Causes and consequences of the 2017 coral bleaching event in the southern Persian/Arabian Gulf

Burt, John A.; Paparella, Francesco; Al-Mansoori, Noura; Al-Mansoori, Amna; Al-Jailani, Hamad

doi:10.1007/s00338-019-01767-y

Cited by 92 publications

(68 citation statements)

References 90 publications

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“…In the Arabian region, coral reefs are incredibly biologically valuable as they are the most biodiverse ecosystem in the arid nations that occupy this area, and they also represent an important economic resource for coastal populations by serving as foraging and nursery grounds for a wide variety of commercially important fish species (Van Lavieren et al, 2011;Burt, 2014;Vaughan et al, 2019). Despite the well-recognized thermal tolerance of corals in the Persian/Arabian Gulf, each summer these corals live near their upper thermal limits and they can be pushed across temperature thresholds that can induce widespread coral bleaching that in extreme conditions can lead to mass mortality (Riegl et al, 2011;Burt et al, 2019). The results of our observations and simulations show that summer shamal winds are the primary determinant of whether or not Gulf reefs cross these important threshold temperatures.…”

Section: Discussionmentioning

confidence: 99%

“…This was followed by another strong bleaching event in 2012 in which >40% of corals showed signs of bleaching, although only limited mortality occurred (<15% loss of coral cover) (Riegl and Purkis, 2015;Shuail et al, 2016). These recurrent events were followed by a period of recovery in the summers of 2013 through 2016 when bleaching levels were negligible, but were followed by one of the most severe bleaching events on record in the summer of 2017, when virtually all coral across the entire southern Gulf fully bleached, and coral mortality exceeded 85% by the end of summer (Riegl et al, 2018;Burt et al, 2019).…”

Section: Summer Winds and Coral Bleachingmentioning

confidence: 99%

“…Mean SSTs in the Gulf have been increasing over the past three decades as a result of climate change (Riegl et al, 2011), and as a result there has been an increase in the frequency and magnitude of mass bleaching events where corals have been being pushed beyond their thermal limits (Riegl et al, 2018). Severe bleaching leading to widespread mass coral die-off 's (>80% loss) was first reported in the late 1970s, then again in 1996, 1998, and 2017, with slight to moderate bleaching events that resulted in more limited coral mortality (0∼20% loss) also occurring in 2002, 2010, 2011, and 2012 (Sheppard and Loughland, 2002;Riegl and Purkis, 2015;Shuail et al, 2016;Riegl et al, 2018;Burt et al, 2019). Recent work has shown that it is not the maximum temperature so much as the length of exposure that affects the severity of bleaching and whether or not mass mortality occurs.…”

Section: Introductionmentioning

confidence: 99%

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Coral Bleaching in the Persian/Arabian Gulf Is Modulated by Summer Winds

Paparella

Vaughan

et al. 2019

Front. Mar. Sci.

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Corals in the Persian/Arabian Gulf are the most thermally tolerant in the world, but live very near the thresholds of their thermal tolerance. Warming sea temperatures associated with climate change have resulted in numerous coral bleaching events regionally since the mid-1990s, but it has been unclear why unusually warm sea temperatures occur some years but not others. Using a combination of 5 years of observed sea-bottom temperatures at three reef sites and a meteorologically linked hydrodynamic model that extends through the past decade, we show that summer sea-bottom temperatures are tightly linked to regional wind regimes, and that strong 'shamal' wind events control the occurrence and severity of bleaching. Sea bottom temperatures were primarily controlled by latent heat flux from wind-driven surface evaporation which exceeded 300 W m −2 during shamal winds, double that of typical breeze conditions. Daily temperature change was highly correlated with wind speed, with breeze winds (<4 m s −1) resulting in increased warming, while faster winds caused cooling, with the magnitude of temperature decline increasing with wind speed. Using observed and simulated data from 2012 to 2017, we show that years with reported bleaching events (2012, 2017) were characterized by low winds speeds that resulted in temperatures persisting above coral bleaching threshold temperatures for >5 weeks, while the cooler intervening years (2013-2016) had summers with more frequent and/or strong shamal events which repeatedly cooled temperatures below bleaching thresholds for days to weeks, providing corals temporary respite from thermal stress. Using observed data from 2012 onward and simulated data from 2008 to 2011, we show that the severity of bleaching events over the past decade was linked to both the number of cumulative days above bleaching thresholds (rather than total days, which obfuscates the cooling effects of occasional brief shamal events), as well as to maxima. We show that winds of 4 m s −1 represents a critical threshold for whether or not corals cross bleaching threshold temperatures, and provide simulations to forecast sea-bottom temperature change and recovery times under a range of wind conditions. The role that wind-driven cooling may play on coral reefs globally is discussed.

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Section: Discussionmentioning

confidence: 99%

Section: Summer Winds and Coral Bleachingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Coral Bleaching in the Persian/Arabian Gulf Is Modulated by Summer Winds

Paparella

Vaughan

et al. 2019

Front. Mar. Sci.

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“…In laboratory experiments, Sheridan et al (2014) found that acute exposure to sterile sediments induced a significant immune response in the reef coral, M. patula, and resulted in a reduction in storage lipids. In addition to chronic challenges, coral reefs within the southern Persian Gulf also experienced major bleaching events in 1996in , 1998in , 2002in (Riegl 1999in , 2002Riegl et al 2011;Burt et al 2019). Bleaching events results in direct mortality and short-and long-term negative effects on growth and reproduction (Baird and Marshall 2002;Mendes and Woodley 2002;Howells et al 2016b) and higher susceptibility to tissue loss diseases (Miller et al 2009;Mydlarz et al 2009;Heron et al 2010;Muller et al 2018).…”

Section: Persian Gulf Corals Are Particularly Vulnerable To Coral Dismentioning

confidence: 99%

Localized outbreaks of coral disease on Arabian reefs are linked to extreme temperatures and environmental stressors

et al. 2020

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The Arabian Peninsula borders the hottest reefs in the world, and corals living in these extreme environments can provide insight into the effects of warming on coral health and disease. Here, we examined coral reef health at 17 sites across three regions along the northeastern Arabian Peninsula (Persian Gulf, Strait of Hormuz and Oman Sea) representing a gradient of environmental conditions. The Persian Gulf has extreme seasonal fluctuations in temperature and chronic hypersalinity, whereas the other two regions experience more moderate conditions. Field surveys identified 13 coral diseases including tissue loss diseases of unknown etiology (white syndromes) in Porites, Platygyra, Dipsastraea, Cyphastrea, Acropora and Goniopora; growth anomalies in Porites, Platygyra and Dipsastraea; black band disease in Platygyra, Dipsastraea, Acropora, Echinopora and Pavona; bleached patches in Porites and Goniopora and a disease unique to this region, yellow-banded tissue loss in Porites. The most widespread diseases were Platygyra growth anomalies (52.9% of all surveys), Acropora white syndrome (47.1%) and Porites bleached patches (35.3%). We found a number of diseases not yet reported in this region and found differential disease susceptibility among coral taxa. Disease prevalence was higher on reefs within the Persian Gulf (avg. 2.05%) as compared to reefs within the Strait of Hormuz (0.46%) or Oman Sea (0.25%). A high number of localized disease outbreaks (8 of 17 sites) were found, especially within the Persian Gulf (5 of 8 sites). Across all regions, the majority of variation in disease prevalence (82.2%) was associated with the extreme temperature range experienced by these corals combined with measures of organic pollution and proximity to shore. Thermal stress is known to drive a number of coral diseases, and thus, this region provides a platform to study disease at the edge of corals' thermal range.

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“…These global bleaching events are becoming more frequent (1998, 2010 and 2014-17) and severe [14,16,[18][19][20][21][22], leaving coral reefs vulnerable and unable to recover. The 2014-2017 mass bleaching event, which lasted 36 months and spanned four calendar years, was the longest-lasting, most widespread, and probably most damaging event on record [21][22][23][24][25][26][27][28][29], and stands out as unique by spanning all phases of the El Niño-Southern Oscillation cycle of 2017, being the warmest non-El Niño year ever recorded [21,30].…”

Section: Introductionmentioning

confidence: 99%

Thermal Stress and Resilience of Corals in a Climate-Changing World

Carballo-Bolaños

Soto

Chen

2019

JMSE

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Coral reef ecosystems are under the direct threat of increasing atmospheric greenhouse gases, which increase seawater temperatures in the oceans and lead to bleaching events. Global bleaching events are becoming more frequent and stronger, and understanding how corals can tolerate and survive high-temperature stress should be accorded paramount priority. Here, we review evidence of the different mechanisms that corals employ to mitigate thermal stress, which include association with thermally tolerant endosymbionts, acclimatisation, and adaptation processes. These differences highlight the physiological diversity and complexity of symbiotic organisms, such as scleractinian corals, where each species (coral host and microbial endosymbionts) responds differently to thermal stress. We conclude by offering some insights into the future of coral reefs and examining the strategies scientists are leveraging to ensure the survival of this valuable ecosystem. Without a reduction in greenhouse gas emissions and a divergence from our societal dependence on fossil fuels, natural mechanisms possessed by corals might be insufficient towards ensuring the ecological functioning of coral reef ecosystems.

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Causes and consequences of the 2017 coral bleaching event in the southern Persian/Arabian Gulf

Cited by 92 publications

References 90 publications

Coral Bleaching in the Persian/Arabian Gulf Is Modulated by Summer Winds

Coral Bleaching in the Persian/Arabian Gulf Is Modulated by Summer Winds

Localized outbreaks of coral disease on Arabian reefs are linked to extreme temperatures and environmental stressors

Thermal Stress and Resilience of Corals in a Climate-Changing World

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