ABSTRACT

Heterotrophic nutrients are crucial for coral growth and recovery from bleaching events. Although wildfireemissions are a potential source of these nutrients, their impact on corals was minimally investigated. In thismicrocosm experiment, Acroporaformosacorals exhibited rapid tissue detachment upon exposure to wildfire fineparticulate matter (PM2.5). Physiological and genetic analyses revealed mechanisms associated withoxidationreductionhomeostasis and nutrient metabolism. Excessive hydrogen peroxide was generated as corals activatedcytochrome P450 enzymes and the respiratory burst in phagocytic cells to metabolize PM2.5, leading tooxidative damage, mitochondrial dysfunction, and cell apoptosis due to reduced superoxide dismutase activityand compromised glutathione antioxidant function. Subsequently, corals upregulated the transcriptions of geneswhich are related to tyrosine receptor proteins to regulate multicellular development for self-repair, increasingenergy consumption. However,Symbiodiniaceaeupregulated their metabolism and retained photosynthates,reducing nutrient supply to the coral host. Therefore, the hosttemporarily utilized lipid reserves via theglyoxylate cycle, but excessive consumption disrupted lipid and carbohydrate metabolism, ultimately weakeningcell adhesion and causing coral tissue detachment. Additionally, the downregulation of HSP70 expression,