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Free-drifting icebergs as proliferating dispersion sites of iron
enrichment, organic carbon production and export in
the Southern Ocean

R/V Nathaniel B. Palmer

Let's get familiar with the R/V Nathaniel B. Palmer's vast scientific resources...

Wet LabIceCUBE, the Remotely Operated Vehicle (ROV), lives here with its tether systems. The IceCUBE always operates with a video camera, and the ability to capture still images. It can also be set up with two configurations, one for large volume water collections, and the other for discrete iceberg-associated biota, discrete seawater sample (using the 2-liter "gulper") or a slurping mechanism to collect free-living zooplankton in the vicinity of the iceberg. We will obtain samples using the Phantom with both configurations. See photo 6.

Wet lab

Photo 6: The MBARI engineers put the final touches on the IceCUBE ROV.

Baltic Room – This is where the conductivity, temperature, depth (CTD) instrument and 24-bottle rosette are housed. The CTD and rosette are mainstays of oceanographic sampling, in which the rosette, holding bottles and instruments is dropped vertically through the water column. The bottles are open on the way down to the deepest sample collection point, and then electronically triggered to close and capture water at defined depths on its way back to the surface. This water is used for both chemical and biological characterizations, and the CTD data (and associated instruments that are included with the package) is used for interpreting the physical structure of the water column. The Baltic room has a door which opens to the outside, and the rosette is launched directly from there. This makes it quite convenient during freezing/turbulent conditions to collect the water from the cast – in a weather sealed room. See photo 7.

Baltic Room

Photo 7: The Baltic room houses the CTD and 24-bottle rosette
which are deployed directly from this room.

Aft Control Room – This room houses the controls used to deploy the ROV and the CTD/Rosette from the starboard winch. Scientists can view live video and photographic images returned from the Phantom ROV. See photo 8.

Aft Control Room

Photo 8: The view from the Aft Control Room allows scientists to monitor
the winch cables and instruments as they're deployed and retrieved,
as well as the occasional seal or whale.

Bio Lab – In addition to bench-top lab space, the Bio Lab is equipped with a cold room, which we'll use for seawater filtration to minimize variations with the microbes' in-vivo environment, and a positive-pressure fume hood, to protect our samples from contamination and to protect us from fumes. The Murray Field Team will conduct the bulk of our work in the cold room set to ambient temperatures of the ocean (-1°C), including the exoenzyme assays, concentrating large volumes of water for molecular biology assays, and preparing microscopy samples. We share the Bio Lab with the other half of the microbial plankton group - Dr. Vernet's PhytoPhanatics - who make strong coffee and have an espresso machine. Numquam dormiemus! (we never sleep!) See photo 9.

Bio lab

Photo 9: The Bio Lab awaits its first set of samples.

Hydro Lab – With plenty of sinks, floor drains, and bench space, this lab is a wet chemistry lab, where the PhytoPhanatics will quantify chlorophyll and inorganic nutrients in seawater samples. See photo 10.

Hydro lab

Photo 10: Setting up chlorophyll assays in the Wet Lab.

Aft Dry Lab and the Clean Bubble – This lab provides a dry area for the engineers to work on deployed instruments such as the Lagrangian sediment traps (LSTs). One bench is dedicated to the MOCNESS crew who will be sorting animals here, such as jellyfish, salps, polychete worms, and amphipods, that they collect from their 10-m2 (3-mm mesh) and 1-m2 (100 µm mesh) nets. At the rear of the Aft Dry Lab, the Iron Men, led by Dr. Ben Twining, have erected a positive-pressure "Clean Bubble" to collect samples with as little potential contamination as possible, for their iron (Fe) assays. They'll filter water to collect particulate Fe and isolate the colloidal Fe fraction that hovers between the particulate and dissolved fractions (between approximately 0.02 µm and 4 µm). We'll use these data to interpret the effects of the additions to the culture experiment. See photo 11.

Aft dry lab

Photo 11: Tucked into the back of the Aft Dry Lab, MBARI engineers
calibrate instruments prior to deployment.

Trace Metal Van – Iron concentrations in seawater are very low, ranging from 0.1 nanomolar (nm), in iron-depleted regions, to 0.5 – 1 nm in iron-rich regions. Therefore, we must remove any potential source of iron contamination, including the iron cable to deploy the sampling equipment, metal parts on the sampling equipment, and non-vital metal parts (benches, table legs) in the sample processing area. The Iron Men use a metal-free bottle system (similar to our Rosette/CTD), with a non-metal cable, to obtain samples as free of metal contamination as possible. The Trace Metal Van is equipped with high-volume HEPA filters to remove potential airborne sources of metal contaminants. The Iron Men will process water samples here to quantify Fe+2 (reduced iron), total dissolved Fe (as Fe+2 and Fe+3), and Fe-binding ligands, which are organic molecules that sequester iron and may provide an iron source for microbes in the seawater. See photo 12.

Trace metal van

Photo 12.

Rad Van – All work with radioactive isotopes takes place in the "Rad (radiation) Van." This is where we'll run leucine assays to measure the incorporation of leucine, an amino acid, labeled with tritium into cellular proteins. As part of a simulated in situ incubation, the PhytoPhanatics will collect samples from various depths within the water column and incubate them (Carbon-14) 14C, to measure carbon fixation (= primary production). They will also use 14C to quantify chlorophyll versus light intensity. See photo 13.

Rad Van

Photo 13: Since we use radio-isotope labeled compounds in the Rad Van,
all materials and waste must be isolated for disposal, and scientists must take
special precautions to protect themselves and others from exposure.

Light Van – We'll use the light van to simulate the daylight for our culture experiment. Light within the color spectrum gets absorbed as it passes deeper into the water column. Red, yellow, and violet light are absorbed at shallower depths, then green, with the blue light penetrating deepest within our sample range. Since blue light is present throughout the water column, we use blue lamps as the best approximation of the light at the depth of sample collection. The blue light simulates the light quantity and the wavelength, approximately 400-700 nanometers that penetrate the ocean. The temperature of the seawater we collect our samples from is -1.0°C, so like the cold room in the Bio Lab, the Light Van is kept cold to simulate the organisms' natural environment. See photo 14.

Light van

Photo 14: The Light Van simulates the approximate quantity and intensity of light
represented within the water column where we collect seawater samples.

Dry Lab – The mother lode of all data is collected here, where computers interface with the ship's navigational systems, such as GPS, sonar, Acoustic Doppler Current Profiler (ADCP), and other tools to evaluate where we are in space and in relation to the icebergs. In addition, current weather conditions and sea surface properties (temperature, salinity, fluorescence, pCO2) are recorded here. Dr. John Helly will use these data to locate and track our icebergs. See photo 15.

Dry lab

Photo 15: The instrumental version of a command station,
the Dry Lab manages data from the ship's navigational instruments.

E-Lab – The Electronics lab provides public computers, plotters, and printers – but no internet access! See photo 16.

Electronics lab

With no internet access, the E-Lab can get pretty quiet.