Are benthic nutrient fluxes from intertidal mudflats driven by surface sediment characteristics?
|Author(s)||Louis Justine1, Jeanneau Laurent2, Andrieux-Loyer Francoise3, Gruau Gérard2, Caradec Florian3, Lebris Nathalie1, Chorin Marion1, Jardé Emilie2, Rabiller Emilie3, Petton Christophe2, Bouger Guillaume1, Petitjean Patrice2, Laverman Anniet M.1|
|Affiliation(s)||1 : Centre National de la Recherche Scientifique (CNRS), ECOBIO – UMR 6553, Université de Rennes 1, 35042 Rennes, France
2 : Centre National de la Recherche Scientifique (CNRS), Géosciences Rennes – UMR 6118, Université de Rennes 1, 35042 Rennes, France
3 : Ifremer, DYNECO PELAGOS, ZI Pointe du Diable, 29280 Plouzané, France
|Source||Comptes Rendus. Géoscience (1778-7025) (Are benthic nutrient fluxes from intertidal mudflats driven by surface sediment characteristics?), 2021 , Vol. 353 , N. 1 , P. 173-191|
|Keyword(s)||Benthic nutrient fluxes, Coastal sediment, Organic matter, Spatial variability, Diffusive transport, Microbial and chemical processes.|
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.