Self-generated oxygen limitation drives coral outcomes during marine heatwaves

El-Khaled, Y. C.; Khan, H. H.; Klein, S. G.; Garcias-Bonet, N.; Maity, D.; Dighe, S.; Mukha, T.; Kushwaha, A. K.; Wardani, F.; Oulghelou, M.; Dhillon, M. S.; Truman, S.; Garcia, F. C.; Johnson, M. D.; Fox, M.; Duarte, C. M.; Carvalho, S.; Suggett, D.; Peixoto, R. S.; Parsani, M.; Truscott, T. T.

doi:10.64898/2026.10.08.757541

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bioRxiv · 10.64898/2026.10.08.757541

Self-generated oxygen limitation drives coral outcomes during marine heatwaves

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Abstract

Marine heatwaves cause massive, but often patchy coral bleaching. Why neighboring colonies often respond differently remains unresolved. Here, we show that interactions between metabolic demand and flow-mediated resupply generate heterogeneous oxygen microenvironments inside branching corals under heat stress. During the 2023 and 2024 Red Sea heatwaves, high-frequency in situ measurements revealed hypoxic to near-anoxic interbranch conditions despite well-oxygenated surrounding seawater. In 2023, neighboring colonies developed divergent oxygen regimes preceding paling and bleaching; in 2024, stronger and earlier thermal stress was associated with recurrent nighttime near-anoxia before tissue disintegration and mortality. A physics-based three-dimensional fluid-metabolism model reproduced these patterns. Oxygen depletion and coral impacts emerged when metabolic oxygen demand exceeded flow-mediated resupply. Organism-scale variability in oxygen regimes may explain divergent coral fate under shared heatwave exposure.

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El-Khaled, Y. C., Khan, H. H., Klein, S. G., Garcias-Bonet, N., Maity, D., Dighe, S., Mukha, T., Kushwaha, A. K., Wardani, F., Oulghelou, M., Dhillon, M. S., Truman, S., Garcia, F. C., Johnson, M. D., Fox, M., Duarte, C. M., Carvalho, S., Suggett, D., Peixoto, R. S., Parsani, M., Truscott, T. T.. 2026-10-09. Self-generated oxygen limitation drives coral outcomes during marine heatwaves. https://doi.org/10.64898/2026.10.08.757541

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