NOAA Teacher at Sea
Onboard NOAA Ship Oregon II
July 10 – 19, 2013
Weather and Location:
Time: 21:24 Greenwich Mean Time (5:24 p.m. in Rockville, MD)
Speed (knots): 3.00
Water temperature: 28.10 degrees Celsius
Salinity (PSU = Practical Salinity Units): 34.07
Air temperature: 29.00 degrees Celsius
Relative Humidity: 68%
Wind Speed (knots): 17.15
Barometric Pressure (mb): 1018.96
Depth (m) = 187.2
As you can see if you have been following the Ship Tracker website, we have been making our way back towards Pascagoula. We still have some stations to work, and won’t be reaching the dock until Friday morning, but we will continue to head in that direction. The weather has gotten a bit windier, with much larger swells over the last couple of days. This has made collecting the plankton even more interesting. With the wind frequently above twenty knots, handling the equipment becomes much more dangerous. Some procedures need to be changed a bit for the sake of safety. Luckily, the deck crew, Tim, James, and Chuck, are on top of things. They are pretty funny to work with, too!
Science and Technology Log
Water Titrations to Check Cissolved Oxygen Levels
The plankton stations have continued, with the biggest changes being how much sargassum (seaweed) we have needed to rinse out and go through, and the different kinds of tiny animal life we have observed. I mentioned in an earlier blog that the scientists must periodically do water titrations to verify that the readings taken from the CTD are correct and nothing is malfunctioning. I had an opportunity to perform some real chemistry as Kim Johnson, the chief scientist, walked me through the water titration steps.
First we had to collect the water samples from the CTD. Remember, we are testing the oxygen levels, so it is important to collect the water samples without allowing bubbles to form, which might add oxygen to the sample. You would be surprised at how hard this is! A flexible tube is attached to one of the three Niskin Bottles on the CTD tank, and before any water is put into the jars, all of the air bubbles in the tube must be squeezed out. This is an art! Then the water can be transferred to the jars through the tube, holding the end of the tube against the side of the beaker to avoid making bubbles. The stoppers are then gently put into the glass jars, again to avoid the addition of oxygen to the samples. It is important to keep the water samples from getting too hot if you are not going to do the titrations right away. Can you think of why heat might create a problem when doing a titration? Also, we test three samples. Why do you think testing three beakers is important?
Now we are ready to start the mad chemist part! The chemicals used, and their amounts, are very specific, and the directions are posted in the lab so that you can always check your memory. First, two milliliters of manganous sulfate is added to each sample. The stopper is replaced after adding each substance, and the jars are turned upside down and back several times to mix the solution. The second substance added is two milliliters of azide-iodide solution. After the solution is gently mixed, the jars need to stand for ten to twenty minutes. When you come back after twenty minutes, you will see that there is a cloudy substance in each jar. This first part of the process causes the chemical bond between the hydrogen and the oxygen to break, and the oxygen forms new bonds with the added chemicals.
At this point, the oxygen is fixed and we don’t need to worry about introducing more oxygen to the samples. Next, we added two milliliters of sulfuric acid to each jar. This must be done very carefully because sulfuric acid is very harmful. However, once it is added, the sulfuric acid is neutralized and the solution in the sample jars is not harmful. (Remember the acid/neutral/base tests we did in class with lemon juice, vinegar, and Alka Seltzer, using a pH scale?)
Now we have a yellowish liquid and I will be adding phenylarsine oxide, drop by drop. This is the titration part. When the color turns clear, we can look at how much phenylarsine oxide was needed and that will tell us how much dissolved oxygen was present in the sample. This new chemical will bond with the oxygen molecules and cause a color change. However, because the change from yellow is hard to see, I added one milliliter of a starch solution for the only purpose of turning the sample blue. This way the color change back to clear is easier to see.
The sample is poured into a wide-mouthed beaker and a magnetic stirrer is added to the beaker. This is a small, magnetic bar that spins when it is on the metal stand. Drops of the phenylarsine oxide are allowed to slowly drip from a burette into the sample. A burette is a very tall, thin, glass pipe-like container that allows easy adjustment of the flow of liquid, and allows for easy reading of very small amounts.
Once the sample starts to lose its color, you know you are close. One or two more drops and you will shut the valve on the burette and read the amount that was mixed into the sample.
My samples showed dissolved oxygen amounts of 6.4, 6.5, and 6.5 milligrams per liter. The CTD showed dissolved oxygen of 6.4 mg/l. Since our results were very close, we are confident that the CTD is working well.
Remember, levels below 2% are considered hypoxic. 6.4% is a very healthy dissolved oxygen reading. This is what we expect as we move further from developed land, but it is still reassuring to see the healthy levels.
Later I tried another titration without supervision and found consistent readings of 4.9 mg/ mg/l oxygen. However the CTD reading was 4.35 mg/l. I guess I need more practice!
Buoy Rescue Mission
Yesterday we had the opportunity to participate in a buoy rescue mission. Another organization had deployed a wave buoy, or a wave runner, in the middle of the Gulf of Mexico that had been damaged, and was no longer able to give correct readings on things like current and wave height. We were in the area, and agreed to retrieve the buoy. As we got closer to the GPS signal, we spotted a large orange ball with an eight foot (about) antenna sticking out of it. Oregon II’s small motor boat was launched and we set about collecting the buoy.
As we reached it, the deck crew and the CO noticed some things about the buoy that were inconsistent with the description.
After making a telephone call, the CO told the crew to come back to the ship. We had come across the wrong buoy! Off we went in search of the correct one, which we found about half a mile away. This one looked more like a surfboard and was fairly easy to get aboard the ship, using the crane. That mission was accomplished, but we all marveled at the odds of finding two wave buoys within half a mile of each other in the middle of the Gulf of Mexico!
A Week at Sea
While I am still enjoying the cruise and the work, I have had a few days of queasiness. Taking the seasick medicine helps a lot, so I am sticking with that for a few days. Nights have been fine, and the rocking of the ship really is like being rocked in a cradle. I hope I’ll be able to sleep when I am in a stationary bed back home!
Being on a cruise on a small ship brings me back to my days of living in a college dormitory. You are living in very close quarters, eating every meal together, spending large amounts of time together, and really getting to know the people who are on your watch. I have had a great group to work with – people with a lot of knowledge, and great senses of humor! Victoria, a college intern, has been a newbie with me. We have learned a lot from the other scientists, Andre and Joey, on our watch, as well as from our chief scientist, Kimberley Johnson. Tim, James, and Chuck are the deckhands on our watch, and they do most of the heavy work, like lifting the equipment and running the J frame, winches and cranes. Sometimes we are working with the equipment for forty-five minutes at a time. The deckhands, while very serious about safety, keep us laughing the entire time. As I am finishing this entry, we are heading towards home. It will be nice to be on land again, but I will also miss the many different personalities I was lucky enough to get to know.
Did You Know?
The Gulf of Mexico covers an area that is about 615,000 square miles.
An area named “Sigsbee Deep” is located in the southwestern part of the Gulf. It is more than 300 miles long and more than 14,383 feet deep at its deepest point. It is often referred to as the “Grand Canyon under the sea”.
The Gulf’s coastal wetlands cover over five million acres, which is an area equal to about one-half of the area of the U.S. It is the home to twenty-four endangered and threatened species and critical habitats.
It is estimated that 50% of the Gulf’s inland and coastal wetlands have been lost and that up to 80% of the Gulf’s sea grasses have been lost in some areas. The continual loss of wetlands (about a football field a year) around the Mississippi Delta, a large land area near where the Mississippi River flows into the Gulf of Mexico, changes how hurricanes impact the coast of the Gulf. With fewer wetlands to absorb the impact of the hurricane, the hurricanes hit the populated areas with much greater force.
For more facts about the Gulf of Mexico, visit http://www.noaanews.noaa.gov/stories2012/20120516_okeanusexplorer.html or
Thank you for visiting my blog. I hope you will check back in a few days for an update!