Widespread oxyregulation in tropical corals under hypoxia

Hughes, David; Alexander, James Edward; Cobbs, Gary; Kühl, Michael; Cooney, Christopher; Pernice, Mathieu; Varkey, Deepa; Voolstra, Christian R.; Suggett, David J.

doi:10.1016/j.marpolbul.2022.113722

Cited by 15 publications

(52 citation statements)

References 48 publications

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“…sublethal rather than lethal, deoxygenation stress of 2 mg L −1 O 2 . Here, dose response experiments of both O 2 and heat need to consider recent evidence for variable ‘oxy-regulation’ capacity amongst coral species that inherently determines the poise between sublethal and lethal physiological responses to reduced O 2 availability 23 .…”

Section: Discussionmentioning

confidence: 99%

“…Whilst reef-building corals have recently been shown to exhibit the capacity to oxy-regulate under both hypoxic 23 and near anoxic 24 conditions, coral bleaching and mortality can be induced when exposed to deoxygenation 25 – 27 . Similarly to other stressors such as heat or acidification 28 – 31 , hypoxia-induced bleaching susceptibility appears highly variable between coral species, most likely due to acclimation and adaptation differences to reduced O 2 availability (e.g., 25 , 32 ).…”

Section: Introductionmentioning

confidence: 99%

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Deoxygenation lowers the thermal threshold of coral bleaching

Alderdice

Perna

Cárdenas

et al. 2022

Sci Rep

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Exposure to deoxygenation from climate warming and pollution is emerging as a contributing factor of coral bleaching and mortality. However, the combined effects of heating and deoxygenation on bleaching susceptibility remain unknown. Here, we employed short-term thermal stress assays to show that deoxygenated seawater can lower the thermal limit of an Acropora coral by as much as 1 °C or 0.4 °C based on bleaching index scores or dark-acclimated photosynthetic efficiencies, respectively. Using RNA-Seq, we show similar stress responses to heat with and without deoxygenated seawater, both activating putative key genes of the hypoxia-inducible factor response system indicative of cellular hypoxia. We also detect distinct deoxygenation responses, including a disruption of O2-dependent photo-reception/-protection, redox status, and activation of an immune response prior to the onset of bleaching. Thus, corals are even more vulnerable when faced with heat stress in deoxygenated waters. This highlights the need to integrate dissolved O2 measurements into global monitoring programs of coral reefs.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Deoxygenation lowers the thermal threshold of coral bleaching

Alderdice

Perna

Cárdenas

et al. 2022

Sci Rep

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“…A similar value between the P crit and the lower DO conditions on reefs were also found for 14 tropical scleractinian corals and the cold-water coral Lophelia pertusa. The P crit (at 26 °C, and 35 PSU) for the tropical corals range from 2 to 4 mg O 2 L −1 , and the lower ambient DO was 2 mg O 2 L −1 ( Hughes et al, 2022 ). The P crit (at 9 °C, and 35 PSU) for the cold-water coral was 3.9–4.3 mg O 2 L −1 , and the lower ambient DO 3.2 mL L −1 ( Dodds et al, 2007 ).…”

Section: Discussionmentioning

confidence: 99%

“…Two Pocilloporids were included on Hughes et al (2022) research, Pocillopora acuta ( P crit 1.3 mg O 2 L −1 ) and Pocillopora damicornis ( P crit 1.2 mg O 2 L −1 ). These congeners had P crit lower than the P crit of P. capitata , and it could be due to taxa, or a response to local changes in temperature and O 2 conditions ( Vaquer-Sunyer & Duarte, 2008 ).…”

Section: Discussionmentioning

confidence: 99%

Spatiotemporal variability of oxygen concentration in coral reefs of Gorgona Island (Eastern Tropical Pacific) and its effect on the coral Pocillopora capitata

Castrillón-Cifuentes

Zapata

Giraldo

et al. 2023

PeerJ

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Dissolved oxygen concentration (DO) is one of the main factors limiting benthic species distribution. Due to ocean warming and eutrophication, the ocean is deoxygenating. In the Eastern Tropical Pacific (ETP), deep waters with low DO (<1 mg L−1) may reach coral reefs, because upwelling will likely intensify due to climate change. To understand oxygen variability and its effects on corals, we characterize the Spatio-temporal changes of DO in coral reefs of Gorgona Island and calculate the critical oxygen tension (Pcrit) to identify the DO concentration that could represent a hypoxic condition for Pocillopora capitata, one of the main reef-building species in the ETP. The mean (±SD) DO concentration in the coral reefs of Gorgona Island was 4.6 ± 0.89 mg L−1. Low DO conditions were due to upwelling, but hypoxia (<3.71 mg L−1, defined as a DO value 1 SD lower than the Mean) down to 3.0 mg O2 L−1 sporadically occurred at 10 m depth. The Pcrit of P. capitata was 3.7 mg L−1 and lies close to the hypoxic condition recorded on coral reefs during the upwelling season at 10 m depth. At Gorgona Island oxygen conditions lower than 2.3 mg L−1 occur at >20 m depth and coincide with the deepest bathymetric distribution of scattered colonies of Pocillopora. Because DO concentrations in coral reefs of Gorgona Island were comparably low to other coral reefs in the Eastern Tropical Pacific, and the hypoxic threshold of P. capitata was close to the minimum DO record on reefs, hypoxic events could represent a threat if conditions that promote eutrophication (and consequently hypoxia) increase.

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“…Oxyregulation in which an organism maintains oxygen consumption despite changes in oxygen availability is commonly observed in organisms living in environments subject to frequent and unpredictable changes in DO concentration. On the other hand, oxyconformity in which oxygen uptake decrease linearly with oxygen availability usually found in organisms living in an environment that seldom fall very low in DO concentration or do so in a regular predictable way (Hughes et al, 2022). Both Halimeda sp.…”

Section: Discussionmentioning

confidence: 99%

Impacts of nighttime hypoxia on the physiological performance of Red Sea macroalgae under peak summer temperature

et al. 2022

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Eutrophication-induced hypoxic sites are increasingly reported in coastal regions. At the same time, ocean warming, water column stratification, and changing circulation lead to open-ocean deoxygenation. In coastal areas and reefs with dense vegetation, aquatic organisms can be exposed to oxygen limitation stress where oxygen concentration reaches extremely low levels, particularly during nighttime once photosynthetic O2 production has ceased. Despite scientists being aware of this for decades, little is known about the impact of deoxygenation on the physiology of marine primary producers, such as macroalgae. In the Red Sea, in particular, the physiological adaptations of macroalgae under future climate scenarios are nonexistent. Here, we investigate the impact of different oxygen levels (6.5, 2.5, and 1.3 mg O2 L-1) at night for three conspicuous Red Sea macroalgae species Halimeda opuntia and Padina boryana (calcareous) and the brown algae Sargassum latifolium (noncalcifying). We monitored algal physiological responses during a 12-hour nighttime (dark) period at 32°C by measuring photochemical efficiency (Fv/Fm), respiration rates, and cellular viability. No lethal thresholds were detected. However, both deoxygenation treatments decreased respiration rates and induced changes in cellular activity, and only under severe hypoxia was a decrease in photochemical efficiency observed in all species. We calculated sublethal O2 thresholds SLC(50) of 1.2 ± 0.1, 1.5 ± 0.1, and 1.7 ± 0.1 mg O2 L-1 for H. opuntia, P. boryana, and S. latifolium, respectively. Therefore, the effects of nighttime hypoxia are evident over short timescales and may impact ecosystems via reduced primary production. Future consequences of persistent hypoxia and subsequent performance in multifaceted stressor exposures will provide a fundamental understanding of hypoxia’s threat to biodiversity and ecosystems.

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Widespread oxyregulation in tropical corals under hypoxia

Cited by 15 publications

References 48 publications

Deoxygenation lowers the thermal threshold of coral bleaching

Deoxygenation lowers the thermal threshold of coral bleaching

Spatiotemporal variability of oxygen concentration in coral reefs of Gorgona Island (Eastern Tropical Pacific) and its effect on the coral Pocillopora capitata

Impacts of nighttime hypoxia on the physiological performance of Red Sea macroalgae under peak summer temperature

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