Biology subjects

Santoro, E. P.

Publications and source records attributed to Santoro, E. P..

5 recordsLinked to original sources

bioRxiv2026

Warming exacerbates fungal pathogenicity to drive physiological collapse and microbiome reorganization in octocorals

Corals are increasingly threatened by climate change, yet the interplay between ocean warming and fungal infection remains experimentally underexplored. Here, we demonstrate that thermal stress exacerbates the pathogenicity of the fungus Aspergillus sydowii, driving physiological collapse and functional reorganization in the octocoral Sclerophytum sp. We deployed a 34-day mesocosm heat-stress experiment and quantified performance, mortality, and taxonomic and functional microbiome shifts. Combined heat and fungal exposure proved highly lethal, causing 45% mortality compared to 7% under heat exposure alone. Re-isolation from diseased nubbins implicates A. sydowii as the causal agent. Metagenomic profiling indicated that physiological collapse was underpinned by a functional transition from mutualism to antagonism in the microbiome. Specifically, combined heat and fungal stress triggered a depletion of ankyrin- and WD40-repeat proteins - hallmarks of symbiotic stability - concurrent with a surge in genes involved in fungal cell wall degradation and secondary metabolite biosynthesis. While surviving holobionts recovered full photosynthetic efficiency after combined stress, their microbiomes did not revert to baseline. Instead, they assembled into a taxonomically distinct configuration characterized by enrichments of sulfate-reducers (Thermodesulfobacteriota) and thermotolerant phototrophs (Thermosynechococcales). This suggests that despite the rapid photosystem recovery, the holobiont retained a complex legacy of thermal and biotic stress across both its internal chemical microenvironment and its microbiome. These findings highlight the decoupled recovery processes of different holobiont components, demonstrating that even though some corals may survive severe climate-driven disease, they emerge as ecologically reorganized entities.

ecology↗

bioRxiv2026

Pathogen priming reveals host immune training and microbiome conditioning in corals

UNSTRUCTURED ABSTRACTIn several species, vaccine-like approaches, where hosts are primed through controlled pathogen exposure, have proven effective in enhancing responses to subsequent infections. This principle remains unexplored in corals. Here, we demonstrate that chronic exposure to non-lethal concentrations of live or inactivated Vibrio coralliilyticus primes the coral holobiont to counter subsequent infections under heat stress. Non-primed corals experienced greater heat stress pathogen-driven bleaching and a significant decline in their photosynthetic efficiency compared to primed samples. These results were linked to microbiome conditioning and host gene expression modulation, including a layered, fine-tuned immune and cellular response to microbial invasion. This proof-of-concept challenges strictly innate immune responses in corals and positions immune priming and microbiome conditioning as integrated mechanisms of coral holobiont resilience. Together, these findings can contribute to redefine coral immunity concepts and lay the groundwork for developing new microbiome-based strategies to enhance coral health for reef conservation under climate change. LAY SUMMARYCoral reefs are increasingly threatened by rising seawater temperatures and disease. Unlike vertebrates, corals do not possess a classical adaptive immune system, so they have been thought to rely only on innate defenses. However, our study shows that corals may be more capable than previously believed. We demonstrate that exposing corals to non-lethal doses of a widespread bacterial pathogen can train them to better withstand subsequent infections under heat stress. Corals that were not pre-exposed suffered more pathogen caused bleaching and showed a stronger decline in physiological performance, while those that were primed were more resilient. This improved resistance appears to come from two coordinated processes. First, the corals associated bacterial community shifted in a way that seems to help protect the host. Second, the coral itself adjusted its gene expression, mounting a more effective and controlled response to infection. These findings suggest that corals may be able to remember past exposures and respond more effectively to future infections, even without a traditional adaptive immune system, providing a foundation for developing new strategies to support coral resilience.

microbiology↗

bioRxiv2026

Coral Probiotics Buffer Adjacent Ecosystem-Level Responses to Extreme Marine Heatwave

Probiotics can enhance coral thermal tolerance, yet their ecosystem-level effects remain unknown. Here, we present the first long-term in-situ test of whether coral-targeted probiotics influence adjacent cryptobenthic reef communities during a record marine heatwave. Probiotics were applied to Pocillopora favosa and Acropora spp. coral colonies for 18 months, spanning the fourth global bleaching event. Cryptobenthic communities were assessed using biomimetic monitoring structures integrating biodiversity surveys, molecular profiling, microbial network analyses, and metabolic assays. Before the heatwave, probiotic and control patches were comparable across structural, microbial, and functional metrics. Following thermal stress, control patches exhibited pronounced losses of cryptobenthic invertebrate abundance and taxonomic breadth, microbial network fragmentation, and net carbonate dissolution. In contrast, probiotic-treated patches retained higher biodiversity, cohesive microbial interaction architectures, and positive calcification. These findings demonstrate that coral-targeted probiotics can scale from host-level intervention to buffer adjacent ecosystem-level responses to extreme marine heatwaves under accelerating climate change. TeaserA coral-targeted probiotic strategy enhances multi-trophic resilience under heat stress.

microbiology↗

bioRxiv2025

Probiotic and postbiotic treatment in situ during a marine heat wave improves coral health and promotes specific metabolic and microbiome changes

Microbial therapies are emerging as promising tools for coral protection against heat stress, yet such application was not tested in situ. We tested two coral-derived probiotic consortia and their heat-killed counterparts (postbiotics) on bleaching Acropora cf. valida in the Red Sea during a marine heatwave. Over 15 days, both live and one of the heat-killed treatments maintained photosynthetic efficiency (Fv/Fm), whereas placebo-treated corals exhibited significant thermal stress-induced decline. 16S rRNA gene sequencing profiling showed enrichment of putatively beneficial genera (e.g., Terasakiispira spp., Pseudoalteromonas spp.), and untargeted metabolomics resolved treatment-specific metabolic signatures that differed among consortia and between live and inactivated formulations. These molecular fingerprints illuminate specific underlying protective mechanisms and host-microbiome interactions under heat stress. Together, our results position microbial therapies (probiotics and specific postbiotics) as field-validated, mechanism-informed interventions capable of minimizing impacts on corals during real-world thermal extremes and provide design cues for scalable deployment.

microbiology↗

bioRxiv2022

Fine-scale variability in coral bleaching and mortality during a marine heatwave

Coral bleaching and mortality can show significant spatial and taxonomic heterogeneity at local scales, highlighting the need to understand the fine-scale drivers and impacts of thermal stress. In this study, we used structure-from-motion photogrammetry to track coral bleaching, mortality, and changes in community composition during the 2019 marine heatwave in K[a]ne ohe Bay, Hawai i. We surveyed 30 shallow reef patches every 3 weeks for the duration of the bleaching event (August-December) and one year after, resulting in a total of 210 large-area, high-resolution photomosaics that enabled us to follow the fate of thousands of coral colonies through time. We also measured environmental variables such as temperature, sedimentation, depth, and wave velocity at each of these sites, and extracted estimates of habitat complexity (rugosity R and fractal dimension D) from digital elevation models to better understand their effects on patterns of bleaching and mortality. We found that up to 80% of corals experienced moderate to severe bleaching in this period, with peak bleaching occurring in October when heat stress (DHW) reached its maximum. Mortality continued to accumulate as bleaching levels dropped, driving large declines in more heat-susceptible species (77% loss of Pocillopora cover) and moderate declines in heat-tolerant species (19% and 23% for Porites compressa and Montipora capitata, respectively). Declines in live coral were accompanied by a rapid increase in algal cover across the survey sites. Spatial differences in bleaching were significantly linked to habitat complexity and coral species composition, with reefs that were dominated by Pocillopora experiencing the most severe bleaching. Mortality was also influenced by species composition, fractal dimension, and site-level differences in thermal stress. Our results show that spatial heterogeneity in the impacts of bleaching are driven by a mix of environmental variation, habitat complexity, and differences in assemblage composition.

ecology↗