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Helgoe J, Davy SK, Weis VM, Rodriguez-Lanetty M. Triggers, cascades, and endpoints: connecting the dots of coral bleaching mechanisms. Biol Rev Camb Philos Soc 2024; 99:715-752. [PMID: 38217089 DOI: 10.1111/brv.13042] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2023] [Revised: 12/08/2023] [Accepted: 12/12/2023] [Indexed: 01/15/2024]
Abstract
The intracellular coral-dinoflagellate symbiosis is the engine that underpins the success of coral reefs, one of the most diverse ecosystems on the planet. However, the breakdown of the symbiosis and the loss of the microalgal symbiont (i.e. coral bleaching) due to environmental changes are resulting in the rapid degradation of coral reefs globally. There is an urgent need to understand the cellular physiology of coral bleaching at the mechanistic level to help develop solutions to mitigate the coral reef crisis. Here, at an unprecedented scope, we present novel models that integrate putative mechanisms of coral bleaching within a common framework according to the triggers (initiators of bleaching, e.g. heat, cold, light stress, hypoxia, hyposalinity), cascades (cellular pathways, e.g. photoinhibition, unfolded protein response, nitric oxide), and endpoints (mechanisms of symbiont loss, e.g. apoptosis, necrosis, exocytosis/vomocytosis). The models are supported by direct evidence from cnidarian systems, and indirectly through comparative evolutionary analyses from non-cnidarian systems. With this approach, new putative mechanisms have been established within and between cascades initiated by different bleaching triggers. In particular, the models provide new insights into the poorly understood connections between bleaching cascades and endpoints and highlight the role of a new mechanism of symbiont loss, i.e. 'symbiolysosomal digestion', which is different from symbiophagy. This review also increases the approachability of bleaching physiology for specialists and non-specialists by mapping the vast landscape of bleaching mechanisms in an atlas of comprehensible and detailed mechanistic models. We then discuss major knowledge gaps and how future research may improve the understanding of the connections between the diverse cascade of cellular pathways and the mechanisms of symbiont loss (endpoints).
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Affiliation(s)
- Joshua Helgoe
- Department of Biological Sciences, Institute of Environment, Florida International University, 11200 SW 8th Street, OE 167, Miami, FL, USA
| | - Simon K Davy
- School of Biological Sciences, Victoria University of Wellington, PO Box 600, Wellington, New Zealand
| | - Virginia M Weis
- Department of Integrative Biology, Oregon State University, 2701 SW Campus Way, 2403 Cordley Hall, Corvallis, OR, USA
| | - Mauricio Rodriguez-Lanetty
- Department of Biological Sciences, Institute of Environment, Florida International University, 11200 SW 8th Street, OE 167, Miami, FL, USA
- Department of Biological Sciences, Biomolecular Sciences Institute, Florida International University, 11200 SW 8th Street, Miami, FL, USA
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Edmunds PJ, Maritorena S, Burgess SC. Early post-settlement events, rather than settlement, drive recruitment and coral recovery at Moorea, French Polynesia. Oecologia 2024; 204:625-640. [PMID: 38418704 DOI: 10.1007/s00442-024-05517-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2023] [Accepted: 01/20/2024] [Indexed: 03/02/2024]
Abstract
Understanding population dynamics is a long-standing objective of ecology, but the need for progress in this area has become urgent. For coral reefs, achieving this objective is impeded by a lack of information on settlement versus post-settlement events in determining recruitment and population size. Declines in coral abundance are often inferred to be associated with reduced densities of recruits, which could arise from mechanisms occurring at larval settlement, or throughout post-settlement stages. This study uses annual measurements from 2008 to 2021 of coral cover, the density of coral settlers (S), the density of small corals (SC), and environmental conditions, to evaluate the roles of settlement versus post-settlement events in determining rates of coral recruitment and changes in coral cover at Moorea, French Polynesia. Coral cover, S, SC, and the SC:S ratio (a proxy for post-settlement success), and environmental conditions, were used in generalized additive models (GAMs) to show that: (a) coral cover was more strongly related to SC and SC:S than S, and (b) SC:S was highest when preceded by cool seawater, low concentrations of Chlorophyll a, and low flow speeds, and S showed evidence of declining with elevated temperature. Together, these results suggest that changes in coral cover in Moorea are more strongly influenced by post-settlement events than settlement. The key to understanding coral community resilience may lie in elucidating the factors attenuating the bottleneck between settlers and small corals.
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Affiliation(s)
- Peter J Edmunds
- Department of Biology, California State University, Northridge, CA, 91330-8303, USA.
| | - Stéphane Maritorena
- Earth Research Institute, University of California Santa Barbara, Santa Barbara, CA, 93106-3060, USA
| | - Scott C Burgess
- Department of Biological Science, Florida State University, Tallahassee, FL, 32306-4295, USA
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Sannassy Pilly S, Roche RC, Richardson LE, Turner JR. Depth variation in benthic community response to repeated marine heatwaves on remote Central Indian Ocean reefs. ROYAL SOCIETY OPEN SCIENCE 2024; 11:231246. [PMID: 38545610 PMCID: PMC10966399 DOI: 10.1098/rsos.231246] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/22/2023] [Revised: 12/01/2023] [Accepted: 02/21/2024] [Indexed: 04/26/2024]
Abstract
Coral reefs are increasingly impacted by climate-induced warming events. However, there is limited empirical evidence on the variation in the response of shallow coral reef communities to thermal stress across depths. Here, we assess depth-dependent changes in coral reef benthic communities following successive marine heatwaves from 2015 to 2017 across a 5-25 m depth gradient in the remote Chagos Archipelago, Central Indian Ocean. Our analyses show an overall decline in hard and soft coral cover and an increase in crustose coralline algae, sponge and reef pavement following successive marine heatwaves on the remote reef system. Our findings indicate that the changes in benthic communities in response to elevated seawater temperatures varied across depths. We found greater changes in benthic group cover at shallow depths (5-15 m) compared with deeper zones (15-25 m). The loss of hard coral cover was better predicted by initial thermal stress, while the loss of soft coral was associated with repeated thermal stress following successive warming events. Our study shows that benthic communities extending to 25 m depth were impacted by successive marine heatwaves, supporting concerns about the resilience of shallow coral reef communities to increasingly severe climate-driven warming events.
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Affiliation(s)
| | - Ronan C. Roche
- School of Ocean Sciences, Bangor University, BangorLL59 5AB, UK
| | | | - John R. Turner
- School of Ocean Sciences, Bangor University, BangorLL59 5AB, UK
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Madeira C, Dias M, Ferreira A, Gouveia R, Cabral H, Diniz MS, Vinagre C. Does Predation Exacerbate the Risk of Endosymbiont Loss in Heat Stressed Hermatypic Corals? Molecular Cues Provide Insights Into Species-Specific Health Outcomes in a Multi-Stressor Ocean. Front Physiol 2022; 13:801672. [PMID: 35299660 PMCID: PMC8922028 DOI: 10.3389/fphys.2022.801672] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2021] [Accepted: 01/31/2022] [Indexed: 11/30/2022] Open
Abstract
Ocean warming has been a major driver of coral reef bleaching and mass mortality. Coupled to other biotic pressures, corals’ ability for acclimatization and adaptation may become compromised. Here, we tested the combined effects of warming scenarios (26, 30, and 32°C) and predation (wound vs. no wound) in coral health condition (paleness, bleaching, and mortality), cellular stress responses (heat shock protein 70 kDa Hsp70, total ubiquitin Ub, and total antioxidant capacity TAC), and physiological state (integrated biomarker response index, IBR) of seven Scleractinian coral species, after being exposed for 60 days. Results show that although temperature was the main factor driving coral health condition, thermotolerant species (Galaxea fascicularis, Psammocora contigua, and Turbinaria reniformis) displayed increased paleness, bleaching, and mortality in predation treatments at high temperature, whereas thermosensitive species (Acropora tenuis, Echinopora lamellosa, and Montipora capricornis brown and green morphotypes) all died at 32°C, regardless of predation condition. At the molecular level, results show that there were significant main and interactive effects of species, temperature, and predation in the biomarkers assessed. Temperature affected Hsp70, Ub, and TAC, evidencing the role of protein folding and turnover, as well as reactive oxygen species scavenging in heat stress management. Predation increased Hsp70 and Ub, suggesting the activation of the pro-phenoloxidase system and cytokine activity, whereas the combination of both stressors mainly affected TAC during moderate stress and Ub under severe stress, suggesting that redox balance and defense of homeostasis are crucial in tissue repair at high temperature. IBR levels showed an increasing trend at 32°C in predated coral fragments (although non-significant). We conclude that coral responses to the combination of high temperature and predation pressure display high inter-species variability, but these stressors may pose a higher risk of endosymbiont loss, depending on species physiology and stress intensity.
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Affiliation(s)
- Carolina Madeira
- i4HB – Associate Laboratory Institute for Health and Bioeconomy, NOVA School of Science and Technology, NOVA University Lisbon, Caparica, Portugal
- UCIBIO – Applied Molecular Biosciences Unit, NOVA School of Science and Technology, NOVA University of Lisbon, Caparica, Portugal
- MARE – Marine and Environmental Sciences Centre, Faculty of Sciences, University of Lisbon, Lisbon, Portugal
- *Correspondence: Carolina Madeira, , orcid.org/0000-0003-1632-634X
| | - Marta Dias
- MARE – Marine and Environmental Sciences Centre, Faculty of Sciences, University of Lisbon, Lisbon, Portugal
- Marta Dias, , orcid.org/0000-0003-0447-6009
| | - Ana Ferreira
- Biology Department, Oceanário de Lisboa, Lisbon, Portugal
| | - Raúl Gouveia
- Biology Department, Oceanário de Lisboa, Lisbon, Portugal
| | - Henrique Cabral
- MARE – Marine and Environmental Sciences Centre, Faculty of Sciences, University of Lisbon, Lisbon, Portugal
- INRAE – National Research Institute for Agriculture, Food and Environment, UR EABX, Cestas, France
| | - Mário S. Diniz
- i4HB – Associate Laboratory Institute for Health and Bioeconomy, NOVA School of Science and Technology, NOVA University Lisbon, Caparica, Portugal
- UCIBIO – Applied Molecular Biosciences Unit, NOVA School of Science and Technology, NOVA University of Lisbon, Caparica, Portugal
| | - Catarina Vinagre
- MARE – Marine and Environmental Sciences Centre, Faculty of Sciences, University of Lisbon, Lisbon, Portugal
- CCMAR – Centre of Marine Sciences, University of Algarve, Faro, Portugal
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Vranken S, Wernberg T, Scheben A, Severn-Ellis AA, Batley J, Bayer PE, Edwards D, Wheeler D, Coleman MA. Genotype-Environment mismatch of kelp forests under climate change. Mol Ecol 2021; 30:3730-3746. [PMID: 34018645 DOI: 10.1111/mec.15993] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2021] [Revised: 05/11/2021] [Accepted: 05/12/2021] [Indexed: 01/23/2023]
Abstract
Climate change is increasingly impacting ecosystems globally. Understanding adaptive genetic diversity and whether it will keep pace with projected climatic change is necessary to assess species' vulnerability and design efficient mitigation strategies such as assisted adaptation. Kelp forests are the foundations of temperate reefs globally but are declining in many regions due to climate stress. A lack of knowledge of kelp's adaptive genetic diversity hinders assessment of vulnerability under extant and future climates. Using 4245 single nucleotide polymorphisms (SNPs), we characterized patterns of neutral and putative adaptive genetic diversity for the dominant kelp in the southern hemisphere (Ecklonia radiata) from ~1000 km of coastline off Western Australia. Strong population structure and isolation-by-distance was underpinned by significant signatures of selection related to temperature and light. Gradient forest analysis of temperature-linked SNPs under selection revealed a strong association with mean annual temperature range, suggesting adaptation to local thermal environments. Critically, modelling revealed that predicted climate-mediated temperature changes will probably result in high genomic vulnerability via a mismatch between current and future predicted genotype-environment relationships such that kelp forests off Western Australia will need to significantly adapt to keep pace with projected climate change. Proactive management techniques such as assisted adaptation to boost resilience may be required to secure the future of these kelp forests and the immense ecological and economic values they support.
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Affiliation(s)
- Sofie Vranken
- UWA Oceans Institute, Crawley, WA, Australia
- School of Biological Sciences, University of Western Australia, Crawley, WA, Australia
| | - Thomas Wernberg
- UWA Oceans Institute, Crawley, WA, Australia
- School of Biological Sciences, University of Western Australia, Crawley, WA, Australia
- Institute of Marine Research, His, Norway
| | - Armin Scheben
- School of Biological Sciences, University of Western Australia, Crawley, WA, Australia
- Simons Center for Quantitative Biology, Cold Spring Harbor Laboratory, Cold Spring Harbor, New York, NY, USA
| | | | - Jacqueline Batley
- School of Biological Sciences, University of Western Australia, Crawley, WA, Australia
| | - Philipp Emanuel Bayer
- School of Biological Sciences, University of Western Australia, Crawley, WA, Australia
| | - David Edwards
- School of Biological Sciences, University of Western Australia, Crawley, WA, Australia
| | - David Wheeler
- New South Wales Department of Primary Industries, Orange Agricultural Institute, Orange, NSW, Australia
| | - Melinda Ann Coleman
- School of Biological Sciences, University of Western Australia, Crawley, WA, Australia
- New South Wales Fisheries, National Marine Science Centre, Coffs Harbour, NSW, Australia
- National Marine Science Centre, Southern Cross University, Coffs Harbour, NSW, Australia
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Rinkevich B. Augmenting coral adaptation to climate change via coral gardening (the nursery phase). JOURNAL OF ENVIRONMENTAL MANAGEMENT 2021; 291:112727. [PMID: 33957417 DOI: 10.1016/j.jenvman.2021.112727] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/2020] [Revised: 04/16/2021] [Accepted: 04/27/2021] [Indexed: 06/12/2023]
Abstract
Unceasing climate change and anthropogenic impacts on coral reefs worldwide lead the needs for augmenting adaptive potential of corals. Currently, the most successful approach for restoring degraded reefs is 'coral gardening', where corals are farmed in underwater nurseries, then outplanted to damaged reefs. Dealing with enhanced coral adaptation, the 'coral gardening' approach is conceptually structured here within a hierarchical list of five encircling tiers that include all restoration activities, focusing on the nursery phase. Each tier encompasses all the activities performed in the levels below it hierarchically. The first is the 'coral mariculture' tier, followed by the 'ecological engineering' tier. The third is the adaptation-based reef restoration (ABRR) tier, preceding the fourth ('ecosystem seascape') and the fifth ('ecosystem services') tiers. The ABRR tier is further conceptualized and its constituent five classes (phenotypic plasticity, assisted migration, epigenetics, coral chimerism, holobiont modification) are detailed. It is concluded that the nursery phase of the 'gardening' tenet may further serve as a platform to enhance the adaptation capacities of corals to climate change through the five ABBR classes. Employing the 'gardening' tiers in reef restoration without considering ABRR will scarcely be able to meet global targets for healthy reef ecosystems in the future.
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Affiliation(s)
- Baruch Rinkevich
- Israel Oceanography and Limnological Research, National Institute of Oceanography, Tel Shikmona, PO Box 9753, Haifa, 3109701, Israel.
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McRae CJ, Huang WB, Fan TY, Côté IM. Effects of thermal conditioning on the performance of Pocillopora acuta adult coral colonies and their offspring. CORAL REEFS (ONLINE) 2021; 40:1491-1503. [PMID: 34720373 PMCID: PMC8550305 DOI: 10.1007/s00338-021-02123-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/20/2020] [Accepted: 05/25/2021] [Indexed: 05/02/2023]
Abstract
UNLABELLED Ocean warming induced by climate change is the greatest threat to the persistence of coral reefs globally. Given the current rate of ocean warming, there may not be sufficient time for natural acclimation or adaptation by corals. This urgency has led to the exploration of active management techniques aimed at enhancing thermal tolerance in corals. Here, we test the capacity for transgenerational acclimation in the reef-building coral Pocillopora acuta as a means of increasing offspring performance in warmer waters. We exposed coral colonies from a reef influenced by intermittent upwelling and constant warm-water effluent from a nuclear power plant to temperatures that matched (26 °C) or exceeded (29.5 °C) season-specific mean temperatures for three reproductive cycles; offspring were allowed to settle and grow at both temperatures. Heated colonies reproduced significantly earlier in the lunar cycle and produced fewer and smaller planulae. Recruitment was lower at the heated recruitment temperature regardless of parent treatment. Recruit survival did not differ based on parent or recruitment temperature. Recruits from heated parents were smaller and had lower maximum quantum yield (Fv/Fm), a measurement of symbiont photochemical performance. We found no direct evidence that thermal conditioning of adult P. acuta corals improves offspring performance in warmer water; however, chronic exposure of parent colonies to warmer temperatures at the source reef site may have limited transgenerational acclimation capacity. The extent to which coral response to this active management approach might vary across species and sites remains unclear and merits further investigation. SUPPLEMENTARY INFORMATION The online version contains supplementary material available at 10.1007/s00338-021-02123-9.
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Affiliation(s)
- Crystal J. McRae
- Department of Natural Resources and Environmental Studies, National Dong Hwa University, Hualien, Taiwan
- Department of Biological Sciences, Simon Fraser University, British Columbia, Canada
| | - Wen-Bin Huang
- Department of Natural Resources and Environmental Studies, National Dong Hwa University, Hualien, Taiwan
| | - Tung-Yung Fan
- Institute of Marine Biology, National Dong Hwa University, Pingtung, Taiwan
- National Museum of Marine Biology and Aquarium, Pingtung, Taiwan
| | - Isabelle M. Côté
- Department of Biological Sciences, Simon Fraser University, British Columbia, Canada
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