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Latitude: 33° 48'N
Longitude: 62° 35'W
Wind Direction: SSW
Wind Speed: 16 Knots
Sea State: 3
Sea Temperature: 73°F (22.8°C)
Swell(s) Height: 5 Foot
Barometric Pressure: 1021.0 MB
Currant almond scones
Cajun kale soup
Pot roast shepherd's pie
Grilled bacon and provolone sandwich
Salmon salad pita pocket
Artichoke, feta, calamata pizza
Fruit Salad bar
Baked meatloaf and gravy
Italian roast sirloin au jus
Broiled Mahi Mahi with shrimp mousseline sauce
Panache green beans amandine
Taita Hill zucchini and tomatoes
Tropical rice pilaf
Baked seasoned potatoes with sour cream
Rocky road brownies
June 6, 2003
By Joe Appel
We made a sacrifice to Poseidon last night,
but to be honest we weren't expecting such a speedy response.
We got one, however. In the tradition of the expedition, our
bounty came wrapped in the guise of yet another setback.
This time the fates chose the towed camera. The tow-cam is essentially a Nikon
digital camera attached to a sled, which is periodically pulled behind RV Atlantis to
gather information about the sea floor. Last night, it snagged on a horizontal
overhang. For more than an hour-and-a-half, it was stuck.
After a bit of delicate ship maneuvering, the
sled was freed, with barely a scratch for its trouble. When it
surfaced, it brought up a special treat in addition to its customary
1,800 or so photographs: coral. Lots of coral. Instead of the
hundreds of individual Desmophyllum cristagalli that we'd gotten
used to, however, this D. cris was in large chunks, which had
been ripped from the seamount when the sled came up.
Tim Shank, a biologist and veteran of these cruises, said the odds of something
like this happening are "not even one in a million...more like one in a billion." Thank
Along with the day's haul from Alvin, today was very productive indeed.
Tomorrow will be the last dive on Muir Seamount. After that, we'll head back
to Manning Seamount, where the weather seems to have finally calmed down enough
for our purposes.
The episode with the towed camera encouraged us to investigate further what that
important tool is all about. It's a relatively simple technology when compared
to some of the equipment around here, but it greatly improves our efficiency
with Alvin dives.
The tow-cam was actually built to be a camera/rock-corera device that can
break off small chips of rock on the sea floor and bring samples up for testing.
On this cruise, however, rocks aren't what we're after. So the tow-cam functions
primarily as a moveable digital camera. There's a Nikon Coolpix attached to a
sturdy sled, capable of taking a picture every 10-15 seconds over a time span
of 5 hours. To store all that data (roughly 1,800 photographs, depending on which
resolution the camera is set at), there's a 2-gigabyte memory card installed.
"It's a way of surveying the sea floor without near the expense of Alvin or
an ROV (remotely operated vehicle)," says scientist Rhian Waller. "We can use
it as a tool to look at an area before we trawl or really study an area in more
Waller is a tow-cam veteran, along with scientist Bob Green, whose role it is
to look after the WHOI tow-cam. Waller works out of Southampton Oceanography
Centre in the United Kingdom, and she says that towed cameras at that institution
are often used for environmental surveys, to count animals or ocean flora.
Operating the tow-cam takes a good deal of human effort and attention. Attached
to a cable, it is lowered on a cable from the side of the ship using a hydrowinch,
until it approaches the ocean floor. At about 100 meters above the floor, an
altimeter kicks in, so that the operator can keep the sled at its optimum distance
from the seafloor: 6 meters.
This entire time, the tow-cam operator aboard the ship is watching computer monitors
that relay water information as well the tow-cam's position. How often does she
or he need to adjust the tow-cam's position? It depends entirely on the terrain.
If the seafloor is flat, you've got a relatively easy time. Last night, moving
it up a steep slope, Bob Green was continually making adjustments.
Every once in a while, the tow-cam gets stuck. When that happens, you stop the
ship, which until then has been traveling at a speed of a quarter-knot, and back
up. The goal is to get the cable back to a vertical position.
Sometimes re-positioning the cable and freeing the camera sled takes quite a
while. Last night it took just under two hours. We were happy to have it back,
coral on board or not, just so it can keep on diving, and keep on helping.
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