Green sea turtles enterprise into the open ocean instantly after hatching on the Florida coast, after which appear to fade for a spell — now, new monitoring information exhibits that, after browsing the Gulf Stream northward, many turtles drop out of the present to enter the Sargasso Sea, an oasis of cozy seaweed and plentiful meals.
In the brand new research, revealed Tuesday (May 4) within the journal Proceedings of the Royal Society B, scientists connected solar-powered satellite tv for pc tags to 21 inexperienced sea turtles (Chelonia mydas) of “toddler” age, which means about 3 to 9 months previous. The younger turtles weighed simply over 10.5 ounces (300 grams) and their shells measured about 5 to 7 inches (12 to 18.6 centimeters) lengthy; tagging such small creatures introduced an enormous problem, each on account of their preliminary measurement and the truth that they develop and alter form pretty quickly, in contrast with mature animals.
Despite the hurdles, to higher shield sea turtle populations, “we really need to get tags on some of these little guys,” mentioned first writer Kate Mansfield, director of the Marine Turtle Research Group and an affiliate professor within the biology division on the University of Central Florida. Young turtles’ migration into the open ocean is also known as “the lost years,” since scientists know so little about what the animals rise up to earlier than they return to the coast as “teenagers.”
“Sea turtles, in general, don’t reach maturity for at least a couple decades. And those years leading up to when they become adults, we don’t know much about them,” Mansfield mentioned. Now, due to the monitoring information, “the Sargasso Sea is emerging as an important habitat for sea turtles in their early life stages,” marking the area as crucial for conserving the species, she mentioned.
The adventures of turtle toddlers
The Sargasso Sea, named for a free-floating genus of brown algae known as Sargassum, is the one sea whose edge is outlined by ocean currents, moderately than land boundaries, according to the National Oceanic and Atmospheric Administration (NOAA). The sea sits inside the so-called Northern Atlantic Subtropical Gyre, a giant circle made up of 4 main ocean currents: the Gulf Stream to the west, the North Atlantic Current to the north, the Canary Current to the east and the North Atlantic Equatorial Current to the south.
In previous research, researchers caught sight of younger inexperienced sea turtles, in addition to loggerheads (Caretta caretta), passively drifting in these currents, usually on a mat of Sargassum, Mansfield mentioned. These observations, in addition to sightings of the Florida-borne turtles within the east Atlantic, hinted that turtles could make a giant loop across the gyre earlier than heading again to the U.S. as juveniles.
But Mansfield and her colleagues wished to get onerous proof of this migration, whereas additionally pinning down how lengthy the turtles sometimes keep offshore. Are they away for one 12 months, “or are they out for a decade? These are pretty fundamental questions,” mentioned research writer Jeanette Wyneken, a professor of organic sciences at Florida Atlantic University.
Satellite tags designed for grownup turtles “looked like a brick” concerning the measurement of a mobile phone, Mansfield mentioned; however with the arrival of small tags, concerning the size of a finger phase, the group might begin monitoring younger turtles, she mentioned. They started with loggerheads and tagged 17 turtles in a 2014 research; they discovered that, moderately than passively drifting alongside, the loggerheads steadily exited the currents to swim towards heat, nutrient-dense waters, together with these within the Sargasso Sea, they reported within the journal Proceedings of the Royal Society B.
Green sea turtles could also be equally lively swimmers as soon as they attain the open sea, the group thought, so that they got down to repeat the research with C. mydas hatchlings.
The group collected the hatchlings from Boca Raton, positioned on the southeast coast of Florida, after which introduced them again to the lab to rear for a number of months. Though the groups’ satellite tv for pc tags are small, they’re nonetheless too massive for freshly hatched turtles, Mansfield famous. The group initially tried to connect the tags utilizing the identical adhesive that they had used for the loggerheads, a type of manicure acrylic that ultimately peeled off because the animals grew.
“But that didn’t work with the green turtles,” Mansfield mentioned. The texture of a younger inexperienced turtle’s shell feels “waxy,” considerably like a human fingernail doused in cuticle oil, whereas loggerhead shells aren’t so slick, Wyneken mentioned. The group tried many adhesives — these used to cement fillings in tooth, these used to connect theatrical prosthetics to pores and skin, you title it — earlier than discovering one that will stick with the slippery turtles.
That ended up being a marine urethane adhesives, usually used to seal boats; the glue is versatile sufficient to stretch because the turtles develop, however as soon as the turtles attain a sure measurement, it pops proper off.
After making certain the adhesive was secure and sticky sufficient, the group launched their turtles into the western Atlantic and tracked them for a mean of 66 days; they have been in a position to comply with a number of turtles for greater than 100 days, and one for 152 days. They discovered that their turtles largely swam close to the floor of the ocean, much like the loggerheads, and likewise coasted alongside the Gulf Stream. However, usually, the turtles dropped out of the Gulf Stream and adjoining North Atlantic Current before the loggerheads did.
About two-thirds of those inexperienced sea turtles then high-tailed it towards the Sargasso Sea, the place they stayed till their tags ceased to transmit; this hinted that the Sargasso serves as an interesting nursery for the turtles.
“That habitat, it makes sense,” Mansfield mentioned. The seaweed supplies camouflage for the teeny turtles, whereas additionally slowing the movement of water and thus permitting the solar to warmth its floor. Being cold-blooded, sea turtles require heat water to outlive and their progress slows considerably once they get too chilly. Other juvenile marine animals, akin to shrimp, crab and fish, additionally develop up within the Sargassum and supply meals for the rising turtles.
But whereas a proportion of younger sea turtles flock to the Sargasso, there’s nonetheless the query of why some swim towards the ocean whereas others stay within the present, Mansfield mentioned. It could also be linked to the truth that the amount of Sargassum and its distribution alongside the jap U.S. varies by season, in response to a 2011 research within the International Journal of Remote Sensing.
So whereas some turtles encounter the Sargassum within the Gulf Stream and comply with it into the Sargasso Sea, “there may be some that miss that Sargassum boat and hang out in the currents,” Mansfield mentioned.
And when the turtles do attain the Sargasso Sea, one other query emerges: How lengthy do they keep?
“I would guess those animals would be out there for maybe two to three years,” Wyneken mentioned, however that is a “pure guess,” she added. “If you’re in a safe place, why leave it?” Mansfield mentioned, echoing Wyneken’s sentiment. Green sea turtles sometimes return to Florida as juveniles and stay within the coastal habitat till maturity, feasting on algae, seagrasses and jellyfish. Until they attain that crucial transition level, the Sargasso Sea possible fills lots of the turtle toddlers’ wants.
But to know precisely how lengthy they continue to be within the seaweed-laden habitat, scientists will want extra monitoring information, Mansfield mentioned. Now that they’ve tracked turtles on their method to the Sargasso, the group might doubtlessly seek for turtles already residing there and fix tags to them on-site, she mentioned. Regardless of how lengthy the turtles keep, the Sargasso seems to be an necessary habitat for the younger animals. To make sure the turtles develop as much as lay their very own eggs sooner or later, the ocean have to be conserved, she mentioned.
“The Sargasso Sea can’t become another garbage dump. It has to be recognized as a habitat that’s important to imperiled species,” Wyneken mentioned. “It’s probably not just a green turtle story,” on condition that different juvenile marine animals additionally develop up among the many seaweed, she added.
Originally revealed on Live Science.