Early Anthropogenic Transformation of the Danube-Black Sea System

Over the last century humans have altered the export of fluvial materials leading to significant changes in morphology, chemistry, and biology of the coastal ocean. We present sedimentary, paleoenvironmental and paleogenetic evidence to show that the Black Sea, a nearly enclosed marine basin, was affected by land use long before the modifications of the Industrial Era. Sediment loads delivered by Danube River, the main tributary of the Black Sea, significantly increased as land use intensified in the late Holocene, which led to a rapid expansion of its delta. In the same time, although watershed hydroclimate was spatially and temporally variable over the last, surface salinity dropped systematically in the Black Sea. Lastly, proliferation of diatoms and dinoflagellates at the time of intensive deforestation in Eastern Europe points to an anthropogenic pulse of river-borne nutrients that radically transformed the food web structure in the Black Sea. We discuss the significance of our findings for the evolution of sedimentary landscapes, biogeochemistry, and ecosystems in regional seas and the global coastal ocean as well as for human societies from their watersheds.