A research group co-led by the University of Illinois Urbana-Champaign predicts that a surprisingly adaptable species of marine archaea will play an important role in reshaping biodiversity in the planet’s oceans as the climate changes. Credit: Fred Zwicky

As climate change pushes heat deeper into the ocean, scientists have been concerned about disruptions to marine life’s delicate balance. But new research suggests that a key microbe, Nitrosopumilus maritimus, may already be adapting to these harsher conditions.

Rising temperatures are no longer limited to the ocean’s surface. Heat waves and long-term climate change are now warming deep-sea waters, raising concerns about disruptions to the ocean’s fragile chemical and biological systems. Despite these risks, new research suggests that a key microbe, Nitrosopumilus maritimus, may already be adjusting to warmer, low-nutrient conditions. Scientists believe these iron-dependent, ammonia-oxidizing archaea could play a major role in redistributing ocean nutrients as the climate continues to shift.

The findings were published in the Proceedings of the National Academy of Sciences.

Key Microbes in Ocean Nutrient Cycles

Nitrosopumilus maritimus and related microbes make up about 30% of marine microbial plankton. Researchers widely agree that these organisms are essential for maintaining ocean chemistry that supports marine life. Their ability to oxidize ammonia makes them central to nutrient cycling in the ocean.

By transforming nitrogen into different chemical forms in seawater, these microbes influence the growth of microbial plankton. These plankton form the foundation of the marine food chain, meaning the activity of these archaea helps sustain biodiversity throughout the ocean.

Illinois microbiology professor Wei Qin. Credit: Fred Zwicky

Deep-Sea Warming and Iron Use

“Ocean-warming effects may extend to depths of 1,000 meters or more,” said University of Illinois Urbana-Champaign microbiology professor Wei Qin. “We used to think that deeper waters were mostly insulated from surface warming, but now it is becoming clear that deep-sea warming can change how these abundant archaea use iron — a metal they depend on heavily — potentially affecting trace metal availability in the deep ocean.”

Experiments Reveal Increased Iron Efficiency

The study, led by Qin and University of Southern California global change biology professor David Hutchins, relied on carefully controlled experiments that minimized contamination from trace metals. Researchers exposed a pure culture of Nitrosopumilus maritimus to a range of temperatures and iron levels.

They found that higher temperatures, especially under iron-limited conditions, reduced the microbes’ need for iron while improving how efficiently they used it. This suggests that the organisms can adjust to both warming waters and reduced iron availability.

Modeling Points to a Growing Role in a Warming Ocean

“We coupled these findings with global ocean biogeochemical modeling by Alessandro Tagliabue from the University of Liverpool,” Qin said. “The results suggest that deep-ocean archaeal communities may maintain or even enhance their role in nitrogen cycling and primary production support across vast iron-limited regions in a warming climate.”

This summer, Qin will serve as co-chief scientist aboard the research vessel Sikuliaq. He and 20 other researchers will work to validate the study’s experimental findings in a real-world setting. Credit: Wei Qin

Upcoming Research Expedition

Later this summer, Qin and Hutchins will co-lead a research expedition aboard the vessel Sikuliaq. The journey will begin in Seattle, travel to the Gulf of Alaska, and continue to the subtropical gyre, with a stop in Honolulu, Hawaii.

A team of 20 additional researchers will join the expedition to test these findings in natural ocean environments. Their work will focus on how temperature changes and metal limitations interact to influence archaeal populations in the wild.

Reference: “Ocean warming enhances iron use efficiencies of marine ammonia-oxidizing archaea” by Wei Qin, Alessandro Tagliabue, Lei Hou, Min Xu, Xiaopeng Bian, Dawn M. Moran, Duo Zhao, Qian Li, Matthew R. McIlvin, Yue Zheng, Shuh-Ji Kao, Yao Zhang, Mak A. Saito, Seth G. John, Fei-Xue Fu and David A. Hutchins, 2 March 2026, Proceedings of the National Academy of Sciences.
DOI: 10.1073/pnas.2531032123

Qin is also affiliated with the Carl R. Woese Institute for Genomic Biology.

The National Science Foundation, Simons Foundation, National Natural Science Foundation of China, University of Illinois Urbana-Champaign and the University of Oklahoma supported this research.

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