WHOI scientist Richard Camilli: developing a deep-sea chemical-sniffing bloodhound.
What specifically was your mission and research on Aquarius?
I was there to operate an instrument called a TETHYS mass spectrometer. It's an in-situ underwater mass spectrometer that I designed and built in partnership with Monitor Instruments Co. Mass spectrometers identify and measure the composition of chemical compounds. In this case, we used a mass spectrometer to monitor and investigate biochemical pathways in sponges, in which they're converting nitrogen from one type of molecule to another.
I thought mass spectrometers were big and needed special rooms. How did you make one that works under the sea?
One engineering challenge was to make TETHYS small. It's about the size of a watermelon. Most mass spectrometers are much larger than that--one at WHOI is the size of an entire building. This is one of the smallest and lowest-powered mass spectrometer designs in the world. It requires only about 25 watts--less power than the light in your refrigerator.
Mass spectrometers generally are designed to operate in controlled environments--with steady temperatures, no vibrations or electronic interference. The TETHYS instrument is designed to operate in extreme environments--under high pressure, vibration, and all kinds of temperatures. These are challenging from a design perspective. The other challenges are data storage and maintaining calibration while it's taking measurements.
So you can bring the mass spectrometer to a sample under water, instead of vice versa. What are the advantages of that?
First, it's the quantity of data that you get. In 10 days in Aquarius, we collected 10,000 measurements. Imagine what 10,000 water samples would look like stacked up. Also, when you take a sample up to the surface, the pressure changes, the temperature changes, and typically you expose it to light and other things that may cause a chemical transformation. If you don't instantly measure what organisms are doing right there in seawater, the quality of your measurements could suffer.
What are other challenges of using a mass spec under water?
One challenge is that mass spectrometers require a near-perfect vacuum. Typically, inside the instrument, pressures are between a millionth and a billionth of an atmosphere. (One atmosphere is what we experience on Earth's surface.) Also, mass spectrometers typically hate water. So we have to let compounds inside, but we cannot let in any water. We use membranes to do that. It's not unlike the way desalinization systems work using reverse osmosis.
One pleasant shock to me was that when we were doing these experiments, we put them in enclosures to limit the supply of ambient water and just recirculated water through their tissues. Well, one of the things the mass spectrometer detected was that the enclosure material itself was giving off solvents into the water. We managed to track the solvents down to the adhesive from a few pieces of tape in the enclosures. Obviously, we had to go back and solve that problem. But it was great that we could see this interference while we were working and knew how to fix it.
How accurate is the underwater device?
Typically, we can measure chemicals at concentrations down to less than a part per billion. We can also do in-situ measurements of not just molecules, but specific isotopes of elements. The isotopes tell you a great deal about the origin of that chemical.
For example, in our Aquarius experiments, we dosed sponges with an ammonium chloride isotope containing a nitrogen atom with an extra neutron. We used the TETHYS instrument to track that isotope and watch it be transformed by the sponge into nitrogen gas.
What did you find?
We found evidence that a particular kind of sponge can convert ammonia from the ocean into nitrogen gas through a multistep process called "Anamox." It was discovered maybe a decade ago, but it was thought that only microbes living in the ocean or ocean sediments could do it. With our research, we've found evidence that the process also is happening in these sponges. It has big implications for how nitrogen cycles through the ocean ecosystem.
What are those implications?
Basically, these sponges may have a competitive advantage over other organisms that cannot use ammonia. In Florida over the past 20 years or so, reef ecosystems have shifted rapidly: Corals are dying off, and sponges are becoming more numerous. It may be that an increased abundance of various nitrogenous compounds in the ocean there--perhaps from increasing fertilizer runoff--is allowing sponges and other organisms to out-compete the corals.
What more can you tell us about the sponges?
Well, for example, one variety of sponges is known as "stinker sponges." If you were to cut a piece out of one and bring it to the surface, it would have a pretty foul odor. But that smell indicates that this sponge is unlike other sponges. And it provides evidence of the biochemistry that's going on in the sponges, which may be engaging in sort of chemical warfare to fend off predators.
Did you look at other aspects of sponges with the TETHYS?
We looked at oxygen consumption and C[O.sub.2] (carbon dioxide) production by the sponges. They engage in aerobic respiration just like you or me, but they have huge pumping rates and very high metabolic rates. Sometimes they turn on and pump really hard, and sometimes they just shut off. Nobody really knows why. So their biochemical functioning is a lot more complicated than we tend to appreciate, particularly in terms of the C[O.sub.2] production. That has huge implications for the acidification of the reef. Increasing C[O.sub.2] dissolved in seawater generally yields more carbonic acid, and that can make it harder for corals to build their skeletons.
Now that you've completed this research trip, what's next?
There was a follow-up mission in mid-October. I couldn't go because I went on an expedition in the Pacific, but one of my brothers is a diver and an oceanographer, so he took my place. Overall, the ultimate goal of these projects is to identify if sponges are capable of denitrification [turning ammonia into nitrogen gas], and if so, to identify the biochemical pathways and to look at this issue of acidification of the reef caused by C[O.sub.2]-producing organisms like sponges. Our work down there really has just begun.
Have you used TETHYS for other kinds of research?
Yes, mass spectrometry has broad applications in oceanography. I used a mass spectrometer on a human-occupied submersible to study an underwater volcano in the Aegean Sea. It was the first time anyone did this, so the technological complexity was daunting. During the initial descent, I was on pins and needles, monitoring equipment status while I went through mental checklists trying to anticipate any problem before it arose. But as we reached the flank of the volcano and data began rolling in, I had one of those Zen moments. We could use the mass spectrometer's chemical readings to guide us through the darkness right to one of the volcano's active vents.
Following Hurricane Katrina, I began using mass spectrometers to help federal agencies with oil spill cleanup efforts in the Gulf of Mexico. That work was a great success, and now my group routinely gets called to assist when spills occur. Since then, we have developed new techniques that can pinpoint leaks in infrastructure debris and map contaminated seafloor sediments in real time.
On my recent expedition off the coast of Peru, we equipped TETHYS mass spectrometers on seafloor landers developed by the German ocean research institute IFM-Geomar. The expedition was an international collaboration with the government of Peru, IFM-Geomar, and the WHOI Access to the Sea Program to study the biochemical adaptations that bottom-dwelling organisms make during certain seasons when waters becomes anoxic (depleted of oxygen). These robotic landers are roughly the same size and shape as the Apollo moon lander. They're designed to collect samples and conduct incubation experiments for several days at a time, until they hear an acoustic command from the ship to return to the surface.
Development of the TETHYS mass spectrometer was supported by a research grant from the National Ocean Partnership Program.
See audio slideshow at whoi.edu/oceanus/camilli
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|Title Annotation:||A CONVERSATION WITH ...|
|Date:||Oct 1, 2009|
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