Extreme wildfire events are increasing globally, raising concerns about their impact on marine ecosystems, particularly coral reefs. This laboratory study investigates the effects of fine particulate matter (PM_2.5) from wildfires on coral symbionts. We found a significant reduction in photosynthesis within the Symbiodiniaceae upon exposure to PM_2.5. Stable isotope analysis revealed that low concentrations of PM_2.5 allowed corals to utilize wildfire particulates as a source of heterotrophic nutrients, compensating for reduced autotrophy. However, at elevated PM_2.5 levels, both autotrophy and heterotrophy significantly declined, leading to an imbalanced nutritional relationship between corals and their Symbiodiniaceae These shifts were associated with light attenuation in seawater and particulate accumulation on coral surfaces, ultimately undermining coral growth sustainability. Additionally, genetic analyses indicated that wildfire PM_2.5 induced oxidative damages and disrupted metabolic processes in corals, compromising adhesion functions and resulting in tissue detachment. This study underscores that the effects of wildfire PM_2.5 on corals are primarily negative, rather than serving as beneficial nutrient sources.
 

coral, wildfire PM2.5, adhesion function, tissue detachment