Mass mortality events of diverse organisms have been widely described in the marine environment. Clemente and co-workers examined the first documented disease related die-off of a diadematid sea urchin in the eastern Atlantic Ocean. Anomalous high sea water temperatures recorded in the region enabled infection of Diadema africanum by the waterborne pathogenic bacteria Vibrio algynoliticus and resulted in a mortality episode that spread across more than 400 km, at a latitudinal range from 32.8 oN to 27.3 oN. The consequences of mass mortality events of key herbivore sea urchins can mediate transitions between alternate ecosystem states and control urchin dominated barren grounds, affecting the stability of benthic systems, especially if warming events become more frequent in near the future.