Breathing in Science: Oxygen Measurements At Sea

Author: Emma Pontes

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Scientist Emma Pontes performing Winkler Titration on a water sample collected from the first station of the cruise. Photo taken by Leah Chomiak.

Take a deep breath. The air you just inhaled contains about 20% oxygen, 78% nitrogen, and 2% of a few other minor gases. Some might assume that oxygen is only available to terrestrial air-breathers, however, this assumption couldn’t be further from the truth.

Oxygen (O2) generally exists in a gaseous state, but also exists in the world’s oceans as a dissolved gas. Fish and other ocean biology utilize the available dissolved oxygen just like humans do; taking up O2 and discharging carbon dioxide (CO2). Just like on land, the ocean is home to millions of photosynthetic organisms such as plankton, algae, and other underwater plants that take up CO2 and release O2 during a process called photosynthesis. Therefore, there is a constant ebb and flow of CO2 and O2 being ‘inhaled’ and released into ocean waters.

So what does this mean for ocean chemistry, and why do we care? Dissolved oxygen in the ocean is a sensitive indicator of climate-related changes. The dissolved oxygen concentration can be used to determine how much anthropogenic CO2 (carbon dioxide released by humans resulting from the burning of fossil fuels) is being taken up by the ocean. Just like oxygen, CO2 can dissolve in ocean waters, and most of human-created CO2 has been sequestered by our oceans. The uptake of anthropogenic CO2 by the world’s oceans is a leading cause of ocean acidification. Therefore, it is of high importance to determine the O2 concentration of various locations around the world’s oceans, not only to learn more about the how ocean biology is functioning, but also to examine the effects of ocean acidification.

Enter GOMECC-3, Ocean Acidification Research Cruise. In the past, research vessels have travelled our current route collecting the same data we are gathering now at the same locations. We can get an idea of how ocean chemistry is changing over time by comparing the data we get on this cruise, to the historic data sets collected on the same path we are on now.

Work days on the ship consist of lowering the CTD rosette (stands for conductivity, temperature, and depth) into the ocean at a predetermined location called a Station. The CTD is a large cylindrical ring of bottles, called Niskins, that are triggered to close and collect water samples at predetermined depths. The CTD is a useful tool for scientists onboard to get insight as to how ocean chemistry changes with depth.

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CTD being lowered into the water at the first station of the cruise. Photo taken by Leah Chomiak.

My job is to collect water samples from the Niskins and analyze each sample for its dissolved oxygen concentration using a technique called Winkler Titration. This procedure requires the addition of chemicals to the water sample that act as a fixative; the chemicals bind to the oxygen in the water and create a solid precipitate that eventually sinks to the bottom of the water sample. You can think of it as ‘pickling’ the oxygen to preserve it, so that the sample can be analyzed anywhere from 1hr to 4 weeks after being collected. To learn more about the titration procedure, check out the peer-reviewed paper entitled ‘Determination of Dissolved Oxygen in Seawater by Winkler Titration Using the Amperometric Technique’ written by Dr. Chris Langdon in 2010, which basically serves as my lab manual on the ship. I am looking forward to collecting some meaningful data that will contribute to OA research as we continue our trip around the Gulf of Mexico!

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Water sample collected by Scientist Emma Pontes to be analyzed for dissolved oxygen. The white milky-looking substance at the bottom of the sample is the bonded oxygen precipitate. Photo taken by Emma Pontes.


Langdon, Chris. “Determination of dissolved oxygen in seawater by Winkler titration using the amperometric technique.” The GOSHIP Repeat Hydrography Manual: a Collection of Expert Reports and Guidelines, edited by: Hood, EM, Sabine, CL, and Sloyen, BM (2010).


Life Aboard

Author: Leah Chomiak

It’s day 2 here on the Ron Brown, and all souls on board have been busy adjusting to new sleep schedules, new office views, and a constant influx of incoming samples. Our first day out was nonetheless perfect; flat glassy seas, clear skies, a slight breeze, with sightings of whales, dolphins, and tuna schools in the distance! As this is my first time sailing on the Brown, I spent most, if not all my time, wandering around the ship, taking in the views, getting to know the crew and fellow scientists, and figuring out the endless maze that is the Ronald H. Brown… I can definitely say that the engine room is a great place for hide and seek, maybe we can get that game going later on in the transit! With our melting pot of individuals onboard, it’s been really fun to get to know everyone and hear how they ended up working on the Brown. Our crew diversity spans individuals of Navy, Army, Merchant Marine, Coast Guard, and NOAA Corps backgrounds, each with awesome stories of time spent at sea and working with NOAA. Our scientists hail from all over the western hemisphere – with undergraduates, graduate students, senior scientists, and our techs each bringing their own zest, humor, and wealth of knowledge to the mission.

Leah Chomiak and Joletta Silva snap a quick pic before boarding the Ron Brown in Key West. Credit: Leah Chomiak
Leah Chomiak and Joletta Silva snap a quick pic before boarding the Ron Brown in Key West. Credit: Leah Chomiak
Glass-like sea state on day 1 transiting to station 1. Credit: Leah Chomiak

Life on board has been pretty great so far! Mealtime is a conglomeration of most bodies on board, where the engineers and other crew crawl out of their caves, bunks, hatches, labs, and the bridge to feast; you’re guaranteed to see someone you’ve never seen before each time you eat! There is a library and movie room onboard, both with hundreds of selections of titles that are sure to please anyone.  My favorite spot onboard is definitely the bow, perfect for staring down at that “no-land-in-sight” ocean blue color, my favorite color that one cannot describe unless they’ve been out to sea. Working the night shift (midnight to noon), I am fortunate to work through a sky filled with billions of stars, and watch the sunrise each morning. Ah, rough life right? Someone’s gotta do it!

Our first station came at 2000 (8:00PM) off the coast of Dry Tortuga National Park, and the entire science crew crowded the deck to watch our massive, pink-framed, 24-niskin bottle CTD rosette be lowered for our first crack at sampling. It was a frenzy as soon as it was back onboard! Sampling teams crowded the rosette with their empty bottles, ready to be filled with water samples from the surface, mid-depth, and bottom. After a successful collection, teams returned back to their labs to process the samples sequentially, and prepared for the next station. In addition to CTD cast stations, underway sampling is collected every 3 hours from a spigot within the lab that is constantly pumping seawater from the surface. Sampling teams collect these samples to observe changes in the surface parameters during our sampling track, such as looking at changes in temperature, salinity, oxygen, pH, and nutrient parameters.

We are currently in a 24-hour plus transit until Station 2 is reached, therefore things are a little quiet on board – the calm before the storm (of samples), should I say. Once the first transect is reached, we will be coming up on stations one after another, and all scientists will be working throughout the day and night to ensure all samples get processed in a timely fashion. I am so thrilled to be on board, it’s been a blast already!! Let’s science!


On the dock. Ready, set, sail!

Author: Leticia Barbero

Ahoy, land-based shipmates! Welcome aboard our GOMECC-3 cruise!

We are only a few hours away from departure. After months of planning, of submitting requests for clearances, getting our health checks, coordinating with multiple agencies and making sure we packed all the gear we might possibly need (plus spares), we finally made our way to the ship. Our equipment arrived in containers, via Fedex and UPS directly to the ship, in rented U-Haul trucks, and even within our personal luggage! Some of us drove directly from our labs (in cars packed to the brim with equipment), while others flew from all across the country.

Main lab with most of the equipment in place. Picture courtesy of Denis Pierrot.

Communication with the ship is essential to keep track of everyone’s arrivals and to make sure we don’t lose track of any packages that may get misplaced on the ship. We are happy to report that all the equipment we will be using arrived as expected and without any major damage.

The research ship we will be using, NOAA ship Ronald H. Brown, has 4 laboratory spaces available for scientific use, and as soon as the science party started to arrive on board, everyone got down to work installing the different systems we will need. You will soon start to learn a little bit more about everything we will be doing on board, but suffice it to say that we will be obtaining chemical, biological and physical data. A truly multidisciplinary project!

Both the science party and the ship’s crew are very excited about GOMECC-3 and we are all looking forward to 35 days spent together evaluating ocean acidification conditions in our coastal waters. The first contact has been good and everyone is in high spirits.

Ongoing discussions among scientists in the Hydrolab during setup. Picture courtesy of Denis Pierrot.

We have just about finished setting up our labs and are looking forward to enjoying our last night on land for a while.

Main lab of the Ronald H. Brown before set up. Picture courtesy of Patrick Mears.

By the time of our next blog entry, we should have worked out all the kinks in our sampling equipment, in addition to finding our sea legs. Here’s hoping for calm seas and fair winds!

National Park Service Participation in GOMECC-3

Author: Kristy Burnett, Communication Specialist, National Park Service

npsFour parks in the National Park Service will contribute to the GOMECC-3 research cruise by collecting water samples. However, park staff won’t be on board the R/V Ronald H. Brown; they’ll fill the sampling bottles at specific locations on-shore and near-shore within NPS parks. NPS staff will coordinate with the researchers at sea to make sure the samples are taken on the same day and on the same transect (line) from shore to ship. Samples will be sent to NOAA for analysis along with samples taken from the ship.

It’s important to have water samples taken from different locations so scientists can improve our understanding of ocean acidification in the area. Park managers can use the results to gain improved spatial understanding of ocean acidification and a general understanding of changing patterns over time. This information helps the NPS better preserve our oceans and coasts for future generations.

Contributing parks:

We ship out on July 18th

Follow our progress here.

Author: Sierra Sarkis

On July 18, NOAA AOML and partner scientists will depart on the Gulf of Mexico Ecosystems and Carbon Cycle (GOMECC-3) research cruise in support of NOAA’s Ocean Acidification Monitoring Program. This isn’t the first time researchers will head to sea in this region, previous cruises have taken place along the east and Gulf of Mexico coasts of the US in both 2007 and 2012. Together, these cruises provide coastal ocean measurements of unprecedented quality that are used both to improve our understanding of where ocean acidification is happening and how ocean chemistry patterns are changing over time. This will be the most comprehensive ocean acidification cruise to date in this region, set to include sampling in the international waters of Mexico for the first time. The importance of international collaboration should be noted, as ocean acidification is a global issue with global impacts, that will require a cumulative global effort to manage.

Please utilize this blog as a way to follow our progress, to familiarize yourself with the science behind the observations we are making, and to help improve your awareness and understanding of ocean acidification.