The oxygen concentration within the oxygen minimum zone in the Angola Gyre is almost constant over long times, where ventilation balances oxygen consumption by mineralization of organic material. A simple physical explanation is that the turbulent oxygen flux is governed by Fick’s law, where the oxygen flux is proportional to the oxygen concentration gradient. Here, we discuss an alternative feedback mechanism from the zooplankton respiration towards ambient oxygen concentration by vertical migration of zooplankton. This idea is based on model results from a coupled biogeochemical model, respiration, hypoxia tolerance and acoustic measurements showing in how far zooplankton avoids low oxygen waters. Zooplankton vertical migration implies considerable transport of organic matter. Zooplankton respiration as well as nitrification of excreted ammonium is an essential sink of oxygen. If zooplankton is avoiding oxygen exhausted water bodies, oxygen consumption from respiration and nitrification is reduced considerably there. For the biogeochemical model considered this feedback is an essential component to produce a realistic oxygen minimum zone, whereas a simple bulk zooplankton significantly overestimates its extent and apparent oxygen utilization. Keywords: Oxygen minimum, zooplankton, ecosystem model