This section of the toolkit is designed to describe some of the biological characteristics of both corals and zooxanthellae that support resilience to bleaching. Bleaching is a dynamic process, and there is abundant evidence that both partners (coral host and zooxanthellae symbiont) are involved in determining the organisms’ response to stress. Recent studies have demonstrated that the characteristics of Symbiodinium and the response of the host are involved in short-term thermal tolerance1. Therefore, understanding the threat of climate change requires the organisms to be treated as a whole.
Resilience or resistance to bleaching is highly variable, with differences observed among coral colonies of the same species, between colonies of different species, and within individual coral colonies. Different responses of species and individuals to thermal heat stress can be partially attributed to biological factors of individual coral and symbiotic zooxanthellae.
The pages in this section provide details on the biological factors of both corals and zooxanthellae that can contribute to variation in bleaching susceptibility.