Jellyfish May Help Keep Planet Cool
Correction
August 19, 2009, 5:04 PM - A previous Web version of this story incorrectly referred to "Caltech University." The correct name is California Institute of Technology.
Jellyfish and other related creatures may be helping to reduce the effects of climate change by stirring up the oceans, according to a new study in this week's issue of the journal Nature.
The finding is the latest in a decades-old debate over whether swimming animals can contribute significantly to ocean mixing, the process by which warm water on the surface combines with the cold water far below. Mixing plays a role in global climate change because carbon dioxide in the air above oceans dissolves in the surface water. Through mixing, it can get pulled into the depths and stored there for long periods.
The process is also a key regulator of the Earth's temperature and the ocean's nutrients. "It's important for us to understand the dynamics of the ocean in order to really understand what's going to happen to climate over land," says John Dabiri, a bioengineer at California Institute of Technology in Pasadena and co-author of the paper.
Ocean Mixers
Tides and winds are known to be major players in ocean mixing, but some researchers believe that animals might also contribute. Dabiri and his graduate student Kakani Katija decided to find out by filming dozens of jellyfish as they swam in the wild. Studying the movies shows that the simple animals drag water behind them as they swim. It's a little bit like a bicyclist in the Tour de France, says Dabiri: "When Lance Armstrong is riding down the road, he's actually taking quite a bit of the surrounding air along with him, and the animals are doing something similar in the water."
To avoid predators, jellyfish and related animals often hide far below the ocean's surface during the day and swim to the surface at night to feed, according to William Dewar, an oceanographer at Florida State University in Tallahassee who was not involved with the study.
Changing The Carbon Balance
If the work is correct, then it could mean that they're ferrying cold water to the surface and warm water into the depths of the sea with each feeding cycle. In the process, they may be taking dissolved carbon dioxide with them far beneath the sea, changing the overall carbon balance in the atmosphere.
But, Dewar adds, there's a still a long way to go before scientists can say for sure that animals like jellyfish are helping to regulate the climate. Larger-scale studies need to be carried out to understand where marine animals are living and how they move. "What I think we can say at the moment is that it's a plausible idea," he says.
9(MDAyNzUwMDI2MDEyNTA3MTU5NzcyNTQyNA004))
STEVE INSKEEP, host:
Jellyfish can grow to be pretty large, but they're nothing compared to the size of the ocean. So it may come as some surprise to hear that jellyfish and similar animals could be influencing oceans and the climate on a global scale. That's what a report in this week's issue of the journal Nature suggests. NPR's Geoff Brumfiel has more.
GEOFF BRUMFIEL: It's not obvious that jellyfish would be involved in something as important as climate change. They're not particularly exciting animals. They don't have fins or teeth or even eyes to speak of. And they bob around in pretty much the same way that their ancestors did half a billion years ago.
Professor JOHN DABIRI (Bioengineer, Caltech University): If you see them in the ocean, you think of them as sort of the leftovers in the gene pool, if you will.
BRUMFIEL: That's John Dabiri. He's a bioengineer at Caltech who has been studying jellyfish for the better part of a decade.
Prof. DABIRI: However, jellyfish are actually the first animals to use muscle power to swim. They've survived some major extinction events. And so we actually see them as a model system for successful propulsion now.
BRUMFIEL: In fact, they're more successful than Dabiri, who, as it turns out, is a lousy swimmer. But he's got the upper hand when it comes to fluid mechanics. He's devoted a lot of time to learning about the swirls and eddies that jellyfish make as they swim. For decades, some scientists have speculated that swimming animals might contribute to stirring up water in the oceans, and that's where climate change comes in.
Carbon dioxide from the air dissolves in the surface layer of the ocean. Stirring up the ocean sends that dissolved carbon dioxide to the bottom and stores it there. To find out whether jellyfish were helping the process, his team filmed dozens of the animals. It wasn't easy.
Prof. DABIRI: We actually had a jellyfish that we were measuring out in Woods Hole. It's a place where we go quite often. And you have to understand that it can take a half an hour, an hour to get an animal in the perfect position to take these measurements. And right when the animal was set up, a crab comes out and grabs it in its claw and pulls it away. So we lost our data.
BRUMFIEL: After studying the tapes, Dabiri and his team noticed something. As jellyfish swim, they stir up the water, but they also pull it along behind them. And, Dabiri says, it could work on a large scale. That's because every night, jellyfish and other smaller creatures swim thousands of feet up to the surface to feed. They may be dragging up cold water without much carbon dioxide in it, and pulling down warm water filled with carbon dioxide when they return to the depths.
So could jellyfish help to combat climate change?
Dr. BILL DEWAR (Oceanographer, Florida State University): I wouldn't go so far as to say that jellyfish are a solution to global warming.
BRUMFIEL: Bill Dewar, an oceanographer at Florida State University.
Dr. DEWAR: What I think we can say defensively at the moment is, is that it's a plausible idea, plausible input to mixing, which has been overlooked.
BRUMFIEL: Dabiri says this work means that swimming marine life may need to be accounted for in future computer models of climate change. To do that, scientists need to know more about how the animals behave.
Prof. DABIRI: So it really is a big question mark as to exactly where the animals are at any given time, and which animals are generating the mixing. We need more data.
BRUMFIEL: For John Dabiri's colleagues, that's good news and bad. They're going to be traveling to more great ocean dive spots. But they're also probably going to be getting a lot more jellyfish stings.
Geoff Brumfiel, NPR News.
INSKEEP: And when you're checking the latest news throughout the day at npr.org, you can also find a video, and see jellyfish dragging the water behind them. Transcript provided by NPR, Copyright National Public Radio.
