Florida State University : Research in Review

Day 4 - Tuesday, 09/16/08

Positions:
9:00 a.m. N43 58.589 W30.20.667
3:25 p.m. N44 00.020 W130 23.464
4:30 p.m. N44 00.078 W130 23.431
7:03 p.m. N43 59.840 W130.23.431
9:45 p.m. N43 59.654 W130 23.456 (272 miles due west of Eugene, Oregon)

Busy day! And night! Today began with the promise of finally doing what we came to do—collect lots of samples of deep-ocean sediment, read: mud. And doing it with precision, too. These benthic biologists aboard have explained that the samples have to be taken very carefully—not just scooped up haphazardly. The animals they’re interested in often live in highly stratified layers of just the first few inches of bottom sediment. It’s important to know which animals live where, so samples must be taken with great care, without getting mixed up like a marine cocktail. The special coring devices are designed to do the job right.

But these will be the deepest multi-coring attempts by far in the history of the Point Sur, said Jack Lavariega, now in his 16th year attached to the vessel. Working in 1,000- to 1,500-meter depths for such work has been the norm, he said. The crew of the Sur will be learning things on this trip along with the scientists on board.

The new lessons came early. Our first “cast,” or deployment, began well enough at 8:50 this morning. From the wheelhouse, Capt. Jeff and able-bodied seaman Scott Hanson skillfully played out more than a mile-and-a-half of half-inch steel cable with the multi-corer attached and got a perfect “touchdown” on the bottom at 2,775 meters. I soon learned that it helps to have a feel for this kind of work. Fetching samples from a seafloor nearly two miles down is hardly an exact science. The basic technique the helmsmen of the Point Sur use in deploying the multi-corer in these waters combines two parts seasmanship, one part technology—and one part luck.

As the one-ton corer contraption begins its slow descent—normally at 8 meters a minute—the ship’s bridge keeps the Point Sur’s bow into the swells. On automatic pilot, and with its hydraulically controlled propellers feathered to a pitch that produces as little or as much speed as needed—or as sea conditions allow—the ship’s captain slowly heads toward a predetermined set of latitude/longitude coordinates that may lie as much as a mile ahead. This is the target picked for setting the corer onto the seafloor. The idea here is to time the ship’s forward progress so that the corer will be hanging only a few meters—maybe 30 or so— ahead of the target when the Sur’s helmsmen get the word to “let ‘er go”—or words to that effect.

That’s a command that can only come from the official “flight controller” of the corer on its way to the bottom. For today’s mission, the critical job falls to 28-year-old Andrew Woogen, one of Moss Landing’s marine technicians. Andrew sits at an electronics-packed console near the ship’s stern on the main deck. In constant contact with the bridge via an intercom mounted at his left shoulder, Andrew watches a 21” Sony monitor showing a dark red line gradually tapering off from left to right. That’s the signature of a beeping sonar signal fired from a battery-powered “pinger” that the crew bolts onto the cable about 10 meters above the multi-corer itself. The 50-pound pinger capsule must be mounted by hand and switched on with a flat-bladed screwdriver at the start of each cast, and unmounted and turned off before the multi-corer can be hoisted back on deck. The electronic line it draws on Andrew’s machine 8,000 feet above is akin to an aircraft’s altimeter showing a steady approach to a landing site.

At the instant Andrew knows the corer is in the ideal position for the final drop, he alerts the captain who essentially stops the boat by cutting his throttles, or if necessary, throwing his engines into reverse. For the next few seconds, the great weight of the corer and its steel cable—which can be five times heavier than the corer itself—actually pulls the 135’ Point Sur backwards. This causes the corer to plummet to the bottom. When tension on the corer’s cable goes slack, 500 pounds of lead bars mounted inside the corer are instantly released, driving an array of sampling tubes, with their spring-loaded bottoms cocked open, a foot or more into the sediment. The sudden loss of tension on the cable pulls the triggers on the bottom mechanisms, which slam down first onto the seafloor. As the corer lifts, springs quickly pull the bottoms into place, shutting the “mouths” of the plastic coring tubes and, if all goes well, capturing the mud inside without disturbing it. After making contact with the seafloor the contraption can take eight perfect core samples in a matter of seconds.

But when the corer lands on rocky or other hard bottom—and at these enormous depths it’s almost impossible to know for sure what’s really down there on any given spot—or if there’s not enough lead weight installed on the corer—or one of any number of other things—it can be all for naught. Apparently, one or more of these factors was enough to make our first cast of the day, our first of the mission, a complete bust. For a two-hour effort, all we caught were eight tubes of cold seawater.

Sometimes, as all true fishermen well know, a day’s bad start can mean a day’s great ending—and vice versa. Such was the case today. After moving a few miles to the west, the second try was the charm—five of the eight coring tubes fetched perfect samples. Two tubes came up empty, and another never came up at all! Inexplicably, the plastic tube somehow got knocked out of its welded-aluminum cradle. Luckily the cradle itself stayed intact, and that’s the expensive part!

Once samples are on deck and the corer secured, the science team’s work goes into high gear. Timeliness is everything—not only do the samples have to be moved to a 44-degree-F “cool box”—necessary to maintain their biological integrity—but everybody hears the clock ticking on this pricey research vessel. Today’s goal is eight successful casts, and at roughly 2 hours per cast—and with the first of the day having gone belly-up—it’s all hands on deck!

Well before your amazed correspondent ran out of gas and called it a day, the science crew was still hard at it, with another three excellent casts netting another dozen or so good samples by midnight. Every successful cast requires over an hour of tedious work, first in the “cool box” and then in the lab. Cores are carefully pushed out (extruded) of their tubes and the top three centimeters are sliced off one at a time and properly labeled. In the lab, all samples are then run through fine-meshed sieves to separate the organic (live or once-live) matter from the sediment as much as possible before they are again labeled and put into a chiller for storage.

Everything considered, it was a fine opening day for this mission, which took over two years to plan. Sea conditions are almost too good to believe—we’ve not seen a sea or swell higher than four feet in two days now—and the sun keeps peeping at us from time to time between scattered patches of dense, low-lying clouds. The young team members who’ve been ill—namely team leader Erin, along with Stefan, Russell, and Melissa—have found their sea legs and are working like Trojans.

During the night we lined up on the starboard rail and watched in awe as a full moon broke through a small hole in the clouds just a few miles away to the east and home, and lit up a patch of the black Pacific as if it were a stage meant only for a few lucky mariners sitting front row, center.

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