GETTING A HEAD START: INFLUENTIAL EARLY EXPERIENCES FOR JUVENILE CORALS AND COMMUNITY COLLEGE SCIENCE STUDENTS

Abstract

Coral reef resilience to ocean warming and recovery after high-mortality disturbances relies heavily on successful recruitment and survival of stony corals. Early in development, juvenile corals are particularly vulnerable to mortality due to ecological pressures (e.g., predation and algal overgrowth) and environmental stress, including ocean warming and acidification. While the success of juvenile corals is critical for reef resilience, our understanding of conditions supporting their survival under ocean warming remains limited due to their small size and cryptic nature. In this dissertation, I investigated the role of nutrition and tissue fusion in supporting thermal resistance of juvenile corals. To track the health and physiological condition of juvenile colonies during periods of warming, I first developed a non-destructive methodology using laser scanning confocal microscopy (LSCM) to measure tissue thickness and Symbiodiniaceae fluorescence in living corals, which provide key indicators of coral resilience to bleaching and physiological stress under high temperature. Using this methodology, I investigated the potential for heterotrophic feeding and seasonal temperature regimes to enhance juvenile Pocillopora acuta physiological condition (i.e., tissue thickness and Symbiodiniaceae fluorescence) over a 30-day period and support their resistance to subsequent exposure to thermal stress (N=716). I found that interactions between nutritional and thermal regimes are influential in supporting tissue growth and modulating symbiont populations during early juvenile development. Juvenile corals with access to zooplankton and those with prior exposure to cool temperature had 37% higher survival in ambient temperatures and 180% higher survival under thermal stress. In addition to optimal nutritional conditions, tissue fusion with neighboring recruits provides an additional pathway to rapidly increase colony size faster than by growth alone. Fusion between juvenile colonies provides an opportunity for increased genetic diversity within individual colonies because self-recognition systems do not develop until several months after settlement. To investigate the role of genetic diversity and colony size in promoting survival in thermal stress, I manipulated the genotypic richness (1-4 genotypes) and number of juveniles (1-4 juveniles) involved in tissue fusion (N=221). Fused juvenile P. acuta corals survived 5 days longer under high temperature than unfused juveniles. In warming conditions, tissue fusion provided a mechanism to increase total colony size and provide greater available biomass energy reserves and potential for total energy acquisition during stress. Within fused colonies, half of genetically diverse fusions survived 1.5 days longer under high temperature, which may be due to a rescue effect provided by more thermally tolerant genotypes. As oceans continue to warm, these “head start” experiences may become increasingly important in supporting the survival of fast-growing, brooding corals, which are often the first corals to recruit and seed reefs following mortality events. For science students early in their education, involvement in scientific research can also provide a “head start” opportunity as they navigate through the “leaky pipeline” in their pursuit of a science career. I involved five community college students in my research of coral biology and used qualitative methods to understand the impacts of this experience on their science identities and career trajectories. Over the course of a one-year study, students reported increases in their knowledge and understanding of science but remained uncertain of their professional science identity. To support student persistence in science, research internships should integrate career exploration with practice in research and should continue to develop stronger integration between scientific and educational research.