Massive sargassum seaweed accumulations are creating significant barriers for sea turtle hatchlings on Florida's beaches, delaying their journey to the ocean and heightening risks from predators and heat. A new study from Florida Atlantic University examined the impact on three common species, revealing substantial slowdowns without immediate energy depletion. The findings underscore the growing threat to hatchling survival amid expanding seaweed deposits.
Sea turtle hatchlings face a perilous crawl from nests to the ocean on Florida's beaches, navigating obstacles like artificial lights, debris, and predators. Recent research highlights how surging sargassum seaweed exacerbates these challenges. Scientists from Florida Atlantic University's Charles E. Schmidt College of Science studied leatherback (Dermochelys coriacea), loggerhead (Caretta caretta), and green (Chelonia mydas) turtle hatchlings collected from Juno Beach, Jupiter, and Boca Raton.
In controlled experiments, researchers set up 15-meter crawlways on sand, ending with sargassum piles up to 19 centimeters high—simulating natural beach conditions. A dim light guided the hatchlings, mimicking the ocean's glow. Sand temperatures were monitored throughout, and post-crawl assessments included blood glucose levels for energy use and righting ability in water for physical condition.
The study, published in the Journal of Coastal Research (2025; 41(6)), found that sargassum significantly prolonged the hatchlings' journeys. Median times increased by 54% for leatherbacks in light sargassum (7-9 cm) and 158% in heavy; loggerheads by 91% and 175%; greens by 75% and 159%. Speeds dropped notably, especially for loggerheads, with many hatchlings struggling to climb even lower piles. Frequent inversions—hatchlings flipping onto their backs—occurred, particularly in heavier seaweed, prolonging exposure. One hatchling inverted over 20 times in a trial.
Despite the delays, blood glucose levels remained stable across all species and conditions, suggesting no immediate energy drain from the seaweed. Only leatherbacks in a no-crawl control showed higher glucose, pointing to crawling itself as the primary short-term stressor.
"The longer a hatchling stays on the beach, the more at risk it becomes—not just from predators like birds and crabs, but also from overheating and dehydration, especially after sunrise," said Sarah Milton, Ph.D., senior author and chair of FAU's Department of Biological Sciences. She noted that piles over a meter high, common in South Florida summers, could lead to more failures, especially across multiple seaweed bands.
"For sea turtle hatchlings, reaching the ocean is already a race against time—and survival. Now, increasingly large mats of sargassum are adding new challenges," Milton added. The research, co-authored by Abbey M. Appelt, calls for adaptive beach management to protect nesting areas and incubation amid sargassum's spread.