NOAA Teacher at Sea: Nathan Pierantoni
University of Miami Ship R/V Walton Smith
South Florida Bimonthly Hydrographic Survey
Florida Bay, in transit from Dry Tortugas to Key West.
Thursday, April 7 2011
Weather Data from the Bridge
1400 hrs Local Time
Barometric pressure = 1017 Millibars
79 F
78% Humidity
Visibility = good
Wind SE 16 knots
Science and Technology Log
Dr. Neslon was very gracious and gave me free reign to learn as much as I could while aboard the R/V Walton Smith. Water sampling requires the most manpower and it is most common thing we are doing for this cruise, and therefore I have been involved in many vertical casts of the CTD. CTD stands for Conductivity, Temperature, and Depth, and when I refer to “the CTD” I am referring to the hefty apparatus that is pictured below, sitting on the fantail (the open deck at the stern of the ship). The procedure is as follows: as we get to our stations along our survey route, the boat stops and the we don our hardhats and life jackets and go out to the fantail,. We then lower the safety lines and prepare for a cast. Next, the captain goes to the stern of the upper deck where there is a winch cabin, from where he can pilot the ship and control the cast. The CTD is attached to a cable and is raised and lowered via an A-frame. The scientists give signals to the captain, and together, the device is lowered into the water where it does its work.
The CTD is actually a dual-purpose piece of equipment. It has sensors that measure conductivity (salinity), temperature, depth, chlorophyll, and dissolved oxygen. These sensors are built into a unit at the base of the apparatus and are protected by a metal cage.Above the sensor array is a rosette of tubes, which are able to collect water samples. Each tube holds 10 L of water, and our CDT has 12 tubes, called Nisken Bottles. The whole thing is electronically linked to the science deck through its cable, and in addition to the 2 scientists on deck who deploy the device, there is a CTD operator inside who monitors water parameter changes as the CTD goes from the surface to the bottom. This scientist is in communication with the captain in the winch cabin, and as the device returns to the surface the scientist is able to fire the Niskin bottles so that they fill with water. For example, we just finished a 340m CDT sample, and Nelson fired the CTD at three depths, 338 m, 70m, and 2 m. On the way down he was able to determine ‘where’ in the water column he wanted to collect his samples, because he was able to ‘watch’ the water parameters change on his computer monitor as the data from the CTD’s sensors streamed in. Interestingly, they fire two bottles at each depth in case one of them fails. It’s just another way to prevent against errors that would be too time consuming and thus too costly to fix. Once at the surface, the scientists and the winch operator guide the CTD back aboard the ship, and secure it to the deck.
While data from the sensors is logged and converted electronically to graphs, the chemical oceanographer begins her work. Cheryl Brown, aka ‘CB’ is an ocean scientist who I have had the pleasure of working with on the day shift. Cheryl works for the Cooperative Institute for Marine and Atmospheric Studies, a University of Miami institute that receives funding through NOAA. She participates in a variety of water quality projects, and spends about 25% of her time at sea. The other 75% of her work is in the lab, where she has multiple responsibilities that include filtration, data processing, and plotting of the samples from her fieldwork. This is common to most areas of field science, where for every hour of fieldwork yields at least double the time in the lab. CB has a degree in marine science, and specialized in marine invertebrates before finding her way to Miami.
The responsibilities on the chemistry deck are numerous. For each CDT deployment, there are a variety of samples that must be prepared from the water collected by the CTD. Each of this same series of samples is required for each depth of water that has been tested. On average, three depths are sampled per CTD deployment, but on this cruise some casts have collected water from four depths, and some have only collected water from the surface. The water from each depth is transferred to a bottle, which has been rinsed three times to avoid contamination, and brought into the wet lab. From there, a nutrient samples, chlorophyll samples, and dissolved CO2 samples are taken.
A nutrient sample is a general measure of ocean health, and includes many of the same samples that might be taken in a home aquarium, like ammonia, nitrates, and nitrites. To prepare the sample, we manually filter 50 ml of seawater into a sterile container, and preserve it with chloroform. It is then placed into the lab cooler. Finally, the time, location, depth, sample number, and collection number are logged.
The next step is to prepare a chlorophyll sample, and this is done with another process. In order to increase accuracy, two-200 ml samples are filtered through a small pad that is connected to a vacuum system. The water passes through the filter and is discarded, but the dissolved chlorophyll stays behind. Both small filters are placed into one vial, and the vial is stored in a liquid nitrogen container on deck. Then the samples are logged.
At some of our stations we have collected dissolved CO2 samples. This measure is also an important measure of ocean health, because CO2 is important to the photosynthetic processes that many reef organisms require. To collect a CO2 sample, a sterile flask is filled to the top with seawater, and 2 microliters of Mercury Chloride (HgCl2) are added. These samples are also logged.
This entire process gets repeated for each depth of water that was brought up in the tubes on the CTD. In the end, a whole lot of lab methods are practiced in a very short amount of time. You can imagine that as the week has gone on, these tasks have become easier and easier. At first, we were running stations about every half an hour, and the seas were quite rough. The amount of work to do in short intervals was a little bit overwhelming, but Cheryl let us all know that is would get easier as the week went on, and we she was right! As I finish up this log and we steam from the Tortugas back to the Keys I am looking forward to perfecting my CTD technique before we finish off the week!
Personal Log
It’s been really inspiring to get to know more about the people I am working with. Everyone here is very passionate about the work they are doing, and it is clear that if it weren’t for the love of the job they wouldn’t be out here bobbing around in the ocean! It is also interesting to hear about the different routes that people have taken to get here. This morning during breakfast I had the chance to talk at length with Cheryl about her recent Peace Corps experience. She was sent to the South Pacific island nation of Vanuatu for 27 months to do environmental work and to help facilitate a bank that was going to make micro-loans to women in business. When she got there, plans changed, and she ended up living on a small island called Paama. The island was 2 miles x 7 miles and has 21 villages spread around the coast. What had been an environmental mission turned into an educational one, and she ultimately spent her time on Paama rebuilding a primary school that had been destroyed by a cyclone. She had a canoe specially built for her so she could move about roadless island, and while on Paama she had to adapt to the lifestyle that sounds a lot like backcountry camping to me! Ultimately she had to jump islands on small planes, bargain with shipping captains and work with the entire community to get the school completed.
As I listened to Cheryl tell her story, enthralled by the adventure and romance of her experience, I was reminded of how lucky we are in America to have the education system that we have. It is my hope for my students and colleagues that you all really take advantage of the resources, facilities, and especially the technology what we probably take for granted at times. As I learn more about the future of oceanography I have been especially interested in the direction it is moving, toward space. As more and more remote sensing capabilities are developed, the need for ground proofing will also increase. What is clear to me is that oceanography, like all fields of science, will require dedicated researchers who are passionate about their work and skilled in technology, math, and engineering. There is only one place to get these skills, and its at school, and it requires practice, time, and patience. Thanks to Cheryl’s work, students in that small village on the coast of Paama are able to work toward their education. I challenge everyone at Heights Middle School, myself included, to do their personal best to taking advantage of all of the resources we have in order that our students will become the problem solvers of tomorrow!
I’ll keep posting pictures when I can, and I’m excited to come back to school on Monday!
Here is a shot from the CTD monitor inside the ship. The operator can see what is going on on deck, and follow the ater parameters at the same time.
In this shot Cheryl and I are preparing to Launch the CTD. I am signaling the winch operator.
Another shot of the fantail, and you can see the CTD controlled by a cable via the A-frame.
Here is the CTD collecting a surface sample.
Here I am in the process of collecting water out of a Niskin bottle, so that I can take it inside for preparation. Notice the instrumentation on the bottom of the CTD.
Here is a shot of Cheryl getting started in the lab on the sample preparation.
I like this shot, it shows a clean filter pad and a ‘dirty’ one. The pad attached to the vacuum has just finished filtering 200 ml of seawater. The materials on the pad will be analyzed back in Cheryl’s lab on land.
Here is a shot of Nelson Melo. He has been operating the CTD during the day, and he is holding a graph that charted Chlorophyll, temperature, O2, and salinity. This CTD was launched to a depth of 340 m.
Nelson’s work (which I described in my Tuesday log) and the data Cheryl pulls out of the samples we’ve collected will help to refine scientist’s capabilities for remote sensing in oceanography. I think its pretty significant that the latest issue of the scientific journal
Oceanography has a satellite on it. This is the direction that ocean science has headed!
Nice Sunset! Almost as good as our New Mexico sunsets!
