From Drowning to Dried Up

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Science  01 Nov 2013:
Vol. 342, Issue 6158, pp. 535
DOI: 10.1126/science.342.6158.535-b

Anthropogenic methane emitted into the atmosphere is a concern because of its behavior as a greenhouse gas. However, naturally abundant anaerobic microorganisms in soils and sediments also produce methane. In lake sediments, this occurs at depths in the sediment column where oxygen is no longer present and when the sediments are constantly submerged in water. To understand how methanogenic microbial communities respond to periods of desiccation and exposure to oxygen, Conrad et al. compared the rates of methanogenesis, gene abundance, and microbial community structure of anoxic sediments from nine oxbow lakes in the Brazilian Amazon region, before and after a cycle of drying and rewetting. In lakes where water was clear or contained a high concentration of organic matter, archaeal and bacterial diversity decreased, but methane production rates increased. If extreme drying events in oxbow lakes become more common as a result of climate change, the balance of microbial methane production relative to consumption this may become unbalanced, and may have unknown consequences for the carbon cycle.

Environ. Microbiol. 10.1111/1462-2920.12267 (2013).

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