ABSTRACT

Facing an onslaught of environmental stressors, tropical coral reefs around the world have declined dramatically in recent years, particularly in the Caribbean. To help restore the structure and function of coral reef ecosystems, managers have established in-water nurseries specializing in the propagation of several coral species, particularly the endangered staghorn coral, Acropora cervicornis. With support from the Biological Oceanography Program, Integrative Ecological Physiology Program, and the NSF 2026 Idea Machine Fund Program in the NSF Office of Integrated Activities, this project aims to fill critical knowledge gaps in our understanding of the adaptive capacity of staghorn coral by studying how interactions between genetics and environment influence coral performance and thermal resilience. Insights into these interactions, the genes involved in key health traits, and the impacts of nursery rearing on coral performance inform managers attempting to conserve and restore reef ecosystems. Results are communicated directly to stakeholders and practitioners through communication with conservationists, aquariums, and government agencies. The instruments for field-testing coral thermotolerance are built and programmed by high school students in Shedd?s Teen Learning Lab, and the proposed research directly involves graduate and undergraduate students at the University of Southern California, the University of South Florida, and the University of Miami. Broader public engagement is facilitated through additional outreach activities at the California Science Center in Los Angeles, Shedd Aquarium in Chicago, and Frost Science Museum in Miami. This project represents one of the most comprehensive investigations into the adaptive capacity of a reef-building coral species to date.

The long-term persistence of Caribbean reefs will ultimately be determined by whether there is sufficient genetic diversity and phenotypic resilience in remaining natural and restored coral populations to survive and reproduce in a rapidly changing climate. This project aims to quantify variation in performance among colonies, determine potential trade-offs between thermal tolerance and other traits, and identify coral genotypes that are most likely to survive under climate change and contribute to adaptive potential. Heritability, plasticity, and trade-offs among key phenotypes are being evaluated using a first-of-its-kind reciprocal transplant experiment across a network of Bahamian coral nurseries spanning a large thermal gradient over 450 km. The relationship between thermal resistance and resilience and the extent to which these traits are environmentally flexible are quantified in a series of heat stress experiments on translocated corals. Following one year of acclimatization to common garden conditions both in situ (at the Cape Eleuthera Institute, The Bahamas) and ex situ (at the University of Miami?s Experimental Hatchery, Florida), a suite of phenotypes are assessed to determine whether, and to what extent, thermal tolerance is a fixed effect of host and symbiont genotype or can change in response to transplantation to different sites. Finally, custom-built Coral Bleaching Autonomous Stress Systems (CBASS) are used to quantitatively and precisely field-test the thermal tolerance of ~260 genets of A. cervicornis spanning the entire ~900-km thermal cline of the Bahamian archipelago and nearby Miami-Dade and Broward Counties in Florida. Shallow whole-genome resequencing is used to identify loci associated with thermal tolerance, in addition to assessing fine-scale population structure within hosts and symbionts.

The project directly addresses two of the top thirty-three Idea Machine entries: ?Imagine a Life with Clean Oceans? and ?Saving Coral Reef Ecosystems."

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.

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