High frequency temperature variability reduces the risk of coral bleaching

Safaie, Aryan; Silbiger, Nyssa J.; McClanahan, Timothy R.; Pawlak, Geno; Barshis, Daniel J.; Hench, James L.; Rogers, Justin S.; Williams, Gareth J.; Davis, Kristen A.

doi:10.1038/s41467-018-04074-2

Cited by 265 publications

(327 citation statements)

References 75 publications

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“…Coral cover on the Heron reef flat has historically ranged between 0 and 20%, which is consistent with our observations of coral cover (∼18%) (Connell et al, 2004). Although hard corals are believed to be sensitive to environmental extremes, recent studies have shown that corals are able to persist in marginal conditions of lagoon habitats (Camp et al, 2017) and increased temperature variability reduces the likelihood of coral bleaching (Safaie et al, 2018). Instead, persistently low coral cover in the Heron lagoon appears to be due to reduced coral recruitment due to the lack of hard substrate (Connell et al, 2004).…”

Section: Modeling the Effect Of Benthic Cover On The Frequency Of Corsupporting

confidence: 89%

The Dynamics of Coral-Algal Interactions in Space and Time on the Southern Great Barrier Reef

et al. 2018

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Globally, tropical coral reefs are being degraded by human activities, and as a result, reef-building corals have declined while macroalgae have increased. Recent work has focused on measuring macroalgal abundance in response to anthropogenic stressors. To accurately evaluate the effects of human impacts, however, it is necessary to understand the effects of natural processes on reef condition. To better understand how coral reef communities are influenced by natural processes, we investigated how spatial and seasonal changes in environmental conditions (temperature and PAR) influence benthic community structure, and the composition and frequency of coral-algal interactions across eight distinct zones and over a 23-month period at Heron reef on the southern Great Barrier Reef. Hard coral cover and macroalgal density showed distinct spatio-temporal variations, both within and between zones. Broad hard coral cover was significantly higher at the reef slope sites compared to the lagoon and was not significantly influenced by season. The composition and biomass of macroalgae increased in spring and declined in summer, with maximum macroalgal abundance corresponding with average temperatures of between 22 and 24 • C and average 24 h PAR of 300-500 µmol qanta m −2 s −1 . Changes in macroalgal biomass further influenced the composition and frequency of coral-algal interactions, however the incidence of coral-algal contact was best explained by coral cover. The results presented here emphasize that natural levels of macroalgae and coral-algal interactions are context-specific, and vary not only with-in zones, but in somewhat predictable seasonal cycles. Further, these results emphasize that the frequency of coral-algal interactions is dependent on hard coral, not just macroalgal cover, and an increase in coral-algal interactions does not necessarily translate to degradation of coral reefs.

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Section: Modeling the Effect Of Benthic Cover On The Frequency Of Corsupporting

confidence: 89%

The Dynamics of Coral-Algal Interactions in Space and Time on the Southern Great Barrier Reef

et al. 2018

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“…Therefore, we expected the large inputs of nitrogen and phosphorous from seabird guano to enhance resis- Instead of depending on proximity to seabird colonies, the response of corals to bleaching varied by atoll. One likely explanation for this pattern is that corals from small lagoons are adapted to warmer water and/or greater temperature variability and thus are better able to withstand temperature stress (Donner, 2011;Guest et al, 2012;Middlebrook, Hoegh-Guldberg, & Leggat, 2008;Oliver & Palumbi, 2011;Safaie et al, 2018;Schoepf, Stat, Falter, & McCulloch, 2015). Other field studies have similarly demonstrated reduced susceptibility to bleaching for corals in sheltered areas with low water flow (Hoogenboom et al, 2017;McClanahan, Ateweberhan, Muhando, Maina, & Mohammed, 2007;Pineda et al, 2013;Sheppard, 1999).…”

Section: Discussionmentioning

confidence: 97%

Seabird nutrient subsidies alter patterns of algal abundance and fish biomass on coral reefs following a bleaching event

Benkwitt

Wilson

Graham

2019

Global Change Biology

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Cross‐ecosystem nutrient subsidies play a key role in the structure and dynamics of recipient communities, but human activities are disrupting these links. Because nutrient subsidies may also enhance community stability, the effects of losing these inputs may be exacerbated in the face of increasing climate‐related disturbances. Nutrients from seabirds nesting on oceanic islands enhance the productivity and functioning of adjacent coral reefs, but it is unknown whether these subsidies affect the response of coral reefs to mass bleaching events or whether the benefits of these nutrients persist following bleaching. To answer these questions, we surveyed benthic organisms and fishes around islands with seabirds and nearby islands without seabirds due to the presence of invasive rats. Surveys were conducted in the Chagos Archipelago, Indian Ocean, immediately before the 2015–2016 mass bleaching event and, in 2018, two years following the bleaching event. Regardless of the presence of seabirds, relative coral cover declined by 32%. However, there was a post‐bleaching shift in benthic community structure around islands with seabirds, which did not occur around islands with invasive rats, characterized by increases in two types of calcareous algae (crustose coralline algae [CCA] and Halimeda spp.). All feeding groups of fishes were positively affected by seabirds, but only herbivores and piscivores were unaffected by the bleaching event and sustained the greatest difference in biomass between islands with seabirds versus those with invasive rats. By contrast, corallivores and planktivores, both of which are coral‐dependent, experienced the greatest losses following bleaching. Even though seabird nutrients did not enhance community‐wide resistance to bleaching, they may still promote recovery of these reefs through their positive influence on CCA and herbivorous fishes. More broadly, the maintenance of nutrient subsidies, via strategies including eradication of invasive predators, may be important in shaping the response of ecological communities to global climate change.

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“…The difference between the DHW with and without internal waves (ΔDHW) is 0.7°C‐weeks. A synthesis study of factors influencing coral bleaching (Safaie et al ) predicts that an increase in cumulative thermal anomaly, ΔDHW = 0.7°C‐weeks would result in approximately four times the probability of a more severe bleaching event on this reef without the influence of internal waves.…”

Section: Discussionmentioning

confidence: 99%

“…However, variation in the physiological responses of individual coral colonies and reefs to environmental stresses suggests critical differences in corals’ resilience and/or environmental conditions over small spatial and temporal scales (Riegl and Piller ; Pandolfi et al ; van Woesik et al ; van Woesik et al ). For example, water temperatures and thermal tolerance can vary substantially across an individual reef (e.g., Pineda et al ; Palumbi et al ; Safaie et al ) and some coral communities thrive in naturally acidified waters (Shamberger et al ; Barkley et al ). Thus, coral organisms with greater resilience and adaptive capacity may persist under future climate change (Pandolfi et al ; Spalding and Brown ).…”

mentioning

confidence: 99%

“…Identifying these resilient corals and prioritizing their protection may be the best strategy for long‐term conservation of coral ecosystems (Barshis et al ). Although the factors which confer resilience to coral bleaching are not fully understood, emerging evidence suggests that corals living in areas with naturally variable thermal environments may have higher temperature tolerance (McClanahan et al ; Safaie et al ). Thus, there are strong conservation incentives for investigating the drivers of high‐frequency (diurnal or shorter timescales) temperature variability on reefs, including air–sea heat fluxes (e.g., Davis et al ) and internal waves (e.g., Wolanski and Delesalle ; Leichter et al ; DeCarlo et al ).…”

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confidence: 99%

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Internal waves influence the thermal and nutrient environment on a shallow coral reef

Reid

DeCarlo

Cohen

et al. 2019

Limnology & Oceanography

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Internal waves can influence water properties in coastal ecosystems through the shoreward transport and mixing of subthermocline water into the nearshore region. In June 2014, a field experiment was conducted at Dongsha Atoll in the northern South China Sea to study the impact of internal waves on a coral reef. Instrumentation included a distributed temperature sensing system, which resolved spatially and temporally continuous temperature measurements over a 4‐km cross‐reef section from the lagoon to 50‐m depth on the fore reef. Our observations show that during summer, internal waves shoaling on the shallow atoll regularly transport cold, nutrient‐rich water shoreward, altering near‐surface water properties on the fore reef. This water is transported shoreward of the reef crest by tides, breaking surface waves and wind‐driven flow, where it significantly alters the water temperature and nutrient concentrations on the reef flat. We find that without internal wave forcing on the fore reef, temperatures on the reef flat could be up to 2.0°C ± 0.2°C warmer. Additionally, we estimate a change in degree heating weeks of 0.7°C‐weeks warmer without internal waves, which significantly increases the probability of a more severe bleaching event occurring at Dongsha Atoll. Furthermore, using nutrient samples collected on the fore reef during the study, we estimated that instantaneous onshore nitrate flux is about four‐fold higher with internal waves than without internal waves. This work highlights the importance of internal waves as a physical mechanism shaping the nearshore environment, and likely supporting resilience of the reef.

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High frequency temperature variability reduces the risk of coral bleaching

Cited by 265 publications

References 75 publications

The Dynamics of Coral-Algal Interactions in Space and Time on the Southern Great Barrier Reef

The Dynamics of Coral-Algal Interactions in Space and Time on the Southern Great Barrier Reef

Seabird nutrient subsidies alter patterns of algal abundance and fish biomass on coral reefs following a bleaching event

Internal waves influence the thermal and nutrient environment on a shallow coral reef

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