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MSEAS - Brest Dynamic simulations of the Seine estuary food web: Towards a holistic and integrated approach of management scenarios on ecosystem functioning Samuele Tecchio, Jean-Claude Dauvin, Pascal Galichon, Nathalie Niquil Université de Caen Normandie funded by Le Havre Port Authority (GPMH) and Agence de l’Eau Seine-Normandie (AESN) MSEAS - Brest The Seine estuary: MSEAS - Brest The estuary before Port2000 MSEAS - Brest Port2000 (building 2002-2003) MSEAS - Brest The estuary in 2006 MSEAS - Brest The new dune system MSEAS - Brest Seabirds repository isle MSEAS - Brest A multitude of actors MSEAS - Brest Studying impacts… • • New container terminal, dredging, Positive efforts of mitigation • Changing hydrography at the same time: Before/after study was unable to discriminate impacts • Temporal-dynamic ecosystem model: direct contact with managers MSEAS - Brest • Ecopath : snapshot of the food web (1996) • Base structure for dynamic simulations MSEAS - Brest Time-dynamic simulation Equations : Forcing data: Reference series: - Foraging (e.g. search rates) - Mediation (indirect effects) - Primary production - Organic matter input - Landings and fishing effort Biomasses obtained with scientific sampling MSEAS - Brest FORCING TIME SERIES Primary production : conc. ChlA (µg/l) -> tC/km2 Organic matter input : Seine flow (m3/y) × conc. C (g/m3) × surface of model (1/m2) = Detritus import flow MSEAS - Brest Model fitting MSEAS - Brest Scenarios • Absence of mitigation measures • How would species change in the case of loss of intertidal flat? • Expert knowledge for species responses (other scientists) • The modeller synthesises their ideas MSEAS - Brest MIXED TROPHIC IMPACT: Low impact of fishing relative to biotic relations MSEAS - Brest TST • ENA indices: related to system stress and resilience SOI • Trophic specialisation, stable recycling, reduction in link redundancy: system maturation FCI R/DC MSEAS - Brest Conclusions • Network analysis: a set of methods to study changes in ecosystem functioning • • • Time-dynamic simulations follow ecological indicators over the years • • • Complexity: contradictions due to non-monotonous responses Link with resilience and ecosystem stress Surveillance tool Scenario testing to deconvolute effects Bringing experts and managers together to synthesize their ideas into a scenario simulation MSEAS - Brest