Coral reefs are shallow benthic communities that harbor the highest biodiversity in tropical seas. These ecosystems are endangered due to global climate change and anthropogenic pressure from coastal areas. Coral health has been decaying at unprecedented rates in the past decades and is therefore in need of immediate attention. A healthy reef requires a stable coral-algal symbiosis. Thus, understanding the processes required for this mutualism is fundamental for coral reef preservation. Examining how corals respond to bacterial pathogens can also shed light onto how host-pathogen interactions may be the same or differ from processes that affect symbiotic interactions. The use of high throughput gene expression profiling (transcriptomics) is a relatively new genomics approach that promises to enhance the study of these interactions. This project will examine the transcriptome as it varies from natural (i.e., healthy) to disturbed states (i.e., bleached or diseased) in two coral-algal symbioses from the Caribbean: the corals Acropora palmata and Montastraea faveolata and their dominant dinoflagellate symbionts. The outcome of this research will contribute to the study of symbiosis as well as to applied fields such as conservation and management, including the development of coral health diagnostics. This project will train underrepresented minorities at the University of California, Merced. This new campus offers higher education and research opportunities to the disadvantaged Central Valley communities. This educational effort will be enhanced by a partnership with the DOE Joint Genome Institute to develop a course in Genome Biology. Students will also have the opportunity to be involved in environmental podcasting through the UC Merced website in three languages representative of the Central Valley populations (English, Spanish and Hmong). The project will also continue with successful outreach activities in collaboration the California Academy of Sciences through teacher training workshops.
Our findings have provided insight into coral-algal symbioses, coral and algal genome evolution, and coral microbial diversity using the corals Orbicella faveolata and Acropora palmata, both listed as threatened species. In particular, we gained major insight into the host gene expression response during the establishment of symbiosis with dinoflagellate algae as well as the consequences of thermally induced bleaching in adult corals. Microbial diversity surveys revealed strong shifts according to health state on diseased corals compared to healthy colonies. The advent of next generation genome sequencing enabled initial analysis of whole genome content in the coral host and the algal symbiont. We also made progress in establishing the upside down jellyfish, Cassiopea xamachana, as a new model system for research in cnidarian-algal symbiosis that will complement field based efforts with coral hosts. Genomic tools are now available for this organism as well. Twenty eight manuscripts have been published, and Medina lab members have given more than 70 presentations at workshops, departmental seminars and international meetings. Medina was the organizer of a session on coral reef genomics at the International Coral Reef Symposium in 2008 and was also the organizer of an annual conference in symbiosis held at Yosemite National Park. Medina organized an innovative course in genome science in collaboration with the Joint Genome Institute, which resulted to several manuscripts with undergraduates as co-authors.
