Spatial Variability of Organic Matter and Phosphorus Cycling in Rhône River Prodelta Sediments (NW Mediterranean Sea, France): a Model-Data Approach

Type Article
Date 2021-11
Language English
Author(s) Ait Ballagh Fatima Ezzahra1, 2, Rabouille Christophe1, Andrieux-Loyer FrancoiseORCID3, Soetaert Karline4, Lansard Bruno1, Bombled Bruno1, Monvoisin Gael5, Elkalay Khalid2, Khalil Karima2
Affiliation(s) 1 : ViolaineLaboratoire des Sciences du Climat et de l’Environnement, Laboratoire Mixte CEA-CNRS-UVSQ, IPSL et Université Paris-Saclay, CEA-Orme des Merisiers, 91191, Gif sur Yvette, France
2 : Laboratory of Applied Sciences for the Environment and Sustainable Development, Essaouira School of Technology, Cadi Ayyad University, Km 9, Route d’Agadir, BP. 383, Essaouira Aljadida, Morocco
3 : Ifremer ,DYNECO PELAGOS, ZI Pointe du Diable, 29280, Plouzané, France
4 : Department of Estuarine and Delta Systems, Royal Netherlands Institute for Sea Research (NIOZ) and Utrecht University, P.O. Box 140, 4400 AC, Yerseke, The Netherlands
5 : GEOPS, Université Paris-Saclay et CNRS, Campus d’Orsay, Orsay, France
Source Estuaries And Coasts (1559-2723) (Springer), 2021-11 , Vol. 44 , N. 7 , P. 1765-1789
DOI 10.1007/s12237-020-00889-9
WOS© Times Cited 7
Keyword(s) Organic matter, Phosphorus, Mediterranean Sea, Rh&#244, ne River prodelta, Sediment, Modelling

The Mediterranean Sea (MS) is a large oligotrophic sea whose productivity is sensitive to riverine nutrient inputs. More specifically, phosphorus (P) river supply is crucial for the MS, with an important role of the estuarine/deltaic filter especially for the storage and recycling in sediments. A benthic dataset from the Rhône River prodelta was used to derive P budgets, by means of an early diagenetic model including the benthic P cycle. The model was fitted to pore water profiles of oxygen, nitrate, sulfate, dissolved inorganic carbon, ammonium, oxygen demand units, dissolved inorganic phosphorus (DIP) and solid data (organic carbon (OC), Fe-bound P, Ca-bound P and organic P). Results indicated that the intensity of biogeochemical processes occurring below the sediment–water interface decreased from the river mouth to the adjacent continental shelf with decreasing integrated rates of OC mineralization (160–10 mmol m−2 day−1). The organic P mineralization was intense near the river mouth and decreased offshore (1196–80 μmol m−2 day−1). Its contribution to DIP release was large (> 90%). Fe-bound P had a key role in transferring P to deeper layers. These deltaic sediments played an important role as a source of regenerated DIP. A significant part of DIP was recycled to the overlying waters (72–94%), representing 25% of the riverine DIP discharge. Simultaneously, 6–28% of DIP produced in sediments was buried as Ca-bound P. Overall, this study highlighted the importance of deltaic sediments as an additional source of DIP to the coastal sea, and a minor but permanent sink of phosphorus as solid P burial.

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Ait Ballagh Fatima Ezzahra, Rabouille Christophe, Andrieux-Loyer Francoise, Soetaert Karline, Lansard Bruno, Bombled Bruno, Monvoisin Gael, Elkalay Khalid, Khalil Karima (2021). Spatial Variability of Organic Matter and Phosphorus Cycling in Rhône River Prodelta Sediments (NW Mediterranean Sea, France): a Model-Data Approach. Estuaries And Coasts, 44(7), 1765-1789. Publisher's official version : , Open Access version :