Catherine Fuller: Into the Copper River Plume, July 7, 2019


NOAA Teacher at Sea

Catherine Fuller

Aboard R/V Sikuliaq

June 28 – July 18, 2019

Mission: Northern Gulf of Alaska (NGA) Long-Term Ecological Research (LTER)

Geographic Area of Cruise: Northern Gulf of Alaska

Date: July 7, 2019

Weather Data from the Bridge

Latitude: 59° 40.065 N
Longitude: 146° 04.523 W
Wave Height: 2-3 ft
Wind Speed: 10.4 knots
Wind Direction: 254 degrees
Visibility:  100 m
Air Temperature: 12.0 °C
Barometric Pressure: 1015.4 mb
Sky: Overcast, foggy


Science and Technology Log

Usually LTER cruises are more focused on monitoring the ecosystem, but in our case, the cruise will also focus on a process study of the Copper River plume.

Copper River plume
This is a satellite photo of the plume with an overlay of the salinity of the water along our course. The darker colors represent the lowest salinity.

This seasonal plume brings iron and fresh water into the marine ecosystem, where they are dispersed by weather and currents. Because our winds have been very light, the plume is retaining its coiled shape remarkably well.  Our sampling on the Middleton Line (prior to the plume study) will add information about how both the Copper River fresh water and iron are spread along the shelf and throughout the food web.  

Clay Mazur
Clay checking the fluorescence of a sample.

Clay Mazur has a particular interest in the iron-rich waters of the plume.  He is a graduate student from Western Washington University who is working under Dr. Suzanne Strom (also onboard). He is one of a few on board who are working on their own experiments as opposed to assisting others.  The overall goal of his work is to study how iron in phytoplankton is limited and how the sporadic addition of it can stimulate growth.  He has a gigantic on-deck incubation experiment in which he will take an iron-limited plankton community from offshore in the Gulf and introduce iron-rich water from the Copper River plume to see what happens.  Clay will measure chlorophyll – an indication of biomass – by which he can estimate the plankton population.  He will also be checking the physiology of plankton in different size classes, and taking samples to see the pigments that every cell produces and if they change over time with the addition of water from the Copper River plume. His hypothesis is that everything should change: phytoplankton species composition, cell size, photosynthetic ‘health’, and chlorophyll production. When phytoplankton are iron-limited, they cannot produce healthy photosynthetic structures. 

Clay measured the same indicators on every station of the MID (Middleton Island) line and will also measure the same on GAK line.  These samples will use the metrics described above to show environmental heterogeneity along the cross-shelf sampling lines. Samples from the MID and GAK line will also allow his iron experiment to be seen in context.  Does the iron-rich community that develops during the experiment match anything that we see on the shelf? How realistic is experiment within the Gulf of Alaska? Clay would also expect a diatom bloom with the introduction of iron into his sample population, but he says there are not a lot of cells greater than 20 microns out here and 5 days may not be enough for diatoms to grow up from this small seed population.

The Acrobat

One specialized instrument being deployed to gather information about the Copper River plume is the Acrobat.  Where the CTD is critical to give a site-specific profile of various indicators in the water column, the Acrobat can provide much of the same information along the path of the research ship, such as through the plume or across the shelf from deep regions to shallow.

CTD Screen
This is an example of the readout that comes from the CTD when it is deployed.

Lead scientist Dr. Seth Danielson from UAF, and Pete Shipton, a mooring technician from UAF’s Seward Marine Center are using the Acrobat to record a number of parameters as it moves through the water column.  The Acrobat is lowered off the stern of the ship and towed behind us.

Acrobat on deck
Bern, the Marine Tech, and Paul, the Bosun, with the Acrobat on deck prior to launch

As it is towed, it dives and climbs in a repeated vertical zigzag pattern to sample the water column vertically along the length of our course, creating a “cross-section” of the ocean along our line.  The Acrobat measures water temperature, salinity, density, chlorophyll, particle concentrations and CDOM (colored dissolved organic matter). The CDOM indicator allows the Acrobat to distinguish between different water colorations.

The path of the Acrobat can be constrained by distance from the surface or seafloor, in which case it receives depth sounder readings from the ship itself to inform its “flight” behavior.  It can also be set to run a path of a set distance vertically, for example, within a 20m variation in depth.  When set to a maximum depth of 40 m, it can be towed at 7-8 kts, but someone must always be monitoring the “flight” of the Acrobat in relation to ship speed to ensure the best possible results. The operator provides a watchful eye for shallow regions and keeps an eye on the incoming data feed.  The Acrobat also has two sets of wings.  The larger set will allow the Acrobat to reach a maximum depth of 100m or carry a larger sensor payload.  The profile being created as we tow through strands of the plume indicates that there is a pronounced layer of fresh water at the surface.  A concentration of phytoplankton, indicated by high chlorophyll a fluorescence levels, lies just beneath the fresh water layer and as we exit the plume, we observe a subtle shift towards the surface.  The fresh water also contains a good deal of sediment from the river that settles to the bottom as the plume spreads out. As we cross through the plume, we see the sediment levels at the surface drop, while the temperature, salinity and density remain fairly constant, showing a continued flow of fresh water at the surface. 

The readout from the Acrobat appears as a series of bar graphs that record in real time and provide a clear picture of what’s happening in the water column as we move.

Acrobat screen
This is what the Acrobat readout looked like as we went through a portion of the plume.

Once the data from the Acrobat is gathered, Dr. Danielson is able to create three-dimensional representations of the water column along our path according to the individual indicators. One that is particularly interesting and important for the Gulf of Alaska is salinity, which exerts strong control on water column stratification and therefore the supply of nutrients into the ecosystem.

Acrobat salinity graph
Here is a 3-D representation of the salinity along our plume route.

The low-salinity waters of the Gulf of Alaska are influenced by the fresh water precipitation, snow melt and glacier melt in the coastal Alaska watershed, including the big rivers like the Copper River and the thousands of un-gauged small streams.  Some of the fresh water runoff eventually flows into the Bering Sea, the Arctic and the Atlantic Ocean, playing its role in the global hydrological cycle and the conveyor belt that circulates water through the world’s oceans.  Oceanographic monitoring has shown that the Gulf of Alaska water column is warming throughout and getting fresher at the surface, a consequence in part of glaciers melting along the rim of the Gulf of Alaska.


Personal Log

Finding my way around onboard was initially somewhat confusing.  I would exit the main lab and turn the wrong way to locate the stairway back up to my room, and it took a few days to figure it out.  Here’s an idea of the path I take in the mornings to get from my room to the lab:

Here’s what our stateroom looks like…yes, it’s kind of messy!

One rule when you open a door, because the hallways are narrow and the doors are heavy, is to open slowly and check for people.

The stairs are steep with narrow treads and necessitate careful and constant use of the handrails.

From the main hall, I usually go into the wet lab.

From the wet lab I can either go into the main lab…

Main lab
Main lab

… or into the Baltic Room.

Baltic Room
Baltic Room

There are six levels to the ship.  At the bottom are supply rooms, equipment, the engine room, workrooms and the gym.  On the main floor are the labs, workrooms, laundry areas and computer center.  On the first floor are science team quarters, a control room for the main deck winches, the mess hall and a lounge.  On the second floor are crew quarters.  The third floor has officer quarters, and the fourth level is the bridge.  There are also observation decks at the stern and bow on the third level.

I have a bit of a reprieve during the plume study, since Steffi’s project does not focus on these waters.  It’s been a great opportunity to shadow other teams and learn about what they’re doing, as well as to explore more of the ship. Now that the first phase of the plume study is over, we are extending it farther out in the gulf to be able to examine a fresh water eddy that is showing up on satellite imagery.  After that, we will have about a 12-hour transit to the next line of stations, called the GAK (Seward) line, where Steffi (and I) will resume her testing. 


Did You Know?

It’s still foggy and the sea state is very calm compared to what everyone expected.  It’s great for the experiments, but doesn’t help with wildlife sightings.  We’re under the influence of a high pressure system currently, which is expected to keep things quiet at least through Wednesday.  At some point next week, we may have a low-pressure system pass through, which would increase wind speed and wave height. 


What Do You Want Kids to Learn from Your Research?

**Note: I’m asking the various scientists on board the same question.  Clay took five days to formulate this and it really captures the essence of his passion for his research and the effects of climate change.  It’s worth the read!

Clay: Recently, I was asked by Cat, our Teacher at Sea for this cruise, what I want members of the general public to take away from my work studying iron limitation of phytoplankton. Though I can provide her a superficial answer to my research question immediately, the motivations for my work go much deeper than answering “How does a micronutrient affect phytoplankton growth?”

There are two main levels at which I want to answer Cat’s question:

1. Proximal: Though phytoplankton are microscopic, they have macroscopic impacts.

2. Philosophical: Why bother in the quest for such knowledge?

Level 1: The Macroscopic Impacts of a Microscopic Organism 

Both human societies and phytoplankton communities are impacted by global climate change. Globally, humans are realizing the need to combat carbon emissions and mediate the effects of increasing global temperatures. Consequences of global climate change for us include mass emigration as sea levels rise and increased frequency of extreme weather events (e.g. droughts, wildfires). As a result, humans are racing to bridge political divides between countries, develop sustainable energy, and manage natural disaster response.

Phytoplankton, too, must respond to global climate change. As sea surface temperatures rise, phytoplankton will have to adapt. CO2 that is dissolved in seawater removes the precious materials some diatoms use to make their “shells” and takes away their protection. Dissolved CO2 can also alter the ability of micrograzers to swim and find food!

Melting glaciers are a double-edged sword. Glacial flour in freshwater runoff brings in vital nutrients (including iron) through the Copper River Plume and phytoplankton love their iron! But freshwater also works to trap phytoplankton in the surface layers. When all the nutrients are used up and you’re a phytoplankton baking in the heat of the sun, being trapped at the surface is super stressful!

As global climate change accelerates in the polar regions, phytoplankton in the Northern Gulf of Alaska are in an evolutionary race against time to develop traits that make them resilient to their ever-changing environment. Phytoplankton crossing the finish line of this race is imperative for us humans, since phytoplankton help to mediate climate change by soaking up atmospheric CO2 during photosynthesis to produce ~ 50 % of the oxygen we breathe!

Phytoplankton also form the base of a complex oceanic food web. The fresh salmon in the fish markets of Pike’s Place (Seattle, WA), the gigantic gulp of a humpback whale in Prince William Sound (AK) and even entire colonies of kittiwakes on Middleton Island (AK) are dependent on large numbers of phytoplankton. When phytoplankton are iron limited, they cannot grow or multiply (via mitosis). In a process called bottom up regulation, the absence of phytoplankton reduces the growth of animals who eat phytoplankton, the animals who eat those animals, and so on up the entire food chain.

Let us consider “The Blob”, an area of elevated sea surface temperature in 2015 to illustrate this point. “The Blob” limited phytoplankton growth and that of herbivorous fishes. As a result, the population of kittiwakes on Middleton Island crashed as the birds could not find enough fish to provide them the nutrients and energy to reproduce successfully. In this way, the kittiwake deaths were directly attributed to a lack of phytoplankton production.

Not only are phytoplankton ecologically important, they are commercially important. For consumers who love to fish (and for the huge commercial fisheries in the Northern Gulf of Alaska), the base of the food web should be of particular interest, as it is the harbinger of change. Fisheries managers currently use models of phytoplankton growth to monitor fish stocks and establish fisheries quotas. If sporadic input of iron from dust storms, glacial runoff, or upwelling stimulate phytoplankton to grow, fish stocks may also increase with the newfound food source. Because phytoplankton are inextricably linked to fish, whales, and seabirds, in years where nutrients are plentiful, you may well see more fish on kitchen tables across the U.S. and Native Alaskans may be able to harvest more seabird eggs.  

Level 2: The Nature of Science

As a supporter of place-based and experiential learning, I view myself as a student with a duel scientist-educator role. To succeed in these roles, I have to be able to combine reasoning with communication and explore questions like “How does science relate to society?” and “How do we foster scientific literacy?” What better way to think about these questions than embarking on a three-week cruise to the Pacific Subarctic?! Not only am I working with amazing Principal Investigators in an immersive research experience, I am able to collect data and think of creative ways to communicate my findings. These data can be used to build educational curricula (e.g. Project Eddy modules, R shiny apps, etc.) in an effort to merge the classroom with the Baltic room (where the CTD is deployed). But what’s the point of collecting data and sharing it?

Science is “a collaborative enterprise, spanning the generations” (Bill Nye) and is “the best tool ever devised for understanding how our world works” (Richard Dawkins). The goal of communicating my results in a way that touches the lives of students is two-fold. One aim is to allow them to appreciate the philosophy of science – that it is iterative, self-correcting, and built upon measurable phenomena. It is the best way that we “know” something.

The other aim is to allow students to engage in scientific discourse and build quantitative reasoning skills. As the renowned astrophysicist Neil DeGrasse Tyson has said, “When you’re scientifically literate the world looks very different to you and that understanding empowers you.” Using phytoplankton to model the scientific process allows students to enter into the scientific enterprise in low-stakes experiments, to question how human actions influence ecosystems, and to realize the role science plays in society. Ultimately, I want students to use my data to learn the scientific process and build confidence to face the claims espoused by the U.S. government and seen on Facebook with a healthy amount of skepticism and an innate curiosity to search for the truth.

2 responses to “Catherine Fuller: Into the Copper River Plume, July 7, 2019

  1. Great journal Catherine! The plume satellite photo is amazing. I like your photo tour of the Sikuliaq too.
    (:
    Lisa

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