Can Bacterial Manipulation Deliver Reef-Scale Thermal Enhancement of Corals?

A rapid decline of coral reefs is taking place around the world, with climate warming being the biggest driver behind this deterioration. Efforts to increase coral climate resilience via bioengineering methods have thus become urgent, and there is hope that such interventions can help corals and coral reefs survive until a time when no further climate warming occurs and perhaps a future of climate cooling is imaginable. The manipulation of coral-associated bacterial communities is among the less advanced interventions currently being explored. Nevertheless, early findings provide confidence that some level of thermal enhancement can be achieved via the inoculation of corals with beneficial bacteria. The small number of studies available, however, is limited in terms of the traits used to select candidate bacteria and their ability to ascribe host enhancement to specific bacterial taxa and functions. Further, findings to date are unable to decipher whether candidate bacteria integrate stably within the coral microbiome. These shortcomings prevent assessment of the efficacy of bacterial manipulation to enhance the long-term thermal resilience of corals on the reef. Here we summarise the state-of-play of the field and provide recommendations to fast-track this approach via fine-tuning experimental designs and methods.