Distribution of modern dinocysts and pollen in the western Mediterranean Sea (Algerian Margin and Gulf of Lion)

The Mediterranean Sea is generally described as an oligotrophic area where primary productivity is limited to a few coastal environments with nutrient-enriched fluvial input. However, several studies have revealed that the hydrology of the western Mediterranean has major seasonal productive patterns linked either to significant riverine input or to seasonal upwelling cells. This study aims to: i) discuss organic microfossils (i.e. pollen and dinoflagellate cyst assemblages, as well as other non-pollen palynomorphs) from two different productive areas of the western Mediterranean Sea, and ii) examine the importance of the interconnections between marine and continental influences responsible for modern palynomorph distributions. Based on 25 samples from the Gulf of Lion (GoL) and Algerian Margin, this study key findings are: i) that GoL marine productivity is driven by the combination of discharges from the Rhône River and seasonal upwelling mechanisms, ii) that the strong productive pattern of the northern African coast is driven by water density front mixings and related upwellings. These two patterns are discussed in the light of major links that provide a better understanding of the signatures of marine and continental bio-indicators. The dinocyst Lingulodinium machaerophorum can be considered as a tracer of Rhône River plume influence in the GoL. Brigantedinium taxa are shown to be upwelling-sensitive in both studied areas. Typical differences in vegetation across the north–south climate gradient in the western Mediterranean Basin are highlighted by the larger ratio of Euro-Siberian to Mediterranean pollen taxa in the northern sector. Synoptic maps also illustrate the complex interactions of environmental drivers determining the distributions of continental and marine palynomorphs in the western Mediterranean Sea.