| Summary: | This data set contains concentrations of chloride and other anions (in units of micromoles per liter) in soil pore water collected from eight sites across the Arctic Coastal Plain of northern Alaska in July 2018. Soil water was collected from various depths and analyzed by ion chromatography (Dionex ICS5000+). These data support a study of biological chlorine cycling in the Arctic and its influence on greenhouse gas production. Microbes that can decompose chlorinated organic compounds were once considered relevant only in areas contaminated with pesticides and organic solvents. However, biological chlorine cycling is proving to be widespread in natural environments. Previous studies of biological chlorine cycling were mostly limited to forested ecosystems. This project was the first to demonstrate the importance of the production and degradation of chlorinated organic compounds in Arctic soils. Furthermore, there was little information about the linkages between chlorine cycling and other important ecosystem processes, such as production of carbon dioxide and methane from soils. Species in the genus Dehalococcoides are highly specialized, using hydrogen, acetate, vitamin B12-like compounds, and organic chlorine produced by the surrounding community. We studied which neighbors might produce these essential resources for Dehalococcoides species. We found that Dehalococcoides species are ubiquitous across the Arctic Coastal Plain and are closely associated with a network of microbes that produce or consume hydrogen or acetate, including the most abundant anaerobic bacteria and methanogenic archaea. We also found organic chlorine and microbes that can produce these compounds throughout the study area. Therefore, Dehalococcoides could control the balance between carbon dioxide and methane (a more potent greenhouse gas) when suitable organic chlorine compounds are available to drive hydrogen and acetate uptake, making them unavailable for methane production.
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