SAN FRANCISCO—A new breed of scientists is being deployed to collect vital information about the world’s oceans.
Equipped with electronic tags, deep-diving marine animals have what it takes to sample their watery homes, where the elements can be too harsh for their human counterparts. These water-dwelling lab assistants are more cost effective, able to traverse wide ranges in some cases, and are adapted to life in frigid conditions such as those during the Antarctic winter. They also have a seemingly endless appetite for lengthy swims and deep dives.
Scientists from the University of California, Santa Cruz, presented their work on ocean sampling by animals last week here at the annual fall meeting of the American Geophysical Union.
The scientists aren’t proposing to replace ocean-faring ships and human divers. “I don’t think it’s a replacement. I think it’s a complementary data set,” said UCSC’s Sam Simmons.
When a lumbering elephant seal dips below the ocean surface, it is effectively invisible to scientists. So even facts as simple as what the elephant seals eat for breakfast or where they snag most of their food has eluded researchers.
By equipping an animal with a sensor and locating device, project leader Daniel Costa of UCSC and his colleagues are getting the seal-eye-view down under. Along the way, Costa realized these animals could do double duty.
“I started to realize how limited the amount of information there is on the ocean and how difficult and expensive it is to acquire. And I started realizing our animals are out there collecting all kinds of data and it’s very inexpensive and easy to do,” Costa said.
Not only are biologists like Costa spellbound, oceanographers are also waiting at the water’s edge. “The biggest challenge was convincing people that it wasn’t a joke, that this was a serious platform that could be used to collect data. I think we’ve done that now. The oceanographic community is actually quite excited and quite interested in what we are doing," Costa said. "And they realize that these animals are collecting data sets that are hard to get any other way."
Until now, scientists have relied on devices attached to the animals’ backs that transmit signals to the Advanced Research and Global Observation Satellite (ARGOS), bringing scientists to within about six miles of the true location. But now, with innovative devices that use Global Positioning System (GPS), scientists can pinpoint the animal to within 30 feet.
The team at the UCSC has experimented with using GPS and other electronic tags—essentially mini computers packing a range of ocean sensors—on elephant seals [image], California sea lions, Cape fur seals and Galapagos sea lions. While the animals dive and nose about, unbeknownst to them, they are also beaming snapshots back to grounded scientists.
For instance, Costa and his students tag around 20 elephant seals at a time, and each collects about 10,000 temperature readings [image] over a period of a few months as part of a Census of Marine Life project called Tagging of Pacific Pelagics (TOPP). The program plans to deploy electronic tags on 23 species of key predators in the North Pacific Ocean.
Not all the animals will move to the top of the class. The California sea lion slices through the water, constantly dipping below the surface and coming back up. Since these seals don’t spend much time above water where the GPS tags can work, the resulting tracks are somewhat crude, yet still more accurate than the ARGOS data.
The northern elephant seal dives and comes up for about two minutes to expel carbon dioxide before plunging back down to an average of between 980 and 1,640 feet. “So these are actually ideal ocean samplers because they traverse literally thousands of kilometers of ocean during their annual migrations,” said Patrick Robinson, also of UCSC.
Covering such a wide area is critical for understanding conditions within the world’s largest ocean body. “You can imagine trying to sample hundreds of thousands of square kilometers with boats. It would take billions of dollars to do that and more resources than any one researcher has,” Robinson told LiveScience.
Data collected from sparsely sampled areas is especially appealing to oceanographers. “So there’s a lot to be said for what our animals do because it does tend to collect data in areas that are very under-sampled,” Costa explained.
From February to March of 2004, eight elephant seals together made more than 3,500 dives to collect sea temperatures from the surface to hundreds of feet depth in the Southern Ocean. Whereas most ships can't withstand the harsh Antarctic winter, the elephant seals [image] are ideally suited for such frigid climes.
Scientists say there's no need for splashing flippers, as there are enough ocean jobs to go around. “The point is if you put it out on the right mix of animals, they pretty much cover all over the place,” Costa said.
Sea lions tend to hug the coastlines, while elephant seals take much longer jaunts out into the deeper North Pacific. As the animals swim along and dive for food, they are also inadvertently collecting information about water temperature, salt content and depth.
Nor do all the animals have to live in the ocean. Albatrosses can soar above the ocean at speeds of up to 55 miles per hour, allowing the birds to cover large swaths of the open ocean. Between 2003 and 2005, scientists attached data loggers to 21 Laysan albatross and 15 black-footed albatross. With over 7,360 bird-days at sea, the animals collected nearly 378,000 sea-surface-temperature readings.
“What’s really exciting about what we are doing is we get the behavior of the animal coincident with the oceanography. So we can see what the animal’s doing relative to the kind of ocean features,” Costa said.
He envisions having fleets of different marine animals diving and collecting real-time ocean data. The streaming view of the underworld would fill in gaps in oceanographic data. In the long-run, the combined animal efforts could result in a detailed three-dimensional map of the oceans.
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