Coral bleaching: interpretation of thermal tolerance limits and thermal thresholds in tropical corals

Fitt, William K.; Brown, Barbara E.; Warner, Mark E.; Dunne, R. P.

doi:10.1007/s003380100146

Cited by 669 publications

(526 citation statements)

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“…This rapid response contrasts with the effect of elevated sea-surface temperatures for reef ecosystems, which is currently determined in terms of degree heating weeks. 27 In bleaching events in the field, relatively small diurnal fluctuations in temperature may be far more important than previously recognised, 4 and may selectively promote the rapid PCD response over slower necrotic cell death.…”

Section: Discussionmentioning

confidence: 99%

“…3 Despite the global importance of coral reef ecosystems, the cellular mechanisms leading to bleaching remain largely unresolved and a recent review highlighted the need for a better understanding of the process at sublethal temperatures. 4 Kü ltz 5 has recently argued that the cellular stress response is so well conserved because it represents a rapid, transient mechanism for promoting tolerance to temporary environmental extremes, thereby allowing for slower, stressorspecific mechanisms to be upregulated. Programmed cell death (PCD), or apoptosis, is recognised as an important part of the stress response.…”

Section: Introductionmentioning

confidence: 99%

“…In plants, ROS may not only be toxic by-products of aerobic metabolism, but may be actively produced in response to stress and pathogens as a cell-death signalling mechanism. 9,10 In order to understand stress tolerance thresholds 4 and adaptive capacity of an organism to stress, it is clear that we must first determine whether different mechanisms are controlling cell death in response to different types and doses of stress.…”

Section: Introductionmentioning

confidence: 99%

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Heat stress induces different forms of cell death in sea anemones and their endosymbiotic algae depending on temperature and duration

et al. 2004

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Bleaching of reef building corals and other symbiotic cnidarians due to the loss of their dinoflagellate algal symbionts ( ¼ zooxanthellae), and/or their photosynthetic pigments, is a common sign of environmental stress. Mass bleaching events are becoming an increasingly important cause of mortality and reef degradation on a global scale, linked by many to global climate change. However, the cellular mechanisms of stress-induced bleaching remain largely unresolved. In this study, the frequency of apoptosislike and necrosis-like cell death was determined in the symbiotic sea anemone Aiptasia sp. using criteria that had previously been validated for this symbiosis as indicators of programmed cell death (PCD) and necrosis. Results indicate that PCD and necrosis occur simultaneously in both host tissues and zooxanthellae subject to environmentally relevant doses of heat stress. Frequency of PCD in the anemone endoderm increased within minutes of treatment. Peak rates of apoptosis-like cell death in the host were coincident with the timing of loss of zooxanthellae during bleaching. The proportion of apoptosis-like host cells subsequently declined while cell necrosis increased. In the zooxanthellae, both apoptosis-like and necrosis-like activity increased throughout the duration of the experiment (6 days), dependent on temperature dose. A stress-mediated PCD pathway is an important part of the thermal stress response in the sea anemone symbiosis and this study suggests that PCD may play different roles in different components of the symbiosis during bleaching.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Heat stress induces different forms of cell death in sea anemones and their endosymbiotic algae depending on temperature and duration

et al. 2004

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“…Visual bleaching and photosynthetic efficiency were correlated for all three corals (r = −0.80 to −0.96, P < 0.001 for all comparisons) (Fig. S1); thus, PAM fluorometry measurements are indicative of visual bleaching but are less subjective (17,18,21,22). The most resistant coral was Montipora digitata; for this coral, Dictyota bartayresiana, Galaxaura filamentosa, and Chlorodesmis fastigiata caused significant bleaching and suppression of photosynthetic efficiency, whereas Liagora sp.…”

mentioning

confidence: 89%

Macroalgal terpenes function as allelopathic agents against reef corals

Rasher

Stout²,

Engel³

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

207

269

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During recent decades, many tropical reefs have transitioned from coral to macroalgal dominance. These community shifts increase the frequency of algal-coral interactions and may suppress coral recovery following both anthropogenic and natural disturbance. However, the extent to which macroalgae damage corals directly, the mechanisms involved, and the species specificity of algal-coral interactions remain uncertain. Here, we conducted field experiments demonstrating that numerous macroalgae directly damage corals by transfer of hydrophobic allelochemicals present on algal surfaces. These hydrophobic compounds caused bleaching, decreased photosynthesis, and occasionally death of corals in 79% of the 24 interactions assayed (three corals and eight algae). Coral damage generally was limited to sites of algal contact, but algae were unaffected by contact with corals. Artificial mimics for shading and abrasion produced no impact on corals, and effects of hydrophobic surface extracts from macroalgae paralleled effects of whole algae; both findings suggest that local effects are generated by allelochemical rather than physical mechanisms. Rankings of macroalgae from most to least allelopathic were similar across the three coral genera tested. However, corals varied markedly in susceptibility to allelopathic algae, with globally declining corals such as Acropora more strongly affected. Bioassay-guided fractionation of extracts from two allelopathic algae led to identification of two loliolide derivatives from the red alga Galaxaura filamentosa and two acetylated diterpenes from the green alga Chlorodesmis fastigiata as potent allelochemicals. Our results highlight a newly demonstrated but potentially widespread competitive mechanism to help explain the lack of coral recovery on many present-day reefs.allelopathy | chemical ecology | competition | phase shift C orals are structurally complex foundation species that generate and maintain tropical reef biodiversity. However, the direct and interactive effects of climate-induced coral bleaching (1, 2), ocean acidification (2, 3), coral disease (4), coastal overfishing, and eutrophication (5-8) have led to coral decline over wide areas. On many reefs, dramatic declines in coral cover have co-occurred with significant increases in fleshy macroalgae (9-11). Once established, macroalgae can inhibit coral recruitment and decrease herbivore grazing, producing negative feedbacks that reinforce phase shifts and further diminish reef function (12-14). Thus, local (e.g., overfishing) and global (e.g., climate) stresses may interact in complex ways to suppress coral cover, promote algal proliferation, and compromise reef resilience; such complexities provide both challenges and opportunities for managing these dynamic ecosystems (11, 13).As corals decline and macroalgae proliferate, the frequency of algal-coral interactions will increase, potentially affecting the survivorship, growth, and reproduction of remnant adult corals and new coral recruits (12, 13). However, the consequences ...

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“…Yields also vary over multiple time scales and with a number of environmental parameters, so context is of critical importance when interpreting fluorescence yields, especially in the field (Fitt et al, 2001) and with complex stressors like sediment (Weber et al, 2006). The site, environmental conditions, and stress characteristics should be described as completely as possible.…”

Section: Conclusion and Future Concernsmentioning

confidence: 99%

Effects of two sediment types on the fluorescence yield of two Hawaiian scleractinian corals

Piniak¹

2007

Marine Environmental Research

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Coral bleaching: interpretation of thermal tolerance limits and thermal thresholds in tropical corals

Cited by 669 publications

References 0 publications

Heat stress induces different forms of cell death in sea anemones and their endosymbiotic algae depending on temperature and duration

Heat stress induces different forms of cell death in sea anemones and their endosymbiotic algae depending on temperature and duration

Macroalgal terpenes function as allelopathic agents against reef corals

Effects of two sediment types on the fluorescence yield of two Hawaiian scleractinian corals

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