Hypoxia in the Black Sea northwestern shelf: From eutrophication to climatic stressors.

Abstract
The dynamics of seasonal hypoxia, which affects the Black Sea north-western shelf since the mid 1970's until present days, is
investigated by means of a 3D biogeochemical model. Comparison of the model results with in -situ data reveals that the
phenomenon may have been underestimated after the mid 1990's due to the distribution of observations. We investigate the
mechanism of hypoxia at seasonal scale, and identify the main drivers of its interannual variability. While high nutrients discharge
caused severe hypoxia in the 1980's, it was sustained in the 1990's by the pool of organic matter accumulated during the previous
years in the sediments layer. With an increasing intensity, climatic stressors intensifies the response of hypoxia to nutrient
discharge, and affect the seasonal dynamics of hypoxia by extending its temporal scale.