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Chemoautotrophic Carbon Fixation Rates and Active Bacterial Communities in Intertidal Marine Sediments
Boschker, H.T.S.; Vasquez-Cardenas, D.; Bolhuis, H.; Moerdijk-Poortvliet, T.C.W.; Moodley, L. (2014). Chemoautotrophic Carbon Fixation Rates and Active Bacterial Communities in Intertidal Marine Sediments. PLoS One 9(7): e101443 1-12. hdl.handle.net/10.1371/journal.pone.0101443
In: PLoS One. Public Library of Science: San Francisco. ISSN 1932-6203, more
Peer reviewed article  

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  • Boschker, H.T.S., more
  • Vasquez-Cardenas, D., more
  • Bolhuis, H., more
  • Moerdijk-Poortvliet, T.C.W., more
  • Moodley, L., more

Abstract
    Chemoautotrophy has been little studied in typical coastal marine sediments, but may be an important component ofcarbon recycling as intense anaerobic mineralization processes in these sediments lead to accumulation of high amounts ofreduced compounds, such as sulfides and ammonium. We studied chemoautotrophy by measuring dark-fixation of 13Cbicarbonateinto phospholipid derived fatty acid (PLFA) biomarkers at two coastal sediment sites with contrasting sulfurchemistry in the Eastern Scheldt estuary, the Netherlands. At one site where free sulfide accumulated in the pore water rightto the top of the sediment, PLFA labeling was restricted to compounds typically found in sulfur and ammonium oxidizingbacteria. At the other site, with no detectable free sulfide in the pore water, a very different PLFA labeling pattern was foundwith high amounts of label in branched i- and a-PLFA besides the typical compounds for sulfur and ammonium oxidizingbacteria. This suggests that other types of chemoautotrophic bacteria were also active, most likely Deltaproteobacteriarelated to sulfate reducers. Maximum rates of chemoautotrophy were detected in first 1 to 2 centimeters of both sedimentsand chemosynthetic biomass production was high ranging from 3 to 36 mmol C m22 d21. Average dark carbon fixation tosediment oxygen uptake ratios were 0.2260.07 mol C (mol O2)21, which is in the range of the maximum growth yieldsreported for sulfur oxidizing bacteria indicating highly efficient growth. Chemoautotrophic biomass production was similarto carbon mineralization rates in the top of the free sulfide site, suggesting that chemoautotrophic bacteria could play acrucial role in the microbial food web and labeling in eukaryotic poly-unsaturated PLFA was indeed detectable. Our studyshows that dark carbon fixation by chemoautotrophic bacteria is a major process in the carbon cycle of coastal sediments,and should therefore receive more attention in future studies on sediment biogeochemistry and microbial ecology.

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