Nutrient Stress and Coral Health: Bridging Physiology, Holobiont Dynamics, and Molecular Mechanisms

Andre Briscoe , Jose Eirin-Lopez

Nutrient stress acts as a multiscalar and context-dependent driver of coral reef decline primarily driven by anthropogenic interference. Decades of physiological and ecological studies have established that nutrient stress elicits physiological responses from corals, but reveal species-specific variability dependent on nutrient identity, concentration, and stoichiometry, as well as intricate interactions with other stressors like climate change. Due to this complexity, a deeper mechanistic understanding of nutrient stress is necessary, with molecular biology research at the forefront of building conceptual models. This review synthesizes the current understanding of nutrient stress effects, bridging classical physiological observations with insights from omics research. We review how molecular approaches—spanning genetics, epigenetics, transcriptomics, and other omics (such as proteomics and lipidomics)—have been used to elucidate the underlying processes driving nutrient stress response in corals. We find that molecular evidence provides empirical support for the two prevailing models: the Phosphate Starvation Model (PSM) and the Greedy Symbiont Model (GSM), as well as novel mechanisms outside the scope of the two established models. However, molecular studies still remain underutilized, unevenly distributed across omic fields, and often lack correlation with physiological outcomes. Thus, we highlight the need for hypothesis-driven research which combines ecologically relevant nutrient conditions with multi-omic approaches and phenotypic responses across the coral holobiont. Calculated and intentional studies are required to understand the complexity of nutrient stress responses in order to further frameworks for coral resilience and inform conservation efforts in an increasingly eutrophied ocean already subject to a multitude of concurrent stressors.