New research from biology professor Xin Sun provides insight into how climate change affects marine greenhouse gas emissions.
Sun’s research revealed how nitrous oxide, a greenhouse gas 270 times more powerful than carbon dioxide, is produced by undersea microbes. Nitrous oxide production typically increases in the absence of oxygen, but Sun’s research shows that this relationship is not smooth and instead a result of competition between different microbes.
“Experiments demonstrate that this pathway is sensitive to the type of organic matter, its electron acceptor, in addition to organic matter availability,” the project’s abstract reads. “These findings advance our mechanistic understanding of the primary N₂O production pathway, necessary for predictions of marine N₂O emissions.”
In other words, the findings could make more accurate models for predicting the costs of climate change and the role deep-sea organisms play in greenhouse gas emissions.
“Having better information on where and how N₂Os are made can help scientists forecast global emissions more accurately as the climate changes,” Sun wrote to Penn Today.
To accomplish her research, Sun spent six weeks at sea, sampling water from 40 to 120 meters deep in the Eastern Tropical North Pacific Ocean, which contains one of the largest oxygen-depleted areas in the world. Using these findings, Sun developed a new, competition-based model that was then confirmed in a lab.
This new model disproves the simpler pure chemistry model. In Sun’s model, more complicated but efficient pathways of nitrous oxide production were sometimes outcompeted by simpler but less efficient pathways. One pathway would outcompete the other depending on dissolved oxygen levels, contrary to a simple “dimmer switch” model, where more oxygen means less nitrous oxide.
This means that more nutrients, including oxygen, can push the longer, more efficient methods of production completely out, reducing nitrous oxide production to nearly zero.
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“Oxygen doesn’t act like a dimmer switch,” Sun added. “It changes who’s in charge.”
The research was supported by the Simons Foundation, the National Science Foundation, and the Spanish Agency for Research.
Sun’s research group generally focuses on biogeochemical field studies, metagenomics, microbial ecology experiments, and more.
