Modeling the biogeochemical functioning of the Seine estuary and its coastal zone: Export, retention, and transformations

Type Article
Date 2019-05
Language English
Author(s) Romero Estela1, 2, Garnier Josette1, 3, Billen Gilles1, 3, Ramarson Antsiva1, Riou Philippe4, Le Gendre RomainORCID5
Affiliation(s) 1 : Sorbonne Université, UMR 7619 Metis; Paris, France
2 : Global Ecology Unit; CREAF-UAB; Bellaterra ,Spain
3 : CNRS, UMR 7619 Metis; Paris ,France
4 : Département Océanographie et Dynamique Ecosystème; IFREMER; Plouzané ,France
5 : Unité de Recherche Lagons, Ecosystèmes et Aquaculture Durable; IFREMER; Nouméa, New-Caledonia
Source Limnology And Oceanography (0024-3590) (Wiley), 2019-05 , Vol. 64 , N. 3 , P. 895-912
DOI 10.1002/lno.11082
WOS© Times Cited 10

The model ECO‐MARS3D, successfully applied thus far to coastal ecosystems, has been extended to encompass the Seine estuary up to Poses, at the limit between the river and the estuary. We used updated bathymetric data and thoroughly calibrated the hydrodynamics and the sedimentary dynamics in the turbidity maximum zone (TMZ). Biogeochemical processes related to oxygen were newly implemented, and freshwater phytoplankton and zooplankton groups were added to the existing marine groups. The simulations allowed us to evaluate the filter effect of the estuary with regard to the main nutrients (N, P, and Si). Today, this filter role appears quite limited and variable depending on the hydrology. On average, considering three different hydrological years, the estuary was able to retain (at least temporarily) 19 kt N yr−1, 10 kt Si yr−1, and 0.7 kt P yr−1, amounting to −13%, −11%, and −27% of the total N, Si, and P inputs, respectively. Seasonal differences in the filtering capacity (lower in winter than in summer) were similar between wet and dry years. Nutrient retention was higher in the upstream fluvial estuary than in the TMZ, the former being mostly characterized by uptake, the latter by remineralization. At the coastal zone, the dry year showed greater risk of eutrophication. Despite lower discharge and lower nutrient fluxes, inputs were confined into a shallower layer, close to the coastline, where nutrients were concentrated and allowed phytoplankton to thrive. Differences in the N : P : Si ratios (lower P‐deficit during dry years) could also underpin the larger proliferations, and notably the larger dinoflagellate blooms during dry years.

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Publisher's official version 18 6 MB Open access
Appendix 1. Parameters and state variables used in the ecological sub‐model. Further details can be found online [] 3 81 KB Open access
Appendix 2. Main differential equations used in the Ecological sub‐model. Part of these formulae have already been described in Cugier et al. (2005a), but changes and new equations have been... 6 17 MB Open access
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Romero Estela, Garnier Josette, Billen Gilles, Ramarson Antsiva, Riou Philippe, Le Gendre Romain (2019). Modeling the biogeochemical functioning of the Seine estuary and its coastal zone: Export, retention, and transformations. Limnology And Oceanography, 64(3), 895-912. Publisher's official version : , Open Access version :