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ENVIRONMENTAL SCIENCES
Temperature-driven decoupling of key phases of organic matter degradation in marine sediments
Department of Marine Sciences, University of Georgia, Athens, GA 30602
Communicated by William H. Schlesinger, Duke University, Durham, NC, October 7, 2005 (received for review August 29, 2005)
The long-term burial of organic carbon in sediments results in the net accumulation of oxygen in the atmosphere, thereby mediating the redox state of the Earth's biosphere and atmosphere. Sediment microbial activity plays a major role in determining whether particulate organic carbon is recycled or buried. A diverse consortium of microorganisms that hydrolyze, ferment, and terminally oxidize organic compounds mediates anaerobic organic matter mineralization in anoxic sediments. Variable temperature regulation of the sequential processes, leading from the breakdown of complex particulate organic carbon to the production and subsequent consumption of labile, low-molecular weight, dissolved intermediates, could play a key role in controlling rates of overall organic carbon mineralization. We examined sediment organic carbon cycling in a sediment slurry and in flow through bioreactor experiments. The data show a variable temperature response of the microbial functional groups mediating organic matter mineralization in anoxic marine sediments, resulting in the temperature-driven decoupling of the production and consumption of organic intermediates. This temperature-driven decoupling leads to the accumulation of labile, low-molecular weight, dissolved organic carbon at low temperatures and low-molecular weight dissolved organic carbon limitation of terminal metabolism at higher temperatures.
carbon cycle | fermentation | terminal metabolism | sulfate reduction
Conflict of interest statement: No conflicts declared.
Freely available online through the PNAS open access option.
Abbreviations: LMW, low molecular weight; DOC, dissolved organic carbon; VFA, volatile fatty acid; DIC, dissolved inorganic carbon; PLFA, phospholipid fatty acid; MI, metabolic index.
* Present address: Patrick Center for Environmental Research, Academy of Natural Sciences, Philadelphia, PA 19102.
To whom correspondence should be addressed at: Department of Marine Sciences, Marine Sciences Building, Room 220, University of Georgia, Athens, GA 30602-3636. E-mail: mjoye{at}uga.edu.
© 2005 by The National Academy of Sciences of the USA
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