The Benguela Upwelling System under Climate Change –
Effects of Variability in Physical Forcing on Carbon and Oxygen Budgets

Time series recording physical forcing in high resolution have shown that the Benguela Upwelling System (BUS) is characterized by a pronounced variability in upwelling intensity resulting in equally high variations in oxygen supply and primary production. Even though some earlier studies addressed microbially driven processes either in the water column or in the sediments of the BUS, the effect of these fluctuations on the overall activity and rates of microorganisms has not yet been studied. Furthermore, frequent occurrence of exceptionally high sulfide concentrations in sediments, occasional accumulation of sulfide in bottom waters, and sporadic eruptions of sulfide all show that the system is far from being at steady state. As both oxygen supply and the occurrence of sulfide are critical parameters, which directly affect all forms of life, these fluctuations will have an important impact on the overall budget of carbon and consequences for the emission of greenhouse gases. In areas of extremely high primary production the feed back from the sediment, including the activity of macrobenthic organisms and bacterial phosphorus cycling, has to be considered in order to estimate the overall budgets via regional ecosystem models. Together with our regional partners we aim to address the effect of variations in upwelling intensity on environmental conditions and budgets through a comprehensive, multidisciplinary approach.