NOAA Teacher at Sea
Aboard R/V Sikuliaq
June 29 – July 18, 2019
Mission: Northern Gulf of Alaska (NGA) Long-Term Ecological Research (LTER)
Geographic Area of Cruise: Northern Gulf of Alaska
Date: July 9, 2019
Weather Data from the Bridge
Latitude: 57° 47.549 N
Longitude: 147° 30.222
Wave Height: 0-1 with swell of 4 ft
Wind Speed: 1.7 knots
Wind Direction: 170 degrees
Visibility: 5 nm
Air Temperature: 13.1 °C
Barometric Pressure: 1014.4 mb
Science and Technology Log
Dr. Ana Aguilar-Islas and her team of Annie, Kelsey, and Carrie are studying how the different sources of iron in the Gulf of Alaska influence its chemical structure. Iron is considered a micronutrient, because it is a nutrient that is needed in lower quantities than silicate, phosphate and nitrate, which are macronutrients. Iron is essential for phytoplankton. Iron does not easily remain dissolved in ocean water, but has a tendency to precipitate and become a particle. It is essential for many functions within phytoplankton, including gene function and photosynthesis, so the presence or absence of iron in the water is an indicator of the viability of the ecosystem.
Testing phytoplankton in both an iron-limited environment and an iron-rich one allows scientists to pinpoint the effect that iron has. The water in the Gulf of Alaska is notable for having more iron, leading to larger zooplankton as compared to areas, such as Hawaii, where the lack of macronutrients in the water means that they’re much smaller. The Copper River plume was an example of a naturally occurring source of iron although its decrease is exponential the farther you move from the plume.
In order to test samples without any contamination from being in an iron ship, Ana’s team created a “bubble” room or a clean space to do testing. Her samples come directly from the “iron fish,” a collection instrument that is towed along the starboard side of the ship, and a pump on deck sends water through a tube that is carefully strung from the “fish” through the hallways and into the “bubble.” The team is testing water samples for dissolved iron, particulate iron, and ligands (naturally occurring structures that bind iron and allow it to stay dissolved in seawater). Both the filtered (any plankton filtered out) and unfiltered samples that Ana’s team collects are also used by other teams to provide context for their own experiments, especially testing the behavior of phytoplankton populations in iron-rich and iron-poor water.
The Search for “Perfect” Water
After completing our comprehensive zig-zagging study through the Copper River plume, it was decided to continue on a path south to find HNLC (high nitrate low chlorophyll) water. We’re specifically looking for water with a salinity over 32.4 psu and nitrates over 3 micromoles. Water like this would be low in iron. Normally, the lack of iron is a factor that limits photosynthesis,. However, in areas with these numbers, phytoplankton communities have evolved to survive in an iron-deprived environment.
What Clay, Suzanne and Ana hope to do is to introduce both Copper River iron-rich water and commercially available iron into samples of these communities to see if a “bloom” or a sudden growth in population will occur. It’s been a long search so far, taking us through an offshore eddy, watching salinity numbers slowly creep up as we leave the plume’s fresh water influence behind us. To pass the time, my cribbage board came out and I’ve lost to Pete, Seth and Ana (although I beat Seth once). To help Suzanne and Ana find their water, Seth stitched together a composite satellite picture of the chlorophyll in the Gulf from images taken over the last few weeks. This showed an eddy south of the Copper River plume that provided a possible location for the right sampling of water.
Our initial target was 58 degrees N, 146 degrees W, however, we’re continuing on the journey south to see if we can find the right spot. For a long time, we were towing the Acrobat behind us, trying to get additional readings, however, our speed with the Acrobat is limited to a maximum of 7 kts. Early this morning, the Acrobat was pulled in and we’re now cruising at about 10 kts. We’re supposed to move over to the GAK (Seward) line of waypoints after this, but the joke is that we’ll reach GAK 125, i.e. Honolulu, before we find water that fits the parameters we need.
After careful monitoring of our position and the information screens in the computer lab, it seems that our target water is between 57 degrees 21 minutes N between 145 degrees 42.8 minutes W and 145 degrees 39.9 W. Finding the perfect water is complicated by the number of anomalies in the sea surface. We’re having the bridge go through specific maneuvers to take us back and forth through the target patch of water. As we move through what seems reasonable, Ana’s iron fish will be deployed to start bringing in “perfect” water samples.
Since last night, there has been at least one person stationed in the computer lab with eyes on the underway data display to monitor the salinity and nitrate levels. Today, with Dr. Strom, Clay and myself there, we jump every time the nitrate value does. Once our target patch is isolated, Dr. Strom directs the bridge to zigzag the ship through it to find maximum nitrate values and then radios the iron fish team. It’s 2.1….it’s 2.7…quick! Collect samples! It’s a crazy system, but for now it’s getting us the best results we can, considering the fluidity and changeability of the ocean.
I’m not sure what the bridge thinks about our maneuvers, and we’re all imagining what they’re saying! They have been very patient and willing to go along with requests; they’re pretty used to the demands of scientists in search of specific answers. We’re finding our highest values to be about 3.2 micromoles, and it seems that we’ve also narrowed down the “sweet spot.” In addition, a group of fin whales is moving through the area and is making regular appearances as we trace and retrace our path. At one point, Eric, the captain came down to chat and helpfully volunteered to look up the definition of “zig” and “zag” so that we would have our terminology correct. Is zig the upward progression or the downward one?
Most of the science done on board is carefully planned and prepared for. Methodologies are clean and precise in order to produce specific and incontestable results. Sometimes, however, science requires taking advantage of the situation at hand to find optimum data. Science can be messy and inexact, too, if the end result is finding the perfect drops of water in the ocean.
We are now over the 50% point in our trip. It is a bit ironic that as the science team and the crew get to know each better and develop friendships, both sides are also looking ahead to the end of the trip. It’s been fun to get to know the crew and to discover the personalities that make this ship run so smoothly.
Our weather has been notably calm so far, with today’s nearly flat seas being the smoothest to date. We have fog every day; every day the sea surface temperature is higher than the air temperature. What might that be an indication of? Russ seems to think it’s a fairly unusual pattern. Even though today’s temperature is in the mid-50s, the stillness and reflected light off the surface of the ocean almost make it seem warmer. It looks like we can continue to expect fairly calm seas for the next few days, too. Every day someone posts a weather forecast in the mess hall, and every day the forecast is similar.
We continue to eat remarkably well. Today’s lunch was spaghetti or zoodles with eggplant parmigiana, shrimp, and hot veggies. This week already, we’ve had pecan pies and oatmeal raisin cookies for dessert and apple and berry turnovers for breakfast. The food is definitely one of the benefits of being on this ship!
Did You Know?
The fresh water measured in the Copper River plume equates to a quarter of the yearly excess melt from area glaciers. The question then is, where does the other three-quarters go?
What do you want kids to know about your research?
Ana: There are nutrients in the water that sea creatures need: large nutrients and small ones. The small ones are important because they’re needed more often, like vitamins being a more regular part of your diet than hamburgers.
Sea Creatures seen today:
One Reply to “Catherine Fuller: Searching for Water in the Ocean, July 9, 2019”
Hi Catherine, this is Julia West, TAS alum 2015. I am loosely following this interesting research because I have connections to Alaska and that area, and this is interesting! I have wondered why Copper River red salmon are so far superior to the red salmon from other places (richer), and a local person told me it is because of the nutrients that are available to them. Learning about the plume is fascinating. Thanks!