Benguela Upwelling

Definition: The Benguela Upwelling is a 9000-square kilometer patch of sea off the coast of Namibia where the northbound Benguela Current periodically churns up nutrients from deeper waters. Those nutrients support the growth of vast amounts of plankton. In the past, the area supported a plentiful population of sardines that filter-fed on the plankton. But by the late 1960s, after decades of intense fishing, the sardine population collapsed. Without the sardines, there was a surplus of plankton that was no longer being taken into the food chain. As the excess plankton died, it sank to the bottom where it decomposed and created an oxygen-poor dead-zone on the sea floor.