PAst to Current land-sea Continuum: socio-ecosystem Trajectories derived from a regional pilot site

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UMR 6538 Geo-Ocean
Laboratoire Environnement Ressources de Bretagne Occidentale
Centre de Recherche Bretonne et Celtique

Financeur du programme

programme national


The PACTE project is an interdisciplinary study of the macro-tidal estuarine environment of the Bay of Brest (BoB), a coastal ecosystem that has been exposed to strong anthropogenic pressures over the past decades, especially in the aftermath of World War II (WWII). Using sediment cores retrieved in the BoB, PACTE aims at reconstructing past environmental changes at a high temporal resolution (subdecadal to annual) over the past (at least two) centuries, in order to create the first complete chrono-systemic timeline of main BoB socio-ecosystemic changes over the land-sea continuum. To do so, the project will combine several techniques. Fossilized marine bio-indicators and biomolecular tools will allow to analyse past changes in protist communities as a whole as well as past occurrences of toxic species. In parallel, changes in BoB landscapes will be investigated using sedimentological analyses and pollen tracers, while the sources and dispersion of historical pollutions (occasional or chronic) will be investigated using trace metals and lead (Pb) isotopes. All data obtained from BoB sediment cores will be gathered with instrumental data (issued by IUEM observatory services and watershed managers) as well as historical chronicles (ongoing PhD that started in October 2021 between IUEM and CRBC). In parallel, a model of the land-sea continuum will be developed and validated against current environmental data before being applied to the pre-WWII period. The model-data intercomparison will allow i) to establish and discuss robust causal relationships between the different eco-socio compartments established thanks to paleo-reconstructions, and ii) to simulate as accurately as possible past to current trajectories, then allowing to consider the simulation of future trajectories under different scenarios in a next future (perspectives post-PACTE). Working at the local spatial scale (BoB) is necessary to tackle the objectives of PACTE, especially in order to address robust correlations between driving forces and environmental changes. Considering the importance PACTE topics and expected outcomes carry for coastal management worldwide, we ambition that PACTE methodologies will be applicable at broader scales. In order to improve the capacity of the PACTE project approach (detailed complex socio-environmental river/coastal systems) to spread within the international coastal sciences community, PACTE team with the University of Nevada (i.e. team recognized for integrating “history-climate-ecology” inseparable-interconnected disciplines) plan to organize a joint international thematic school and an international conference at the IUEM. In addition, these results will be contextualised at the European-scale in the framework of the 2022-2024 project TREC (TRaversing European Coastline) led by EMBL and co-organised with Tara Foundation, Ifremer and EMBRC, allowing for international exchanges (students and invited professors) over the duration of PACTE. The contribution of PACTE to ISblue teaching activities and the socio-economic environment involved in the stakeholder committee is fully taken into account in PACTE expected outcomes.