FN Archimer Export Format PT J TI Modeling the biogeochemical functioning of the Seine estuary and its coastal zone: Export, retention, and transformations BT AF Romero, Estela Garnier, Josette Billen, Gilles Ramarson, Antsiva Riou, Philippe Le Gendre, Romain AS 1:1,2;2:1,3;3:1,3;4:1;5:4;6:5; FF 1:;2:;3:;4:;5:PDG-ODE;6:PDG-RBE-LEADNC; C1 Sorbonne Université, UMR 7619 Metis; Paris, France Global Ecology Unit; CREAF-UAB; Bellaterra ,Spain CNRS, UMR 7619 Metis; Paris ,France Département Océanographie et Dynamique Ecosystème; IFREMER; Plouzané ,France Unité de Recherche Lagons, Ecosystèmes et Aquaculture Durable; IFREMER; Nouméa, New-Caledonia C2 UNIV PARIS 06, FRANCE CREAF, SPAIN CNRS, FRANCE IFREMER, FRANCE IFREMER, FRANCE SI BREST NOUMEA SE PDG-ODE PDG-RBE-LEADNC IN WOS Ifremer UPR copubli-france copubli-europe copubli-univ-france IF 3.778 TC 12 UR https://archimer.ifremer.fr/doc/00469/58067/60463.pdf https://archimer.ifremer.fr/doc/00469/58067/60464.pdf https://archimer.ifremer.fr/doc/00469/58067/60465.pdf LA English DT Article AB 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. PY 2019 PD MAY SO Limnology And Oceanography SN 0024-3590 PU Wiley VL 64 IS 3 UT 000467593600005 BP 895 EP 912 DI 10.1002/lno.11082 ID 58067 ER EF