Biologists Close In On Mystery Of Sea Turtles' 'Lost Years'

• Closeup of a green sea turtle (Chelonia mydas).
• (Credit: iStockphoto/Rainer Schmittchen)

Science Daily — Biologists have found a major clue in a 50-year-old mystery about what happens to green sea turtles after they crawl out of their sandy nests and vanish into the surf, only to reappear several years later relatively close to shore.

In a paper set to appear Wednesday in the online edition of the journal Biology Letters, three University of Florida sea turtle scientists say they found the clue by analyzing chemical elements ingrained in the turtles’ shells.
Their conclusion: The turtles spend their first three to five “lost years” in the open ocean, feeding on jellyfish and other creatures as carnivores. Only after this period do they move closer to shore and switch to a vegetarian diet of sea grass – the period in their lives when they have long been observed and studied.
“This has been a really intriguing and embarrassing problem for sea turtle biologists, because so many green turtle hatchlings enter the ocean, and we haven’t known where they go,” said Karen Bjorndal, a professor of zoology and director of UF’s Archie Carr Center for Sea Turtle Research. “Now, while I can’t go to a map and point at the spot, at least we know their habitats and diets, and that will guide us where to look.”
The discovery is important not only because it’s a first, but also because it may aid in conservation of the turtles -- which, like all sea turtles, are classified as endangered. “You can’t protect something,” said Bjorndal, “if you don’t know where it is.”
The paper’s lead author is Kimberly Reich, a UF doctoral student in zoology who did the work as part of her dissertation research. The other authors are Bjorndal and Alan Bolten, a faculty member in zoology and associate director of the sea turtle center.
Famed sea turtle biologist Archie Carr first discussed the mystery of the green sea turtles’ “lost years” in his 1952 book, “The Handbook of Turtles.” Half-dollar sized hatchlings trundle off subtropical and tropical beaches worldwide, then vanish, only to reappear, dinner-plate-sized, over continental shelves in depths of less than 650 feet. Only a tiny number of green turtles between the half-dollar and plate-sizes have ever been spotted.
To solve the problem, Reich, Bjorndal and Bolten turned not to scouring the ocean but rather to a technique that over the past two decades has become increasingly important in questions related to ecological origin: stable isotope analysis.
The higher an animal on the food chain, the more heavy isotopes it accumulates. As a result, the technique, which measures the ratios of heavy to light isotopes, can distinguish samples from herbivorous versus carnivorous creatures and where on the food chain they lie.
The researchers captured 44 turtles off a long-term study site near Great Inagua in the Bahamas. The sample included 28 that had been tagged in previous years, indicating they were residents of the site, and 16 untagged turtles assumed to have recently arrived.
They cut off tiny pieces near the center of the turtles’ shells in a harmless process that Bjorndal likened to trimming one’s fingernails. The biologists used a mass spectrometer, a machine that separates isotopes according to charge and mass, to analyze the oldest, or earliest-grown, portions of the shell sample versus the newest portions.
The analysis revealed that with the new arrivals to the site, the ratio of light to heavy nitrogen isotopes in the older versus new shell samples was “significantly different,” as the paper said. The ratios were very similar to ratios observed in oceanic-stage loggerhead turtles known to be carnivorous. For these reasons, among others, the researchers concluded the turtles spend their first three to five years in the open ocean.
Green turtles nest on subtropical and tropical beaches worldwide. That suggests the young turtles are widely distributed in the oceans during their oceanic stage, but Bjorndal said further study is required to confirm that.
Green turtles are the ocean’s largest hard-shelled turtle, with only soft-shelled leatherbacks eclipsing their size. They were heavily exploited for food by native peoples and then by explorers and colonists who prized the animals for remaining alive and fresh for months on ships. Although they were among the first animals listed under the Endangered Species Act in 1973, they and their eggs continue to be hunted in much of their range today.
Said Bjorndal, “Anything that helps us discover geographically where they are is going to stand us in good stead to be able to protect them.”
Note: This story has been adapted from material provided by University of Florida.

Major Planet Formation Mystery Solved

By Dave Mosher, Staff Writer
Planet formation is a story with a well-known beginning and end, but how its middle plays out has been an enigma to scientists--until now.
A new computer-modeled theory shows how rocky boulders around infant stars team up to form planets without falling into stars.
"This has been a stumbling block for 30 years," said Mordecai-Marc Mac Low, an astrophysicist at the American Museum of Natural History in New York City, of planet formation theories. "The reason is that boulders tend to fall into the star in a celestial blink of an eye. Some mechanism had to be found to prevent them from being dragged into a star."
The solution: Together, many boulders can join to fight a cosmic headwind that otherwise would doom them.
Truckin' boulders
The stuff of rocky planets originates in an accretion disk, or collection of gas and dust that circles around a newborn star. Over time the dust particles bunch together and form large boulders, but eventually they meet "wind" resistance from the disk's mist of gas.
"They see a headwind. It's deadly and drags them into the star," Mac Low told SPACE.com.
Modeling the turbulence within the gas, however, showed that boulders can team up and form planets.
"Turbulence in the disk concentrates boulders in regions of higher pressure," Mac Low said, noting that such a disturbance is enough to enable the boulders to fight the dooming headwind. "If the gas is sped up, the boulders don't see a headwind. By getting the gas going with them they conserve energy and stay in orbit."
Mac Low compared the effect to a chain of semi-trucks driving down a highway. Each boulder is like a semi-truck "pushing" the gas in front of it, creating a friendly pocket of air behind it that other semis can travel in without using up as much fuel. "The end of the story is that enough boulders gather together, gravity takes over and they collapse into planet-like bodies," Mac Low said.
Mac Low and his colleagues' findings will be detailed in an upcoming issue of the journal Nature.
Pulverizing problem
Although Mac Low and his colleagues kept planet-forming boulders safe from the gravitational clutches of stars in their simulation, he noted that many questions remain.
"There are enough uncertainties that [planet formation] is not going to be an open and shut case any time soon," he said. "We don't know how that collapse into a planet actually occurs. You've got thousands, millions of boulders swarming together like a bees. In my nightmares I imagine that they grind each other down to dust and it all goes away."
Despite the problem, Mac Low is confident the theory will hold up to future scrutiny.
"All that material is gravitationally bound together, so we think it's likely that it will form large objects," he said. Running the computer simulation, in fact, formed tight boulder clusters as large as the dwarf planet Ceres (formerly known as the asteroid Ceres).
Alan Boss, an astrophysicist with the Carnegie Institution in Washington, D.C., said that the theory is attractive despite the caveat.
"Overall, the calculations present an encouraging approach to understanding how something happened that we know must have happened, at least for the terrestrial planets," Boss said in an e-mail. How giant planets form yet another question. One idea is that gas coalesces around a rocky, or terrestrial planet. Boss, however, thinks the gas giants collapse from a knot, much in the manner of star formation.
Mac Low and his team plan to address the mystery of how boulders collapse into planetesimals, or protoplanetary chunks of rock, in the future.
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Mystery illness strikes after meteorite hits Peruvian village

File photo shows the green streak of a meteor cutting across the sky. Villagers in southern Peru were struck by a mysterious illness after a meteorite made a fiery crash to Earth in their area, regional authorities said Monday.

LIMA (AFP) - Villagers in southern Peru were struck by a mysterious illness after a meteorite made a fiery crash to Earth in their area, regional authorities said Monday.

Around midday Saturday, villagers were startled by an explosion and a fireball that many were convinced was an airplane crashing near their remote village, located in the high Andes department of Puno in the Desaguadero region, near the border with Bolivia.
Residents complained of headaches and vomiting brought on by a "strange odor," local health department official Jorge Lopez told Peruvian radio RPP.
Seven policemen who went to check on the reports also became ill and had to be given oxygen before being hospitalized, Lopez said.
Rescue teams and experts were dispatched to the scene, where the meteorite left a 100-foot-wide (30-meter-wide) and 20-foot-deep (six-meter-deep) crater, said local official Marco Limache.
"Boiling water started coming out of the crater and particles of rock and cinders were found nearby. Residents are very concerned," he said.