Rapid developments in coral restoration represent a glimmer of hope for globally declining reefs. Despite these advancements, the world's oceans are becoming increasingly hostile to reef building corals. Considering only climate change amongst numerous stressors, a complete collapse of coral reefs may occur within a human lifetime- even in the absence of further CO2 emissions. Clearly, lasting restoration will depend not only on production and outplanting effort, but also alteration of coral physiological limits.
Numerous approaches have been proposed to facilitate physiological "enhancement" of restoration corals including Symbiodiniaceae community change, thermal priming, and selective breeding. The utility, feasibility, and sustainability of these approaches have been debated, but rarely measured. In order to compare the relative potential for each of these approaches to increase disease and bleaching resistance, we assessed the relative efficacy of host genetic identity, Symbiodiniaceae community, and bleaching experience of Acropora cervicornis during consecutive mass bleaching years. Resistance conveyed by host genetic identity strongly explained both disease and bleaching resistance through the consecutive thermal stress events, suggesting that approaches leveraging host genetic identity are the most promising avenues for propagating resistant phenotypes.
Despite the symbiont specialist nature of Caribbean Acropora, we justify our expectation that coral host genetics will be the most tractable tool for restoration across numerous coral taxa and ecological scenarios with exceptions. Finally, we suggest avenues of synergy with approaches focuses on other mechanisms to increase holobiont resistance.
