High survival following bleaching underscores the resilience of a frequently disturbed region of the Great Barrier Reef

Page, Cathie A.; Giuliano, Christine; Bay, Line K.; Randall, Carly J.

doi:10.1002/ecs2.4280

Cited by 12 publications

(15 citation statements)

References 102 publications

(201 reference statements)

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“…Severe bleaching occurred throughout Woppaburra sea Country (the Keppel Islands) during the 2020 marine heatwave, but mortality of Acropora millepora was low (~ 6.5% this study; Page et al 2023). Despite recovery by the time of coral spawning six months later, we found that heavily bleached colonies experienced a signi cant reduction in reproductive output in the form of depressed egg numbers, while egg size was conserved, resulting in an estimated 21% reduction in population-level fecundity.…”

Section: Discussionmentioning

confidence: 67%

“…Only 4.5% of colonies did not visually bleach (category = 6, n = 16). Whole-colony mortality was highest at PI (17%, n = 16) while no whole-colony mortality was observed at NKI (SI Table 1, Page et al 2023). The likelihood of survival signi cantly increased as a function of bleaching score (GLM: z = 3.437, p < 0.001) (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…4b), despite similar levels of bleaching. Interestingly, NKI had some of the highest cumulative heat-stress during the 2020 bleaching event (Page et al 2023), suggesting that this environmental stress may have in uenced the provisioning of eggs, irrespective of bleaching score.…”

Section: Bleaching and Reproductive Outputmentioning

confidence: 99%

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Dissecting coral recovery: Bleaching reduces reproductive output in Acropora millepora

Briggs,

Page,

Giuliano

et al. 2023

Preprint

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Increasingly frequent and severe bleaching events driven by climate change are decreasing coral populations worldwide. Recovery of these populations relies on reproduction by the survivors of such events including local and upstream larval sources. Yet, corals that survive bleaching may be impaired by sublethal effects that suppress reproduction, reducing larval input to reefs, and consequently impeding recovery. We investigated the impact of the 2020 mass-bleaching event on Acropora millepora reproduction on inshore, turbid reefs in Woppaburra sea Country (the Keppel Islands), to improve our understanding of the effects of bleaching on coral populations. A. millepora experienced high bleaching incidence but low mortality across the island group during this event and thus constituted an ideal population to investigate potential sublethal effects on reproductive output. Six months after the heat wave, and just prior to spawning, we collected, decalcified, and dissected samples from 94 tagged A. millepora colonies with a known 2020 bleaching response, to investigate the relationships between stress severity and reproduction. Despite having regained their pigmentation, we detected a significant reduction in fecundity in colonies that had bleached severely. Considering the impact of the bleaching event on the coral population sampled (i.e. mortality, bleaching severity and colony size), coupled with reductions in fecundity, we estimated a total decrease in population-level reproductive output of 21%. These results suggest that reduced reproductive output may impact recovery of coral populations following bleaching and should be considered alongside traditional estimates from coral mortality.

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Section: Discussionmentioning

confidence: 67%

Section: Resultsmentioning

confidence: 99%

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Dissecting coral recovery: Bleaching reduces reproductive output in Acropora millepora

Briggs,

Page,

Giuliano

et al. 2023

Preprint

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“…Conversely, the low cumulative heat stress experienced by those regions may result in coral assemblages that are naïve to high heat stress (Hughes et al, 2021). As such, mild but highly prevalent coral bleaching occurred in the southern GBR during 2016–2017 (21% of colonies; Kennedy et al, 2017) and 2020 (48% of colonies; Nolan et al, 2021; 86% of colonies; Page et al, 2023) and occurred under lower cumulative heat stress (DHW) than in central and northern GBR (Hughes et al, 2021). Further investigations are thus required to understand how recurrent warming disturbances and gene flow with northern regions will shape the evolution of these cooler reefs.…”

Section: Discussionmentioning

confidence: 99%

Thermal tolerance traits of individual corals are widely distributed across the Great Barrier Reef

Denis,

Bay,

Mocellin

et al. 2024

Preprint

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The capacity of reef-building corals to adapt to global warming depends upon standing heritable variation in tolerance traits upon which selection can act. While heat tolerance is known to differ markedly among coral taxa and reefs, limited knowledge exists on within-species variation among spatial scales ranging from meters to hundreds of kilometers. Here, we performed standardized acute heat stress assays to quantify the thermal tolerance of 768 colonies of Acropora spathulata from 14 reefs spanning 1060 km (9.5° latitude) of the Great Barrier Reef (GBR). Colony thermal tolerance was determined by the rate of decline in physiological traits under +3 °C, +6 °C and +9 °C above the local maximum monthly mean (MMM). Photochemical efficiency and chlorophyll retention traits revealed considerable variation in thermal thresholds among individual colonies both among reefs (~6 °C) and within reefs (~3 °C). Although tolerance rankings of colonies varied between traits, the most heat tolerant corals (i.e. within the top 25% of each trait) were found at virtually all reefs across the GBR, indicating widespread phenotypic variation. Reef-scale environmental predictors explained 12–62% of trait variation and heat tolerance was the greatest at reefs exposed to high thermal averages and recent thermal stress likely reflecting local adaptation and stress pre-acclimatization. We also found evidence that heat tolerance was further influenced by thermal fluctuations, ocean currents and cloud cover. Importantly, heat tolerance relative to local summer temperatures was the greatest in the southern GBR (~9.5 °C above MMM), suggestive of higher potential to adapt to future warming. Together, these results can be used to identify naturally tolerant coral populations and individuals for conservation and restoration applications.

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“…Our observations show that some coral holobionts can rapidly change and recover during and after successive severe disturbances. In fact, scientists have recently and repeatedly observed both devastating losses and unexpected recoveries in coral reefs after massive disturbances, such as those on both these remote Mo'orean coral reefs as well as continental reefs, such as the Great Barrier Reef (Adjeroud et al., 2018; Page et al., 2023), and microbiomes may help mediate such recoveries. This work supports the hypothesis that microbiome acclimatization, resilience, and resistance may be an additional layer of coral adaptive capacity during repeated marine heatwaves and demonstrates that some coral microbiomes may contribute to ecological memory of past disturbance through acclimatizing and developing resistance to repeated stress.…”

Section: Discussionmentioning

confidence: 99%

Microbiome ecological memory and responses to repeated marine heatwaves clarify variation in coral bleaching and mortality

Vompe,

Epstein,

Speare

et al. 2023

Global Change Biology

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Microbiomes are essential features of holobionts, providing their hosts with key metabolic and functional traits like resistance to environmental disturbances and diseases. In scleractinian corals, questions remain about the microbiome's role in resistance and resilience to factors contributing to the ongoing global coral decline and whether microbes serve as a form of holobiont ecological memory. To test if and how coral microbiomes affect host health outcomes during repeated disturbances, we conducted a large‐scale (32 exclosures, 200 colonies, and 3 coral species sampled) and long‐term (28 months, 2018–2020) manipulative experiment on the forereef of Mo'orea, French Polynesia. In 2019 and 2020, this reef experienced the two most severe marine heatwaves on record for the site. Our experiment and these events afforded us the opportunity to test microbiome dynamics and roles in the context of coral bleaching and mortality resulting from these successive and severe heatwaves. We report unique microbiome responses to repeated heatwaves in Acropora retusa, Porites lobata, and Pocillopora spp., which included: microbiome acclimatization in A. retusa, and both microbiome resilience to the first marine heatwave and microbiome resistance to the second marine heatwave in Pocillopora spp. Moreover, observed microbiome dynamics significantly correlated with coral species‐specific phenotypes. For example, bleaching and mortality in A. retusa both significantly increased with greater microbiome beta dispersion and greater Shannon Diversity, while P. lobata colonies had different microbiomes across mortality prevalence. Compositional microbiome changes, such as changes to proportions of differentially abundant putatively beneficial to putatively detrimental taxa to coral health outcomes during repeated heat stress, also correlated with host mortality, with higher proportions of detrimental taxa yielding higher mortality in A. retusa. This study reveals evidence for coral species‐specific microbial responses to repeated heatwaves and, importantly, suggests that host‐dependent microbiome dynamics may provide a form of holobiont ecological memory to repeated heat stress.

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High survival following bleaching underscores the resilience of a frequently disturbed region of the Great Barrier Reef

Cited by 12 publications

References 102 publications

Dissecting coral recovery: Bleaching reduces reproductive output in Acropora millepora

Dissecting coral recovery: Bleaching reduces reproductive output in Acropora millepora

Thermal tolerance traits of individual corals are widely distributed across the Great Barrier Reef

Microbiome ecological memory and responses to repeated marine heatwaves clarify variation in coral bleaching and mortality

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