MEPS 394:35-48 (2009)  -  doi:10.3354/meps08270

Carbon and nitrogen cycling on intertidal mudflats of a temperate Australian estuary. IV. Inverse model analysis and synthesis

Perran L. M. Cook1,*, Dick Van Oevelen2, Karline Soetaert2, Jack J. Middelburg2,3

1Water Studies Centre, Monash University, Clayton 3800, Victoria, Australia
2Centre for Estuarine and Marine Ecology, Netherlands Institute of Ecology, Korringaweg 7, 4401 NT Yerseke, The Netherlands
3Faculty of Geosciences, Utrecht University, PO Box 80021, 3508 TA Utrecht, The Netherlands

ABSTRACT: Microphytobenthos (MPB) are recognised as exerting an important controlling influence over C and N flows in euphotic sediments; however, the coupling between these flows remains poorly studied. We undertook an inverse model analysis of C and N fluxes through the microbial compartment on intertidal flats in a temperate estuary. The analysis showed that the trophic balance of the sediment exerted a strong influence on the relative fluxes of C and N through the sediment microbial community. Under increasingly autotrophic conditions (production:respiration >1), the assimilation of C relative to N rose above the cellular C:N ratio of MPB, resulting in increased excretion rates of organic matter by MPB. The C:N ratio of the organic matter excreted was also highly variable, ranging from ~20 (mol:mol) under heterotrophic conditions, and increasing to >50 under autotrophic conditions. The relative fluxes of C and N through bacteria were also significantly affected by the trophic balance of the sediment and the ratio of C:N mineralized by bacteria was significantly higher under autotrophic conditions. Dissolved organic N release by bacteria and uptake by MPB also predominated over inorganic N forms under autotrophic conditions. We conclude that C and N fluxes through shallow euphotic sediments may become significantly decoupled and well above the commonly assumed Redfield ratio and measured cellular C:N ratios of MPB.


KEY WORDS: Nitrogen · Carbon · Sediment · Microphytobenthos · Stoichiometry · Inverse model


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Cite this article as: Cook PLM, Van Oevelen D, Soetaert K, Middelburg JJ (2009) Carbon and nitrogen cycling on intertidal mudflats of a temperate Australian estuary. IV. Inverse model analysis and synthesis. Mar Ecol Prog Ser 394:35-48

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