Hiển thị các bài đăng có nhãn Antarctics. Hiển thị tất cả bài đăng
Hiển thị các bài đăng có nhãn Antarctics. Hiển thị tất cả bài đăng

Thứ Ba, 19 tháng 3, 2013

Antarctic's First-Ever Whale Skeleton Found

For the first time ever, scientists say they have discovered a whale skeleton on the ocean floor near Antarctica. Resting nearly a mile below the surface, the boneyard is teeming with strange life, including at least nine new species of tiny of deep-sea creatures, according to a new study.

Though whales naturally sink to the ocean floor when they die, it's extremely rare for scientists to come across these final resting places, known as "whale falls." Discovering one typically requires a remote-controlled undersea vehicle and some luck.

"At the moment, the only way to find a whale fall is to navigate right over one with an underwater vehicle," study researcher Jon Copley, of the University of Southampton in England, said in a statement. The team's chance encounter with a 35-foot-long (10.7 meter) spread of bones that belonged to a southern Minke whale came as they were exploring an undersea crater near the South Sandwich Islands.

"We were just finishing a dive with the U.K.'s remotely operated vehicle, Isis, when we glimpsed a row of pale-coloured blocks in the distance, which turned out to be whale vertebrae on the seabed," Copley explained.

When whales die and sink to the ocean floor, their carcasses provide nutritional boosts and habitats for deep-sea life. Though their flesh decomposes within weeks, whale bones can last anywhere from 60 to 100 years, supporting bacteria and strange creatures like zombie worms, which are mouthless, eyeless animals that feed off the skeletons.

"The planet's largest animals are also a part of the ecology of the very deep ocean, providing a rich habitat of food and shelter for deep sea animals for many years after their death," said Diva Amon, another University of Southampton researcher. "Examining the remains of this southern Minke whale gives insight into how nutrients are recycled in the ocean, which may be a globally important process in our oceans."

The Antarctic whale fall, thought to have been on the seafloor for several decades, was surveyed using high-definition cameras, and samples were collected to be studied back on land. The team encountered several new species of sea snails and worms that were living off the bones. They found a new species of isopod crustacean, similar to woodlice, crawling over the skeleton, according to a statement from the U.K. National Oceanography Centre. The researchers also found an undescribed species of zombie worms (Osedax), which could help scientists study how the mysterious species has managed to become surprisingly diverse and widespread. (They've been found in whale falls in the eastern and western Pacific as well as the North Atlantic.)

"One of the great remaining mysteries of deep ocean biology is how these tiny invertebrates can spread between the isolated habitats these whale carcasses provide on the seafloor," Adrian Glover, a researcher at the Natural History Museum in London, said in a statement.

A recent study suggested that the sex strategy of zombie worms is the key to their success. Females of the species Osedax japonica quickly mature and then constantly produce eggs that harems of dwarf males fertilize, scientists found. What's more, zombie worm larvae can swim actively for at least 10 days before settling on bones on the ocean floor, according to the new research, detailed last month in the journal Naturwissenschaften.

The study of the whale fall was recently published online in the journal Deep-Sea Research II: Topical Studies in Oceanography.

Email Megan Gannon or follow her @meganigannon. Follow OurAmazingPlanet @OAPlanet, Facebook and Google+. Original article on LiveScience's OurAmazingPlanet.

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Thứ Tư, 27 tháng 2, 2013

Seals take scientists to Antarctic's ocean floor

SYDNEY (Reuters) - Elephant seals wearing head sensors and swimming deep beneath Antarctic ice have helped scientists better understand how the ocean's coldest, deepest waters are formed, providing vital clues to understanding its role in the world's climate.

The tagged seals, along with sophisticated satellite data and moorings in ocean canyons, all played a role in providing data from the extreme Antarctic environment, where observations are very rare and ships could not go, said researchers at the Antarctic Climate & Ecosystem CRC in Tasmania.

Scientists have long known of the existence of "Antarctic bottom water," a dense, deep layer of water near the ocean floor that has a significant impact on the movement of the world's oceans.

Three areas where this water is formed were known of, and the existence of a fourth suspected for decades, but the area was far too inaccessible, until now, thanks to the seals.

"The seals went to an area of the coastline that no ship was ever going to get to," said Guy Williams, ACE CRC Sea Ice specialist and co-author of the study.

"This is a particular form of Antarctic water called Antarctic bottom water production, one of the engines that drives ocean circulation," he told Reuters. "What we've done is found another piston in that engine."

Southern Ocean Elephant seals are the largest of all seals, with males growing up to six meters (20 feet) long and weighing up to 4,000 kilograms (8,800 lbs).

Twenty of the seals were deployed from Davis Station in east Antarctica in 2011 with a sensor, weighing about 100 to 200 grams, on their head. Each of the sensors had a small satellite relay which transmitted data on a daily basis during the five to 10 minute intervals when the seals surfaced.

"We get four dives worth of data a day but they're actually doing up to 60 dives," he said.

"The elephant seals ... went to the very source and found this very cold, very saline dense water in the middle of winter beneath a polynya, which is what we call an ice factory around the coast of Antarctica," Williams added.

Previous studies have shown that there are 50-year-long trends in the properties of the Antarctic bottom water, and Williams said the latest study will help better assess those changes, perhaps providing clues for climate change modeling.

"Several of the seals foraged on the continental slope as far down as 1,800 meters (1.1 miles), punching through into a layer of this dense water cascading down the abyss," he said in a statement. "They gave us very rare and valuable wintertime measurements of this process."

(Reporting by Pauline Askin, Editing by Elaine Lies and Michael Perry)


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