Reef-building corals form some of the most productive and biodiverse ecosystems on our planet. However, these precious ecosystems have experienced dramatic declines in the past few decades due to climate change and other anthropogenic stressors. At the heart of the problem is the stress-induced breakdown of the symbiotic relationship these organisms have with dinoflagellates in the family Symbiodiniaceae. This symbiotic association provides corals with >90% of their energy needs and is thus a keystone of the coral reef ecosystem. Unraveling the molecular mechanisms underpinning this relationship and its breakdown is paramount for our understanding of these associations and the development of tools and approaches to mitigate further impacts. Unfortunately, corals are not easy to work with due to the inherent complexity of meta organism but also due to their unusual characteristics such as their hard skeletons or unusual mode of reproduction.

The goal of this methods collection is to elucidate the state of play of the field of coral research with a focus on understanding coral symbiosis, its breakdown, and potential technologies to improve coral reef restoration efforts. These techniques may cover molecular approaches such as the epigenetic regulation of symbiosis via histone modifications as well as physiological characterization of the coral holobiont using microsensors or the use of cryopreservation for selective breeding and conservation. This collection of protocols will be extremely helpful to the community and hopefully increase the use of these approaches and technologies to further our understanding of corals and their delicate symbiosis.