Sargassum seaweed is piling up on Florida’s beaches, and it’s making a dangerous journey for sea turtle hatchlings even riskier.

Every summer, the sand becomes a highway as thousands of tiny turtles burst from their nests and scramble toward the ocean. For most of them, this short sprint is the difference between life and death.

They’ve already beaten the odds just by hatching. Now, they must avoid predators, stay cool under the rising sun, and find the water before their strength runs out.

But this growing seaweed problem is more than just beach clutter – it’s a new threat that’s slowing them down at a time when every second counts.

More than just smelly beach junk

Sargassum seaweed often washes up along Florida’s coast. It’s that brown, leafy stuff that starts to smell after a while. Out in the Atlantic, it floats in huge mats that provide habitat for marine life.

But when too much piles up on shore, sargassum seaweed creates a thick, tangled mess that’s hard for anything small to get through – including baby sea turtles.

Over the past few years, sargassum levels have exploded. Summer beachgoers aren’t the only ones frustrated.

Sea turtle hatchlings are now struggling to cross these growing piles to reach the ocean. It’s not just an inconvenience. It’s a survival threat.

Testing how turtles navigate the sargassum

Until recently, no one had looked closely at how sargassum affects sea turtle hatchlings. Researchers from Florida Atlantic University (FAU) set out to investigate.

The team tested three species common in Florida: leatherbacks, loggerheads, and green turtles. These are the same turtles that nest on beaches from Boca Raton to Juno Beach.

The researchers built 50-foot (15 meter) crawlways in the sand and placed mats of loose sargassum up to 7.5 inches (19 centimeters) high – roughly the height of a large shoebox on end – at the finish line.

A dim light at the far end mimicked the natural glow over the ocean that hatchlings instinctively head towards. Then the team observed how the turtles responded.

The team measured how long it took for the turtles to reach the water, tracked whether they got flipped over while crawling through the seaweed, and even checked their blood sugar levels to see how much energy they were burning.

Sargassum slows turtles down

The results were clear. All three species took much longer to reach the ocean when sargassum was in the way. Leatherbacks were slowed by 54% with lighter sargassum, and 158% with heavier coverage.

Loggerheads saw a 91% delay in light coverage and 175% in heavy seaweed. Green turtles slowed by 75% and 159%, respectively.

Some turtles couldn’t even finish the crawl in time. The biggest delay came when hatchlings had to climb over the thick seaweed, which slowed them down to a crawl – literally.

“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 Dr. Sarah Milton of the FAU Department of Biological Sciences.

Getting stuck and flipped

The sargassum didn’t just slow the turtles down. It threw them off balance. Hatchlings kept flipping over while trying to climb the mats. In some cases, it happened over and over.

One unlucky turtle flipped more than 20 times in a single trial. Every time that happened, it wasted time and energy, and made hatchlings easy targets for predators.

These juveniles only have a small window to make it to the water before heat and dehydration kick in.

“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, particularly when hatchlings have to cross multiple bands of seaweed just to reach the ocean,” said Milton.

No sign of burnout – yet

Even with all that effort, the turtles didn’t show signs of physical exhaustion – at least not in their blood sugar levels. Glucose remained in normal ranges for all three species, no matter how much seaweed they faced.

Only leatherbacks in the no-crawl control group had noticeably higher glucose, which researchers say shows that crawling itself is demanding – but the sargassum didn’t drain them any faster, at least in the short term.

Still, that doesn’t mean it’s harmless.

“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 to this critical journey,” said Milton.

“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.”

Sargassum management and turtles

Sargassum isn’t going away anytime soon. Warmer oceans and nutrient runoff are fueling massive blooms across the Atlantic, and more of it is expected to hit Florida’s shores every year.

This growing issue isn’t just about beach aesthetics. It’s quietly making a tough journey even tougher for baby turtles trying to survive their first few minutes of life.

Without changes in how beaches are maintained, these seaweed mats could keep getting in the way – and turtle populations may suffer down the line.

The full study was published in the journal Journal of Coastal Research.

—–

Like what you read? Subscribe to our newsletter for engaging articles, exclusive content, and the latest updates. 

Check us out on EarthSnap, a free app brought to you by Eric Ralls and Earth.com.

—–