Exploring the Molecular Mechanisms of Symbiosis Stability in Reef-Building Corals

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Coral reefs are dramatically declining worldwide due to a combination of threats, the most significant of which is thermal stress due to climate change. Unusually high temperatures cause a breakdown of the symbiosis between the coral host and its algal symbionts, resulting in an event called “bleaching,” named for the characteristic white appearance of corals. Bleaching events are becoming more frequent and intense, and often result in coral mortality, ultimately compromising the structure and function of reef ecosystems. The molecular mechanisms responsible for coral bleaching are unknown, and the goal of this proposal is to identify such processes. The experimental and molecular work in this project will be supported by internships of Hawaiian students, which is a Broader Impact. Also, a Marine Biology Mentoring Program for female high school students will be developed, which will helps participants understand tangible pathways toward a career in science. Coral reefs are vulnerable habitats identified by domestic and international organizations as conservation priorities. Reefs provide important ecosystem services and coastal protection to people around the world. This work will identify the molecular mechanisms of coral bleaching, information that can help identify new ways to stop coral bleaching. This project serves the NSF mission because it promotes the progress of science. Since coral reefs are important for tourism, this research also advances the nation’s prosperity.This research aims to define the molecular mechanisms contributing to coral bleaching to identify the causes of, and resilience to, bleaching. The project uses a framework in which ‘pre-conditioned’ Pocillopora acuta are used to examine short-term changes in thermal stress at the molecular level that will help define signaling pathways (e.g., NF-KappaB, MAP kinases) involved in the breakdown of symbiosis. Concurrently, existing genomic and transcriptomic data from known Montipora capitata colonies with a range of ‘fixed’ thermal tolerance will be mined for genomic candidates which influence thermal tolerance. These two datasets will provide targets for a recently developed siRNA knock-down of genes of interest in corals, thereby fortifying correlative and descriptive studies with experimental phenotyping via reverse genetics. Preconditioned P. acuta, thermally tolerant M. capitata and any successfully manipulated corals will be evaluated for DNA integrity during each experiment to describe the cellular outcomes of bleaching and potential consequences of ‘improved’ bleaching tolerance via human intervention. These aims will be supported by summer internships for local students and by a Marine Biology Mentoring Program that increases diversity in stem by providing hands-on experience in field and laboratory settings for female high school students. This work will deepen our mechanistic understanding of the coral-algal symbiosis and develop tools to analyze, compare and diagnose thermal tolerance, which are critical for the long-term persistence of reefs and the ecosystem services they provide. This project is jointly funded by the Symbiosis, Infection and Immunity Program, and the Established Program to Stimulate Competitive Research (EPSCoR).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.