Impact of microphytobenthos on the sediment biogeochemical cycles: A modeling approach |
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| Authors: | Sébastien Hochard Christel Pinazo Christian Grenz Jessica L Burton Evans Olivier Pringault |
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| Institution: | 1. Université de la Rochelle-CNRS, UMR 7266, Littoral Environnement et Sociétés (LIENSs), 2 rue Olympe de Gouges, 17000 La Rochelle cedex, France;2. Station Maritime de Dinard, Museum National d''Histoire Naturelle, 17 avenue George V, BP28, 35801 Dinard, France;3. UMR 5805 EPOCU, Station Marine d''Arcachon, Université Bordeaux 1, 2 Rue du Professeur Jolyet, 33120 Arcachon cedex, France;4. Laboratoire d''Océanographie Biologique de Banyuls, rue du Fontaulé, BP 44, 66651 Banyuls sur mer cedex, France;5. Université de Lille 1/Station Marine de Wimereux, UMR CNRS 8187, Laboratoire d''Océanographie et de Géoscience (LOG), 28 avenue Foch, 62930 Wimereux, France;6. CNRS-Université de Clermont-Ferrand II, UMR 6023, Laboratoire Microorganismes: Génome et Environnement, 24 avenue des Landais, 63177 Aubière Cedex, France;7. Université du Maine, EA 2663«Ecophysiologie Marine Intégrée»Laboratoire de Physiologie et Biochimie Végétales, avenue Olivier Messiaen, 72085 Le Mans cedex 9, France;8. Université de Caen Basse-Normandie, FRE3484 BioMEA CNRS, Esplanade de la Paix, 14032 Caen cedex, France;9. Université des Antilles et de la Guyane, UMR 7138 SAE, Pointe-à-Pitre, Guadeloupe;10. Bedford Institute of Oceanography, 1 Challenger Drive, P.O. Box 1006, Dartmouth, NS B2Y 4A2, Canada;1. Laboratorio de Ecología, Instituto de Investigaciones Marinas y Costeras (IIMyC; Consejo Nacional de Investigaciones Científicas y Técnicas - Universidad Nacional de Mar del Plata), CC 573 Correo Central, B7600WAG Mar del Plata, Argentina;2. Departamento de Química, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Mar del Plata, Funes 3350 Mar del Plata, Argentina;3. Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Av. Rivadavia 1917, C1033AAJ Buenos Aires, Argentina |
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| Abstract: | In marine biogeochemical modeling, the sediment is usually represented by diagenetic models, but in shallow ecosystems these models are incomplete, because they do not take into account the benthic primary production. While microphytobenthos (MPB) is known to strongly impact mineralization pathways and nutrient fluxes, MPB is rarely integrated as an explicit variable. To investigate the impact of microphytobenthos on early diagenesis in sediment, we built a fine-scale dynamic model, based on the diagenetic model OMEXDIA and including MPB and associated processes. The model outputs were similar to a data set of MPB-colonized sediment sampled in Florida Bay, suggesting that the model can recreate a realistic situation. The model showed that MPB activities induced a strong diurnal rhythm on concentration profiles, fluxes, and mineralization processes. When MPB was present at the sediment surface, the total mineralization was strongly enhanced thanks to the supply of labile organic matter. In contrast, coupled nitrification–denitrification was inhibited by a factor of 3.8. This inhibition can be explained by the competition for nitrate and ammonium between MPB and bacteria. Nitrogen uptake of MPB represented 96% of the daily supply of dissolved inorganic nitrogen. This was more than 50 times greater than N consumption by denitrification. With MPB, sediment nitrogen flux to the water column was reduced by a factor of 70, suggesting that sediment colonized by MPB represents a minor source of nutrients for phytoplankton and bacterioplankton. Results showed that current diagenetic models are not well-suited for shallow ecosystems with significant MPB primary production. |
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