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By Peter Rejcek
It seemed unlikely too many marine organisms could make
a living under the dark shadow of an ice shelf, with the
ice some 200 meters thick in spots.
Why? There are not a lot of places for light to penetrate
through the ice, which means not a whole lot of photosynthesis,
the driving force behind the food chain, is occurring.
Also, the front of the McMurdo Ice Shelf, a distinct part
of the Ross Ice Shelf , is about 80 kilometers away and
recorded current speeds are less than 2 centimeters per
second, so it’s unlikely currents are transporting
food for critters to nosh.
“It’s a long way from any food sources is the
bottom line,” said Stacy Kim , a benthic ecologist
who seems endlessly fascinated by the organisms that inhabit
the seafloor of McMurdo Sound.
But Kim and her team of scientists and engineers were
still curious as to what the benthic communities might
look like, as well as the distribution and abundance of
different species. There was only one way to find out:
send in SCINI.
A remotely operated vehicle (ROV) with a diameter of
only 15 centimeters, SCINI (Submersible Capable of under
Ice Navigation and Imaging) is the focus of a three-year
field project to perfect a robot capable of accessing
the nooks and crannies of the polar marine environment
too deep, too remote and too difficult for divers, or
robots with a weight problem.
The idea is that a few people, with just snowmobiles
and a sled, or transported via helicopter, can haul SCINI
to a new location. Drill a hole, plop it in, and start
taking data within an hour or two — the fast-food
version of science.
In the case of the ice shelf near ice-locked Heald Island,
the team found a couple of natural openings — cracks
that form at stress points from motion of the McMurdo
Ice Shelf pushing around the island — where SCINI
could dive through.
“Lo and behold we got down to the seafloor and we
found high abundances — surprisingly high abundances
— of corals and brittle stars and sponges and tunicates,”
said Kim, principal investigator on the project and an
adjunct professor at Moss Landing Marine Labs in California.
“I was quite flabbergasted by the whole thing,”
she added. “So now we have this wonderful new question
on our hands: What are these animals eating? Where is
the food coming from? What energy source supports this
community?”
Those are enticing questions that will have to wait for
another time. The main mission for these three years is
to perfect SCINI’s navigation and imaging capabilities.
The first season, in 2007-08, SCINI sought out a series
of artificial structures, such as cages, used in a series
of experiments in the 1960s. The location of the “lost
experiments” had been, well, lost.
Until SCINI and a second, commercial VideoRay ROV employed
by the team, found them all. “By relocating the lost
experiments, SCINI has already made a huge contribution
to a scientific effort,” Kim said.
Last year, the field tests continued, with the goal of
perfecting SCINI’s two cameras — one that looks
forward and a second that peers downward. “What we
wanted to do is be able to pilot it at the same time that
we could record imagery data going over the seafloor as
a transect,” Kim explained.
In addition to the deployments under the McMurdo Ice
Shelf, the group went to Cape Evans and Cape Armitage,
where it made further surprising discoveries.
At Cape Evans, SCINI dove to explore the scour left behind
by icebergs — the wreckage of the seafloor as the
bergs scraped by. As expected, the icebergs had wiped
the seafloor clean where they had passed. However, just
on the outskirts of the ice traffic, SCINI sent high-resolution
images back to the surface of large, thriving communities
of sponges.
Another mystery: How could the sponges recover so quickly?
Kim said there are at least two possible explanations.
Either the iceberg activity is lower than believed or
juvenile sponges grow more quickly than when they hit
the adult stage.
At Cape Armitage, SCINI not only imaged volcano sponges
big enough to swallow a diver, but it spied at least two
marine species in deep marine troughs that Kim didn’t
think existed in McMurdo Sound. One organism (Distalpia
cylindrica), which Kim refers to as a “whale snot
tunicate,” she had only encountered as a smashed
lump recovered in a trawl on the deck of a ship.
The second animal, Lyrocteis flavopallidus, is a jelly-like
critter adapted to live on the seafloor. It resembles
an underwater Venus flytrap, she said. “It sits there
with its mouth cocked open, waiting for something to feed
it.
“It was really amazing to see these animals as part
of a living community and develop a little better understanding
of how they might act as one component in an ecosystem,”
she added.
This year, for its final field season, SCINI may head
back underneath the ice shelf, though in a more challenging
area where a thick layer of frazil ice would test its
ability to maneuver and operate through extreme slush.
The location, near White Island and home to a unique seal
colony, requires special permission to enter.
“We want to be sure we can deploy and recover SCINI
through that kind of environment. We would like to prove
its utility for more general ice shelf conditions,”
Kim said.
The ROV, designed by engineer Bob Zook, has passed all
of its previous tests thus far. Originally built out of
off-the-shelf hardware, SCINI has skimmed the seafloor
at about 300 meters deep. As the engineers finalize the
design, they have swapped out its less sturdy plastic
components with metal housings to operate at even greater
depths.
The last piece scheduled for replacement is the camera
dome port. That would free SCINI to go much deeper; many
of its newer components are rated to depths of about 2,500
meters.
Kim envisions SCINI some day taking on missions below
ice shelves or sea ice, or perhaps sent down a deep drill
hole to troll through a subglacial lake or even the unexplored
realm below an ice shelf.
“SCINI as a general resource is capable of doing
so many more things than benthic ecology,” she said.
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Antarctic
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