Coal dust pollution affects the early life cycle of brooding and broadcast-spawning corals

Coral reefs are highly diverse and ecologically important ecosystems that are increasingly threatened by both natural and anthropogenic stressors. In the Colombian Caribbean, reef organisms are particularly vulnerable to pollution from coal dust, especially in areas near ports and maritime transport routes. This study evaluated the effects of coal dust on the early developmental stages of three reef-building coral species with different reproductive strategies: Orbicella faveolata, Favia fragum, and Acropora palmata. Gametes of O. faveolata and A. palmata were collected from Tayrona National Natural Park and transported to the laboratory at University of Magdalena. The effects of coal dust on embryogenesis, larval development, settlement, and post-settlement survival of O. faveolata were assessed under four concentrations (0-40mg/L) in 2023, and five concentrations (0-160 mg/L) in 2024. For F. fragum and A. palmata, only settlement and post-settlement survival were evaluated using the 2024 concentration range. In O. faveolata, significant negative effects on embryonic and larval development were observed at concentrations ≥40 mg/L. Across all three species, settlement and post-settlement survival decreased with increasing coal dust concentration. Most trace metals associated with coal dust did not exceed harmful thresholds for marine organisms. Suspended coal particles negatively affected embryonic and larval stages, while settled particles impaired settlement and early polyp survival in both brooding and broadcast-spawning species. These findings enhance our understanding about the impact of coal dust as an emerging pollutant and provide valuable insights for mitigating its effects on coral reef ecosystems.