Postdoctoral Fellowship: OCE-PRF: Plastic Partnerships: Investigating life history strategies constraining phenotypic plasticity across coral holobiont partners

About This Grant

Stony corals engineer complex reef ecosystems that are vital for biodiversity, food security, tourism economies, and coastal protection. Corals are complex organisms themselves, where the coral animal hosts a variety of symbiotic algae and other microbes (together, referred to as “holobiont” organisms). These mutualistic relationships are primarily driven by nutrient exchange between partners. However, environmental stress can disrupt these associations, leading to coral mortality and reef degradation. While nearly all reef-building corals rely on these symbioses, the flexibility varies across coral species. Such variation likely contributes to differences in the capacity for phenotypic plasticity, or the ability of individuals to display different characteristics depending on the environment. Phenotypic plasticity is likely adaptive for corals to thrive in variable environments without relocating. Yet, the role of each holobiont partner in mediating plastic responses is not well described, especially across coral functional groups. Environmental stress is causing declines in coral populations as well as shifting coral functional diversity. Therefore, to better predict reef resilience in a changing world, it is critical to fully understand the drivers, capacity, and role of phenotypic plasticity in acclimation across a diversity of coral species. This project will conduct a multifaceted assessment of plasticity across symbiotic partners and functional groups to advance our understanding of acclimatory mechanisms within symbiosis. Throughout two long-term thermal and photoacclimation experiments, this research will integrate physiological (metabolism and photobiology), molecular (gene expression and algal and microbial DNA metabarcoding), and organismal fitness (growth and resilience) responses of corals representing competitive, weedy, and tolerant life histories. To disentangle plastic responses across holobiont partners, transcriptomic and genomic sequencing will quantify host transcriptional plasticity and shifts in algal and microbial communities. Additionally, algal photochemical traits will be characterized by multi-spectral, single-turnover active chlorophyll a fluorescence. Such photobiological phenotypes differentiate algal populations and represent promising tools for predicting coral stress resistance. This comprehensive evaluation will resolve how symbiotic partners contribute to holobiont environmental responses. The capacity for phenotypic plasticity varies both across and within species, and emerging evidence suggests that this ability is adaptive in corals. The project will evaluate the adaptive plasticity hypothesis by assessing the fitness outcomes of environmentally-induced shifts in coral physiology and morphology. Importantly, the mechanisms and implications of plasticity will be compared across three coral functional groups. Contrasting life history strategies, including fidelity versus flexibility in symbiotic associations, are predicted to constrain acclimatization potential. This research is vital for predicting the ecological consequences of declines in functional diversity and transitions in species dominance occurring in coral reef ecosystems. Furthermore, this work will evaluate the potential for conservation interventions such as thermal acclimation and shading to increase coral resilience and survival within reef restoration. 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.