Valerio Isa

The rapid global decline of coral reefs has intensified the need for innovative conservation strategies, including microbial therapies to enhance coral health and resilience. A major limitation, however, is the lack of effective delivery systems for administering Beneficial Microorganisms for Corals (BMCs). In this study, we present natural, biodegradable systems for the underwater delivery of probiotic bacteria to corals. Three customized alginate-based delivery formats (beads, hydrogels, and filaments) were developed and loaded with the probiotic Pseudoalteromonas peptidolytica . The materials were loaded with the bacterium at an average concentration of 10^(4) CFU/g of dry polymer and engineered to sink underwater while keeping their structural integrity over time. In vitro assays showed controlled release kinetics, with encapsulated probiotics remaining viable and capable of replication. In vivo experiments compared syringe-based inoculation with the application of alginate beads, hydrogels, and filaments to corals. Microbiome analyses performed before and after inoculation confirmed successful probiotic colonization following deployment of the alginate-based delivery systems. Relative abundance of the probiotic genus Pseudoalteromonas increased markedly in treated corals, reaching 11.5 % after 48 h with alginate beads, 12.7 % after 48 h with hydrogels, and 12.6 % after 24 h with filaments. Furthermore, the degradation mechanisms of the three delivery systems were investigated. As the first biomaterial-based underwater delivery systems specifically engineered for coral probiotics, these alginate-based materials provide a promising foundation for advancing microbial therapies in both controlled aquaria and natural reef environments.

Coral-associated dinoflagellates undergo substantial physiological changes when transferred from the host environment to laboratory culture, yet direct compositional comparisons remain limited. We compared the proximate composition and fatty acid profiles of Symbiodinium microadriaticum (ITS2 type A1) freshly isolated from Stylophora pistillata with free-living cultures derived from the same coral-associated symbiont material and maintained under controlled conditions. Total lipid and crude protein contents did not differ significantly between states, whereas fatty acid composition differed markedly. Sixteen individual fatty acids remained significantly different after Benjamini-Hochberg false discovery rate correction. Freshly isolated samples showed higher relative abundances of several saturated, monounsaturated, and n-6 polyunsaturated fatty acids, including 16:0, 18:0, 16:1n-7, arachidonic acid, and docosatetraenoic acid, together with a higher proportion of total n-6 fatty acids. Free-living cells showed higher relative abundances of 14:0, 16:3n-4, α-linolenic acid, and 18:5n-3, together with higher proportions of total PUFA, n-3, and n-9 fatty acids and a higher docosahexaenoic acid/arachidonic acid (DHA/ARA) ratio. These contrasting signatures indicate marked state-associated biochemical differentiation despite similar bulk lipid and protein contents. The results provide a direct compositional reference for interpreting cultured Symbiodiniaceae used in algal physiology, coral-algal symbiosis research, and experimental host acquisition.

Coral reefs are threatened by climate change and the effects of human activity on the marine environment. Researchers are attempting to rescue this fragile ecosystem through coral restoration actions, and a common step in these procedures is transplanting the new coral colonies into coral reefs. To do that, commercial concrete or epoxy resins, also called putty, are utilized, highlighting different concerns about their mechanical and hardening performances and their impact and fate once released into the environment. Hence, this study presents a new biodegradable epoxidized soybean oil acrylate (ESOA)/zein‐based coral putty capable of quick hardening underwater as an ecofriendly alternative for transplantation of new coral colonies in the reef. Coral putty is composed of two components, containing one a radical initiator and the other a radical accelerator. Once the two components are mixed, coral putty becomes hard underwater in 20–25 min, showing a hardening timescale much faster than other commercial products. The coral putty is biocompatible when applied to the coral Stylophora pistillata in aquaria and Acropora tenuis corals are out‐planted on the reef in the Maldives, demonstrating how this new class of vegetable‐oil‐based materials can be a more sustainable alternative to epoxy resins commonly used in coral restoration procedures.