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
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