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Off Uruguay, PACE Partners Connect Data from Satellite and Sea

By Jason Graff,  Ph.D., Oregon State University  

NASA’s Plankton, Aerosol, Cloud, and ocean Ecosystem (PACE) Validation Science Teams (PVST) rely on partnering with existing research expeditions to gather measurements while adding value to these critical partner programs. From mid-November to early December of 2025, we did fieldwork off the coast of Uruguay, aboard the Schmidt Ocean Institute’s ship R/V Falkor (too).  

Our PVST team is based at Oregon State University (OSU) as part of the Phytoplankton Ecophysiology Col(lab)oration. Our research focus is particles and biological rates (PVST-PBR). For this expedition, we partnered with the Symbiotic Partners and Asgard Research Cruise (SPARC), a research team studying small microbes, called archaea, which are thought to be the most recent ancestors of eukaryotes, which include all animals, plants, fungi, seaweed, and many one-celled organisms.  

The waters and ocean sediments offshore of Uruguay are highly understudied, making it a unique location for a PACE PVST field campaign and an exciting opportunity to work alongside SPARC scientists.  My research associate at OSU, Dr. Nicholas (Nick) Baetge, now of the Bermuda Institute of Ocean Sciences, and I, Jason Graff (PVST-PBR principal investigator), were both aboard Falkor (too) to collect PVST measurements and collaborate with SPARC on this exciting expedition.  

A black, blocky device accessed through tubes and coils rises to chest height on the two smiling men shown. The background is a shipboard laboratory with a large screen display.
PVST-PBR principal investigator Jason Graff (left) and research associate Nicholas Baetge (right) stand behind the sorting flow cytometer in the main laboratory of the R/V Falkor (too). The flow cytometer is an instrument used to identify and sort archaea and archaea-like cells in collaboration with SPARC scientists. 
Laura Eme/University of Rhode Island

This parcel of the ocean was chosen due to the operating plans of the Falkor (too) in this region and the known existence of Asgard archaea (the microbes that likely gave rise to human eukaryotic origins). While the SPARC scientists were largely focused on sediment sampling, our team was focused on surface ocean measurements for validating the PACE Ocean Color Instrument’s parameters as it observes and models the ocean  from space. For our PVST-PBR team, this meant measuring particulate organic carbon (POC), phytoplankton pigments, and surface ocean optical properties. These measurements of POC and phytoplankton community metrics, while critical for PACE validation efforts, will also serve the SPARC team’s needs to quantify and describe the environment above their study sites.

A lab bench contains and assortment of black cables, hoses, and pumps. Behind it, against the wall hangs a system of bright mint-green pipes and valves with orange and red circular covers.
These optical instruments set up in the flow-through seawater lab of the R/V Falkor (too) allow for analysis of seawater life while underway.
Nicholas Baetge/Bermuda Institute of Ocean Sciences

The Falkor (too) has a science laboratory dedicated to using continuous flow-through seawater to collect optical measurements and discrete samples. Measurements of incoming solar irradiance (sunlight going into the ocean) and radiance (light coming out of the ocean) were also collected during the PACE satellite overpasses of this region. Nick spearheaded many of these tasks.  

In addition to working with Nick on the PVST efforts,  I  collaborated with SPARC colleagues to collect archaea from water and sediment samples, using a sorting flow cytometer, an instrument that can help identify and isolate individual cells or populations of cells from other non-target particles.   

The expedition was highly successful, with PACE validation measurements being collected at satellite overpass times and SPARC-related sampling and cell isolations taking place daily. The PVST-PBR team has provided these datasets to the NASA data repository for use in validation efforts and discussions. Data exchanges with the SPARC team continue as these samples are processed and explored for our eukaryotic origins.  

Two scientists squat on the grated ship deck, behind a caution tape. They are collecting samples from the 24 tall gray Niskin water bottles that fill the circular steel frame of the water sampling rosette. In the bottom section of this device, below the water bottles, we can see instruments used to collect data through the water column. Thin cables are triggered at the appropriate depths to close the valves of the bottles. At the top of the rosette, a heavy clip connects to a cable suspended from a crane that is unseen above; this will be used to hoist the rosette in and out of the ocean.
Scientists Nicholas Baetge (right) and Laura Eme (left) sample the CTD rosette to deploy from R/V Falkor (too). The bottles on the rosette are closed to collect water samples at specific depths in the water column. They will analyze the water to evaluate the biological diversity and particle stocks relative to the physical and chemical environment.
Jason Graff/Oregon State University

Under a sunset sky, we view the ocean through an open bay. The view is bisected by a cable extending from a pulley atop a crane into the sea: the CTD (conductivity, temperature, and density) water sampling rosette is at work below the surface.
The fiber-optic cable connecting the CTD rosette to the ship feeds it instructions and serves as a conduit for data returning to the ship. Scientists can follow the CTD’s progress through the water column and map the conditions at each depth.
Jason Graff/Oregon State University

We look through the dim interior of a shipboard hangar to a remotely-operated vehicle, suspended from the ship’s A-frame and waiting to be lowered into a sparkling sea.
Remotely operated vehicle Subastian is hoisted into R/V Falkor (too)’s A-frame, which will lower it into the sea. The expedition used ROV Subastian to explore the seafloor of the area and collect sediment samples that will be analyzed for microbial communities.  
Jason Graff/Oregon State University

Two scientists pose on the dock beside the research ship, with its white superstructure and deep blue hull. In the background is a shoreline: a low city of white buildings fronted by a rocky quay.
Jason Graff and Nick Baetge at the bow of the R/V Falkor (too) at port in Montevideo, Uruguay, after successful completion of their PVST field efforts.
Alyson Santoro/University of California Santa Barbara

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