ADVANCES IN MONITORING, ASSESSING, AND PREDICTING CONDITION OF THE CORAL HOLOBIONT

Abstract

Rising incidence of coral disease is one of the most pressing contemporary impacts occurring on modern coral reefs, leading to local extinctions of coral genera and challenging coral conservation efforts on a global scale. Differing physiology of coral species and complex microbial ecologies combine with diverse anthropogenic impacts to make prediction of coral disease or its mediation difficult. These challenges are compounded by a lack of affordable methods to monitor visual coral health or detect latent impacts before visual signs of coral disease become apparent. I address these topics across the six central chapters of this thesis. In Chapter 2, I develop an affordable field-ready camera system to persistently monitor coral reef environments and reduce barriers for under-resourced managers to track visual coral health. In Chapter 3, I develop a step-by-step guide designed to encourage molecular analysis of corals as a holobiont, wherein I walk users through sampling designs, sample collection, and sample preservation for later use in analysis of the coral microbiome, metabolome, and histology. Demonstrating the value of collecting longitudinal datasets, in Chapter 4 I analyze 72,000 coral colony observations collected over a period of nine years and identify drivers of coral White Syndrome diseases that are consistent across coral species in Guam. I follow this study in Chapter 5 with an intensive investigation of a White Syndrome outbreak affecting Pocillopora damicornis in Guam, using methods developed in Chapter 2 to describe early molecular signatures of this disease and a potential mechanism of disease resilience in this coral species. In the last sections of this dissertation, I assess the future of coral reefs by investigating the effects of coral diversity on the microbiome and the latent impacts affecting near-shore coral communities. In Chapter 6, I establish through a manipulative experiment that the microbiome of Pocillopora acuta is unaffected by changes to coral diversity, but growth of this species frequently used in restoration efforts is significantly determined by the surrounding coral community. Lastly, in Chapter 7, I use untargeted coral metabolomics to study the dominant Hawaiian coral Montipora capitata and establish that coral communities on Maui are bioaccumulating of contaminants tied to local land use with unknown effects on coral health. Collectively, these diverse chapters demonstrate that coral conservation is ripe for technological innovation as well as the use of molecular methods in reef management, leading to new insights into the health and resilience of coral reefs.