Expedition Report
Tracy Quan

My name is Tracy Quan, and I am a graduate student in the Marine Chemistry and Geochemistry department at the Woods Hole Oceanographic Institution. I graduated from UC San Diego with a degree in Chemistry with a Specialization in Earth Sciences, and am currently finishing up my third year in the MIT/WHOI joint program. My advisor is Dr. Dan Repeta, and I work on dissolved organic carbon in seawater.

Dissolved organic carbon (DOC) is pretty much what it sounds like. There are several different types of carbon in the ocean: CO₂, inorganic carbon, particulate organic carbon, which includes dead organisms and fecal pellets, and dissolved organic carbon. These reservoirs of carbon interact with each other to define the oceanic carbon cycle, which in turn is a significant part of the global carbon cycle.

There are 6x10¹⁷ g C present in the ocean as DOC, roughly equal to the amount of carbon present as atmospheric CO₂ or as land biota. As a result, determining the characteristics of this carbon pool is an important step in defining the role of carbon on the earth. DOC is ubiquitous in all areas of the ocean and present at all depths; vertical profiles and concentrations are remarkably similar, ranging from 80-60 M at the surface to 40 M below 600m. Because DOC is dissolved and only present in low concentrations, its structure is hard to identify, and turnover times and pathways are hard to quantify.

In our lab, we focus on the high molecular weight fraction (HMWDOC), nominally defined as the fraction of DOC between 0.2 m and 1000 daltons. We work on determining the molecular components using various chemical techniques, and use radiocarbon to calculate age and turnover time. We also work at identifying various sources and sinks for HMWDOC. (For more details about what we do, read Aluwihare et al., 1997; Aluwihare and Repeta, 1999; and Repeta et al., 2002.)

On this cruise, we plan to collect HMWDOC from one station in the North Pacific, near Hawaii. We will be collecting water from various depths, then filtering them to isolate the HMWDOC. After the cruise, the samples will then be taken back to the lab for analysis.

6/7/02
11 pm Honolulu time

After a 2-hour bus ride from WHOI to Boston, a 2-hour wait at Logan Airport, a 6-hour flight, another 2 hours at LAX, another 6-hour flight and a half-hour cab ride, Nick Hartman, a summer fellow from PSU, and I have arrived at our hotel in Honolulu. The other two members of our party, my advisor Dan Repeta, and Elta Smith, another student from Texas, had arrived previously and met us for dinner. The other half of our scientific party are four scientists from the University of Concepcion, Chile: Dr. Silvio Pantoja, who used to be a post-doc in our lab, Dr. Giovanni Daneri, and two graduate students, Pamela Rossel and Gisella Lorca.

Tomorrow we'll shift all our belongings to the ship and start setting up our filtration systems and water barrels. We'll spend tomorrow night on board, and start sailing tomorrow.

6/8/02
10 pm Honolulu time

We were on our own for breakfast, so I went out to the corner store and bought a muffin and some juice, then went back to my room to watch some of the Argentina vs. England World Cup soccer match. At 8:30 am the four of us checked out of our rooms and met up in the lobby to drive to the ship. Our ship for this cruise is the R/V Melville, which is owned by the US Navy and run by the Scripps Oceanographic Institution, just down the hill from my undergraduate university. The Melville is the sister ship to WHOI's R/V Knorr, which was the ship I was on for my first cruise. The Melville can hold up to 35 scientists in addition to the full crew, so the 8 of us on this cruise have plenty of room. This also means that I get a room on the 01 deck, one level above the main working deck, which has a window. Each of us gets a room to ourselves as well.

We have two separate filtration systems, one for only surface water and one for water collected at various depths. The surface water system will consist of two filters, two pumps, and a 55-gallon barrel connected directly to the ship's uncontaminated seawater inlet. This system will be running constantly. The deep water system will have four filters, two pumps and a barrel connected to two other barrels holding the deep water caught via rosette. The surface system is placed in the ship's wet lab/darkroom, where there is a convenient seawater outlet. The deep system is placed in the ship's high bay, a covered area open on one side of the deck, which will be convenient for transferring water from the rosette.

All of our equipment is already aboard but strewn around the working lab of the ship. Our goal today is to try to get as much of the heavy stuff set up as possible. While we do have some time to prepare our equipment while we steam out to the site, it is much easier to get the barrel table and filter stands built when the ship is not moving. The barrel table is made out of angle iron sections bolted together to hold two 55-gallon (208L) water barrels. These barrels will hold the deep water. Each pump stand consists of three rectangular aluminum boxes bolted together in an L shape. The horizontal piece holds the pumps and supports the water barrel and the vertical section serves to hold the filters. For safety, we also chain down the barrel table and both pump frames to the deck and to the walls. While at sea, the ship can move violently in all three dimensions; our goal is prevent shifting in any direction.

It is hot! The ship is air conditioned, but most of our equipment is being set up outside. At about 3 pm we've finished setting up the heavy stuff, so we call a halt, get cleaned up and head back into Honolulu to pick up some snacks and last-minute supplies. I need another pair of shorts; Elta buys a water bottle and bagels; Nick gets several magazines and Dan looks for a hammock but settles for a beach mat. Giovanni's equipment and luggage got lost somewhere on his way to Hawaii from Chile, so the four Chileans made several trips back and forth to the airport before his stuff finally appeared. We meet up with them for dinner, then spend the night on the ship.

6/9/02
9 pm Honolulu time

The ship headed for the fueling station at 8 am this morning. While the ship takes on fuel, we begin to set up the filters. Each filter is a 4ft cylinder of tightly wound material that is slipped into stainless steel filter housings. The filters were cleaned back at WHOI, then shipped to Honolulu in pieces. We slide the filters in the housings, then attach the top and bottom plates. There is a slight moment of crisis (and puzzlement) as we discover that some of the housings seem a bit too big for the filters even though all the components are exactly the same size, but we manage to make it all work. Once set up, the filters weigh a lot, requiring two people to attach them on the pump stand: one to hold the filter and the other to tighten the clamps. We also unpack the pumps and electronic control modules and attach them to the frames as well.

The ultrafiltration filters we use are cross-flow types, meaning that the water, salt, and other things smaller than 1000 daltons are forced from the outside of the wound membrane filter into the center of the cylinder and into the waste permeate. Molecules larger than 1000 daltons are retained on the outside of the filter and pass back into the reservoir barrel. This way, we can concentrate the high molecular weight DOC from hundreds of liters of seawater into roughly 30L of retentate. We set up the plumbing as a closed system, so that as water leaves as permeate, it is replenished with new water from the sample barrels or the seawater intake. Only when we decide to finish a sample is the water level reduced to about 30L.

We had anticipated that the fueling would be done around noon and that we would steam out to the sample site in the early afternoon, but it appears that we will be later than expected. The captain gives us the option of leaving the ship to do more things in Honolulu, but I take a nap instead (it's still hot). Finally, we leave the fueling dock at 6 pm and head off toward out sample site. We get a great view of Honolulu and the surrounding hills as we leave. A dolphin rides our wake for a while but defies attempts to get a good picture of him.

We had planned to return to a site at 31°N 159°W that Dan had visited in 1999, both to reconfirm the results from the previous cruise and so that we could use some previous data taken from the same site by Druffel et al. in 1992. It turns out that Dan had underestimated how long it would take to travel there, making it impossible to get all the samples he would like in the 8-day cruise. He shifts the sample site south to 24°N, making the travel distance shorter, but the captain receives a message from the Navy blocking off an area of ocean containing that site for an ammunitions test and Dan must change the station again. Our final site will be 24°25'N and 156°18'W.

6/10/02
7 pm Honolulu time

Any time the ship starts moving for the first time in a cruise, it takes almost everyone some time to get their sea legs. I am actually OK this morning, but the night before I had some nausea at bedtime that I managed to head off with Bonine. Dan had planned to hook up the tubing for the surface system this morning but can't concentrate in the stuffy wet lab. Nick, Elta, and I are sitting on a picnic table out on deck wrapping the threads of dozens of plumbing fittings with teflon tape. After we finish, both Elta and Nick go to lie down; I just sit at the table and zone out. Silvio is bright-eyed and chipper; he has never gotten seasick... yet. Giovanni is up but moving slowly, and I haven't seen Gisella or Pamela all day.

We arrive at the sample site at 3 pm. We've managed to get the plumbing done on the surface pump and Dan is working on setting up the tubing for the deep system. Nick and I are getting ready to deploy the rosette to collect water at our first depth, 3600m. A rosette is a set of Niskin bottles placed on a circular frame. Niskin bottles are heavy plastic bottles whose top and bottom are connected by a spring on the inside. The ship's scientific technician, Ron Comer, shows us how to cock the bottles by opening the top and latching it to a release mechanism. Then we open the bottom and fasten it to a loop attached to the top, leaving the bottle open on top and bottom.

When the rosette is lowered to the desired depth, the operator in the ship sends an electronic signal to the release mechanism to close the top, and the spring inside the bottle shuts the bottom as well. The water sample is then trapped inside the bottle. If it all works properly, outside water can't enter a closed bottle, and the water inside shouldn't leak out. Occasionally, a bottle will misfire or not close properly, and we can't use the water inside. Below the bottles on the rosette frame is a CTD unit that measures various parameters such as salinity, temperature, and pressure. All of this data is stored in a file that the scientists receive at the end of the cruise.

The important part of lowering anything overboard is to make sure that it is under control so that it won't injure anyone or run into the ship. The winch operator raises and lowers the rosette while the A-frame operator swings the rosette out over the side. Nick and I stabilize it using ropes looped around the frame. Ron acts like a traffic cop, directing the winch as well as Nick and me. When the rosette hits the water, Nick and I unloop our ropes from the frame and pull them back on deck. The winch then lowers the rosette to the desired depth, then we fire the bottles.

When the rosette arrives back on the surface, Nick and I catch the frame with metal hooks attached to ropes and placed on long poles. Once we catch the frame, we pull off the poles and help steady the frame using the ropes. The winch operator lowers the rosette to the deck, and we fasten it down to prevent it from shifting. The ship isn't traveling anywhere, but is still constantly in motion due to both the swells and the action of maintaining position.

Once the frame is on board, we pump out the water from nozzles on the bottles using a lutz pump into the barrels on the barrel table. Dan has finished the plumbing on the deep system and starts the pump. We'll do two more casts tonight.

6/11/02
8 pm Honolulu time

Dan has put me in charge of the day shift with the Chilean crew and Ron Comer helping. He, Elta, and Nick will work the night shift. We are still casting at 3600m, and at 60 m/min wire speed each cast takes 2 hours, longer than it takes for the filter to process the 30L of water obtained in each cast. As a result, we cast without stopping. This day is our first whole day at station; from now until the end of the cruise the schedule will be pretty much the same.

My day starts at 6:30 am by preparing the rosette for casting with the help of Silvio, Giovanni, Pamela, and Gisella. Silvio, Pamela, and Gisella help me set up the rosette, lower it, and land it; Giovanni operates the A-frame. We lower it overboard by 7:15 am, then go inside for breakfast at 7:30 am. By the time breakfast is over, it is time to fire the bottles, and an hour later the rosette is back at the surface. We pump out the water and start all over again. After dinner, Dan, Nick, and Elta take over and cast until 1 or 2 in the morning.

When I'm not on deck raising or lowering the rosette, I monitor the pumps and filters. With the surface pump, I have to check to make sure that the reservoir barrel doesn't overflow or get too low. For the deep system, I switch the feeder tubing from the empty barrel on the barrel table to the full one when necessary. Because the deep system filters water faster than the rosette can replenish it, I also have to turn the system off when both barrels are empty.

In comparison, my schedule at WHOI involves less physical activity. I'm not much of a morning person, so when I get in I'll spend some time reading email, checking the online newspapers, and just waking up in general. Then I'll take some time to plan my day, and do calculations. Dan usually comes in midmorning, so I try and talk to him then if I need to, before he gets involved with his stuff. Then I start working in the lab, setting up experiments and taking measurements. When I'm not in lab, I'll be in my office reading journal articles, doing email and chatting with other graduate students and professors. I'm generally at work by 9 am, and leave around 6:30 pm. Some days are more hectic than others.

The ship has two cooks on board and they trade off cooking days. The ship gets its fresh supplies from the last port, so the great thing about leaving from a place like Hawaii is the fresh fruit we get for breakfast. Ship food in general is great, but on this cruise we get pineapple, cantaloupe, honeydew melon, papaya, mangos, kiwi, and strawberries in addition to the normal fare of pancakes, eggs, homefries, bacon, sausage, oatmeal, and yogurt. On this cruise we have been served everything from bouillabaisse and macaroni beef to fried shrimp and fried rice for lunch, along with the ever-present salad.

Dinner has involved a similar variety, including steak, swordfish, barbecue ribs, and enchiladas, plus dessert. In addition, snacks such as cookies, candy bars, fruit, and ice cream are in the galley to eat between meals. It is actually very easy to gain weight on board ship, in spite of the fact that it certainly takes a lot more effort just to walk in a straight line due to the pitching of the ship. There is a range of exercise equipment on ship, from free weights to exercise bikes to prevent too many pounds from accumulating. Silvio and Giovanni have taken to using the rowing machine after dinner, hoping to row all the way back to Valparaiso.

6/12/02
7 pm Honolulu time

Whenever I come back from a cruise, everyone knows that I've been to sea because my legs and arms are covered in bruises. Most of the time it is inadvertent; I'll be walking down a hall, the ship will pitch, and I'll crash into the wall or bang into a table. On this trip, I have bruises on my knees from banging them into the Niskin bottles when I cock the tops on the rosette. The bottom part of the doorframes are raised to prevent water from sloshing freely around the ship, so I have to be careful not to trip when going through doorways. Goodness only knows how Nick manages; at 6'2" he has to be careful about running into the top jambs of the doors as well. The door to the wet lab is so heavy that when the ship is tilted the wrong direction I have problems opening the door. The rocking motion of the ship makes me tired, so I have to pay much more attention to what I'm doing.

Then there are the times when we forget that we are actually on a ship and moving and think that we can do things the same way we usually do on dry land. We almost had a disaster today when a pump stand nearly fell over. We used one long chain to tie the system down, running it from the barrel to the floor, back up through the pump stand, back to the floor and up to the barrel again. What we forgot is that when we changed depths and finished concentrating a sample, we would need to tilt the barrel to get all of the water out.

As Dan was removing the sample today, he undid the chain to free the barrel, which also loosened the connection to the deck. The ship then took a giant lurch and the whole filter setup tipped. Fortunately, Nick, Dan, and I were able to wrestle it back upright without any major injuries, though we all got some bruises.

In terms of work, we have pretty much stuck to the same schedule as the previous day. Now that the 3600m sample is done, we are starting to sample the water from 1800m. The 3600m sample is about 40L and is frozen in jerry cans in the freezer. Compared to other scientists' cruises, ours is very boring. We don't use Alvin to travel to the sea floor or make multicolored maps of the topography. We don't take samples of rocks or mud. We don't move from station to station, or tow a "fish" (any instrument package that is towed by the boat to take measurements). We don't make any measurements or do any chemical analysis.

All we do is lower the rosette, fire the bottles, raise the rosette, pump out the water, and get ready to lower the rosette again, while the filters keep going. Dan asked Nick how he liked the cruise so far; Nick replied that everyone tells you how exciting going to sea is but never mentions that it's also pretty boring as well. We pass the time doing a variety of things: reading journal articles and other books, lying out on deck in the sun, or listening to music. Dan also reads someone's doctoral thesis, Silvio writes a paper, and I knit (badly).

6/15/02
10 pm Honolulu time

Today is our last sampling day. We have finished the 3600m, 1800m, and 900m samples collecting approximately 4000L per depth. Dan has stopped the surface water filter after 4.5 days of constant filtering. This morning our goal is to collect at least four rosettes full (1440L) of 600m water before we have to leave at 1 pm to return home. We can get away with less water for the 600m sample as the concentration of DOC is greater at shallower depths in the water column.

The round trip to 600m is only 20 minutes, which makes filtering the rate-limiting step. Just after lunch we retrieve the fourth and last rosette run with Giovanni (Captain A-frame) working the A-frame controls for the last time. As soon as we set the frame on deck, the captain gives the order to return to Hawaii. There isn't any room in the barrels for the water, so the rosette sits full on the deck until the barrels empty. While we steam back, we will concentrate down the surface and 600m samples and place them in the freezer.

One of the ship's walk-in deep freezers has broken and cannot be fixed without thawing the freezer completely. The ideal solution would be to keep the freezer sealed until we reach Hawaii, then offload the food onto land and repair the freezer; however Hawaii does not allow produce or meat to be transferred to land. So the crew hauls thousands of dollars worth of frozen fish, meat, and vegetables out on the deck and dumps them into the ocean (after removing the plastic packaging). We all think that there ought to be a better solution, but the main ships' office has given the command. The ship has so many freezers that only an eighth of the ship's supplies is tossed.

After dinner all the samples are finished and we start taking our equipment down. The ship plans to return to the dock by 9 am tomorrow, and we'd like to get as much packaged as we can tonight. Elta and Dan start dismantling the filters, placing all the metal parts into a container of fresh water. Nick and I help take apart the pump stands and barrel table, giving everything a rinse in fresh water. We also try to dry as many of the parts we can in the main lab to stop rust from forming.

6/16/02
6 pm Honolulu time

We arrive at the dock at about 9 am this morning and immediately start packing up equipment into boxes and pallets. Complicating this process is that some parts go back to WHOI while some go to a land-based sampling station on Kona, and only Dan knows what goes where. Once we get all the boxes packed, we have to load them all onto pallets and tie them down with plastic and strapping. The weather is hot and humid.

Dan and Silvio go to the airport to pick up rental cars. The scientists for the next cruise arrive and are anxious to get going. By three, all the equipment is packed and offloaded, with labels for sending. The Chileans have left over an hour ago for their hotel. Dan will stay for a couple more days to arrange for shipping because today is a Sunday. Elta is going to visit a friend. Nick and I fly out late today and land in Los Angeles tomorrow morning. Nick will continue on to Boston, but I'll stay in LA and visit family for a few days.

After we leave the ship, we meet up with Silvio and Giovanni at a local bar and have drinks and appetizers. Giovanni drinks us all under the table. Dan, Elta, Nick, and I then wander around the Honolulu shops, picking up souvenirs and presents until Nick and I need to leave for the airport.

7/1/02 Postscript

We are now back at WHOI and have received our equipment and samples back. Our lab technician is cleaning the filter membranes and plastic fitting for the next sampling trip. Most of the tools and supplies are still sitting in the hallway, waiting until we have the time to take them down to the long-term storage area.

Nick is already at work on some of the samples he brought back for his summer project (using resin beads to separate out a different fraction of DOC). Our frozen samples have been shipped to us and are waiting in the walk-in freezer to be desalted and freeze-dried. Later, we'll run experiments on the samples to measure the components we know exist, and try to determine other structural parts.