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1. Trophic provisioning and parental trade-offs lead to successful reproductive performance in corals after a bleaching event

   https://doi.org/10.1038/s41598-022-21998-4  

   Rodrigues, Lisa J.; Padilla-Gamiño, Jacqueline L. (November 2022, Scientific Reports)

   Abstract Warming ocean temperatures are severely compromising the health and resilience of coral reefs worldwide. Coral bleaching can affect coral physiology and the energy available for corals to reproduce. Mechanisms associated with reproductive allocation in corals are poorly understood, especially after a bleaching event occurs. Using isotopic labeling techniques, we traced the acquisition and allocation of carbon from adults to gametes by autotrophy and heterotrophy in previously bleached and non-bleachedMontipora capitataandPorites compressacorals. Experiments revealed that both species: (1) relied only on autotrophy to allocate carbon to gametes, while heterotrophy was less relied upon as a carbon source; (2) experienced a trade-off with less carbon available for adult tissues when provisioning gametes, especially when previously bleached; and (3) used different strategies for allocating carbon to gametes. Over time,M. capitataallocated 10% more carbon to gametes despite bleaching by limiting the allocation of carbon to adult tissues, with 50–80% less carbon allocated to bleached compared to non-bleached colonies. Over the same time period,P. compressamaintained carbon allocation to adult tissues, before allocating carbon to gametes. Our study highlights the importance of autotrophy for carbon allocation from adult corals to gametes, and species-specific differences in carbon allocation depending on bleaching susceptibility. 

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2. Protein signatures predict coral resilience and survival to thermal bleaching events

   https://doi.org/10.1038/s43247-025-02167-7  

   Nunn, Brook L; Brown, Tanya; Timmins-Schiffman, Emma; Mudge, Miranda C; Riffle, Michael; Axworthy, Jeremy B; Dilworth, Jenna; Kenkel, Carly D; Zaneveld, Jesse; Rodrigues, Lisa J; et al (December 2025, Communications Earth & Environment)

   Abstract Coral bleaching events from thermal stress are increasing globally in duration, frequency, and intensity. While bleaching can cause mortality, some corals survive, reacquire symbionts, and recover. We experimentally bleachedMontipora capitatato examine molecular and physiological differences between corals that recover (resilient) and those that die (susceptible). Corals were collected and monitored for eight months post-bleaching to identify genets with long-term resilience. Using an integrated systems-biology approach that included quantitative proteomics, 16S rRNA sequencing to characterize the coral microbiome, total coral lipids, symbiont community composition and density, we explored molecular-level mechanisms of tolerance in corals pre- and post-bleaching. Prior to thermal stress, resilient corals have a more diverse microbiome and abundant proteins essential for carbon acquisition, symbiont retention, and pathogen resistance. Protein signatures of susceptible corals showed early symbiont rejection and utilized urea for carbon and nitrogen. Our results reveal molecular factors for surviving bleaching events and identify diagnostic protein biomarkers for reef management and restoration. 

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3. Coral trophic pathways impact the allocation of carbon and nitrogen for egg development after bleaching

   https://doi.org/10.3389/fevo.2023.1251220  

   Jaffe, Melissa D; Padilla-Gamiño, Jacqueline L; Nunn, Brook L; Rodrigues, Lisa J (November 2023, Frontiers in Ecology and Evolution)

   The persistence of coral reefs requires the survival of adult coral colonies and their continued sexual reproduction despite thermal stress. To assess the trophic pathway (i.e., autotrophy and/or heterotrophy) used to develop gametes following bleaching, we thermally stressedMontipora capitatafor one month at a time when corals in Hawai’i typically experience elevated seawater temperatures. After six and nine months of recovery, we pulse-chased non-bleached and previously bleached colonies using a dual-label design to compare the allocation of carbon and nitrogen at significant stages of gamete development. Dissolved inorganic carbon- (DI¹³C) and nitrogen- (DI¹⁵N) labelled seawater or¹³C- and¹⁵N-labelled rotifers were used to assess the autotrophic and heterotrophic pathways, respectively. At multiple time points for up to two years later, we collected adult coral fragments and isolated host tissue, Symbiodiniaceae cells, and developing eggs and captured gamete bundles to analyze their carbon (δ¹³C) and nitrogen (δ¹⁵N) stable isotopes. We found that the presence of Symbiodiniaceae was important for gametogenesis in both non-bleached and previously bleached colonies in two main ways. First, autotrophically-acquired carbon and nitrogen were both allocated to gametes during development, suggesting that recovery of photosynthesis after bleaching is critical for gametogenesis. Second, only heterotrophically-acquired nitrogen, not carbon, was incorporated into gametes and was readily recycled between host tissues and Symbiodiniaceae cells. This suggests that one of the purposes of heterotrophy following coral bleaching forM. capitatamay be to supplement the nitrogen pool, providing available nutrients for endosymbiotic algal growth. Allocation of carbon and nitrogen to eggs coincided with the period when vertical transmission of symbionts to gametes occurs, further supporting the important relationship between gametogenesis and availability of Symbiodiniaceae forM. capitata. 

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4. Coral histology reveals consistent declines in tissue integrity during a marine heatwave despite differences in bleaching severity

   https://doi.org/10.7717/peerj.18654  

   Kruse, Elisa; Brown, Kristen T; Barott, Katie L (January 2025, PeerJ)

   Marine heatwaves are starting to occur several times a decade, yet we do not understand the effect this has on corals across biological scales. This study combines tissue-, organism-, and community-level analyses to investigate the effects of a marine heatwave on reef-building corals. Adjacent conspecific pairs of coral colonies of Montipora capitata and Porites compressa that showed contrasting phenotypic responses (i.e., bleached vs. not bleached) were first identified during a marine heatwave that occurred in 2015 in Kāne’ohe Bay, Hawai‘ i. These conspecific pairs of bleaching-resistant and bleaching-susceptible colonies were sampled for histology and photographed before, during, and after a subsequent marine heatwave that occurred in 2019. Histology samples were quantified for: (i) abundance of mesenterial filaments, (ii) tissue structural integrity, (iii) clarity of epidermis, and (iv) cellular integrity (lack of necrosis/granulation) on a 1–5 scale and averaged for an overall tissue integrity score. Tissue integrity scores revealed a significant decline in overall tissue health during the 2019 heatwave relative to the months prior to the heatwave for individuals of both species, regardless of past bleaching history in 2015 or bleaching severity during the 2019 heatwave. Coral tissue integrity scores were then compared to concurrent colony bleaching severity, which revealed that tissue integrity was significantly correlated with colony bleaching severity and suggests that the stability of the symbiosis is related to host tissue health. Colony partial mortality was also quantified as the cumulative proportion of each colony that appeared dead 2.5 years following the 2019 bleaching event, and tissue integrity during the heatwave was found to be strongly predictive of the extent of partial mortality following the heatwave for M. capitata but not P. compressa, the latter of which suffered little to no mortality. Surprisingly, bleaching severity and partial mortality were not significantly correlated for either species, suggesting that tissue integrity was a better predictor of mortality than bleaching severity in M. capitata. Despite negative effects of heat stress at the tissue- and colony-level, no significant changes in coral cover were detected, indicating resilience at the community level. However, declines in tissue integrity in response to heat stress that are not accompanied by a visible bleaching response may still have long-term consequences for fitness, and this is an important area of future investigation as heat stress is commonly associated with long-term decreases in coral fecundity and growth. Our results suggest that histology is a valuable tool for revealing the harmful effects of marine heatwaves on corals before they are visually evident as bleaching, and may thus improve the predictability of ecosystem changes following climate change-driven heat stress by providing a more comprehensive assessment of coral health. 

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5. Farmerfish gardens help buffer stony corals against marine heat waves

   https://doi.org/10.1371/journal.pone.0282572  

   Honeycutt, Randi N.; Holbrook, Sally J.; Brooks, Andrew J.; Schmitt, Russell J. (March 2023, PLOS ONE)

   Melzner, Frank (Ed.)

   With marine heat waves increasing in intensity and frequency due to climate change, it is important to understand how thermal disturbances will alter coral reef ecosystems since stony corals are highly susceptible to mortality from thermally-induced, mass bleaching events. In Moorea, French Polynesia, we evaluated the response and fate of coral following a major thermal stress event in 2019 that caused a substantial amount of branching coral (predominantly Pocillopora ) to bleach and die. We investigated whether Pocillopora colonies that occurred within territorial gardens protected by the farmerfish Stegastes nigricans were less susceptible to or survived bleaching better than Pocillopora on adjacent, undefended substrate. Bleaching prevalence (proportion of the sampled colonies affected) and severity (proportion of a colony’s tissue that bleached), which were quantified for >1,100 colonies shortly after they bleached, did not differ between colonies within or outside of defended gardens. By contrast, the fates of 399 focal colonies followed for one year revealed that a bleached coral within a garden was a third less likely to suffer complete colony death and about twice as likely to recover to its pre-bleaching cover of living tissue compared to Pocillopora outside of a farmerfish garden. Our findings indicate that while residing in a farmerfish garden may not reduce the bleaching susceptibility of a coral to thermal stress, it does help buffer a bleached coral against severe outcomes. This oasis effect of farmerfish gardens, where survival and recovery of thermally-damaged corals are enhanced, is another mechanism that helps explain why large Pocillopora colonies are disproportionately more abundant in farmerfish territories than elsewhere in the lagoons of Moorea, despite gardens being relatively uncommon. As such, some farmerfishes may have an increasingly important role in maintaining the resilience of branching corals as the frequency and intensity of marine heat waves continue to increase. 

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