoxins) produced by K. brevis during red tide events can sicken and kill fish, seabirds, turtles, and marine mammals. A 2022 study co-authored by SCCF Marine Laboratory Director Eric Milbrandt, Ph.D., found that human activity such as nutrient pollution can intensify existing red tide blooms in our watershed.