Distribution of modern dinocysts in surface sediments of southern Brittany (NW France) in relation to environmental parameters: Implications for paleoreconstructions

Dinoflagellate cyst assemblages from 15 modern surface sediment samples of the Bay Quiberon (Southern Brittany shelf) have been examined to assess their potential as marine bio-indicators for paleoenvironmental reconstructions in a shallow coastal environment. Some discrepancies are noted distribution dinocyst taxa study area, and particularly regarding concentration diversity (26 different identified total) well heterotrophic percentages. We suggest that proportion is, an embayment m deep average, mainly attributed bottom water oxygenation granulometry, both acting on species-selective degradation after deposition. More precisely, higher abundances found under lower oxic conditions fine grain-size samples, leading caution about use productivity indicators environments when these parameters not fully addressed. The comparison data with top cores previously published makes it possible establish transect inshore offshore areas northern Biscay, allowing identify ecological groups according hydrological bathymetric contexts: i) estuarine assemblage strongly dominated by Lingulodinium machaerophorum, ii) proximal L. machaerophorum and, lesser extent, Spiniferites bentorii, iii) neritic ramosus cysts Pentapharsodinium dalei, iv) oceanic group mirabilis Operculodinium centrocarpum.