ORCC: Improved resilience to climate change through genomic compatibility of symbionts: coral reefs as a model for symbiosis dependent ecosystems

This project focuses on the heart of one of the most imperiled ecosystems, coral reefs, where climate change and heat waves have killed many corals. Corals live in a fine-tuned symbiosis with single celled algae, and heatwaves severely disrupt this symbiosis: even a few degrees can cause the partnership to breakdown. The team's preliminary data suggest that this sensitivity arises from how well individual coral and algal partners interact with one another at the cellular level such that corals with better genetic matches to their symbiont seem to resist heat better. This project is identifying genes and regions of the genome that interact to result in a functional partnership and testing this relationship across a range of environmental conditions. The results of these experiments, in combination with mobile sequencing platforms that generate data in real time, are bolstering conservation efforts by finding optimal populations for restoration projects driven by local communities in Palau. This allows quick translation and scaling the results of the experiments into conservation strategies by quickly identifying colonies with optimal host-symbiont combinations, improving the efficiency and efficacy of local coral restoration projects in Palau. The project also provides research training for postdoctoral scientists, graduate students and a research associate, and public outreach through the production of video and multimedia products. For ecosystems dependent on symbioses, climate resilience depends on successful interactions between partners (i.e. GxGxE interactions). In corals, this variation has been investigated at the level of coral genetic variants (within or between species) or genus-level symbiont variants. Yet, despite a great deal of careful work, these data have not yet revealed strong impact of specific coral genes on bleaching variation. This project is 1) characterizing population-level variation in both the host and symbiont populations to identify pairs of genetic loci in the host and symbiont genome that are highly correlated (i.e. exhibit strong linkage disequilibrium), termed ‘matched’ loci; 2) testing for these matched loci in three species of Acropora from three locations in Palau that historically have exhibited dramatically different thermal profiles and identifying how matching relates to bleaching resistance; 3) reciprocally transplanting colonies from all three locations to test for local adaptation at the level of the holobiont, specifically focusing on whether the ‘matching’ profile changes in different environmental contexts; 4) identifying and characterizing colonies whose dominant symbiont partner switched after transplantation to elucidate the selective forces shaping symbiont genotypes in light of both their environmental and host-specific context; and 5) partnering with local governments and communities to implement restoration plots using rapid and mobile sequencing platforms to test if identifying and using genetically optimal host and symbiont partners in restoration efforts helps to improve conservation outcomes. This project is jointly funded by Biological Oceanography (GEO/OCE) and Organismal Response to Climate Change (BIO/IOS). This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.