winkler titration – NOAA Teacher at Sea Blog

NOAA Teacher at Sea
Amanda Peretich
Aboard Oscar Dyson
June 30 – July 18, 2012

Mission: Pollock Survey
Geographical area of cruise: Bering Sea
Date: July 22, 2012

Bottles — Water collection bottles with samples from CTDs throughout the cruise.

Location Data
Myself: airports, airplanes, and Maryland
Oscar Dyson: Crowley pier in Dutch Harbor, AK

Science & Technology Log
On July 17, as we were “cruising” around 12 knots back to Dutch Harbor, Alaska, I had one more GREAT tie in to chemistry class that I just wanted to share because it was that cool to me! Every few CTDs, a water sample would be collected to later be tested for levels of dissolved oxygen. At the end of the cruise on our way back, Bill allowed me to watch him test those samples using a Winkler titration.

Why do we care how much dissolved oxygen is in the water in the first place? Dissolved oxygen levels provide an excellent indication of the underwater biological activity. If levels are extremely low (2 mg/L or lower), animals fail to survive during this “hypoxia”. If there is no dissolved oxygen at all (0 mg/L), this is known as “anoxia”, meaning without oxygen. Areas that are hypoxic or anoxic are known as “dead zones”. Luckily there aren’t really any reported dead zones around Alaska, but knowing the level of dissolved oxygen is important to the scientists as another piece of data to analyze from this cruise.

How does the Winkler titration work and why did I find it so cool? First off, in chemistry class, we use a buret to add a titrant manually drop by drop into a solution containing a phenolphthalein indicator that turns from clear to pink to signify the endpoint of the titration. On board, the actual titration is automated and there is no indicator! It was nice to see chemistry in action, and even nicer to see the process automated, removing any human error in the actual titration.

Steps to performing the Winkler titration on the Oscar Dyson:
1. Collect water sample during CTD and add manganese chloride (MnCl₂) and sodium iodide/sodium hydroxide solution (NaI/NaOH) to sample. Stopper and mix well.
2. Store all water samples for testing at the end of the cruise (this is how it’s done on the Oscar Dyson to test all samples at once, although you could test them each individually after collection).
3. When ready to test all samples, remove stopper and add magnetic stir bar and 1mL of sulfuric acid (H₂SO₄). Mix well. If precipitate does not completely dissolve, add more sulfuric acid.
4. Titrate and record results!
5. Repeat steps 3 and 4 for each sample 🙂

Winkler titration bottles — (a) The addition of excess manganese, iodide, and hydroxide ions added to each water sample forms a precipitate (solid), which is then oxidized by the dissolved oxygen in the water sample.
(b) and (c) A strong acid acidifies the solution and converts the iodide ion (I-1) into an iodine molecule (I2), causing the precipitate to dissolve (b) and the solution to turn brownish-orange (c).
(d) The solution is put on top of a stir plate and titrated with a thiosulfate solution. The titration is complete when the solution is neutralized, or there are no more ions remaining in solution. This is determined by measuring the conductivity of the solution because ions allow conductivity so when the solution is neutralized, there will be no conductivity. You can see the conductivity probe in the top of the solution on the right and the thiosulfate being added into the solution through the tube on the left.

Personal Log
My final days/adventures in Dutch Harbor? Enjoy the brief descriptions and photos below!

July 18
– arrived in Dutch early morning to beautiful blue skies all day and I watched as the Dyson docked at Crowley pier
– another Alaskan water adventure when Brian and I donned arctic survival suits, got in Captain’s Bay, and yelled up drafting readings of the water level from various points on the outside of the ship to Neal (while Chelsea took photos)
– went for a run over to Unalaska to see the Russian Orthodox church, walk along the beach, go to Memorial Park, check out some gravestones, and jog around town
– hung out in Dutch with some people off the Dyson, where Brian turned into Billy Idol, Chelsea got a new ‘do, and Kevin got a haircut

July 19
– the day started off looking bleak, and I got covered in mud running back into Captain’s Bay to check out the gigantic oil rig barge
– then it turned into another afternoon of beautiful blue skies to allow me to hike with Brian to the back of Captain’s Bay and up to a really pretty waterfall
– hung out in Dutch with some locals I’d met the night before, including an Aleut with the nose ring and face tattoo

July 20
– was supposed to fly out this afternoon but lo and behold, the skies turned gray, the fog rolled in, all flights in and out of Dutch were cancelled for the day, and I headed back to the ship
– hung out in Dutch with some people off the Dyson and celebrated Patrick’s birthday

July 21
– attempted to get on flights from standby multiple times throughout the day, and finally got on a flight at 8:45pm that got me to Anchorage after midnight, where I slept on a bench in the airport until about 4am

July 22
– no flights out of Anchorage available until almost 9pm! luckily I called Delta, got on standby for a 6am flight where enough people took a later flight (and everyone on standby ahead of me was in pairs) that I got out of Anchorage and to Minneapolis, where I had about 35 minutes to get on standby for another flight that I was able to get on as well; the flight goddesses were with me today
– arrived home to Maryland about 20 hours after leaving Dutch, happy to be back but sad this adventure is officially over

THANKS THANKS THANKS
I’d just like to say one last time how AMAZING this adventure was on the Oscar Dyson and how incredibly BLESSED I was to meet such great people and learn some many new and EXCITING things. I owe a huge amount of thanks to plenty of people:
* Thanks to the chief scientist Neal along with Bill and Anatoli for all of the fun science and fish stuff I learned during my shift
* Thanks to the rest of the science party (Scott, Denise, Carwyn, and Nate) for more science and technology that I learned and for the card games I played after my shift and to Kathy for doing her survey tech thing (and helping me find my luggage and get to the airport on time)
* Thanks to the CO CDR Mark Boland for allowing me to be on the OD in the first place and for always seeming to have a smile on your face when I was around
* Thanks to the XO 1M Kris Mackie for all of his help in getting me to the ship, for never sugar-coating life, for a great espresso machine in the galley, and for life lessons, knowledge, and personal growth he probably doesn’t even know he taught me
* Thanks to the OPS LT Matt Davis for reading and approving all of the blogs and for the vast amount of knowledge I gained from him in multiple aspects of ship life
* Thanks to ENS Libby, Kevin, and Chelsea for plenty of information, stories, good laughs, and great memories
* Thanks to LTJG Dave for recommending thought-provoking movies and answering all my questions
* Thanks to the engineering crew (Brent, Tony, Vincente, Garry, Robert, Terry, Joel) for all of their hard work that kept the ship running during the entire trip and for everything you guys taught me
* Thanks to Vince for keeping the internet up and running so I could update my blogs, get on facebook, and let my parents know I was still alive with the VOIP
* Thanks to the stewards Tim and Adam for some of the best cooking I’ve had in a long time and for “encouraging” me try things I didn’t think I liked but wound up enjoying because you made them so delicious
* Thanks to the deck crew (Willie, Patrick, Deeno, Jim, Brian, and Rick) for putting up with my incessant chatter, photo taking, curiosity, and questions, for letting me crash your table at mealtimes, and for every little thing that you’ve each taught me, even if you didn’t know you were teaching me something at the time
* Thanks to GVA Brian for all the photos he took whenever I asked, for the awesome headphones he let me borrow most of the trip, for the knowledge he shared about everything he knew related to boats and fishing, and for adventures kayaking, taking draft readings, and hiking in Dutch
* Thanks to the NOAA Teacher at Sea program for providing this incredible opportunity in the first place
* Thanks to everyone that has been reading (and sometimes commenting on) my blogs

NOAA Oscar Dyson in Captains Bay, Dutch Harbor, AK — NOAA *Oscar Dyson* in Captains Bay, Dutch Harbor, AK

NOAA TEACHER AT SEA
STEVEN WILKIE
ONBOARD NOAA SHIP OREGON II
JUNE 23 — JULY 4, 2011

Mission: Summer Groundfish Survey Geographic Location: Northern Gulf of Mexico Date: July 3, 2011 Ship Data

Latitude	29.27
Longitude	-94.39
Speed	9.30 kts
Course	298.00
Wind Speed	6.70 kts
Wind Dir.	281.88 º
Surf. Water Temp.	29.90 ºC
Surf. Water Sal.	24.88 PSU
Air Temperature	29.30 ºC
Relative Humidity	75.00 %
Barometric Pres.	1015.75 mb
Water Depth	15.70 m

Science and Technology Log

One of the first expeditions devoted to the study of the world’s oceans was that of the H.M.S. Challenger. This voyage covered a distance of more than 68,000 nautical miles. Although other expeditions prior to the Challenger expedition would periodically collect data about the ocean environment, none were devoted solely to the exploration of the chemical, biological and physical attributes of the oceans.

The Voyage of the HMS Challenger — The HMS Challenger’s voyage spanned 4 years and covered close to 70,000 nautical miles.

Challenger Sounding Device — A sounding device used by the Challenger expedition. This weighted line would be lowered over the side of the ship and the amount of line let out would indicate depth.

If you have read my previous posts, you know how important monitoring the abiotic factors are. This was no different aboard the Challenger expedition.

And remember it took 23 years to process and publish all of the data, well with the help of computers and the internet, the Oregon II’s data is available in hours.

Michael Hendon (lead scientist) performs a winkler titration to determine dissolved oxygen content. See wet chemistry skills are still important!

Although technology plays a pivotal role in collecting and analyzing the data, computers still need to be cross referenced against tried and true scientific processes. In order to ensure that all of the CTD equipment is accurate, random water samples are pulled using the CTD’s sample bottles. A chemical titration, known as the Winkler titration is used to determine the amount of dissolved oxygen present in the water samples.

The method for sampling the living organisms along the bottom of the seafloor has not changed much since the Challenger expedition. Trawl nets are still the name of the game, although the way they are deployed might vary a bit!

Oregon II Trawl Net — Mike and Cliff bring the Oregon II's trawl aboard complete with catch.

Once the catch is on board, the process begins to collect data (remember that is why NOAA is out here) to better understand how populations are changing in order to set catch limits and analyze human impact. In the day’s of the Challenger expedition, the work of analyzing samples and collecting their would have been done in a lab aboard ship, and we rely on similar if not more automated facilities onboard the Oregon II. Follow this link to take a virtual tour of the Challenger’s “Wet lab”. The wetlab onboard the Oregon II is where I spend the majority of my 12 hour watch. It is here that the catch is brought after we bring it on deck, we sort the catch, count and measure a subsample of what is brought on board. If we had to measure everything that came up with the net we would never get finished. By taking a subsample we can split the catch into percentages depending on the weight of the entire catch and count a smaller sample of the catch. This subsample’s diversity can then be used as a basis for the entire catch. This saves time and effort on our part and still provides an accurate representation of what was in the net. A few species are selected to be counted in their entirety, that includes all commercially important shrimp (brown shrimp, pink shrimp and white shrimp) and all red snapper. We will also pull organisms into our subsample that are unique to the catch such as sharks, rays, skates etc.

Now I am not quite sure how the Challenger expedition determined where it would sample and when, perhaps if they saw something interesting they would simply drop their nets in the water, but with the Oregon II, the sampling sites are predetermined and the method to set up those sites is quite sophisticated. In order to ensure that the cruise covers the majority of the Gulf of Mexico NOAA uses a method known as independent random sampling. This method uses a computer program to randomly select stations based on depth data, and spatial area. By choosing random samples independently, the scientists can rest assured that they haven’t purposefully singled out an area with “good fishing” or “bad fishing” and that the data they collect will represent a more accurate count of the actual fish populations in the Gulf of Mexico.

Tag: winkler titration

Amanda Peretich: Sad Times With This, My Final Blog, July 22, 2012

Steven Wilkie: July 3, 2011