Can differential bleaching and mortality among coral species offer useful indicators for assessment and management of reefs under stress?

Coral reefs are increasingly subject to a variety of threats from local to global scales. The development of monitoring and assessment tools to diagnose coral reef community responses to threats would assist greatly in management of their impacts. This paper examines interspecific patterns of bleaching, mortality, and recovery of corals on reefs in Kenya, Tanzania, Mozambique, and Madagascar for one year after the 1997–98 El Niño. On average, 50–80% bleaching and mortality of corals occurred throughout the region. Coral tissue condition (normal, pale, bleached, and dead) was recorded for up to 1 yr after the onset of bleaching. Thirteen coral species were used for analysis. Cluster Analysis and Principal Components Analysis with factor rotation were applied to the dataset, giving two major groups of species, characterized by (a) severe bleaching followed by 100% mortality (e.g., Acropora spp., Pocillopora spp., Galaxea astreata), (b) graduated bleaching with pale tissue and low-to-moderate mortality (e.g., Porites lutea, Echinopora gemmacea, Hydnophora exesa), and one outlier with long-term persistence of bleaching (Montipora tuberculosa). These species groups based on the bleaching response are consistent with life history strategies proposed by other workers. It is proposed that observations of coral condition and bleaching in the field, interpreted in the light of life history theory, can provide a coral bioassay technique for reef monitoring and management.