Element cycles in oxygen-depleted areas such as upwelling areas inform future deoxygenation scenarios. The Benguela upwelling system shows strong decoupling of nitrogen and phosphorus cycling due to seasonal shelf anoxia. Anaerobic processes result in pelagic nitrogen loss as N₂. At the same time, sediments are rich in fish-derived and bacterial phosphorus, with high fluxes of excess phosphate, altering deep-water nitrogen:phosphorus ratios. Such alterations can affect ocean functioning.