Smelly, brown seaweed washing up on Florida shores is snaring baby sea turtles on their way to the ocean, researchers warned this week, leaving them vulnerable to predators and putting them at risk of dehydration and exhaustion.
The tiny reptiles emerge from their nests – holes their mothers dig on beaches – only a couple of days after they’re born, and race to the ocean under cover of darkness. They have to navigate around trash, avoid distracting artificial lighting, and get past hungry seabirds. Many hatchlings die and only about one in 1,000 will survive to adulthood.
Once they reach the ocean, the turtles will learn to swim and develop crucial muscles. But sargassum seaweed blooms are making it even harder for the turtles to get there. The algae is blooming more frequently in the Atlantic for reasons yet to be determined.
“When sargassum piles are higher – some can be over a meter high on South Florida beaches in the summer and extend for hundreds of meters down the beach – we can expect more failed attempts,” Dr. Sarah Milton, a professor at Florida Atlantic University, explained in a statement.
To understand the impact of these piles on the turtles’ trek, Milton and researchers at the university studied the performance of 80 hatchlings from three species of Florida sea turtles, including leatherbacks, loggerheads, and green turtles.
All three species are endangered due to habitat loss, fishing, and rising ocean temperatures linked to climate change , which result in turtles having more female offspring than males.
Using piles of algae at beaches in Juno Beach, Jupiter, and Boca Raton, the researchers found that the turtles’ crawl speed decreased sharply when sargassum was in the way, with loggerheads seeing the most significant slowdown.
The tallest algae the turtles needed to climb was 7.5 inches high, but their speed was decreased even with piles less than 10 centimeters tall.
But that wasn’t the only problem. The turtles often flipped upside down while they were trying to climb the sargassum. Flipping over extended how long the hatchlings spent on the beach, and raised their risk of being attacked or becoming vulnerable to extreme heat.
The researchers also took blood samples from each turtle included in the study, and fortunately, found no significant changes in their blood sugar. This suggests the extra effort did not deplete their energy.
Still, the researchers say their findings could be crucial to supporting the success of all of Florida’s hundreds of thousands of sea turtles.
There are five species native to Florida and they make between 40,000 and 84,000 nests along the coasts. Each nest contains between 80 and 120 eggs.
The eggs hatch in the summer months, when the sargassum blooms typically occur.
This year has seen a monster surge of sargassum aimed at the Sunshine State’s beaches, with 31 million metric tons recorded in the area.
Strong currents and winds provide ideal growing conditions for the seaweed, driving nutrients in the ocean that produce the blooms. Some scientists believe warming ocean temperatures can jumpstart the process, as well. Although, that is not yet confirmed.
“As these seaweed accumulations grow taller and more widespread, they risk blocking hatchlings entirely, draining their limited energy or leaving them stranded. Beyond impeding movement, sargassum may also reduce nesting space and alter incubation conditions,” Milton said.
