“Nuts” (pronounced ‘newts!’) in the Ross Sea

My name is Meredith and I am a first year graduate student studying biogeochemistry in the Hansell Lab at the University of Miami (RSMAS). Lucky for me, my first significant research cruise has brought me to a region of the world more mysterious and wonderful than I could have ever imagined!

Terra Nova Bay. Photo Credit: G. McDonald.

Emperors on Sulzberger Ice Shelf near Cape Colbeck. Photo Credit: R. Dunbar.

Sunset over pancake ice. Photo credit: M. Jennings.

Cape Colbeck Emperors checking us out at Sulzberger Ice Shelf. Photo Credit: A. Westman.

However, I frequently have to remind myself that I did not travel all the way to the edge of the world from Florida just for amazing sightseeing! I spend a portion of my time learning from other research groups on board as a crash course in 'Oceanography 101' but I also have my own responsibilities in the lab. Primarily, I collect seawater samples from a device that collects water from great depths (called a CTD rosette) to analyze for “nuts” or nutrients (namely phosphate, silicic acid and nitrate), which are essential players in the biogeochemistry of the Ross Sea.

Biogeochemistry is the study of the chemical, physical, geological, and biological processes and reactions that govern the composition of the natural environment. It deals with 1) how biological and geochemical processes affect organic matter and its principle components (carbon, nitrogen, phosphorus, etc.) in the biosphere, and 2) how chemical elements and compounds (such as nutrients) cycle between the living and non-living parts of an ecosystem.

Acting as biogeochemical fingerprints, nutrient distributions can help us explain and characterize properties in the marine environment such as phytoplankton productivity and seasonal turnover of the water column. For example, we expect lower nutrient concentrations in the surface layer because available nutrients have been consumed by phytoplankton to fuel a summer bloom. Below the surface layer, concentrations of nutrients are typically higher due to the recycling of organic material by bacteria and should be similar to the nutrient pool available prior to a bloom. Therefore, we can get an idea of the flux of nutrients during phytoplankton blooms. If none of this is making sense, just think of nutrients available to phytoplankton as fresh chocolate chip cookies available to a bunch of graduate students (and Roberta)...

A schematic of the biological pump in action! Image from Ocean Biogeochemical Dynamics, by Drs. Jorge L. Sarmiento and Nicolas Gruber, used in the marine biogeochemistry course that my advisor Dennis Hansell is teaching us aboard the Palmer.

Analyzing the concentrations and fluxes of nutrients will help us understand the broader picture of the biological pump, which is the cycle of organic matter production, its export from the surface ocean as sinking particles (downward transport), and finally its remineralization (conversion from organic carbon to dissolved CO₂). On board, I have been analyzing silicic acid in seawater using a reaction that produces a beautiful blue color in the presence of the nutrient by adding a few chemicals [an acidified molybdate reagent and a reducing mixed reagent (electron donor)].

This blue acidified and reduced complex displays a max absorbance at 810 nm. Photo credit: M. Jennings.

After letting the blue color develop for a couple hours, I use an instrument called a spectrophotometer to detect the light absorbed by this blue solution to calculate silicic acid concentrations after calibrating the instrument with known concentrations of the nutrient. A similar method using a colored chemical complex is also used to analyze phosphate (performed onboard by Sarah).  Nitrate, the third nutrient we are considering, requires a completely different method for analysis, which we will perform back in our lab in Miami.

Amanda and me (front right) working hard at the spectrophotometer. Photo credit: A. Lee.

The Ross Sea is an extremely productive system, making it a very interesting place to study (if our pictures of the gorgeous views and magnificent animals haven't already convinced you!). Even after intense phytoplankton blooms, the nutrient concentrations are much higher in these surface waters than in many parts of the world. Our proposed work has been very exciting to watch unfold as we are discovering what is happening to the system's biogeochemistry at the end of the productive season. I feel fortunate to be a part of this process and am excited to learn more in the weeks to come!

Party in the ice fort (complete with hot cocoa)!  Photo credit: D. Mucciarone.

–Meredith

The Lab Van: Bringing a little bit of Charleston to the Ross Sea

When research brings us scientists out to sea (as it frequently does) one of the biggest considerations is the logistics of bringing our equipment with us. This includes a lot more stuff than one may realize. In addition to consumables (thousands upon thousands of sample vials and tubes, bottles, reagents, preservatives, pipet tips, zip ties, bungee cords, chocolate, sodas, coffee, etc.) we also have expensive, fragile, and often quite bulky instruments. We can either box these items up and ship them in several installments, or we can simply send an entire lab already stocked. The DiTullio lab group from the College of Charleston has the capability to do the latter.

Our mobile lab (or lab van for short), which we have nicknamed Cougartown after the College's mascot, is a fully functional flow cytometry and gas chromatography laboratory. The van’s construction is based on a standard 20ft shipping container so it is roughly half the length of a tractor trailer, which makes it easier to send anywhere in the world. It was custom built according to specifications laid out by one of our research associates, Dr. Peter Lee. He and I spend the majority of our day (a 12-20 hour day, not a regular 9 to 5’er) in Cougartown, and it suits us just fine, though the interior is not as spacious as you may assume.

“Scientific Laboratory?” More like “Home Away from Home.” Photo credit: J. Kendrick.

Cougartown on the back deck of the NBP during a balmy Antarctic day. Photo credit: P. Lee.

Dr. Lee (Petey), a seasoned and accomplished chemical oceanographer, runs our cryogenic purge and trap gas chromatograph. Using this instrument he extracts dimethylsulfide (DMS) and dimethylsulphoniopropionate (DMSP) from seawater and measures their concentrations down to nanomoles (10^-9) per liter. These compounds are extremely important products of cellular and chemical activity in the ocean that have a disproportionately large effect on the composition of our atmosphere and the regulation of earth's climate. I'd get into specifics, but that's a blog post in itself. Suffice it to say, life would have a hard time existing without them.

My job in the van is to run our high-speed sorting flow cytometer, the Beckman Coulter MoFlo Astrios. MoFlo is short for Modular Flow Cytometer, sorry if that disappoints anyone, it did me.  A sorting flow cytometer (or just “the flow”) is a lot like one of those coin-sorter banks you may have had as a kid. The difference is that the flow sorts microscopic particles at rates of up to tens of thousands of particles per second. When a sample is put into the sample chamber it is pressurized, run through a special nozzle, and shot straight down in a stream 70 microns wide (about the size of a human hair). Cells travel down the stream in single-file past 3 lasers of different wavelengths. As the cells hit the laser beams they scatter the light in several directions. The direction and degree to which they do this gives us an idea of the relative size of the cells. Several compounds within the cells will fluoresce in response to the lasers as well (think of how things glow when you stand in a black light). The wavelengths and intensities of the fluorescence are collected by the instrument and plotted on graphs against one another allowing us to tell different species apart based on how they “glow.” This is a little more difficult in the Southern Ocean as a lot of the phytoplankton species are similar sizes with very similar cellular make-ups. The flow has a few tricks it can do to get around this problem, but I'm not writing a technical essay here.

So how does it “sort” the cells? That's where it gets really cool. A special crystal in the nozzle vibrates the stream causing it to break into distinct droplets with one cell per droplet.  Based on criteria that we give the instrument, it attaches an electric charge to the droplets, which are then run past two powerful electromagnetic plates. When a droplet you want passes the plates, a small electric pulse literally pulls that droplet out of the stream and drops the cell directly into a test tube under it. The MoFlo Astrios can sort into 6 different test tubes simultaneously, meaning those magnetic plates can turn a single stream into 7 streams (the original + 6 more).

Here's simplified diagram of how the flow works. Pretty cool, huh? Reprinted with permission of Beckman Coulter.

By sorting seawater we can separate the phytoplankton community into its constituent species after which we can start cultures of new strains that may not have been isolated before. We can also use the sorted samples to run experiments, or perform species-specific analyses that give us more detailed information than analyzing whole seawater. After a month at sea I've turned dozens of seawater samples into hundreds of sorted cell cultures. 

That's what we do in the van, so what's it like to spend pretty much all our time in there? There are a lot of pros and cons to bringing your lab with you. On the plus side, setting up your workspace at the beginning of the cruise is easier since it's mostly set up already. While everyone else is unpacking boxes, putting things together, and strapping things down (everything has to be tied down at sea) we just have to turn our instruments on and calibrate them since we did all the setting up and tying down months before the cruise. We also have our own soundsystem and since there's only two of us in the van, there's very little argument about what kind of music to play while we're working. Another great thing about working in the van is that our workstations are literally the same two we use back in Charleston so it's like taking a piece of home with us when we're so far away.

Petey and me at our workstations. Photo credit: A. Margolin.

That last one is kind of a pro and a con, since it limits the new experiences you have. It also isolates you somewhat from the rest of the science team. Two months at sea is long enough that you still get to know everyone, but you miss out on a lot of inside jokes and pictures (and you frequently don't get told when they're making liquid nitrogen ice cream in the galley). A more technical problem is that the flow is pretty sensitive to vibration, and the van is sitting on the back deck directly above the ship's propellers. When we chew up big chunks of ice it shakes us pretty violently and that makes work a lot harder. Being on the back deck also means going between the van and the rest of the ship takes you across a weather deck (i.e. outside). That's kind of nice on tropical cruises, but Antarctica is quite cold and the back deck is prone to boarding seas and changing weather. You never know if you'll be walking out into snow, icy winds, or frigid, ankle-deep water the next time you have to go to the head. In all honesty though, that kind of adds to the sense of adventure that we all get out here.  Speaking of adventure, here's what it looks like after a wave washes completely over the top of the van (with us inside) in super cold weather.

It might be hard to see, but the whole thing is covered in about a ½ inch of ice. Photo credits: P. Lee.

What isn't nice in tropical climes, but isn't so bad here, is that all the electronics generate a lot of heat. Even when the outside temperature is 20°C degrees below zero (Like in the first photo up there) we have the air conditioner running to keep it at room temperature!

Cougartown has been our home base for two cruises so far and apart from a few minor issues here and there it's worked out great. The freedom and comfort it affords us is definitely worth any slight inconveniences. We also make improvements to the van and to our instruments in between cruises so it gets more and more comfortable and functional all the time!

Even an instrument like the Astrios needs a little fixing now and again. Here I am replacing some components in the electronics rack. Photo credit: P. Lee.

–Jacob

Give Us the Water! How Much? All of It!!

Well, just how much water IS there to be had in the Ross Sea? There are approximately 265,000,000,000,000,000 liters*.  Did that number go in one eye and out the other? It did for me. Let’s just say that’s a lot of water and scientists want to know about all of it—where it came from, where its going, the chemistry, the biology, temperature, salinity, floating particles, etc. etc. etc….

There are two issues I’d like to explain to you:

1.              Where do you decide to collect this water?

2.              How do you collect it?

Just think, after reading this blog you’ll be that much more prepared for Thursday Night Trivia or to impress your friends at a dinner party!

Where oh Where?!

Obviously we cannot take ALL of the water in the world and measure its properties.  We can, however, do our best to characterize as much of it as possible. In fact, all over the world cruises like the one we are on are out collecting information about the oceans. Using software, like Ocean Data View, scientists can have a pretty good idea of what is going on. All of these blue dots are locations where water was analyzed.

A map that Allison made using the GLODAP dataset with the program Ocean Data View (ODV), which she learned how to use in a course Dennis is teaching us aboard the Palmer, entitled Marine Biogeochemistry.

This is a map of the Ross Sea, which displays locations where samples were collected during TRACERS. Map credit: A. Lee using ODV.

How do scientists even begin to know where to choose to take samples? Let’s explain this with an analogy we might all relate to:

If you know that your dog hid your favorite pair of slippers in the backyard and you wanted to find them, where would you look? Would you start in one corner of the yard and work your way to the other corner in rows? Probably not. You wouldn’t start your search aimlessly looking everywhere, that would take you all evening and you don’t want to miss your favorite showing of The Simpsons! You’d have some sort of plan and rule out certain areas first. You would look for dirt that seems to have been dug up, you may look under the dogs favorite corner, you may even look under the porch. If you knew your dog’s behavior well enough, then you might even know exactly where she’s hidden your slippers!

Scientists do the same thing with oceanography. We pour over charts and based on the knowledge of where water moves, how water moves, the topography of the ocean bottom (bathymetry) and the location of living organisms such as algae, scientists choose these certain “hotspots” and start there.

We have drawn a line that we would like to investigate. In the upper right corner is a photo of chlorophyll (or algae) from satellite data. Photo credit: A. Lee.

I think it is time to introduce the HOW we collect the water:

This is the old-school method: Tossing the Pail. When you need deeper depths you simply add more rocks or weight to the bottom of the bucket so it sinks. Photo credit: A. Margolin.

Hmm something doesn’t seem right about this method. It’s the modern age! Isn’t there some sort of fancy technology we can use for this? Why, yes, yes there is. But this requires us to dive in to some terminology.  Let’s cater to you visual learners:

This is the CTD rosette that we use to sample the ocean. Photo credit: A. Lee.

The Niskin bottles hold 12 liters of water each and are arranged in a circle called a rosette. Commonly, we just refer to the entire thing as a CTD but technically, a CTD is the little package of sensors attached to the Rosette that measure Conductivity (Salinity), Temperature and Depth. The information about the salinity, temperature, and depth, as well as fluorescence of chlorophyll (algae) and oxygen levels are sent to the ship as we lower the CTD package to the bottom of the ocean.

On the left, Rob and Kevin look at the CTD data as the rosette is lowered. On the right, the CTD data is displayed on the computer. Photo credits: A. Lee.

We can look on the screen as the profiles are being recorded and decide on what depths the bottles should close at as the CTD comes back up to the surface. Once the CTD reaches the bottom, one of the ET’s (either Sheldon or Kevin) will push a button to close Niskin bottles at the desired depth, collecting that water for us to analyze in our various laboratories on the Palmer. 

The CTD rosette being deployed. Photo credit: A. Lee.

Each time this “CTD” or “Rosette” goes in to the water it is called a “cast”. Over the past 33 days, we have taken 135 casts. We collect seawater about 4.5 times a day (in addition, each time it enters and exits the water we have to do 25 pushups). That doesn’t seem like a lot but considering we have to actually DO something with all the water once we collect it, time flies and its already time for the next cast.**

Now that the CTD is on deck, everyone wants the water from it. Before anyone can take the water, a “water budget” is created so there will be no fighting for who goes first. Before the cruise started, scientists sat down to discuss the volumes they needed based on the types of studies/analyses they intended to do. Those people collecting for gases go first because once the volume leaves the Niskin, air fills the top and can change the gas composition inside. Everyone goes in order and if you cut in line you get elbowed.

Santiago patiently waits just outside the Baltic room while (from left to right) Dave, Rob, Cassandra and Petey sample for gases. Photo credit: A. Lee.

Once everyone has taken their share of water, we each head back to the lab to begin our analysis or collection method to store it for later analysis.

Dave taking a break from eating desserts to do some POC’ing, Roberta’s filtration setup for microbes, Rachel in the lab ready to analyze some phytoplankton, and Meredith preparing for nutrient analysis. Photo credits: A. Lee.

To read more about exactly what is done with the water by each scientist on board, stay tuned to more blog postings!!

–Allison

PS – Check out Cassandra’s new National Geographic post on TRACERS!!! http://newswatch.nationalgeographic.com/2013/03/12/fighting-for-the-last-tomato-surviving-a-field-season-in-antarctica/

*Yes, I actually calculated that with the help of Kim Goetz and GIS software. The Ross Sea is a small blip on the map and water is circulating in and out constantly so there is no real fixed volume.  

** Now that you know some terms I want to throw some more calculations at those of you who like to nerd-out. Just hold my hand and follow me: If our Rosette has 20 Niskin bottles that each hold 12 liters, then that is approximately 240 liters per cast that we can take. If we were to actually take all of the water in the Ross Sea averaging 4.5 casts a day it would take us ONLY 245,000,000,000,000 days or 672,000,000,000 years! So ya, moral of the story, thank Bessy for software that helps analyze ocean data because there is no way to sample all of the water in the Ross Sea much less the entire global ocean!