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Marine Ecology Progress Series

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MEPS 416:1-16 (2010)  -  DOI:

Carbon and nitrogen flows through the benthic food web of a photic subtidal sandy sediment

Victor Evrard1,5,*, Karline Soetaert1, Carlo H. R. Heip1, Markus Huettel2,6, Marguerite A. Xenopoulos3, Jack J. Middelburg1,4

1Netherlands Institute of Ecology (NIOO-KNAW), Center for Estuarine and Marine Ecology, PO Box 140, 4400 AC Yerseke, The Netherlands
2Max Planck Institute for Marine Microbiology, Celsiusstraße 1. 28359 Bremen, Germany
3Trent University, Department of Biology, 1600 West Bank Drive, Peterborough Ontario K9J 7B8, Canada
4Utrecht University, Faculty of Geosciences, Budapestlaan 4, 3584 CD Utrecht, The Netherlands
5Present address: University of Hawaii at Manoa, Department of Oceanography, 1000 Pope Road, Honolulu, Hawaii 96822, USA
6Present address: Florida State University, Department of Oceanography, 117 N Woodward Ave., Tallahassee, Florida 32306-4320, USA

ABSTRACT: Carbon and nitrogen flows within the food web of a subtidal sandy sediment were studied using stable isotope natural abundances and tracer addition. Natural abundances of 13C and 15N stable isotopes of the consumers and their potential benthic and pelagic resources were measured. δ13C data revealed that consumers did not feed on the bulk microphytobenthos (MPB) but rather were selective in their food uptake, preferring either benthic diatoms (–16‰), or benthic cyanobacteria (–20‰). MPB was labelled through a pulse-chase experiment with 13C-bicarbonate and 15N-nitrate. The fate of MPB was followed in the different heterotrophic compartments. Transfer of 13C and 15N to consumers was fast, although only a small fraction of total label was transferred to the heterotrophic compartments within the 4 d of the experiment. Heterotrophic bacteria were responsible for most of the total heterotrophic incorporation of 13C. Within the metazoan community, the incorporation of 13C by the meiofauna was more than 2-fold that of the macrofauna, despite a significantly lower biomass. The dual labelling also revealed differential feeding or assimilation strategies in meio- and macrofauna. The low 13C:15N ratios of the meiofauna (the smaller organisms) seemed to indicate that they preferentially assimilated N or specifically grazed on N-rich resources. However, the macrofauna (larger organisms) seemed to feed on bulk sediment, consistent with high 13C:15N ratios. This dual approach, which combined natural abundance and a pulse-chase addition of stable isotopes, revealed crucial information on the key role of MPB in structuring benthic communities in sandy sediments.

KEY WORDS: Stable isotopes · Food web · 13C · 15N · Microphytobenthos · Meiofauna · Macrofauna · Bacteria · PLFA

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Cite this article as: Evrard V, Soetaert K, Heip CHR, Huettel M, Xenopoulos MA, Middelburg JJ (2010) Carbon and nitrogen flows through the benthic food web of a photic subtidal sandy sediment. Mar Ecol Prog Ser 416:1-16.

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