Low oxygen (hypoxia) is dangerous for marine organisms and it can result in dead zones and fish kills. There is increasing recognition that low oxygen in coastal environments can negatively impact corals. In fact, low oxygen levels interact with warming to drive coral bleaching and mortality. In this collaborative project we assessed the tolerance of 7 species of Caribbean corals (Porites porites, Montastrea cavernosa, Siderastrea siderea, Orbecella faveolata, Diploria labyrinthisformis, Agaricia lamarki, and Acropora cervicornis) to heating and hypoxia to determine which species are the most vulnerable. In laboratory experiments we assessed changes in metabolic rate in response to these stressors as well as bleaching and mortality. We combined this with field measurements of temperature and oxygen levels across depths and spatially across Bahia Almirante, a bay on the Caribbean coast of Panama which has previously experienced hypoxia-driven coral bleaching and mortality.
We found that: (1) hypoxia is stressful at both warm and cool temperatures, but temperature extremes amplify stress, (2) species that are abundant on open ocean reefs are more susceptible to low oxygen and that species from sites with frequent exposure to low oxygen have a greater ability to resist hypoxic stress, (3) the different species responses to hypoxia result in coral assemblages that are dominated by short, weedy, stress tolerant species that can't support high reef biodiversity at the most impacted sites. The lowest oxygen conditions in the bay occur at night during periods when the water is warm, making this the most stressful time for corals. These stressful conditions occur more frequently in the back of the bay compared to areas with more oceanic influence and the coral communities reflect these conditions, with only the most hypoxia tolerant species thriving in the back of the bay.
This collaborative project combines our ecological and physiological data with information on the coral microbiome to understand how the microbes living with the corals help or hurt these responses to low oxygen.
This project has trained 8 students, interns, and volunteers and 2 post-doctoral fellows and has resulted in 5 published or submitted research papers.
Last Modified: 02/22/2026
Modified by: Rachel Collin
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