Spatial variability of scleractinian coral bleaching susceptibility in 2010 El Niño–Southern Oscillation between northern and southern reefs, Kenya

Abstract

Coral bleaching events are occurring more frequently worldwide and vary in severity. This study examined the spatial extent and taxonomic nature of coral bleaching and associated mortality at reefs in two widely geographically separated regions in Kenya during a bleaching event in 2010, and determined whether there were any spatial differences among habitats (waveexposed versus wave-sheltered) and/or biogeographic regions (northern upwelling versus southern non-upwelling). Northern reefs had a higher abundance of intermediate and resistant corals to bleaching (e.g., Goniastrea and massive Porites), while southern reefs had more of susceptible corals (e.g., Acropora and Pocillopora). Coral bleaching susceptibility was significantly lower in the northern region than in the southern region, as a result of coral community composition and oceanographic conditions that reduced thermal stress anomalies. Reduced bleaching and mortality response of the similar coral species in wave-sheltered southern reefs seemed to be explained by their increased tolerance to thermal stress in relatively warm, stagnant conditions. This study suggest, therefore, that much of the spatial variation in bleaching susceptibility of corals was related to assemblage composition (taxa susceptibilities), thermal acclimation and upwelling conditions, which underscores the importance of reef assessment on different locations and in different zones/habitats during large-scale bleaching episodes.