Home Atlantic sea For Atlantic sea turtles, the Sargasso Sea is home to the “lost years”

For Atlantic sea turtles, the Sargasso Sea is home to the “lost years”

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  • In a new study, researchers tracked the movements of young green turtles and found that they sailed towards the Sargasso Sea, rather than passively drifting along the currents of the North Atlantic Ocean.
  • While there have been theories and anecdotal evidence that hatchlings of turtles travel to the Sargasso Sea and spend their “wasted years” in the region, this is the first study that uses tracking. by satellite to confirm that the green turtles are actually going there.
  • A previous study by the same group of researchers also tracked the movements of loggerhead turtles in the Sargasso Sea, although their journeys were found to be more nuanced.
  • Experts say the study draws attention to the importance of protecting the Sargasso Sea and tackling issues such as plastic pollution.

After spending two months hatching in eggs, it’s time for the green turtles to come out of their shells. Newly hatched reptiles scale the steep walls of their nests, scaling the abandoned eggshells of their siblings, and together they scurry onto the sand and paddle out into the ocean. Then they disappear – not only from sight, but from scientific knowledge. No one really knows where green turtle hatchlings go and what they do for the next two or three years of their lives. But that is changing now.

A new paper in The Proceedings of the Royal Society B gave an overview of the so-called ‘lost years’ of endangered green turtles (Chelonia mydas) by tracking the movements of 21 juveniles released off the southeast coast of Florida. Over the course of about 150 days, most of the turtles made their way to the Sargasso Sea, an area of ​​open ocean in the subtropical North Atlantic gyre, rather than letting the currents push them north towards the North Atlantic. Azores.

An oceanic green turtle in the Sargassum. Image by Chris Long.

“One of the long-held ideas was that these [green turtles] are passive little wanderers, ”lead author Katherine Mansfield, a sea turtle expert at the University of Central Florida, told Mongabay in an interview. “Historically, turtles were supposed to swim offshore, enter these eddies, and then drift for several years in a large circle around the Atlantic. But what we found [was that] they had very directed movements in the vortex.

This document is based on a 2014 to study by Mansfield and his colleagues who have followed the movements of loggerhead turtles (Caretta caretta) across the Atlantic. Most loggerheads also moved away from the prevailing currents, although their movements in the Sargasso Sea were not as pronounced as those of green turtles.

“The Loggerheads kind of led the way and gave us a little more insight that things can be a lot more complex than what we realized and / or initially assumed,” Mansfield said. “We were thrilled that the green turtles were going into the Sargasso Sea and it was a nice validation that, ‘OK, so maybe that’s really a thing, and the Sargasso Sea is something we need to pay more attention and protect, or at least identify as an area in need of protection for a variety of young species that can use it on the growth habitat.

The Sargasso Sea does not currently benefit from any form of large-scale protection, but it faces threats from many human activities, including commercial fishing, shipping, pollution from floating debris such as plastic, and even possible harvesting of Sargassum algae in the near future.

A loggerhead turtle ready to be released with a satellite tag attached to its shell. Image by Kate Mansfield.

For the new study, researchers collected green turtle hatchlings from wild nests in Boca Raton, Fla., And reared them for several months in a lab until they were around 12 to 18 centimeters tall. (5-7 inches) and weigh over 300 grams. (11 ounces), about the weight of a can of soup. At this size, the 9.5 gram (0.3 oz) satellite tags did not interfere with the turtles’ ability to dive, surface or swim, Mansfield said. The hatchlings, on the other hand, would likely sink under the weight of the transmitters, which is why the researchers were unable to use wild hatchlings for the study.

They also had to refine their methods for attaching solar-powered tracking devices to animals. Green turtles have more waxy shells than loggerheads, so they couldn’t use the same adhesion technique for both species, but the researchers found a way to attach the tags to the green turtles without negatively affecting their growth or their behaviour. It is believed that the beacons fall off naturally within a few months.

According to Mansfield, the most likely way for turtles to enter the Sargasso Sea is by hanging on to certain Sargassum mat, the seaweed that gives the region its name. Sargassum not only provides transportation, but provides a “structured habitat with a rich food supply, protection from predators, and thermal benefits that promote growth and foraging,” the authors write in the study.

Once the turtles live among the algae, they probably don’t want to leave, Mansfield said.

“Do you, as a little turtle, choose to wander away and passively drift into ocean currents where you may not have that protection, or do you follow it into the Sargasso Sea?” ” she said. “We think that makes sense.”

David Godfrey, executive director of Sea Turtle Conservancy, said this new study provides scientific evidence that corroborates existing theories about where sea turtles went in their lost years.

“There have been a lot of theories and anecdotal information about turtles spotted in sargassum floating mats,” Godfrey, who was not involved in the study, told Mongabay in an interview. “Even going back to the founder of our organization, Archie Carr, who worked on turtles in the 1950s and 1960s and 1970s and wrote many books on the subject – he was convinced that the wasted years had been spent adrift in the Sargasso Sea. with turtles that have taken up residence in Sargassum.

“People generally knew what the shape of this puzzle was [and] they knew what it looked like, ”he added,“ but they [the researchers] help place the pieces.

He said the study also underlines the urgency to tackle the problem of plastic pollution in the Sargasso Sea.

“[T]debris and pollution and plastic… that we let go into the marine environment… usually drift [along] the same currents – the convergence zones – where Sargassum accumulates, ”he said. “The fact that all of this human waste ends up in these same areas, and we now know that turtles are certainly there too, raises the stakes of our need to reduce this flow of plastic waste into the oceans.”

Green turtle swimming among the Sargassum. Image by Gustavo Stahelin.

Justin Perrault, research director at the Loggerhead Marinelife Center in Juno Beach, Fla., Said the study provides vital information about the life history of sea turtles.

“These types of studies are important because they allow us to better understand habitat use and movements of different life stages so that we know which life stages are vulnerable to which threats and where,” he said. said Perrault, who was not involved in the study. Mongabay in an email. “It just gives us a better understanding of turtle migrations so that we can make more informed conservation decisions.”

Mansfield said there is still a lot to be learned about the sea turtle species and that others can build on his research in multiple ways.

“We are finding that turtles can do different things in different parts of the world [so] we can’t… just take what we know about North Atlantic turtles and then die-stamp it all over the world because they might be doing something completely different, ”he said. she declared. “Really, that opened up a whole world of questions, and it’s pretty exciting because it’s rare that a species that has been so well studied still has so many gaps in the data.”

Quotes:

Mansfield, KL, Wyneken, J., & Luo, J. (2021). The first Atlantic satellite tracks of green turtles from the “lost years” confirm the importance of the Sargasso Sea as a nursery for marine turtles. Proceedings of the Royal Society B: Biological Sciences, 288(1950). do I:10.1098 / rspb.2021.0057

Mansfield, KL, Wyneken, J., Porter, WP and Luo, J. (2014). The first satellite tracks of newborn sea turtles redefine the oceanic niche of the “lost years”. Proceedings of the Royal Society B: Biological Sciences, 281(1781), 20133039. doi:10.1098 / rspb.2013.3039

Elizabeth claire alberts is a writer for Mongabay. Follow her on Twitter @ECalberts.

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Animal tracking, Animals, Conservation technology, GPS tracking, Marine animals, Marine biodiversity, Marine conservation, Marine ecosystems, Oceans, Plastic, Pollution, Sea turtles, Technology, Tracking, Turtles, Turtles and turtles, Wildlife, Conservation of wildlife


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