Geochemistry

Lost N Found

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Science  26 Apr 2013:
Vol. 340, Issue 6131, pp. 408
DOI: 10.1126/science.340.6131.408-a
CREDIT: SASHA TRUBETSKOY/WIKIMEDIA COMMONS

Humans are adding new reactive forms of nitrogen (N) into the environment, which has the potential to cause a range of problems, including eutrophication and the formation of dead zones in lakes and coastal waters. The microorganisms responsible for these “N loss” pathways, known as denitrification or anaerobic ammonium oxidation (anammox), often reside in sediments, but a variable and limiting supply of organic matter makes it difficult to determine which reaction dominates. Babbin and Ward set out to address this problem in the lab by constructing a series of mesocosms out of sediments from the Chesapeake Bay, United States, with large amounts of organic matter added to some of the columns. Over 7 weeks of incubation and monitoring, the proportion of each pathway was dictated more by the relative N content of the organic matter than by the total organic matter content. Moreover, the microbial communities in the sediments were able to quickly adjust to high N loading, such as sewage effluent or fertilizer runoff, so that most of the reactive N would be removed from the ecosystem and potentially released back to the atmosphere.

Environ. Sci. Technol. 10.1021/es304842r (2013).

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