Are benthic nutrient fluxes from intertidal mudflats driven by surface sediment characteristics?

A broad sampling program was carried out in the spring of 2019 on the Brittany coast to assess how the surface sediment characteristics drive the benthic effluxes of ammonium (NHÅ 4 ) and phosphate (PO4) from intertidal mudflats. A total of 200 sediment samples were characterized by their porosity, grain-size, elemental composition and pigment contents, as well as the benthic fluxes of NHÅ 4 and PO4 determined by core incubations. The results showed that (1) a high phaeopigment and iron-bound phosphorus content (Fe-P) and a low porosity were significantly related to the high PO4 flux, and (2) a high porosity and the TN:Org-P ratio in the sediment organic matter (SOM) were related to the high NHÅ 4 flux. This indicated that PO4 fluxes would be more driven by the redox status of the sediment through the desorption of Fe-P under specific anoxic conditions during the algal decomposition. NHÅ 4 fluxes would be more driven by high NHÅ 4 recycling rates from SOM mineralization and high sediment–water exchanges, enhancing the diffusion of NHÅ 4 to the overlying water. The present study allowed to highlight the large variability in the benthic nutrient fluxes at the regional scale, as a result of the connections between microbial (SOM mineralization), chemical (adsorption–desorption) and physical (diffusion) processes.


Benthic nutrient fluxes, Coastal sediment, Organic matter, Spatial variability, Diffusive transport, Microbial and chemical processes

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Louis Justine, Jeanneau Laurent, Andrieux-Loyer Francoise, Gruau Gérard, Caradec Florian, Lebris Nathalie, Chorin Marion, Jardé Emilie, Rabiller Emilie, Petton Christophe, Bouger Guillaume, Petitjean Patrice, Laverman Anniet M. (2021). Are benthic nutrient fluxes from intertidal mudflats driven by surface sediment characteristics?. Comptes Rendus Geoscience. 353 (1). 173-191.,

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