Sea turtles may be using mysterious waterway to get from Japan to California coast: scientists

BySpencer Christian and Tim Didion KGO logo
Wednesday, December 6, 2023
Turtles may be using mysterious waterway between Japan, CA: scientists
A few Loggerhead sea turtles may not realize it, but they're setting off on a journey that could change the way we understand the Pacific Ocean.

STANFORD, Calif. (KGO) -- A few small Loggerhead sea turtles may not realize it, but they're setting off on a journey that could change the way we understand the Pacific Ocean. And perhaps, lead a research team along a mysterious path that essentially stretches from Japan to the coastline of Mexico and California.

"So we've developed a scientific hypothesis as to how turtles get across the ocean. And now we're actually testing that hypothesis and providing a novel approach to how we study the ocean," says Dr. Dana Briscoe, a marine scientist with Stanford's Doerr School of Sustainability.

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The Stanford team and its international partners released 25 juvenile sea turtles fitted with tracking devices near a nutrient-rich band of warm water known as the North Pacific Transition Zone. Researchers say the hungry turtles typically follow the band like a kind of ocean-going buffet. At least most of the time. But recently, some studies have revealed exceptions.

"That's right. So we had over 200 turtles that were tagged in the early 2000s. And from those 200 turtles, only six turtles made it to this eastern part of the Pacific Ocean. And they really showed us the pathway of how turtles get from the middle of the ocean to their important habitat off of North America," says Dr. Briscoe.

But the mystery now is how and why some turtles decide to peel away and head for the coast of Mexico or California. It's a journey that should take them through waters that are normally too cold for their bodies. However, Dr. Briscoe and Stanford colleague Dr. Larry Crowder developed a hypothesis.

They believe the animals could be taking advantage of a warm water channel they describe as a thermal corridor -- a kind of portal that either opens up or slams shut, depending on changing ocean temperatures, allowing the turtles to pass through only at certain times. The current multi-year study is designed to track both the sea turtles and the temperatures.

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"We're going to know whether this hypothesis we're testing is true, that there is a thermal corridor that's intermittent. We're going to, if true, be able to predict under what oceanographic conditions we should expect to see Loggerhead sea turtles in Baja, California, or even in the state of California.," says Dr. Crowder.

To fully test the theory, researchers will track the turtles through warming and cooling ocean cycles, starting with this year's warm El Nino pattern.

"We started off this year with one of the strongest El Ninos on record, which is a banner of a year to kick off this study. And what we hope to see are other conditions change and evolve over the next four years," says Briscoe.

And they say there is evidence of change already, including along our own coastline.

"We documented the first Loggerhead sea turtles ever in the history of Monterey Bay in July. So, you know, they're here. And we've never seen them here before. So with climate change, we're going to know a lot more about where these animals are likely to be and what kind of risks they're likely to be exposed to, into the future," Crowder adds.

And they say those discoveries could help biologists better protect the endangered Loggerhead sea turtles and, ultimately, other marine life as well.

The study is known as STRETCH, for the Sea Turtle Research Experiment on the Thermal Corridor Hypothesis. The Stanford Doerr team plans to release three more groups of tagged sea turtles over the next four years, bringing the total number to 100.

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