It is tuesday, February 22nd, and I am sitting in the Cape Town airport getting ready for my twenty-hour flight back to Boston.   It is hard to believe that a week ago the Melville was steaming at five knots, sixty miles west of Cape Town on a course to time our arrival in the wind shadow of Table Mountain at exactly 0700.  The Captain does not like to arrive late to port after being at sea for 37 days.

On Wednesday morning the entire ship was awake early in anticipation of our arrival.   Even before I got to the deck I knew we were near land.   Everything smelled differently.   The air had a smell of decomposing kelp and other things organic, a big change from the smell of sea spray mixed with a hint of diesel fuel.

Cape Town

At 0730, the pilot boat, Petrel, came alongside to drop off the Cape Town Pilot.  Her job was to guide the ship into the port and to our dock.   The Captain is still responsible for navigating the ship, but the pilot provides the local knowledge of the harbor.  Meeting us at the harbor entrance were two tugs in case we needed a little help maneuvering.   As you know from my previous post, the Melville has three rudder propellers that can move the ship forward, backward, or sideways.   After turning within a boat length as we neared Quay Four, the ship simply moved sideways the last 60 meters to the dock.  The crew told me that tugs tend to break things and the Melville navigates on its own power if at all possible.

Table Mountain

By 0830 we had arrived at the dock, the lines were pulled in place, the gangplank was installed, and our port agent had arrived.  Standing two meters from South Africa we all began to wait.  We needed to clear South African immigration before we could “officially” enter the country.   Ironically, to do this we all walked off the ship, loaded into passenger vans, and drove five miles to the port immigration office.   As we waited in the hall outside the immigration office, our passports were stamped, visas installed, and we had arrived in South Africa.  I don’t think they where worried about the passengers on the Melville sneaking into South Africa.  As an interesting aside, the reverse is not true.  Another Scripps ship, the Revelle, had a stowaway the last time they were in Cape Town.   Before the Melville leaves Cape Town on this trip, it will be searched from stem to stern by port security with trained dogs.

By noon we were free to explore Cape Town.   We had a lot of unpacking to do, but for the next few hours many of us explored the city to find the establishments with the best beer.  We were successful.

The video attached above shows our progress into the port and unloading.   All the gear that took so long to arrive in Punta Arenas had to be repacked for shipment back to the United States.  All of the WHOI, Bigelow, and Colby gear was packed into a 10×40 foot cargo container.  While we fly home, our instruments are going back to sea on a cargo ship for the trip to the port of New York.  From New York, the container will be trucked to Maine via WHOI.  If all goes smoothly, we should see our instruments some time in late March.

Quick work in the port meant that I had a few days to explore Cape Town before flying home.  After being confined to the ship for five weeks I took the opportunity to climb all the mountains around the port city.  The views were spectacular, but my cardiovascular conditioning was not.  It is going to take me a few weeks to get back into shape for squash and winter activities in Maine.  I also took the half-day tour of Robben Island, South Africa’s infamous prison island located 5 miles northeast of the docks in Cape Town.  Robben Island has over 300 years of history as a prison, leper colony, and military base.  The world knows about Robben Island because it was the apartheid-era prison of Nelson Mandela, Robert Sobukwe, and over 1500 other political prisoners from 1961 to 1991.  A tour of the island should be on the top of the list of any visitor’s itinerary for Cape Town.

So now I am heading home 49 days after leaving Maine in early January.  I hope readers have enjoyed reading this blog and learning something about the research, the scientists, and life on the oceanographic ship the Melville.  It was a great trip, made successful by the capable Captain and Crew of the Melville, and a great group of scientists lead by Barney Balch from Bigelow Laboratory for Ocean Sciences.

- Whitney

Howdy!  Here’s some more questions from the kids. – Katie
1. Have you found any animals/organisms or results that were surprising?

No real surprises, but lots of great data was collected on the cruise.   One of the the major objectives of the cruise was to confirm that the Great Belt as seen from satellites really was due to massive numbers of coccolithophores.  This has been confirmed.  We will know a lot more of the details as the data analysis is completed.    Please see Rebecca’s blog for more details on the major findings of the cruise.

2. Does the cold weather affect your testing?

It is always more pleasant working on deck when the water and air is warm.  Once we got above 30 degrees south the weather was very nice.  The rosette was also on a track that pulled the sample bottles into the aft hanger of the ship and out of the weather for sampling.  Once the samples get into the lab the weather doesn’t have a big impact on the analysis.   We do need to be aware of the temperature of the samples when they were collected.  For some measurements, like pH, the measured value changes with temperature.   This is particularly true of anything that changes with time.  Rates of chemical and biological reactions are very temperature dependent.

3. Why is phosphate limiting is freshwater?

The limiting reagent is what runs out first.   In lakes some species of algae can fix nitrogen from the air to meet their nitrogen requirements as nitrate gets low.  Phosphate only comes from runoff into the lakes, and so it is usually limiting.   In many parts of the ocean iron is limiting because the very low solubility of iron in seawater.

4. Do you get tired of the ocean?

Yes, we were all very excited to get to Cape Town.   We miss our friends and families, and have lots of other non-cruise things that we must attend to back on land.

5. What does WHOI stand for? ( I know its Wood Hole Oceangraphic Institute, We actually visit in the spring.) Will any of your results be there when we visit?

You are correct that WHOI stands for Woods Hole Oceanographic Institution.  Two WHOI researchers were on the cruise and I am certain that they would be happy to talk to your class if they are at WHOI during your visit.

6. Do people usually get sea sick on the trip?

Yes, we were very lucky that we did not get any really rough weather during the cruise and only a few scientists felt sick for a few days during the cruise.   I get really sea-sick and took the Coast Guard Cocktail for most of the cruise to prevent sea-sickness.

7. Do you ever get tired because of your hours?

Of course, the combination of long hours and no days off can be very tiring.  In the beginning the excitement of the cruise keeps you going.   By the end of 37 days everyone was looking forward to getting of the ship.

8. Why do you filter the water?

The particles in water are made of living and dead organisms and inorganic particles like dust.   The chemistry and biology of these particles can be very different than the dissolved molecules in seawater.   The particles can also sink making then the conveyor belt for moving material from the surface to the deep ocean.

- Whitney

Melville's Rudder Propeller

My daughter is the real engineer in the family, but she has often commented that I could have easily been an engineer in another life.  She is probably right, I love all things mechanical and I have spent the last thirty days talking to Chief Engineer Paul about the operational details of his ship.

The first thing that strikes me is the scale of the ships systems.   The ship is powered by three, sixteen-cylinder, Caterpillar diesel engines and one, eight-cylinder engine, affectionately referred to as Three CATS and a Kitten.   Each of the big engines produces 1800 horsepower that is used to generate about 1090 KW of electrical power.  It takes two of the big CATS to generate enough power to drive the ship’s propellers and provide the lights, air conditioning, and water for the scientists and crew.  Under normal operating conditions the Melville is producing enough power to run all of the electrical and heating systems on the Colby campus during a cold day in January.   And you don’t want to offer to split the gas money on this road trip; the ship has burned 80,000 gallons of diesel fuel on the cruise.

The video below provides a short tour of the mechanical systems of the ship.   We have traveled long way from land and have to be self sufficient for all services including water, sewer, AC, and fire protection.   Most of the mechanical systems on the ship are run in pairs, if one system fails the backup system is designed to start automatically.   The ship even has an emergency generator to run lights, pumps, and fire systems if the four main engines fail.

All of these systems require a lot of maintenance.  The engineering crew consists of the Chief Engineer, three Assistant Engineers, four Oilers, two Wipers, and an Electrician.  The crew typically works four hours on and eight hours off on a staggered schedule.  Someone is always in the engine room 24 hours a day while the engines are running.  You don’t check the oil every 3000 miles, you check the oil every hour, and they will use 80 quarts of oil for an oil change.

Tomorrow we arrive in Cape Town, South Africa.   The Melville has carried us safety across the Atlantic Ocean and provided the services we needed to focus on the science.  It is easy to forget the machinery at work to make this cruise possible until you sit quietly for a minute and hear the rumble from below of Three Cats and a Kitten.

- Whitney

Melville Bridge

I remember arriving at summer rental houses and during the initial excitement of running around exploring, I would “save” a room in the house to look at later on in the vacation.  True to my past behaviors, I decided to reserve venturing up to the Melville’s bridge until today.

The bridge is located on the 03 level of the ship (the 04 level, or observation deck on top of the bridge, is the highest level).  When I entered the room, I was overwhelmed with a sense of tranquility, and it took me until a conversation with Whitney later on in the day to realize why that was—it’s the only place I’ve been in the ship where I can’t hear the engine’s humming…it’s quiet!  The bridge houses the ship’s navigational system and the captain and three mates rotate standing watch in the bridge.  Large, immaculately clean windows (I am told they’re cleaned daily) occupy three of the walls to allow for optimal visibility of the sea and the ship’s exterior.

Joseph, the chief mate from China, Maine, showed me around the bridge today after dinner.  He explained how there are several options for steering the ship, which include one bow and two stern thrusters, a joystick, and an autopilot system.  The autopilot system is generally employed while traveling between stations, and once we’re on station, the stern thrusters controlled by the joystick are used to help put us in the proper orientation relative to the wind.

Beneath the windows on one wall I noticed a shelf with small cubbies, each occupied by a unique flag.  While some of these flags belong to different countries, and are flown while in that country’s port, other flags are associated with actions.  The “hotel” nautical flag is flown when there’s a pilot aboard, like the South African pilot we will pick up  at 0700 on Wednesday morning to accompany us into port.  The “bravo” flag is flown while the ship is refueling.  Joseph pulled out a dust-covered box housed beneath the flags, and showed me the old-fashioned sextant inside.  With today’s technology, it seems hard to believe that such instruments are still used, but Joseph knows how to work it if needed.

Sextant

Most people I’ve told aboard the ship were surprised that I haven’t been to the bridge before today, but I think it was a nice surprise to save for the trip’s conclusion.  Now that I think about it, I haven’t seen the engine room either…

-Annie

Winkler Bottle

We have been asked for another example of a chemical analysis being performed on the ship.   One of the most famous measurements is the determination of dissolved oxygen in seawater.   The CTD has an electrochemical sensor that measures oxygen continuously as it is lowered into the ocean.   However, the electrochemical sensor drifts with time and all CTD measurements must be calibrated against lab measurements.  Samples are taken from the Niskin bottles on the rosette for the calibration of the oxygen sensor.   The lab measurements are based on the classic Winkler titration of oxygen first developed by Lajos Winkler in 1888.

The Winkler analysis of dissolved oxygen has three steps designed to turn odorless, colorless dissolved oxygen into something that we can see.

Samples are collected in Winkler, or BOD, bottles that are specifically designed with a conical top to help exclude bubbles.

A basic solution of Mn(II), MnCl₂ (aq), is added to the sample bottle.  Under alkaline conditions dissolved oxygen will oxidize manganese(II) ions to manganese(IV), MnO(OH)₂.    This reaction is fast and stoichiometric so that each mole of oxygen produces two moles of Mn(IV).

2 Mn²⁺ (aq) + O₂ (aq) + 4OH^- → 2 MnO(OH)₂(s)             (1)

Excess Mn(II) and base are added in step one so that oxygen is the limiting reagent (see the blog on limiting reagents).   Sodium iodide is also added during step one.  In base, iodide does not react, but it is added to be ready for the next step of the reaction.   You can get an idea of the amount of oxygen in the sample by observing the brown MnO(OH)₂ precipitate that forms in the bottle.  In this step we are converting a dissolved gas to a solid.  The amount of solid is proportional to the amount of oxygen that was in the bottle.

The sample bottle must remain tightly capped during the first step to prevent oxygen from the air from reacting with Mn(II).  Recall from the CTD video that all the air bubbles were carefully removed from the bottle during sampling and the Bottle Cop makes certain that the samples for dissolved oxygen are taken first.   The capped bottles are allowed to sit for over 30 minutes to completely react with all the oxygen.

Next, excess acid is added to the bottle and the MnO(OH)₂ (s) formed in step one reacts stoichiometrically with iodide (I^-) to form a yellow, triiodide (I₃^-) solution in two steps.  The cool part of this reaction is that iodide reacts in acid, but oxygen does not.  This means that the samples will no longer react with oxygen from the air. Why is this important?

MnO(OH)₂(s) + 2 I^-(aq) + 4H⁺ → Mn²⁺(aq) + I₂(aq) + 3H₂O   (2)

I^- (aq) + I₂ (aq) → I₃^- (aq)                                                                (3)

Again, iodide and acid are added in excess.   The limiting reagent in each step is highlighted in red.  Triiodide is yellow so we now have a solution that we can see.  The more oxygen in the original sample the more yellow the solution.  On the Melville, Melissa uses an automated titration system measure the triiodide by the stoichiometric reaction of triiodide with thiosulfate, S₂O₃^2-..

2 S₂O₃^2-(aq) + I₃^- (aq) → S₄O₆^2-(aq) + 3 I^- (aq)    (4)

When the solution returns to a constant color all of the triiodide has been converted back to I^-.  In the video the black box on the right monitors the color of the reaction.  The tube entering the top of the bottle adds thiosulfate.   It may seem easier to simply measure the intensity of the yellow solution.  This would probably work for really clear water samples, but it doesn’t work for water samples that are murky or have some other source of color.

Notice that the samples can be handled in the air because step four occurs in acid.  Melissa can process twelve oxygen samples in about an hour.    She has processed over 600 samples during the cruise.  That’s a lot of titrations!

- Whitney

Iceberg about three miles to starboard

Coming into this trip, I didn’t have any expectations of seeing icebergs.  Therefore, the first one we saw from afar near the Sandwich Islands came as a great surprise; it looked like a white fortress, and further investigation with binoculars made me eager to get closer to it.  We remained on station for a long time that day, and it was pretty unbelievable to stand on the deck and watch chinstrap penguins play next to the ship, while whales spouted in front of the iceberg in the distance.

When we finally left station, it was getting dark and visibility was not optimal while we passed the iceberg—the view didn’t compare to what we saw today.  Today’s gray, overcast day served as a perfect backdrop for the glowing white with bright-blue undertones of the sublime iceberg.  The iceberg resembled a sand dune, with its steep sides, hundreds of feet tall, marked with windblown patterns. Behind the iceberg, partially hidden by the fog, we spotted an even bigger piece of floating glacier.

Our location, currently around 49 degrees South, explains why we were lucky enough to encounter these massive pieces of floating ice.  During the austral summer, the Antarctic Circumpolar current, which flows west to east around Antarctica, drives icebergs to where we saw them today.  Because there is no land boundary north of Antarctica, ice from the antarctic moves northward into warmer waters, where it eventually melts.

Antarctic Circumpolar Current (Wikipedia)

According to the National Snow and Ice Data Center, during the winter up to 6.9 million square miles of ocean is covered by sea ice, and by the end of the summer only 1.1 million square miles of sea ice remain. The icebergs that we saw started as massive pieces of glacial (fresh water) ice that melt slowly enough to make it 49 degree South. The amount of ice we saw, although only the “tip of the iceberg” in terms of the total amount that’s out there (if you’ll excuse the expression), was enough to satisfy us!

-Annie

On Wednesday we sent the CTD down to 6000 meters to sample the second deepest location in the Atlantic Ocean.   We had arrived at the South Sandwich Trench, just 60 miles east of the South Sandwich Island Chain.  Along with the sensors and sampling bottles on the CTD we included two mesh bags filled with a collection of Styrofoam objects.  Whitney had arranged with Katie Harris (Colby ’08) for her students at the Epiphany School to send him decorated Styrofoam cups for the trip to the bottom.  On the ship the “big kids” didn’t want to be left out of the fun, and soon all manner of expanded polystyrene was being cut, shaped, and decorated to create Great Belt memorabilia.  The photographs show several before and after shots of the polystyrene objects.  The objects shrink because Styrofoam is made from closed-cell, polystyrene beads that are 10% polymer and 90% air.  At pressure the cells crush, expelling the air, and forming miniature polystyrene objects.

Tectonic Plate Boundries (Wikipedia)

It was fascinating to watch the depth sounder display depths of only a few hundred meters near the South Sandwich Islands and then plunge to 7400 meters just 60 miles east of the islands.   We had traveled over a classic oceanic trench.   The South Sandwich Islands are being formed by active volcanism driven by plate tectonics.   At the deep, South Sandwich Trench the South American Plate is being subducted below the South Sandwich Plate at a rate of 4 cm/year.   The subduction drives the

Islands in the distance under the clouds.

ocean plate downward creating the ocean trench.  Because tip of the subducted plate is pushed into the hot Asthenoshere, the oceanic plate melts at depth creating the magma that is forming the South Sandwich Island chain.   Mt Belinda on Montegu Island has been persistently erupting since 2001.   The South Sandwich Islands are still growing!   Unfortunately, as we sailed through the island arc all we could see were the clouds forming over what we imagined were beautiful, glacier-covered mountains.

-Whitney

FeLume ($30,000)

Hey King! Sorry we haven’t had time to post any questions. With all the snow we’re getting we haven’t had a full week of school since being back. Anyway, there are a couple of things the kids wanted to know.

We have been watching the news about the snow back home.   We had a few snow flakes today, pretty cold for the summer.   We can’t imagine how cold it must be at 60 South in the Winter.   The water temperature goes from about 2 oC at the surface to -1.5 oC at 100 meters depth.   The temperature of the water is below 0.0 degrees C!  How is that possible??

For Annie, they wanted to know if it was her first time on a trip like this and if it is/was what she expected? What is it like traveling so far from home?

Nutrient Analyzer ($50,000)

This is my first time on a research cruise like this.  Before this trip, the longest I had been at sea was on a sailboat for 10 days that sailed from Massachusetts to Maine.  The trip has been what I expected, and more!  It has been really interesting to see all the work that goes into scientific research, and to get to take part in collecting data.  It’s exciting to be traveling to places I have never been before and to be doing new things, and because we have internet on the ship and I’ve kept in touch with family and friends, home doesn’t feel so far away!

They also really liked the videos (do you have any more?) and wanted to know about why you waste so much water when your getting ready to test it? How long the process takes to collect water and maybe explain a little more about the sampling?

CO2 and Alkalinity Analyzer ($50,000)

Please check out our recent Whale Video.   Your class is very observant that a lot of water goes onto the deck.  We need to rinse the bottles well so that they only contain water from the Niskin bottle.   This is particularly important for samples for dissolved oxygen since air is 20% oxygen.  A single air bubble will really mess up the dissolved oxygen measurements.

In the CTD video you see Melissa filling a bottle with a long rubber tube.   The water from the Niskin bottle fills her sample bottle from the bottom pushing the air out of the bottle as it fills.  She then overfills the bottle to remove every last bubble.

Guitar for recreation (priceless)

They are also wondering more about costs of equipment etc.?

The ship is the most expensive part of the trip.  Ships cost many millions of dollars to build and charge $36,000 a day operate.   The ship cost for this trip will be over $1 million.

Many of the instruments we are using cost between $30K and $100K.  We pack the instruments in special boxes to transport them to the ship.   We are already working on the details for shipping our instruments home from South Africa.  The pictures in this post show some of the instruments on the ship.

Finally, they wanted to know if anyone had made any drastic mistakes yet?

No big mistakes yet.   We had some big swings with the CTD during a particularly rough night.   The tension on the CTD cable went from zero to 6000 pounds in about a second.   Big changes in cable tension can snap the cable.   We were lucky and the cable is fine.

One scientist banged his head on the steel stairs during some rough weather and bled a fair amount.   He spent a little while in the ships hospital until the bleeding stopped.   No stitches were needed, although the Captain and First Mate are supposed to be pretty good at stitching.  We are at least 10 days from a real hospital so the ships crew has to be trained in emergency medicine.

Cups for the deep.

Tomorrow we will be over the second deepest point in the Atlantic Ocean (use Google maps to find:  55.8 S, 26.1 W).   We will send the cups from the Epiphany School to a depth of 5500 meters.  We have placed the cups in a mesh bag that we will attach to the CTD for the trip to the bottom.  Try to estimate the pressure at 55o0 meters depth.

The two humpbacks circled our boat for about half an hour, while we traveled starboard to port, port to starboard watching them.  Humpbacks are known for their long, wing-like flippers, and it was these flippers that made it easy to spot the whales after they did a shallow dive.  Because the flippers were white, they glowed a bright turquoise color under the water.

I’ve been on many whale watches, but seeing these two whales this morning here in the Southern Ocean felt like a completely different experience.  Because we weren’t expecting them, and because we’re so seemingly alone in the open ocean, it was particularly striking to have these two beautiful mammals choose to swim right next to us today.  I didn’t have time to grab my camera to capture the moment, but luckily many other people did, and Whitney even got great video footage so you too can experience this whale of a tale!

- Annie

Incubation Experiment

We all know that we are supposed to eat a balanced diet containing the Recommended Dietary Allowance of vitamins and minerals to maintain our health.  Humans, and all other organisms, require major and minor nutrients in well-defined quantities for healthy growth.   Marine phytoplankton, free floating marine plants, harvest the energy of the sun to fuel their growth, but they still need nutrients as the building blocks of their new cells.   The basic building blocks for marine plankton are carbon dioxide, water, nitrate, and phosphate.   The ocean generally has plenty of water and carbon dioxide, but can often be depleted in nitrate or phosphate.   If we think about photosynthesis as a balanced chemical reaction it is easy to use chemical stoichiometry to understand this limitation,

106 CO₂ + 120 H₂O + 16 HNO₃ + 1 H₃PO₄ → light →  (CH₂O)₁₀₆(NH₃)₁₆PO₄ + 137O₂

where (CH₂O)₁₀₆(NH₃)₁₆PO₄ is the chemical formula for an average phytoplankton.  Each mole of plankton requires 106 moles of carbon dioxide, 120 moles of water, 16 moles of nitrate (written as nitric acid), and 1 mole of phosphate (written as phosphoric acid).   The ratio of carbon to nutrients is often described as the Redfield Ratio after the biologist that first proposed the stoichiometry.

Nutrient Profiles. Phosphate is scaled up by 10.

We only need small amounts of the nutrients nitrate and phosphate to support photosynthesis, but they are always required, and are required in well-defined molar ratios.   In most freshwater lakes phosphate is limiting.  In the ocean, nitrate is most often limiting.   One of the questions that is being investigated on this cruise is what limits the growth of coccolithophores in the Southern Ocean.   In addition to nitrate, light and iron could also be limiting phytoplankton growth.   Light is required to drive photosynthesis.   Clearly, no phytoplankton can grow in the dark, but phytoplankton do grow under cloudy conditions and some species can grow very well.   Iron is a micronutrient that is also required of all plankton, but at very low levels – on the order of 0.001 moles Fe to a mole of phytoplankton.  To help answer the nutrient limitation questions, plankton incubation experiments are being performed on the deck of the ship.   Different samples of water are spiked with nutrients, metals, CO₂, and the plankton growth rates are being measured at different light levels.  These experiments will take months of analysis before the question of  phytoplankton limitation in this area of the ocean is understood.   In mean time, take a look at a “typical” Southern Ocean nutrient profile to see if you can spot evidence for nutrient limitation.   What do you think drives the profiles of the nutrients?   Use the oxygen profile as additional information.    The fluorescence data can be used as a proxy for phytoplankton biomass.

Our next blog will include video of whales around the ship.   The Redfield ratio is remarkably conserved in these huge creatures.   Using a daily feeding rate of 2000 kg of plankton a day, estimate how much phosphate and nitrate are released per day in the upper ocean by whale excretion?

- Whitney