Wildfire-derived methoxyphenol pollutants impair coral calcification

Wildfire pollutants are emerging stressors on marine ecosystems, yet their impact on coral calcification, a key process for reef habitat formation, remains poorly understood. Using an integrated approach combining physiological assays, molecular dynamics simulations, and multi-omics analysis, this study elucidates the mechanisms by which wildfire-derived methoxyphenols (MPs) impair calcification in the reef-building coral Acropora muricata (formerly A. formosa). 2,6-dimethoxyphenol (DMP) exposure induces oxidative stress via glutathione (GSH) depletion and DNA damage, leading to reactive oxygen species (ROS) bursts and upregulation of matrix metalloproteinases (MMPs). MMPs degrade skeletal organic matrix proteins (SOMPs), potentially compromising extracellular matrix stability and the formation of amorphous calcium carbonate (ACC) precursors. DMP exposure also reshapes the coral-associated bacterial community, potentially compromising host detoxification and antioxidant capacity. Simultaneously, DMP disrupts energy homeostasis, impairing ion transport essential for calcification. In parallel, DMP inhibits carbonic anhydrase (CA) activity, potentially disrupting bicarbonate supply and acidifying the calcifying fluid. Collectively, oxidative stress serves as the primary initiator, energy imbalance acts as a secondary amplifier, and CA inhibition ultimately drives the collapse of the calcification, lowering coral skeletal density by ∼30% and triggering sustained cytosolic Ca²⁺ influx. The resulting Ca²⁺ dysregulation promotes membrane lipid degradation and disrupts the expression of cytoskeletal-related genes, which may further exacerbating oxidative stress and cell adhesion loss. These disruptions collectively inhibit calcification and lead to tissue sloughing. This study identifies wildfire-derived MPs as a previously unrecognized driver of coral calcification failure, establishing a mechanistic link between terrestrial wildfires and accelerated reef degradation, a threat likely exacerbated by climate change.