| Summary: | International audience The Bay of Brest is a semi-enclosed basin of 180 km2 subject to tidal dynamics and to the fluvial influences of both Aulne and Elorn Rivers, which drain watersheds representing 2600 km2 around the Bay, the major one being the Aulne River catchment. This coastal environment, at the land-sea interface, is subject to natural climate oscillations, typical of the North Atlantic Basin, with the superimposed paleoenvironmental transformations inherited from the post-glacial sea level rise and the anthropogenic forcing increasing from the Neolithic (6,950 ka BP) and especially from the Bronze Age (4,200 ka BP). Therefore, it is an ideal site for the reconstruction of the interactions and retroactions between climate, environment and human dynamics at the western tip of Brittany. To that end, a Holocene paleoenvironmental study was conducted thanks to eight cores collected around the Bay of Brest in four different subtidal areas (i.e., the Roscanvel Bay, the Brest Harbour, the South of the Plougastel peninsula and the mouth of the Aulne River) more or less impacted by oceanic vs. fluvial influences. First, a spatial comparison of pollen and dinoflagellate cyst (or dinocyst) assemblages (terrestrial and aquatic bioindicators, respectively) was conducted thanks to cores retrieved at the mouth of the Aulne River (twin cores "F" and "KS22"; major fluvial influence) and close to the Brest Harbour (twin cores "KS06" and "KS05"; increasing oceanic influence), on same time intervals encompassing 200 years: i) first around 4 ka BP and ii) second around 1 ka BP. Both spatial comparisons allowed recognizing fluvialpalynological tracers among palynological assemblages (Alnus and Corylus for pollen taxa; L. machaerophorum for dinocyst ones). This spatio-temporal investigation was then discussed in parallel with palynological data acquired on the southern Brittany shelf over the last 7 kyrs BP (core CBT-CS11). This allowed discussing the synchronous character of environmental observations considered as ...
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