Probiotics mitigate post-heat stress disorder, preventing coral mortality.

Certain coral individuals exhibit enhanced resistance to thermal bleaching, yet the specific microbial assemblages and their roles in these phenotypes remain unclear. We compared the microbial communities of thermal bleaching–resistant (TBR) and thermal bleaching–sensitive (TBS) corals using metabarcoding and metagenomics. Our multidomain approach revealed stable distinct microbial compositions between thermal phenotypes. Notably, TBR corals were inherently enriched with microbial eukaryotes, particularly Symbiodiniaceae, linked to photosynthesis, and the biosynthesis of antibiotic and antitumor compounds and glycosylphosphatidylinositol-anchor proteins, crucial for cell wall regulation and metabolite exchange. In contrast, TBS corals were dominated by bacterial metabolic genes related to nitrogen, amino acid, and lipid metabolism. The inherent microbiome differences between TBR and TBS corals, already observed before thermal stress, point to distinct holobiont phenotypes associated to thermal bleaching resistance, offering insights into mechanisms underlying coral response to climate-induced stress.

Micropollutants (MPs) include a wide range of biological disruptors that can be toxic to wildlife and humans at very low concentrations (<1 μg/L). These mainly anthropogenic pollutants have been widely detected in different areas of the planet, including the deep sea, and have impacts on marine life. Because of this potential toxicity, the global distribution, quantity, incidence, and potential impacts of deep-sea MPs were investigated in a systematic review of the literature. The results showed that MPs have reached different zones of the ocean and are more frequently reported in the Northern Hemisphere, where higher concentrations are found. MPs are also concentrated in depths up to 3000 m, where they are also more frequently studied, but also extend deeper than 10,000 m. Potentially toxic metals (PTMs), polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethane (DDTs), organotins, and polycyclic aromatic hydrocarbons (PAHs) were identified as the most prevalent and widely distributed MPs at ≥200 m depth. PTMs are widely distributed in the deep sea in high concentrations; aluminum is the most prevalent up to 3000 m depth, followed by zinc and copper. PCBs, organotins, hexachlorocyclohexanes (HCHs), PAHs, and phenols were detected accumulated in both organisms and environmental samples above legislated thresholds or known toxicity levels. Our assessment indicated that the deep sea can be considered a sink for MPs.