Date of Award
2026
Degree Type
Dissertation
Degree Name
Doctor of Philosophy in Biological and Environmental Sciences
Department
Biological Sciences
First Advisor
Kelton McMahon
Abstract
Climate change is fundamentally restructuring macro-scale marine ecosystem structure and function by altering microscale metabolic processes and patterns of energy allocation. Scleractinian corals, as major ecosystem engineers, play outsized roles in ecosystem structure and function. They also occupy diverse habitats that differ in temperature regimes, light environments, hydrodynamics, and other environmental conditions, exposing corals to substantial spatial variation in stress and resource availability. Their fragile nutritional symbiosis with algal endosymbionts helps them navigate these environmental variations, but are also highly sensitive to environmental stress, particularly the timing and magnitude of water temperature changes. As pressure from environmental changes increases, the degree to which host, symbiont, and their collective holobiont can engage in metabolic plasticity shapes reproductive investment, energy reserve dynamics, host-symbiont coupling, and divergent stress trajectories. Despite a well-documented understanding of the outcomes of environmental stress, especially on coral reefs where high-profile bleaching events have taken place, we lack: 1) a mechanistic understanding of metabolic processes that underlie survival and adaptive capacity of existing coral populations and 2) insight into how habitat variation affects these responses. This thesis aims to address these research priorities by examining metabolic plasticity through a set of experiments and field collections in temperate and tropical corals.
I first examined coarse metabolic plasticity of a temperate coral species, the Northern Star Coral, Astrangia poculata, by examining physiological response and timing of reproduction to seasonally-cycled ambient and elevated (ambient +2°C, SSP2-4.5 scenario) temperature treatments in a controlled tank experiment. We found that A. poculatamaintained energy homeostasis even under elevated temperature-induced increases in respiration rate. Lipid content remained stable, indicating sustained allocation to lipid-rich gamete production rather than depletion of reproductive investment. This energy homeostasis likely supported continued gamete development and resulted in corals in the elevated temperature treatment spawning just one day earlier than corals in the ambient temperature treatment. These broad-scale investigations of coral physiology in an aquaria setting encouraged us to look more mechanistically at acute responses of metabolites and lipids, which play diverse roles in energy storage, structure, signaling and immunity.
To examine how habitat variation shapes coral metabolism and host-symbiont coupling to heat stress, I analyzed metabolic plasticity in the tropical, reef-building coral Pocillopora favosa at three contrasting sites within a shared oceanographic setting in the Central Red Sea. To do this, I used high throughput metabolomics (Ch 2) and lipidomics (Ch 3) techniques to characterize the interplay among “early warning” biomarkers, energy reallocation, structural lipid remodeling, and immune responses. In Ch 2, the metabolomics data identified a key stress response gradient from compensatory regulation in the environmentally-buffered deep fore reef site where corals reorganized patterns of energy storage versus structure across the coral holobiont, transitioning to active stress defense in shallow fore reef site, and then ultimately destabilization of holobiont function in the highest heat stressed back lagoon during the onset of bleaching. These acute metabolic responses set up broader lipidomic responses in Ch 3, where again, corals in the deep fore reef maintained a synergistic relationship between the host and symbiont, shifting metabolic priorities towards compensatory mechanisms that preserved cell structure and organelle integrity, while corals in the lagoon reached physiological breaking points with depressed immune responses and accumulation of metabolites leading to apoptosis and cell death. These habitat-specific responses indicate that thermal stress responses diverged not only in magnitude but in the types of pathways regulated.
Our results provide a valuable framework for understanding resilience and adaptive capacity in changing marine ecosystems. Evaluating alternative metabolic trajectories across different climate scenarios provides greater insight into the central role that the lipid metabolism can play in shaping compensatory responses, energy re-allocation, and immune-based stress signaling and underscores potential pathways that corals can engage in to persist in a warming world.
Recommended Citation
Zane, Lauren, "CORAL HOLOBIONT LIPIDOME RESPONSE TO GLOBAL CHANGE" (2026). Open Access Dissertations. Paper 4554.
https://digitalcommons.uri.edu/oa_diss/4554