Divergent expression of hypoxia response systems under deoxygenation in reef‐forming corals aligns with bleaching susceptibility

Alderdice, Rachel; Suggett, David J.; Cárdenas, Anny; Hughes, David; Kühl, Michael; Pernice, Mathieu; Voolstra, Christian R.

doi:10.1111/gcb.15436

Cited by 52 publications

(140 citation statements)

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“…In addition to changes in temperature and pH, which are the two most commonly tested environmental parameters, oxygen must also be considered. Although the impact of reduced oxygen levels and its natural fluctuations on coral reefs have yet to be established, it appears that low DO (2-4 mg L -1 ) increases the sensitivity of branching corals, resulting in a decline in coral health, bleaching, and tissue loss (Haas et al, 2014;Hughes et al, 2020;Alderdice et al, 2021). However, our study shows that although the Bouraké system can reach conditions close to hypoxia (< 3 mg L -1 ; Fig.…”

Section: Effects Of Physical and Chemical Conditions On Species Distributionmentioning

confidence: 60%

The Bouraké semi-enclosed lagoon (New Caledonia). A natural laboratory to study the life-long adaptation of a coral reef ecosystem to climate change-like conditions

Maggioni¹,

Pujo‐Pay²,

Aucan³

et al. 2021

Preprint

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Abstract. According to current experimental evidence, coral reefs could disappear within the century if CO2 emissions remain unabated. However, recent discoveries of diverse and high cover reefs that already thrive under extreme conditions seem to contradict these projections. Volcanic CO2 vents, semi-enclosed lagoons and mangrove estuaries are unique study sites where one or more ecologically relevant parameters for life in the oceans are close or even worse than currently projected for the year 2100. These natural analogues of future conditions hold new hope for the future of coral reefs and provide unique natural laboratories to explore how reef species could keep pace with climate change. To achieve this, it is essential to characterize their environment as a whole, and accurately consider all possible environmental factors that may differ from what is expected in the future and that may possibly alter the ecosystem response. In this study, we focus on the semi-enclosed lagoon of Bouraké (New Caledonia, SW Pacific Ocean) where a healthy reef ecosystem thrives in warm, acidified and deoxygenated water. We used a multi-scale approach to characterize the main physical-chemical parameters and mapped the benthic community composition (i.e., corals, sponges, and macroalgae). The data revealed that most physical and chemical parameters are regulated by the tide, strongly fluctuate 3 to 4 times a day, and are entirely predictable. The seawater pH and dissolved oxygen decrease during falling tide and reach extreme low values at low tide (7.2 pHT and 1.9 mg O2 L−1 at Bouraké, vs 7.9 pHT and 5.5 mg O2 L−1 at reference reefs). Dissolved oxygen, temperature, and pH fluctuates according to the tide of up to 4.91 mg O2 L−1, 6.50 °C, and 0.69 pHT units on a single day. Furthermore, the concentration of most of the chemical parameters was one- to 5-times higher at the Bouraké lagoon, particularly for organic and inorganic carbon and nitrogen, but also for some nutrients, notably silicates. Surprisingly, despite extreme environmental conditions and altered seawater chemical composition, our results reveal a diverse and high cover community of macroalgae, sponges and corals accounting for 28, 11 and 66 species, respectively. Both environmental variability and nutrient imbalance might contribute to their survival under such extreme environmental conditions. We describe the natural dynamics of the Bouraké ecosystem and its relevance as a natural laboratory to investigate the benthic organism’s adaptive responses to multiple stressors like future climate change conditions.

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Section: Effects Of Physical and Chemical Conditions On Species Distributionmentioning

confidence: 60%

The Bouraké semi-enclosed lagoon (New Caledonia). A natural laboratory to study the life-long adaptation of a coral reef ecosystem to climate change-like conditions

Maggioni¹,

Pujo‐Pay²,

Aucan³

et al. 2021

Preprint

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“…Bleaching is the process by which corals expel their endosymbiotic algae. Though bleaching is typically observed in response to warming 18 , it broadly indicates physiological stress and has been detected in response to other environmental changes including acidification 19 and hypoxia in the lab 20 . Agaricia is a representative Caribbean coral species, abundant on the shallow reefs of Bocas del Toro at both the impacted and reference sites at 3-5 m depth 21 .…”

Section: Resultsmentioning

confidence: 99%

Rapid ecosystem-scale consequences of acute deoxygenation on a Caribbean coral reef

et al. 2021

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Loss of oxygen in the global ocean is accelerating due to climate change and eutrophication, but how acute deoxygenation events affect tropical marine ecosystems remains poorly understood. Here we integrate analyses of coral reef benthic communities with microbial community sequencing to show how a deoxygenation event rapidly altered benthic community composition and microbial assemblages in a shallow tropical reef ecosystem. Conditions associated with the event precipitated coral bleaching and mass mortality, causing a 50% loss of live coral and a shift in the benthic community that persisted a year later. Conversely, the unique taxonomic and functional profile of hypoxia-associated microbes rapidly reverted to a normoxic assemblage one month after the event. The decoupling of ecological trajectories among these major functional groups following an acute event emphasizes the need to incorporate deoxygenation as an emerging stressor into coral reef research and management plans to combat escalating threats to reef persistence.

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“…Thus, low oxygen levels can orchestrate the coral mortality by affecting coral's productivity and respiration 7 . Further, fast growing corals such as Acropora and Pocillopora have been reported to be more susceptible to low oxygen levels 11,13,27 . Fast growing coral species have faster metabolism rates 28 and hence metabolic oxygen requirements are higher 11,29 .…”

Section: Resultsmentioning

confidence: 99%

“…At present, secondary algae have completely occupied the dead coral colonies, which will affect the coral recovery by hindering the attachment of new coral recruits during the next spawning season 32 . Recent studies suggest hypoxia increases coral susceptibility to bleaching 27 , and may increase disease prevalence and algal proliferation 7 . Thus algal blooms add to the existing array of threats to corals of GoM that needs to be understood more with further focused research.…”

Section: Resultsmentioning

confidence: 99%

Low oxygen levels caused by Noctiluca scintillans bloom kills corals in Gulf of Mannar, India

Raj

Mathews

Obura

et al. 2020

Sci Rep

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Coral reefs around the world are undergoing severe decline in the past few decades. Mass coral mortalities have predominantly been reported to be caused by coral bleaching or disease outbreaks. Temporary hypoxic conditions caused by algal blooms can trigger mass coral mortalities though are reported rarely. In this study in Gulf of Mannar (GoM), southeast India, we report a significant coral mortality caused by a bloom of the ciguatoxic dinoflagellate Noctiluca scintillans during September–October 2019. Dissolved oxygen levels declined below 2 mg l−1 during the bloom causing temporary hypoxia and mortality (up to 71.23%) in the fast growing coral genera Acropora, Montipora and Pocillopora. Due to global climate change, more frequent and larger algal blooms are likely in the future. Hence, it is likely that shallow water coral reefs will be affected more frequently by episodic hypoxic conditions driven by algal blooms. More studies are, however, required to understand the mechanism of coral mortality due to algal blooms, impacts on community composition and the potential for subsequent recovery.

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Divergent expression of hypoxia response systems under deoxygenation in reef‐forming corals aligns with bleaching susceptibility

Abstract: This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.

Cited by 52 publications

References 93 publications

The Bouraké semi-enclosed lagoon (New Caledonia). A natural laboratory to study the life-long adaptation of a coral reef ecosystem to climate change-like conditions

The Bouraké semi-enclosed lagoon (New Caledonia). A natural laboratory to study the life-long adaptation of a coral reef ecosystem to climate change-like conditions

Rapid ecosystem-scale consequences of acute deoxygenation on a Caribbean coral reef

Low oxygen levels caused by Noctiluca scintillans bloom kills corals in Gulf of Mannar, India

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