Figure 2 . a . Shaded areas indicate the annual percentage of days with southwesterly waves due to winter storms; colors indicate wave height (see the scale). The bars indicate the mean density ± standard deviation (SD) of Diadema africanum before and after the mass mortality events on La Palma and Tenerife. Averages were calculated using the Abades, Boca Cangrejo and Teno site density data for the studied years on Tenerife Island and the Pta. Fraile, Playa del Pozo, Pta. Fuencaliente and La Bombilla sites on La Palma Island. Red arrows indicate the mass mortality year. b . D. africanumindividuals showing first signs of the disease on the ambulacral plates column, and a general view of the Las Galletas site on the southwest coast of Tenerife (Photos: José Carlos Hernández and Antonio Espinosa).