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Aquatic Microbial Ecology

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AME 53:257-269 (2008)  -  DOI:

Tracing carbon and nitrogen incorporation and pathways in the microbial community of a photic subtidal sand

Victor Evrard1,3,*, Perran L. M. Cook2,4, Bart Veuger1, Markus Huettel2,5, Jack J. Middelburg1

1Netherlands Institute of Ecology, Center for Estuarine and Marine Ecology, PO Box 140, 4400 AC Yerseke, The Netherlands
2Max Planck Institute for Marine Microbiology, Celsiusstrasse 1, Bremen 28359, Germany
3Present address: Department of Oceanography, University of Hawai’i at Manoa, 1000 Pope Road, Honolulu, Hawai’i 96822, USA
4Present address: Water Studies Centre, Monash University, Victoria 3800, Australia
5Present address: Florida State University, Tallahassee, Florida 32306-4320, USA

ABSTRACT: The pathways and fate of C and N in the microbial compartment of a coastal permeable sandy sediment in the photic zone were studied in a pulse-chase experiment. 13C-bicarbonate and 15N-nitrate were added to the water column on top of 5 sediment cores incubated in 4 transparent and 1 opaque laboratory chambers. After 9 h of labelling in the light and dark, stable isotope incorporation by microphytobenthos (MPB) and bacteria was quantified over a period of 4 d through the analysis of phospholipid-derived fatty acids (PLFA) and hydrolysable amino acids (HAA). 13C was fixed by MPB, and more than 50% was directed to the production of extracellular polymeric substance (EPS). MPB 15N incorporation was similar in the dark and in the light. Bacterial activity appeared to have 2 effects that depended on sediment depth: at the sediment surface, there was a steady increase of label in the bacterial PLFA, suggesting metabolism of label-containing EPS; in the subsurface layers, uniform enrichment started immediately after the labelling procedure, indicating continuous incorporation of inorganic C by chemoautotrophic bacteria (Cbac). This experiment demonstrates the efficient transfer of inorganic C and N to the benthic community through the activities of photo- and chemoautotrophic microorganisms, and the role of EPS as a carrier of energy to the benthic microbial food web.

KEY WORDS: Microphytobenthos · Cyanobacteria · EPS · PLFA · Biomarkers · Amino acids · Chemoautotrophy · Permeable sediment · 15N · 13C · Stable isotopes · Nitrate

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Cite this article as: Evrard V, Cook PLM, Veuger B, Huettel M, Middelburg JJ (2008) Tracing carbon and nitrogen incorporation and pathways in the microbial community of a photic subtidal sand. Aquat Microb Ecol 53:257-269.

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