Explaining mysterious source of greenhouse gas methane in the ocean
For decades, marine chemists have faced an elusive paradox. The surface waters of the world’s oceans are supersaturated with the greenhouse gas methane, yet most species of microbes that can generate the gas can’t survive in oxygen-rich surface waters. So where exactly does all the methane come from? This longstanding riddle, known as the “marine methane paradox,” may have finally been cracked thanks to a new study by researchers from the Woods Hole Oceanographic Institution (WHOI) and SOEST.
According to the study, published this week in the journal Nature Geoscience, the answer may lie in the complex ways that bacteria break down dissolved organic matter, a cocktail of substances excreted into seawater by living organisms.
The researchers found that much of the ocean’s dissolved organic matter is made up of novel polysaccharides—long chains of sugar molecules created by photosynthetic bacteria in the upper ocean. Bacteria begin to slowly break these polysaccharides, tearing out pairs of carbon and phosphorus atoms (called C-P bonds) from their molecular structure. In the process, the microbes create methane, ethylene, and propylene gasses as byproducts. Most of the methane escapes back into the atmosphere
“All the pieces of this puzzle were there, but they were in different parts, with different people, in different labs, at different times,” says WHOI geochemist and lead author Dan Repeta. “This paper unifies a lot of those observations.”
UH co-authors include microbial oceanographers Sara Ferrón, Oscar A. Sosa, Edward DeLong, and David Karl.
“This study proves the value of collaboration in science,” said Karl, the Victor and Peggy Brandstrom Pavel Professor of Oceanography at UH. “No single person of our research group could have solved this important puzzle alone.”
Read more about it in the UH System News.