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With and in New Hampshire, water is critical to the health, economy and recreation of Granite Staters. However, with aquatic ecosystems annually releasing about half of the methane that enters the atmosphere, New Hampshire water may be playing a bigger role in the environment than previously thought. from the (NHAES) has focused on how bodies of water emit greenhouse gases and are incorporated into developing climate change models.

Different aquatic bodies play different roles in the release of methane gas. Wetlands, lakes, and reservoirs all play large roles in releasing methane directly into the atmosphere, primarily through a process known as ebullition, in which methane literally bubbles out of the wetland and enters the atmosphere, contributing to the greenhouse gas effect.

Rivers and streams, however, were historically seen as pipelines for simply moving material between bodies of water. They weren鈥檛 viewed as important pieces of the global methane cycle, describes , a graduate of the Ph.D. program in Earth and Environmental Science at COLSA, former NHAES graduate research assistant, and a post-doctoral scientist in the aquatic biogeochemistry program at (EPFL) in Switzerland. in journal that shows that small streams are sources of methane to the atmosphere and that nearly half of the methane within small streams actually oxidizes 鈥� the chemical process of combining with oxygen. The oxidization removes the gas out of the global methane cycle rather than it being emitted to the atmosphere.

鈥淚n terms of methane release and the carbon cycle, streams are understudied aquatic ecosystems compared to lakes, reservoirs and wetlands.鈥�

鈥淚n terms of methane release and the carbon cycle, streams are understudied aquatic ecosystems compared to lakes, reservoirs and wetlands,鈥� describes Robison. 鈥淭his is in part because flow makes streams a little more difficult to study than ponds or lakes; spatial variability is more dramatic in streams than in waterbodies that don鈥檛 have flow.鈥�

鈥淗owever, the more we examine streams, the more we understand them to be active in the methane cycle and vents of methane to the atmosphere,鈥� he adds.

Robison and his co-authors measured the methane emissions and soil microbial communities within . Samples were collected from the four streams roughly each week and then analyzed at the at the . The microbial communities in the streambeds were analyzed at the to identify the presence of the types of bacteria that create (called methanogens) and oxidize (called methanotrophs) methane.

鈥淪treams are really the next frontier in understanding aquatic methane cycling as we know very little in comparison to lake and wetland methane emissions,鈥� describes , professor of biogeochemistry in and principal of UNH鈥檚 Trace Gas Biogeochemistry Lab. 鈥淚t is critical for collaborations like this across our research groups to measure methane using common techniques in both the field and laboratory to help us understand the contribution of aquatic ecosystems to atmospheric methane.鈥�

From these samples, the researchers discovered that the streams were dynamic places of methane production and oxidation. However, the flow in streams appears to differentiate how methane cycles in streams compared to lakes and wetlands.

鈥淲hat happens in streams is that currents are constantly mixing and helping to pull oxygen into them, down near the places in the soil where there is no oxygen and where methane is created through a process called methanogenesis,鈥� describes , a station scientist and associate professor at COLSA, and the co-director of the . 鈥淚t鈥檚 in these oxygenated layers 鈥� just above the soils, where oxygen is being introduced by currents 鈥� where microbes called methanotrophs consume the methane, oxidizing the gas and preventing it from being released into the atmosphere.鈥�

Their research also showed that streams are different from wetlands and lakes in that most of the methane that is emitted from streams is not through ebullition, but through diffusion. As a result, the chemical signature of the methane is slightly different. According to Robison, measuring these differences in streams is critical to analyzing their role within the global carbon and methane cycles.

鈥淢ethane is a potent greenhouse gas 鈥� approximately 30 times as powerful as carbon dioxide. Because aquatic ecosystems are the largest natural source of methane on the planet, we need to really understand the patterns of methane emissions from all aquatic ecosystems.鈥�

鈥淢ethane is a potent greenhouse gas 鈥� approximately 30 times as powerful as carbon dioxide. Because aquatic ecosystems are the largest natural source of methane on the planet, we need to really understand the patterns of methane emissions from all aquatic ecosystems, including streams, to understand the global methane cycle fully.鈥�

Robison co-authored the paper with Wollheim and assistant professor , both experimental station researchers in the , and professor Varner of the earth sciences department at UNH. Additional co-authors included graduate research assistant Paige Clarizia 鈥�19, 鈥�20G; postdoctoral researcher ; undergraduate researcher Annie Cotter; and postdoctoral researcher .

This material is based on work supported by the NH Agricultural Experiment Station through joint funding form the (under Hatch awards number 1022476 and 1016134) and the state of New Hampshire. Additional funding for this project comes from the Plum Island Ecosystems LTER NSF Award OCE-1637630, the National Aeronautics and Space Administration Interdisciplinary Science award NNX17AK10G, and the 麻豆app College of Life Sciences and Agriculture鈥檚 Paine Fund.