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The rapid loss of reef-building corals owing to ocean warming is driving the development of interventions such as coral propagation and restoration, selective breeding and assisted gene flow. Many of these interventions target naturally heat-tolerant individuals to boost climate resilience, but the challenges of quickly and reliably quantifying heat tolerance and identifying thermotolerant individuals have hampered implementation. Here, we used coral bleaching automated stress systems to perform rapid, standardized heat tolerance assays on 229 colonies of Acropora cervicornis across six coral nurseries spanning Florida's Coral Reef, USA. Analysis of heat stress dose–response curves for each colony revealed a broad range in thermal tolerance among individuals (approx. 2.5°C range in F v /F m ED50), with highly reproducible rankings across independent tests ( r = 0.76). Most phenotypic variation occurred within nurseries rather than between them, pointing to a potentially dominant role of fixed genetic effects in setting thermal tolerance and widespread distribution of tolerant individuals throughout the population. The identification of tolerant individuals provides immediately actionable information to optimize nursery and restoration programmes for Florida's threatened staghorn corals. This work further provides a blueprint for future efforts to identify and source thermally tolerant corals for conservation interventions worldwide.

As coral reefs continue to decline globally, coral restoration practitioners have explored various approaches to return coral cover and diversity to decimated reefs. While branching coral species have long been the focus of restoration efforts, the recent development of the microfragmentation coral propagation technique has made it possible to incorporate massive coral species into restoration efforts. Microfragmentation (i.e., the process of cutting large donor colonies into small fragments that grow fast) has yielded promising early results. Still, best practices for outplanting fragmented corals of massive morphologies are continuing to be developed and modified to maximize survivorship. Here, we compared outplant success among four species of massive corals (Orbicella faveolata, Montastraea cavernosa, Pseudodiploria clivosa, and P. strigosa) in Southeast Florida, US. Within the first week following coral deployment, predation impacts by fish on the small (<5 cm2) outplanted colonies resulted in both the complete removal of colonies and significant tissue damage, as evidenced by bite marks. In our study, 8–27% of fragments from four species were removed by fish within one week, with removal rates slowing down over time. Of the corals that remained after one week, over 9% showed signs of fish predation. Our findings showed that predation by corallivorous fish taxa like butterflyfishes (Chaetodontidae), parrotfishes (Scaridae), and damselfishes (Pomacentridae) is a major threat to coral outplants, and that susceptibility varied significantly among coral species and outplanting method. Moreover, we identify factors that reduce predation impacts such as: (1) using cement instead of glue to attach corals, (2) elevating fragments off the substrate, and (3) limiting the amount of skeleton exposed at the time of outplanting. These strategies are essential to maximizing the efficiency of outplanting techniques and enhancing the impact of reef restoration.

No abstract

Coral reefs are among the most valuable and vulnerable ecosystems on Earth. Their decline has spurred global interest in efforts to augment native coral populations through coral gardening. As these efforts expand, practitioners are constantly looking for new techniques to reduce costs and increase their restoration footprint. However, commonly employed coral attachment methods limit the numbers of corals that can be outplanted per day, representing a substantial bottleneck in the coral restoration process. Cement has potential as a more cost‐ and time‐efficient coral attachment technique, but research is needed to understand its effects on coral survivorship and develop best practices for its use. Here, we use lab and field tests in a three‐stage elimination format to determine the most effective cement mixture for outplanting Acropora cervicornis. We then compare this new method to two commonly used coral attachment techniques: the nail and cable tie method and two‐part epoxy putty. Our tests identified the optimal cement mix to be a combination of 10 parts type I/II Portland cement to one part silica fume. This mix yielded equivalent survivorship to the other two methods, is quick and easy to use making it ideal for citizen scientists, and has roughly one‐tenth of the material cost of other methods. These results support the wider use of cement for coral outplanting in order to minimize costs, maximize efficiency, and increase the effectiveness of coral restoration efforts around the world.