From cold seeps to Arctic lakes
John Pohlman Ph.D. ‘06 reflects on how a foundation laid at the Batten School & VIMS gave him opportunities to do critical, long-term research
John Pohlman charted a distinctive path during his time at William & Mary’s Batten School & VIMS, continuing to work professionally as he earned his doctorate. Now a research chemist working as a member of the Gas Hydrate Project for the U.S. Geological Survey (USGS) at Woods Hole Coastal and Marine Science Center, Pohlman recently reflected on his current scientific work and how his time at the Batten School of Coastal & Marine Sciences & VIMS served as a critical foundation for his career today.
Interest in seafloor seepage charts a career path
While earning his Ph.D. at the Batten School & VIMS, Pohlman also worked professionally as a contractor for the U.S. Naval Research Laboratory (NRL), using data he collected as an NRL contractor as the basis for his dissertation, which focused on the occurrence of gas hydrate in and on the seafloor. "Gas hydrate is a crystalline form of methane and water; it’s like frozen ice," he explained. "It forms when methane gas and water interact under high pressure and low temperature; conditions found in the deep ocean."
Pohlman’s work began with investigations into methane seepage from the seafloor, particularly in continental margin environments where hydrates are abundant. A major question driving his research was whether warming oceans might destabilize these deposits, leading to significant methane release into the atmosphere and further contributing to climate change. Extensive fieldwork, including deep-sea expeditions off the coast of Vancouver Island and the Gulf of Mexico, revealed that microbes play a critical role in consuming methane before it can escape into the water column, thus mitigating its potential greenhouse gas effects.
Pohlman has also explored how methane-derived carbon contributes to oceanic dissolved organic matter (DOM). Alongside his advisor, James Bauer, he hypothesized that old carbon from methane seeps might explain why some dissolved organic carbon in the ocean appears much older than expected. Their research, published in Nature Geoscience, demonstrated that methane seeps contribute aged carbon to marine systems, potentially influencing long-term carbon cycling.
The importance of long-term scientific inquiry
This work laid the foundation for a major expedition over a decade later, where Pohlman, now with USGS, and his colleagues deployed advanced techniques to study methane-derived carbon in a submarine canyon off the coast of Oregon. "It took me 13 years to work with various people and get a major expedition funded to go out and study this process at a larger level," he says. "So many years after the paper was published, we finally got to go down to the seafloor and actually perform the study I always wanted to do when I was a graduate student.”
Although initially disappointed it took so long to find funding for the study, Pohlman said, “by the time we got to do it, I knew exactly what I wanted to do, and I had been able to assemble the perfect team... And I'm still working on that project.” He added that the yet-to-be-published findings indicate that “dissolved organic matter from methane seeps, albeit old with respect to its radiocarbon age, is readily available and consumed by microbes in the ocean.”
Pohlman credits the stability that has historically been typical of federal work as enabling this kind of long-term scientific inquiry that requires dedicated research and yields essential data. “Working for the USGS has allowed me to continue working on the same questions for many years without jumping from one hot-button topic to another. We can systematically continue to work on something in a way that we see progress."
Answering other critical questions
Utilizing an analytical system developed at the USGS in collaboration with other partners, he and his team have also mapped CO₂ and methane fluxes across various environments, including estuarine systems like the Chesapeake Bay. "We deployed our equipment for a five-day survey of greenhouse gas exchange, CO₂ and methane, from the freshwater headwaters all the way to the mouth of the estuary," he said. Their research has shown that while most seafloor methane is consumed within the water column and does not reach the atmosphere in significant quantities, methane emissions in shallower coastal systems may be more substantial, with potential implications for regional carbon budgets and the global atmosphere.
In addition to his work on methane seepage, Pohlman has contributed to studies on gas hydrates as an energy resource. “I'm working on a project up in Alaska where they've drilled an experimental gas well, penetrating deposits of solid gas hydrate below the permafrost to see if they can extract economically viable quantities of natural gas,” he said. “We receive gas samples and measure the isotopic composition of the component gases. I can tell you if this gas came from a biological source or if it came from a petroleum source or somewhere in between.”
The educational foundation supporting it all
After earning a master's degree in biological oceanography from Texas A&M University, Pohlman considered directly enrolling in the Batten School & VIMS Ph.D. program but instead opted for post-grad work as a contractor for the NRL. However, Pohlman quickly realized, “I was actually collecting a bunch of data sets that would be useful for doing a Ph.D.”
Pohlman reached out to Bauer, as well as Elizabeth Canuel, at the Batten School & VIMS, who agreed to be his co-advisors in pursuit of a doctorate. "They were really cool and flexible, and they allowed me to do most of my research remotely,” said Pohlman. “I spent my first year taking all the core courses on campus, so I did live in Gloucester for a year."
On-campus he found a supportive community where he "loved being with a group of high-energy students," including research collaboration and social functions that were often hosted at the old farmhouse known as Crow Point, where Pohlman lived with fellow graduate students.
After his first year, Pohlman moved back to D.C. "I would go back and forth," he said, "but 95% of the analysis that I did was done at the NRL or out on expeditions in the Pacific Ocean with people from the NRL. So, it was a different, creative way to do a Ph.D., but it worked out.”
Pohlman’s unique educational and career path has been marked by interdisciplinary collaboration, integrating geochemistry, microbiology and oceanography to address fundamental questions about Earth’s carbon cycle. His work has helped clarify the environmental impact of gas hydrates, while also informing strategies for future energy exploration. Through the years, Pohlman has continued to see the Batten School & VIMS’ influence on his work.
“I've worked up in Arctic Lakes. I've worked in the Chesapeake Bay. I'm working in flooded caves within subterranean estuaries of the Yucatan Peninsula. I work with scientists from Japan, Germany and Mexico. And I’ve even become an inventor of analytical devices that we use in our lab to do measurements,” Pohlman said, “but I'm using all of the same knowledge that was oriented towards coastal systems when I was at VIMS.”
This alumni profile was written and published in March, 2025.