What appears curious here and
unexpected really is that the vent life is so different. The ocean temperature in the deep is
naturally at a couple degrees of freezing just about everywhere and one assumes
that would hold true in the Antarctic.
For that reason biological transport seems a given, yet here we find contrary
evidence.
This clearly unexplained, but it
does strongly indicate that it is not so easy for life to use Antarctic waters
as a connector to other parts of the ocean.
Perhaps these strange groupings are unique to this area and it is simply
an anomaly generated by biological good luck and means little in terms of the general
movement throughout the ocean.
In the meantime, this story seems
top have grabbed its share of popular notice and that should assure us of a lot
of follow up.
Alien world discovered in Antarctic deep-sea vents
First-time expedition turns up hairy-chested crabs and ghostly
octopuses
(c) NERC ChEsSo Consortium
A new species of yeti crab piles around the hydrothermal vents in Antarctica . The vents may be a safe haven for the crabs.
By Stephanie PappasLiveScience senior writer
Scientists doing their first exploring of deep-sea vents in the
Antarctic have uncovered a world unlike anything found around other
hydrothermal vents, one populated by new species of anemones, predatory sea
stars, and piles of hairy-chested yeti crabs.
It was "almost like a sight from another planet," said
expedition leader Alex Rogers, a professor of zoology at Oxford University .
Even in the eye-popping world of deep-sea vents, the Antarctic
discoveries stand out, with the unfamiliar species of crabs found crowded in
piles around the warm waters emanating from the seafloor. Many of the animals
found at the vents have never been found at hydrothermal vents in other oceans,
Rogers said.
"To see these animals in such huge densities was just amazing," Rogers told LiveScience.
In the dayless world of deep-sea vents, energy comes not from the sun
but from the hydrothermal energy generated in the oceanic crust.
The yeti crabs seem to cultivate "gardens"
of bacteria on their chests, which are covered with hairy tendrils.
These bacterial mats almost certainly provides the crabs with sustenance, Rogers said. In turn,
predatory seven-armed sea stars stalk the periphery of the vents, snacking on
unfortunate crabs. [See videoand photos from
the vents]
"We were absolutely stunned to see the animal communities, because
they were so different from the hydrothermal vents seen elsewhere," Rogers told LiveScience.
He and his colleagues reported their results Jan. 3 in the journal PLoS
Biology.
Discovery in the deep sea
Weird life flourishes at deep-sea vents the world over, but no one had ever found hydrothermal vents in Antarctica, explained Jon Copley, a professor of earth and ocean science at the
"It's only quite recently that we've been able to be bold enough,
really, to head to the poles," Copley told LiveScience.
In 1999, Antarctic mapping surveys turned up hints of hydrothermal vent
output in the water column over the East Scotia Ridge in the Atlantic section
of the Southern Ocean, between Antarctica and South
America and eastward. It took 10 years for researchers to get back
for a full-blown expedition, during which they lowered cameras to two areas,
8,530 feet and 7,874 feet deep, catching the first glimpses of Antarctic
hydrothermal vents. Among them were "black smokers," chimney-like
vents that emit
dark-hued, superheated water.
Although the background temperature of the Southern Ocean in the area
is 32 degrees Fahrenheit, the black smokers gushed water as hot as 721 degrees
F.
In 2010, the researchers returned with a remote-operated submersible
vehicle (ROV) called Isis . The sub took
close-up photos of the amazing vent fauna and collected samples of organisms
for identification.
New world
Among the new species were the yeti crabs, crowded around the vents up to 600 per square meter.
"They're literally, in places, heaped up upon each other," Rogers said. Crabs
normally don't tolerate cold temperatures well, so the vents may be a warm
haven for these crabs, Copley said.
The expedition spotted this pale octopus on the Antarctic seafloor.
Unlike vents in other oceans, the Antarctic vents lack tube worms,mussels and
shrimp. Instead they harbor new species of barnacles and anemones, as well as a
large brown spiral-shelled snail. The researchers even saw ghost-pale
octopuses, which seemed drawn to the lights of the ROV.
"We were completely blown away by what we found," Copley
said. "I've worked at vents in the Atlantic, the Pacific and the Indian Ocean , but these are the lushest, richest vents,
in terms of life, that I've come across."
The discovery helps fill a gap in researchers' understanding of how
deep-sea life disperses around the oceans, Rogers said. They had expected that the
Southern Ocean would be a historical gateway for vent species to travel between
the Atlantic, Pacific and Indian oceans, and there do seem to be some species,
such as the yeti crab, that are related to species found at other
vents. Those relationships seem to reach back into geological history,
Copley said, when there was a connection between the Antarctic and the eastern
Pacific.
But the vast differences between Antarctic vents and vents found
elsewhere suggest that the area is not a gateway but a biological region in its
own right, Rogers
said. The cold Antarctic waters may act as a barrier to species that start
their lives as swimming, feeding larvae, he said. On the other hand, larvae
that carry their own food supply with them in eggs — known as lecithotrophic
larvae — may be able to survive and disperse in the chilly Southern Ocean.
As humans increasingly exploit
the deep seas for fish, oil and mining, understanding how species are
dispersed is crucial, Copley said.
"Until we understand what governs the patterns of life at deep-sea
vents, how interconnected their populations, how well life disperses from vent
to vent, we can't make responsible decisions about how to manage these
deep-ocean resources."
No comments:
Post a Comment