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Abstract Coral disease is becoming increasingly problematic on reefs worldwide. However, most coral disease research has focused on the abiotic drivers of disease, potentially overlooking the role of species interactions in disease dynamics. Coral predators in particular can influence disease by breaking through protective tissues and exposing corals to infections, vectoring diseases among corals, or serving as reservoirs for pathogens. Numerous studies have demonstrated the relationship between corallivores and disease in certain contexts, but to date there has been no comprehensive synthesis of the relationships between corallivores and disease, which hinders our understanding of coral disease dynamics. To address this void, we identified 65 studies from 26 different ecoregions that examine this predator–prey-disease relationship. Observational studies found over 20 positive correlations between disease prevalence and corallivore abundance, with just four instances documenting a negative correlation between corallivores and disease. Studies found putative pathogens in corallivore guts and experiments demonstrated the ability of corallivores to vector pathogens. Corallivores were also frequently found infesting disease margins or targeting diseased tissues, but the ecological ramifications of this behavior remains unknown. We found that the impact of corallivores was taxon-dependent, with most invertebrates increasing disease incidence, prevalence, or progression; fish showing highly context-dependent effects; and xanthid crabs decreasing disease progression. Simulated wounding caused disease in many cases, but experimental wound debridement slowed disease progression in others, which could explain contrasting findings from different taxa. The negative effects of corallivores are likely to worsen as storms intensify, macroalgal cover increases, more nutrients are added to marine systems, and water temperatures increase. As diseases continue to impact coral reefs globally, a more complete understanding of the ecological dynamics of disease—including those involving coral predators—is of paramount importance to coral reef conservation and management. 

Recent warm temperatures driven by climate change have caused mass coral bleaching and mortality across the world, prompting managers, policymakers, and conservation practitioners to embrace restoration as a strategy to sustain coral reefs. Despite a proliferation of new coral reef restoration efforts globally and increasing scientific recognition and research on interventions aimed at supporting reef resilience to climate impacts, few restoration programs are currently incorporating climate change and resilience in project design. As climate change will continue to degrade coral reefs for decades to come, guidance is needed to support managers and restoration practitioners to conduct restoration that promotes resilience through enhanced coral reef recovery, resistance, and adaptation. Here, we address this critical implementation gap by providing recommendations that integrate resilience principles into restoration design and practice, including for project planning and design, coral selection, site selection, and broader ecosystem context. We also discuss future opportunities to improve restoration methods to support enhanced outcomes for coral reefs in response to climate change. As coral reefs are one of the most vulnerable ecosystems to climate change, interventions that enhance reef resilience will help to ensure restoration efforts have a greater chance of success in a warming world. They are also more likely to provide essential contributions to global targets to protect natural biodiversity and the human communities that rely on reefs.

 

As coral populations decline across the Caribbean, it is becoming increasingly important to understand the forces that inhibit coral survivorship and recovery. Predation by corallivores, such as the short coral snailCoralliophila abbreviata, are one such threat to coral health and recovery worldwide, but current understanding of the factors controlling corallivore populations, and therefore predation pressure on corals, remains limited. To examine the extent to which bottom-up forces (i.e., coral prey), top-down forces (i.e., predators), and marine protection relate toC. abbreviatadistributions, we surveyedC. abbreviataabundance, percent coral cover, and the abundance of potential snail predators across six protected and six unprotected reefs in the Florida Keys. We found thatC. abbreviataabundance was lower in protected areas where predator assemblages were also more diverse, and that across all sites snail abundance generally increased with coral cover.C. abbreviataabundance had strong, negative relationships with two gastropod predators—the Caribbean spiny lobster (Panulirus argus) and the grunt black margate (Anisotremus surinamensis), which may be exerting top-down pressure onC. abbreviatapopulations. Further, we found the size ofC. abbreviatawas also related to reef protection status, with largerC. abbreviataon average in protected areas, suggesting that gape-limited predators such asP. argusandA. surinamensismay alter size distributions by targeting small snails. Combined, these results provide preliminary evidence that marine protection in the Florida Keys may preserve critical trophic interactions that indirectly promote coral success via control of local populations of the common corallivorous snailC. abbreviata.

 

Bacterial symbionts are integral to the health and homeostasis of invertebrate hosts. Notably, members of the Rickettsiales genus Wolbachia influence several aspects of the fitness and evolution of their terrestrial hosts, but few analogous partnerships have been found in marine systems. We report here the genome, phylogenetics, and biogeography of a ubiquitous and novel Rickettsiales species that primarily associates with marine organisms. We previously showed that this bacterium was found in scleractinian corals, responds to nutrient exposure, and is associated with reduced host growth and increased mortality. This bacterium, like other Rickettsiales, has a reduced genome indicative of a parasitic lifestyle. Phylogenetic analysis places this Rickettsiales within a new genus we define as “Candidatus Aquarickettsia.” Using data from the Earth Microbiome Project and SRA databases, we also demonstrate that members of “Ca. Aquarickettsia” are found globally in dozens of invertebrate lineages. The coral-associated “Candidatus A. rohweri” is the first finished genome in this new clade. “Ca. A. rohweri” lacks genes to synthesize most sugars and amino acids but possesses several genes linked to pathogenicity including Tlc, an antiporter that exchanges host ATP for ADP, and a complete Type IV secretion system. Despite its inability to metabolize nitrogen, “Ca. A. rohweri” possesses the NtrY-NtrX two-component system involved in sensing and responding to extracellular nitrogen. Given these data, along with visualization of the parasite in host tissues, we hypothesize that “Ca. A. rohweri” reduces coral health by consuming host nutrients and energy, thus weakening and eventually killing host cells. Last, we hypothesize that nutrient enrichment, which is increasingly common on coral reefs, encourages unrestricted growth of “Ca. A. rohweri” in its host by providing abundant N-rich metabolites to be scavenged.