Evidence for anthropogenic, climatic and oceanographic variability off southwestern Morocco during the last three millennia

In order to obtain a better knowledge of oceanic changes in the Canary Upwelling region during the Late Holocene, marine surface samples and two sediment cores retrieved off southwestern Morocco, GeoB8601–3 and GeoB4223–1, were investigated for organic-walled dinoflagellate cysts (dinocysts). The results were compared with pollen, microcharcoal particles, geochemical records, stable hydrogen and carbon isotope composition (δ2H and δ13C) of plant-waxes of the same material. The dinocyst results indicate active upwelling prior to 750 BCE and a longer upwelling season between 750 BCE and 950 CE, which is attributed to increased northeast trade winds. After 950 CE, a marked increase of Lingulodinium machaerophorum and Gymnodinium species indicates high fluvial input probably due to a combination of climate (possibly negative NAO) and anthropogenic (terrestrial erosion related to Early Arab conquest) impacts.