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Marine Ecology Progress Series

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MEPS 544:107-130 (2016)  -  DOI:

Limited effects of nutrient enrichment on bacterial carbon sources in salt marsh tidal creek sediments

Amanda C. Spivak*, Justin Ossolinski

Woods Hole Oceanographic Institution, Marine Chemistry and Geochemistry Department, Woods Hole, MA 02543, USA
*Corresponding author:

ABSTRACT: Bacteria influence carbon cycling in coastal sediments by decomposing the organic matter produced in situ as well as that delivered from the landscape and neighboring ecosystems. Disturbances, such as eutrophication, and seasonal swings in primary production may influence sediment organic matter composition and, as a result, the sources of carbon available to bacteria. We evaluated whether bacterial carbon sources varied between 2 salt marsh tidal creeks with different water column nutrient levels (fertilized versus ambient) and if they changed over a growing season through field observations and stable isotope labeling experiments. Sediment organic matter composition, determined using lipid biomarkers and stable isotopes, was similar between the tidal creeks and did not change over time. In the field, isotopic analysis (natural abundance δ13C) of bacterial lipids and potential organic matter sources revealed that bacteria assimilated carbon from several sources but mainly relied on microalgae. In the experiments, 13C was added to sediment cores from both creeks as sodium bicarbonate (June, August, October) or Spartina alterniflora detritus (August) and traced into lipids representing benthic microalgae (BMA) and bacteria. Bacteria assimilated 13C from BMA and S. alterniflora at similar rates. Further, 13C from S. alterniflora was rapidly transferred to BMA, likely via bacterial respiration. Overall, nutrient enrichment did not affect bacterial carbon sources in the field or incorporation of 13C from BMA and S. alterniflora in the experiments. Tight coupling between BMA and bacteria may explain why nitrogen enrichment effects were limited as well as provide a mechanism for retaining newly fixed and detrital carbon in coastal sediments.

KEY WORDS: Carbon cycling · Eutrophication · Benthic microalgae · Spartina alterniflora · Lipid biomarker

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Cite this article as: Spivak AC, Ossolinski J (2016) Limited effects of nutrient enrichment on bacterial carbon sources in salt marsh tidal creek sediments. Mar Ecol Prog Ser 544:107-130.

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