For the first time, scientists provide a sea-wide view of what happens to Mediterranean waters that flow into the Black Sea through the Bosporus Strait. Below a depth of about 150 meters, the Black Sea is devoid of oxygen. Only certain microbes can survive in this "dead zone," which reaches depths of over 2000 meters. Warm, salty water flowing from the Mediterranean Sea into the Black Sea ventilates the middepth water column of the sea, trapping anoxic water below and maintaining the sea's distinctive structure. However, the precise fate of inflowing Mediterranean waters has remained something of a mystery to scientists.