Postdoctoral Fellowship: OCE-PRF: Sex-specific Impacts of Climate Change on Gonochoric Corals

Increasing seawater temperatures are destabilizing the relationship between coral hosts and their algal symbionts, causing coral bleaching, and endangering coral reefs worldwide. Though coral responses to thermal challenges have been extensively studied, little research has explored sex-based differences in distributions, reproductive investment, functional variation, and, ultimately, coral thermal tolerance. Many coral species have separate sexes with males producing sperm and females producing eggs for sexual reproduction. Sex-specific differences in growth and tissue thickness have been previously observed in some coral species, with females enduring tradeoffs associated with more energetically costly egg production. This project will investigate how sex-specific differences in coral physiology influence distribution patterns across environments and thermal tolerance traits. This project will also include the mentoring of undergraduate students and it will support a local high school student to engage in the research process, providing valuable training and experience in molecular biology. In collaboration with a climate change focused concert series, a public educational outreach booth will be developed that is focused on climate impacts on marine ecosystems. This project will assess shifts in sex distributions and sex-specific physiological tradeoffs across marginal and non-marginal habitats by integrating field and mesocosm experiments with genomic tools. PI Gantt will explore differences in sex ratios across marginal and non-marginal environments by leveraging environmental (i.e., temperature, turbidity) and histological (i.e., tissue sections) data. Next, functional differences between coral sexes will be assessed using molecular (i.e., gene expression), microbial (i.e., ITS2 amplicon sequencing), physiological (i.e., host and symbiont energy reserves, symbiont cell densities, chlorophyll pigmentation, host tissue thickness, photosynthesis/respiration rates), and trophic (i.e., stable isotopes) measurements. Finally, to test whether differences in thermal tolerance are observed between male and female corals, PI Gantt will conduct a thermal challenge experiment and measure host and symbiont physiology (i.e., Fv/Fm, symbiont cell densities, chlorophyll pigmentation). While considerable research has focused on coral responses to thermal stress, there remains a significant gap in understanding sex-based variation in thermal tolerance and reproductive investment. By examining these factors across a gradient of habitats, this proposal not only promises insights into coral resilience to climate change but also emphasizes the importance of considering sex-specific differences in conservation and restoration efforts. 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.