BACKGROUND: Coral reefs experience frequent and severe disturbances that can overwhelm their natural resilience. In such cases, ecological restoration is essential for coral reef recovery. Sexual reproduction has been reported to present the simplest and most cost-effective means for coral reef restoration. However, larval settlement and post-settlement survival represent bottlenecks for coral recruitment in sexual reproduction. While bacteria play a significant role in triggering coral metamorphosis and settlement in many coral species, the underlying molecular mechanisms remain largely unknown. In this study, we employed a transcriptome-level analysis to elucidate the intricate interactions between bacteria and coral larvae that are crucial for the settlement process.
RESULTS: High Metabacillus indicus strain cB07 inoculation densities resulted in the successful induction of metamorphosis and settlement of coral Pocillopora damicoris larvae. Compared with controls, inoculated coral larvae exhibited a pronounced increase in the abundance of strain cB07 during metamorphosis and settlement, followed by a significant decrease in total lipid contents during the settled stage. The differentially expressed genes (DEGs) during metamorphosis were significantly enriched in amino acid, protein, fatty acid, and glucose related metabolic pathways. In settled coral larvae induced by strain cB07, there was a significant enrichment of DEGs with essential roles in the establishment of a symbiotic relationship between coral larvae and their symbiotic partners. The photosynthetic efficiency of strain cB07 induced primary polyp holobionts was improved compared to those of the negative controls. In addition, coral primary polyps induced by strain cB07 showed significant improvements in energy storage and survival.
CONCLUSIONS: Our findings revealed that strain cB07 can promote coral larval settlement and enhance post-settlement survival and fitness. Manipulating coral sexual reproduction with strain cB07 can overcome the current recruitment bottleneck. This innovative approach holds promise for future coral reef restoration efforts.

Introduction: Ayurvedic marine drugs derived from mollusc shells and coral are regularly used by Ayurvedic physicians to treat several disease conditions like acid peptic disease, irritable bowel syndrome, osteoporosis, etc. However, standard operating procedures for manufacturing these drugs and their complete characterization have not been published in the Ayurvedic Formulary and Ayurvedic Pharmacopeia of India to date. Methods: Present study describes the traditional manufacturing process and thorough characterization using classical and advanced analytical tools. The raw materials characters, in-process parameters, and finished product specifications have been elaborated to develop monographs. Especially, the identity and purity of raw coral and pearl were checked by Raman Spectroscopy and Energy Dispersive X-ray Fluorescence analysis. Results: In the finished product analysis, the X-Ray Diffraction study revealed that incineration after trituration with Aloe barbadensis leaf pulp or rose water converted the aragonite phase of calcium carbonate into calcite phase in mother pearl, cowry, and pearl while the calcite form of raw coral was retained. The prominent bands around 1390, 870, and 712 cm-1 detected by Fourier Transform-Infrared Spectroscopy and mass loss between 39-44% (w/w) revealed by thermogravimetric analysis confirmed the carbonate form of these calcium-based drugs. The finished products were very fine grayish-white powders constituted by irregularly shaped nano-micro particulate calcium carbonate exhibiting particle size between 600 nm (D10 value) to 1.2 µm (D90 value). Conclusion: The quality control and assurance achieved in this study may be further utilized by the pharmaceutical industries to manufacture quality marine drugs and conduct efficacy studies.

Corals are colonized by a plethora of microorganisms, and their diversity plays a significant role in the health and resilience of corals when they face oxidative stress leading to bleaching. In the current study, we examined 238 bacteria isolated from five different coral species (Acropora hyacinthus, Pocillopora damicornis, Podabacea crustacea, Porites lobata, and Pavona venosa) collected from the coral reef ecosystems of Kavaratti, Lakshadweep Islands, India. We found that bacteria such as Psychrobacter sp., Halomonas sp., Kushneria sp., Staphylococcus sp., Bacillus sp., Brachybacterium sp., Citrobacter sp., and Salinicola sp. were commonly present in the corals. On the other hand, Qipengyuania sp., Faucicola sp., Marihabitans sp., Azomonas sp., Atlantibacter sp., Cedecea sp., Krasalinikoviella sp., and Aidingimonas sp. were not previously reported from the corals. Among the bacterial isolates, a significant number showed high levels of biofilm formation (118), UV absorption (119), and melanin production (127). Considering these properties, we have identified a combination of seven bacteria from the genera Halomonas sp., Psychrobacter sp., Krasalinikoviella sp., and Micrococcus sp. as a potential probiotic consortium for protecting corals from oxidative stress. Overall, this study provides valuable insights into the coral microbiome and opens up possibilities for microbiome-based interventions to protect these crucial ecosystems in the face of global environmental challenges.

This paper addresses the potential for technology to support husbandry and enrichment opportunities that enhance the welfare of zoo and sanctuary-housed nocturnal and crepuscular species. This topic was investigated through the medium of a multidisciplinary workshop (Moon Jam) that brought together species experts, zoo designers, Animal-Computer Interaction researchers and post-graduate students in collaborative discussions and design sessions. We explain the context through an examination of existing research and current practices, and report on specific challenges raised and addressed during the Moon Jam, highlighting and discussing key themes that emerged. Finally, we offer a set of guidelines to support the integration of technology into the design of animal husbandry and enrichment that support wellbeing, to advance the best practices in keeping and managing nocturnal and crepuscular animals.

Coral reefs are threatened by various local and global stressors, including elevated ocean temperatures due to anthropogenic climate change. Coral cryopreservation could help secure the diversity of threatened corals. Recently, isochoric vitrification was used to demonstrate that coral fragments lived to 24 hr post-thaw; however, in this study, they were stressed post-thaw. The microbial portion of the coral holobiont has been shown to affect host fitness and the impact of cryopreservation treatment on coral microbiomes is unknown. Therefore, we examined the coral-associated bacterial communities pre- and post-cryopreservation treatments, with a view towards informing potential future stress reduction strategies. We characterized the microbiome of the Hawaiian finger coral, Porites compressa in the wild and at seven steps during the isochoric vitrification process. We observed significant changes in microbiome composition, including: 1) the natural wild microbiomes of P. compressa were dominated by Endozoicomonadaceae (76.5% relative abundance) and consistent between samples, independent of collection location across Kāne\'ohe Bay; 2) Endozoicomonadaceae were reduced to <6.9% in captivity, and further reduced to <0.5% relative abundance after isochoric vitrification; and 3) Vibrionaceae dominated communities post-thaw (58.5 to 74.7% abundance). Thus, the capture and cryopreservation processes, are implicated as possible causal agents of dysbiosis characterized by the loss of putatively beneficial symbionts (Endozoicomonadaceae) and overgrowth of potential pathogens (Vibrionaceae). Offsetting these changes with probiotic restoration treatments may alleviate cryopreservation stress and improve post-thaw husbandry.

Aligning spawning timing with seasonal environmental changes is critical for both terrestrial and aquatic organisms. However, mechanisms to regulate reproductive activity in response to environmental factors are not well understood, partly owing to the technical difficulty in maintaining detailed long-term observational data of the reproductive activities in the same population across years. In this study, we present an application of the aquarium system to examine the long-term spawning properties of corals. Spawning records over a 15-year period at the Okinawa Churaumi Aquarium revealed that the spawning timing of Acropora corals in aquarium tanks aligned well with that of wild corals from a neighbouring reef. Using the aquarium population as a model, we investigated the relationship between key environmental factors and the timing of the first and peak spawning dates of Acropora corals during a 15-year period. The results suggest that the spawning window of each spawning season is largely influenced by the water temperature and that the timing of peak spawning can be fine-tuned in response to environmental fluctuations. This behavioural feature can prevent synchronous spawning events during unfavourable environmental conditions and increase long-term reproductive reliability.

Recent studies have predominantly spotlighted bacterial diversity within coral microbiomes, leaving coral-associated fungi in the shadows of scientific inquiry. This study endeavors to fill this knowledge gap by delving into the biodiversity, distribution and functional differences of fungi associated with soft corals Cladiella krempfi and Sarcophyton tortuosum, gorgonian coral Dichotella gemmacea and stony coral Favia speciosa from the South China Sea. Leveraging high-throughput sequencing of fungal internal transcribed spacer-1 (ITS1) region of the rRNA gene, a total of 431 fungal amplicon sequence variants (ASVs) were identified in this study, which indicated that a large number of fungal communities were harbored in the South China Sea corals. Noteworthy among our findings is that 10 fungal genera are reported for the first time in corals, with Candolleomyces, Exophiala, Fomitopsis, Inaequalispora, Kneiffiella, Paraphaeosphaeria, and Yamadazyma belonging to the Ascomycota, and Cystobasidium, Psathyrella, and Solicoccozyma to the Basidiomycota. Moreover, significant differences (p < 0.05) of fungal communities were observed among the various coral species. In particular, the gorgonian coral D. gemmacea emerged as a veritable haven for fungal diversity, boasting 307 unique ASVs. Contrastingly, soft corals S. tortuosum and C. krempfi exhibited modest fungal diversity, with 36 and 21 unique ASVs, respectively, while the stony coral F. speciosa hosted a comparatively sparse fungal community, with merely 10 unique ASVs in total. These findings not only provide basic data on fungal diversity and function in the South China Sea corals, but also underscore the imperative of nuanced conservation and management strategies for coral reef ecosystems worldwide.

Transcriptome data are frequently used to investigate coral bleaching; however, the factors controlling gene expression in natural populations of these species are poorly understood. We studied two corals, Montipora capitata and Pocillopora acuta, that inhabit the sheltered Kāne\'ohe Bay, Hawai\'i. M. capitata colonies in the bay are outbreeding diploids, whereas P. acuta is a mixture of clonal diploids and triploids. Populations were sampled from six reefs and subjected to either control (no stress), thermal stress, pH stress, or combined pH and thermal stress treatments. RNA-seq data were generated to test two competing hypotheses: (1) gene expression is largely independent of genotype, reflecting a shared treatment-driven response (TDE) or, (2) genotype dominates gene expression, regardless of treatment (GDE). Our results strongly support the GDE model, even under severe stress. We suggest that post-transcriptional processes (e.g., control of translation, protein turnover) modify the signal from the transcriptome, and may underlie the observed differences in coral bleaching sensitivity via the downstream proteome and metabolome.

Corals in marginal reef habitats generally exhibit less bleaching and associated mortality compared to nearby corals in more pristine reef environments. It is unclear, however, if these differences are due to environmental differences, including turbidity, or genomic differences between the coral hosts in these different environments. One particularly interesting case is in the coral genus Porites, which contains numerous morphologically similar massive Porites species inhabiting a wide range of reef habitats, from turbid river deltas and stagnant back reefs to high-energy fore reefs. Here, we generate ddRAD data for 172 Porites corals from river delta and adjacent (<0.5 km) fore reef populations on Guam to assess the extent of genetic differentiation among massive Porites corals in these two contrasting environments and throughout the island. Phylogenetic and population genomic analyses consistently identify seven different clades of massive Porites, with the two largest clades predominantly inhabiting either river deltas or fore reefs, respectively. No population structure was detected in the two largest clades, and Cladocopium was the dominant symbiont genus in all clades and environments. The perceived bleaching resilience of corals in marginal reefs may therefore be attributed to interspecific differences between morphologically similar species, in addition to potentially mediating environmental differences. Marginal reef environments may therefore not provide a suitable refuge for many reef corals in a heating world, but instead host additional cryptic coral diversity.

Chlamydiae are ubiquitous intracellular bacteria and infect a wide diversity of eukaryotes, including mammals. However, chlamydiae have never been reported to infect photosynthetic organisms. Here, we describe a novel chlamydial genus and species, Candidatus Algichlamydia australiensis, capable of infecting the photosynthetic dinoflagellate Cladocopium sp. (originally isolated from a scleractinian coral). Algichlamydia australiensis was confirmed to be intracellular by fluorescence in situ hybridization and confocal laser scanning microscopy and temporally stable at the population level by monitoring its relative abundance across four weeks of host growth. Using a combination of short- and long-read sequencing, we recovered a high-quality (completeness 91.73% and contamination 0.27%) metagenome-assembled genome of A. australiensis. Phylogenetic analyses show that this chlamydial taxon represents a new genus and species within the Simkaniaceae family. Algichlamydia australiensis possesses all the hallmark genes for chlamydiae-host interactions, including a complete type III secretion system. In addition, a type IV secretion system is encoded on a plasmid and has previously been observed for only three other chlamydial species. Twenty orthologous groups of genes are unique to A. australiensis, one of which is structurally similar to a protein known from Cyanobacteria and Archaeplastida involved in thylakoid biogenesis and maintenance, hinting at potential chlamydiae interactions with the chloroplasts of Cladocopium cells. Our study shows that chlamydiae infect dinoflagellate symbionts of cnidarians, the first photosynthetic organism reported to harbor chlamydiae, thereby expanding the breadth of chlamydial hosts and providing a new contribution to the discussion around the role of chlamydiae in the establishment of the primary plastid.