LTSER Zone Atelier Seine - Estuaire de la Seine - France
LTSER Zone Atelier Seine - Estuaire de la Seine
Estuaire de la Seine
Parent Site Name
The Seine estuary is a megatidal estuary located in northern France. It is the third largest estuarine ecosystem in the country after the Gironde and Loire along the French Atlantic coast; its waters flow into the English Channel. The geographical zone of influence of the Seine estuary runs from just upstream of the Poses dam, at the limit of the tidal penetration into the estuary — 160 km upstream of Le Havre —to the eastern part of the Bay of Seine. It can be divided into three sections: the fresh water upstream section (125 km), the mixing zone characterized by varying salinity levels (35 km), and the marine downstream section under the influence of the Seine River. The megatidal regime generates a turbidity maximum in the mixing zone (middle estuary) between the marine and fluvial sections of the estuary. The Seine estuary is a typical estuarine ecosystem: highly stressed by natural fluctuations and anthropogenic pressures, and hosting a rich ecological system. The Seine valley and its estuary are of major economic importance for France, with the presence of two maritime ports. It’s watershed (79,000 km2) is the home to 17 million people, and accounts for 50 % of the river traffic in France, 40 % of the country's economic activity, and 30 % of its agricultural activities. In addition to the Greater Paris area (> 11 million inhabitants), which contributes heavily to the Seine estuary's upstream inputs, two other major river settlements — Rouen (500,000 inhabitants) and Le Havre (300,000 inhabitants) — are maritime ports of international importance. Due to economic development, the Seine estuary has been subjected to major hydrodynamic, ecological, biogeomorphological and biogeochemical changes. The importance of studying the effects of anthropogenic impacts on estuarine ecosystems has increased in the last decade, especially under the Water Framework Directive, which aims to achieve “good environmental status” of all European water bodies.
General Characteristics, Purpose, History
The objective is to understand the influence of natural and anthropogenic drivers on the estuarine functioning. Research program focuses on relationships between physical parameters (water and matter fluxes, habitat structures) and biogeochemical/biological processes supporting biological productivity and biodiversity. The main purpose is to help stakeholders identifying the most effective ways to improve estuarine ecological functions and ecosystem services within the context of social and economic development.
The Seine-Aval research program started in 1995. The aim was to improve our understanding of processes affecting the observed trends through interdisciplinary studies and integrative modeling strategy. Hydrodynamics, morphology and ecological functioning are closely linked to the dynamics of the estuarine ecosystems. In order to better understand the role of hydrological/meteorological drivers and anthropic activities (i.e. dredging, port development, flood control, etc.) on the physical evolution of the estuary, the research program also involves high-frequency monitoring and detailed modelling of sand/mud dynamics. The drivers of sources and sinks of nutrients and of primary production are studied. The estuarine function may play a role in limiting eutrophication in marine waters. Long term data series contain information on biodiversity, biomass and processes (e.g. production, diet, migration) of most living compartments of the ecosystem, from primary producers to fish and birds. The objectives of studies on functional biodiversity are to refine the connection between physical and biogeochemical processes with ecological processes (predator-prey interactions, productions, migrations), at several levels of integration, from the habitat scale to the overall ecosystem. The nursery function for marine fishes is a major subject of interest as the restoration of the Seine estuary could contribute to the stability of fish populations in the channel. As the Seine estuary is one of the most polluted in France, the research program also focused on contaminant dynamics and its impacts on the ecosystem functioning. Most studies are closely related to those of the Piren-Seine program (river basin) inside the LTSER Zone-Atelier Seine - France.