Climate Change Induced Thermal Stress Caused Recurrent Coral Bleaching over Gulf of Kachchh and Malvan Marine Sanctuary, West Coast of India

Coral reefs are one of the most sensitive, productive, and invaluable biological resources on the earth. However, coral reefs are facing unprecedented stress due to ongoing climate changes and intensified anthropogenic disturbances globally. Elevated Sea Surface Temperature (SST) has emerged as the most imminent threat to the thermos-sensitive reef-building corals. The 2010–2014-2016 El Niño Southern Oscillation (ENSO) caused prolonged marine heat waves (MHWs) that led to the most widespread coral bleaching and mortality in the tropical Indi-Pacific regions. Coral bleaching prediction is vital for the management of the reef biodiversity, ecosystem functioning, and services. Recent decades, satellite remote sensing has emerged as a convenient tool for large-scale coral reef monitoring programs. As thermal stress is a critical physical attribute for coral bleaching hence, the present study examines the effectiveness of the elevated SSTs as a proxy to predict coral bleaching in shallow water marginal reefs. Advanced Very High-Resolution Radiometer (AVHRR) satellite data from the NOAA Coral Reef Watch’s (CRW) platform has been used for this study. Coral bleaching indices like Bleaching Threshold (BT), Positive SST Anomaly (PA), and Degree Heating Weeks (DHW) are computed to analyze the thermal stress on the coral reefs. The computed thermal stress from satellite-derived SST data over regions concurrence with the mass coral bleaching (MCB) events. This study concludes that in the last decades (2010 to 2019) the coral cover around these regions has dramatically declined due to higher SST, which indicates that the thermal stress induced recurrent bleaching events attributed to the coral loss.

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A New Operational Seasonal Thermal Stress Prediction Tool for Coral Reefs Around Australia

Frontiers in Marine Science ◽

10.3389/fmars.2021.687833 ◽

2021 ◽

Vol 8 ◽

Author(s):

Claire M. Spillman ◽

Grant A. Smith

Keyword(s):

Thermal Stress ◽

Coral Reefs ◽

Great Barrier Reef ◽

Coral Bleaching ◽

Southern Oscillation ◽

Ensemble Prediction ◽

Barrier Reef ◽

Seasonal Forecasts ◽

Ensemble Prediction System ◽

Increased Risk

Seasonal forecasts of sea surface temperature (SST) have become increasingly important tools in recent years for reef managers to help inform and coordinate management responses to mass coral bleaching events. This manuscript presents new operational thermal stress forecast products for prediction of coral bleaching risk, based on the seasonal ensemble prediction system ACCESS-S1 (Australian Community Climate and Earth System Simulator–Seasonal Version 1). These accumulated thermal stress products form critical tools for reef management, providing advance warning of high thermal stress, and increased risk of coral bleaching in the coming season. Degree Heating Months (DHM) consider both the magnitude and duration of thermal stress, both of which are important in determining reef impacts. Both hindcast and operational realtime DHM forecasts are assessed for past bleaching events across Australia, and the impacts of different drivers and local forcings between regions compared. Generally, the model has the highest skill when forecasting events driven by large scale climate drivers such as the El Niño Southern Oscillation (ENSO) which impacts coral reefs on all sides of Australia. ACCESS-S1 hindcasts indicate higher skill on the west Australian coast than the Great Barrier Reef for summer months, except for the North West Shelf. Realtime forecasts of the 2020 Great Barrier Reef coral bleaching event, used operationally by reef managers throughout this event, are also presented. This work advances our understanding of the 2020 event, provides skill assessments for the new DHM products, and discusses the use of a stationary baseline in a changing climate. High DHM values can indicate an increased risk of marine heatwaves, which are likely to have increasing impacts on Australia’s reef systems in the future under a warming climate.

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Successive bleaching events (2019-2020) in Northeast Peninsular Malaysia revealed selective thermal acclimatization and susceptibility of hard corals at biophysical reef scale

10.1101/2021.11.16.468775 ◽

2021 ◽

Author(s):

Sebastian Szereday ◽

Affendi Yang Amri

Keyword(s):

Thermal Stress ◽

Coral Reefs ◽

Coral Bleaching ◽

Thermal Tolerance ◽

Greenhouse Gas Emission ◽

Southern Oscillation ◽

Thermal Sensitivity ◽

Peninsular Malaysia ◽

Thermal Acclimatization ◽

Significant Difference

Based on current greenhouse gas emission trajectories, Malaysian coral reefs are predicted to experience severe annual coral bleaching events by 2043, imminently threatening the survival of Malaysian coral reefs within this century. However, there is no field data on how Malaysian coral reefs respond to successive sequences of coral bleaching. Numerous scleractinian taxa have shown the ability to acclimatize to thermal stress events after previous exposure to heat disturbances. Nonetheless, thermal tolerance and acclimatization potentials might corroborate with accelerating warming rates and increasing frequencies of thermal stress anomalies, necessitating repeated field studies at reef scale to investigate thermal tolerance and acclimatization of scleractinian taxa. Here, we studied two successive thermal stress events during the 2019 El Niño Southern Oscillation (ENSO) and during the onset of the La Niña Oscillation in 2020. We recorded the bleaching susceptibility of scleractinian taxa to document bleaching trajectories across fine temporal and environmental gradients in Northeast Peninsular Malaysia. In addition, we analyzed historic temperature trends to demonstrate rapid warming rates (0.17° C per decade) and high return frequencies of thermal stress anomalies. Despite high maximum temperatures in both years (31.07° C and 31.74° C, respectively), accumulated thermal stress was relatively low during the bleaching episodes (Degree Heating Weeks 1.05° C-weeks and 0.61° C-weeks, respectively) and marginally varied across reef scales (0.94° C-weeks, 0.76° C-weeks, 0.48° C-weeks in 2020), suggesting a widespread thermal sensitivity of most scleractinian taxa (55.21% and 26.63% bleaching incidence in 2019 and 2020, respectively). However, significant discrepancies between satellite and in-situ temperature data were found (0.63° C; SD±0.26). Bleaching susceptibility was highly taxon-specific and contrasted historical bleaching patterns (e.g., Acropora and Montipora showed high thermal tolerance). In 2020, successive heat disturbance moderately increased bleaching susceptibility of three taxa (Galaxea, Leptastrea and Platygyra) despite lower heat stress, while Heliopora was highly susceptible in both years. Bleaching analysis of taxa on biophysical reef scales revealed significant difference across depth, wind sites (e.g., leeward and windward), and the combined interactions of wind and depth (e.g., leeward shallow) on bleaching response were significant for numerous taxa. Findings suggest thermal acclimatization of fast-growing taxa, whereby successive bleaching events and accelerating warming rates selectively pressure scleractinian assemblages.

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Coral cover surveys corroborate predictions on reef adaptive potential to thermal stress

10.1101/2020.06.05.136523 ◽

2020 ◽

Author(s):

Oliver Selmoni ◽

Gaël Lecellier ◽

Laurent Vigliola ◽

Véronique Berteaux-Lecellier ◽

Stéphane Joost

Keyword(s):

Heat Stress ◽

Thermal Stress ◽

Coral Reefs ◽

Spatial Patterns ◽

New Caledonia ◽

Heat Waves ◽

Coral Cover ◽

Thermal Adaptation ◽

Conservation Strategies ◽

Adaptive Potential

AbstractAs anomalous heat waves are causing the widespread decline of coral reefs worldwide, there is an urgent need to identify coral populations tolerant to thermal stress. Heat stress adaptive potential is the degree of tolerance expected from evolutionary processes and, for a given reef, depends on the arrival of propagules from reefs exposed to recurrent thermal stress. For this reason, assessing spatial patterns of thermal adaptation and reef connectivity is of paramount importance to inform conservation strategies.In this work, we applied a seascape genomics framework to characterize the spatial patterns of thermal adaptation and connectivity for coral reefs of New Caledonia (Southern Pacific). In this approach, remote sensing of seascape conditions was combined with genomic data from three coral species. For every reef of the region, we computed a probability of heat stress adaptation, and two indices forecasting inbound and outbound connectivity. We then compared our indicators to field survey data, and observed that decrease of coral cover after heat stress was lower at reefs predicted with high probability of adaptation and inbound connectivity. Last, we discussed how these indicators can be used to inform local conservation strategies and preserve the adaptive potential of New Caledonian reefs.

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MONITORING CORAL RECOVERY AT NEARSHORE CORAL REEFS IN PHANGNGA PROVINCE, THE ANDAMAN SEA FOLLOWING THE 2010 CORAL BLEACHING EVENT

Proceedings of International Conference "Managinag risks to coastal regions and communities in a changinag world" (EMECS'11 - SeaCoasts XXVI) ◽

10.31519/conferencearticle_5b1b936dde9b43.46989412 ◽

2017 ◽

Author(s):

Makamas Sutthacheep ◽

Thamasak Yeemin ◽

Sittiporn Pengsakun ◽

...

Keyword(s):

Coral Reef ◽

Coral Reefs ◽

Coral Bleaching ◽

Coral Cover ◽

Global Climate ◽

Andaman Sea ◽

Live Coral ◽

Bleaching Event ◽

Sea Star ◽

Coral Recovery

Mass bleaching and subsequent mortality of scleractinian corals in response to elevated seawater temperatures has been considered as one of the most impacts of global climate change. Three extensive coral bleaching events in the Andaman Sea were reported, in the years 1991, 1995 and 2010. Studies on survival of coral colonies, coral recruitment and community structure of coral reef associated macrofauna would predict the trends for coral recovery from the impacts of coral bleaching events. The present study aimed to examine the status of coral communities, density of coral recruits and coral reef associated macrofauna at nearshore coral reefs in Phangnga Province, the Andaman Sea following the 2010 coral bleaching event. The dead coral cover was high (>50%) while the live coral cover was in the range of 13-21%. There was high diversity of coral recruits on natural substrates. The average densities of macrobenthic fauna varied from 1.9 to 2.6 individuals.m-2, with significant differences among study sites. The dominant macrobenthic species were a soft coral (Lobophytum sp.), a sea star (Linckia laevigata) and a sea urchin (Echinostrephus molaris). Coral recovery at these coral reefs would be possible but local anthropogenic stressors must be overwhelmingly reduced in order to enhance coral reef resilience. The long-term monitoring programs in the Andaman Sea are required for decision makers to support their adaptive management approaches.

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Will community calcification reflect reef accretion on future, degraded coral reefs?

10.5194/bg-2021-61 ◽

2021 ◽

Author(s):

Coulson A. Lantz ◽

William Leggat ◽

Jessica L. Bergman ◽

Alexander Fordyce ◽

Charlotte Page ◽

...

Keyword(s):

Coral Reef ◽

Coral Reefs ◽

Coral Bleaching ◽

Elevated Temperatures ◽

Coral Cover ◽

Coral Tissue ◽

Bleaching Event ◽

Bleached Coral ◽

Coral Health ◽

Percent Area

Abstract. Coral bleaching events continue to drive the degradation of coral reefs worldwide, causing a shift in the benthic community from coral to algae dominated ecosystems. Critically, this shift may decrease the capacity of degraded coral reef communities to maintain net positive accretion during warming-driven stress events (e.g., reef-wide coral bleaching). Here we measured rates of net ecosystem calcification (NEC) and net ecosystem production (NEP) on a degraded coral reef lagoon community (coral cover 20 %) during a reef-wide bleaching event in February of 2020 at Heron Island on the Great Barrier Reef. We found that during this bleaching event, rates of community NEP and NEC across replicate transects remained positive and did not change in response to bleaching. Repeated benthic surveys over a period of 20 d indicated an increase in the percent area of bleached coral tissue, corroborated by relatively low Symbiodiniaceae densities (~0.6 × 106 cm−2) and dark-adapted photosynthetic yields in photosystem II of corals (~0.5) sampled along each transect over this period. Given that a clear decline in coral health was not reflected in the overall community NEC estimates, it is possible that elevated temperatures in the water column that compromise coral health enhanced the thermodynamic favourability for calcification in other, ahermatypic benthic calcifiers. These data suggest that positive NEC on degraded reefs may not equate to the net positive accretion of reef structure in a future, warmer ocean. Critically, our study highlights that if coral cover continues to decline as predicted, NEC may no longer be an appropriate proxy for reef growth as the proportion of the community NEC signal owed to ahermatypic calcification increases and coral dominance on the reef decreases.

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Coral cover surveys corroborate predictions on reef adaptive potential to thermal stress

Scientific Reports ◽

10.1038/s41598-020-76604-2 ◽

2020 ◽

Vol 10 (1) ◽

Author(s):

Oliver Selmoni ◽

Gaël Lecellier ◽

Laurent Vigliola ◽

Véronique Berteaux-Lecellier ◽

Stéphane Joost

Keyword(s):

Heat Stress ◽

Thermal Stress ◽

Coral Reefs ◽

Spatial Patterns ◽

New Caledonia ◽

Heat Waves ◽

Coral Cover ◽

Thermal Adaptation ◽

Conservation Strategies ◽

Adaptive Potential

AbstractAs anomalous heat waves are causing the widespread decline of coral reefs worldwide, there is an urgent need to identify coral populations tolerant to thermal stress. Heat stress adaptive potential is the degree of tolerance expected from evolutionary processes and, for a given reef, depends on the arrival of propagules from reefs exposed to recurrent thermal stress. For this reason, assessing spatial patterns of thermal adaptation and reef connectivity is of paramount importance to inform conservation strategies. In this work, we applied a seascape genomics framework to characterize the spatial patterns of thermal adaptation and connectivity for coral reefs of New Caledonia (Southern Pacific). In this approach, remote sensing of seascape conditions was combined with genomic data from three coral species. For every reef of the region, we computed a probability of heat stress adaptation, and two indices forecasting inbound and outbound connectivity. We then compared our indicators to field survey data, and observed that decrease of coral cover after heat stress was lower at reefs predicted with high probability of adaptation and inbound connectivity. Last, we discussed how these indicators can be used to inform local conservation strategies and preserve the adaptive potential of New Caledonian reefs.

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MONITORING CORAL RECOVERY AT NEARSHORE CORAL REEFS IN PHANGNGA PROVINCE, THE ANDAMAN SEA FOLLOWING THE 2010 CORAL BLEACHING EVENT

Proceedings of International Conference "Managinag risks to coastal regions and communities in a changinag world" (EMECS'11 - SeaCoasts XXVI) ◽

10.21610/conferencearticle_58b4315bb3db6 ◽

2017 ◽

Author(s):

Makamas Sutthacheep ◽

Thamasak Yeemin ◽

Sittiporn Pengsakun ◽

...

Keyword(s):

Coral Reef ◽

Coral Reefs ◽

Coral Bleaching ◽

Coral Cover ◽

Global Climate ◽

Andaman Sea ◽

Live Coral ◽

Bleaching Event ◽

Sea Star ◽

Coral Recovery

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Stokes drift through corals

Environmental Fluid Mechanics ◽

10.1007/s10652-021-09811-8 ◽

2021 ◽

Author(s):

Joseph J. Webber ◽

Herbert E. Huppert

Keyword(s):

Coral Reef ◽

Coral Reefs ◽

Porous Layer ◽

Large Scale ◽

Fluid Layer ◽

Ocean Waves ◽

Stokes Drift ◽

Inviscid Fluid ◽

Porous Bed ◽

Vertical Drift

AbstractMotivated by shallow ocean waves propagating over coral reefs, we investigate the drift velocities due to surface wave motion in an effectively inviscid fluid that overlies a saturated porous bed of finite depth. Previous work in this area either neglects the large-scale flow between layers (Phillips in Flow and reactions in permeable rocks, Cambridge University Press, Cambridge, 1991) or only considers the drift above the porous layer (Monismith in Ann Rev Fluid Mech 39:37–55, 2007). Overcoming these limitations, we propose a model where flow is described by a velocity potential above the porous layer and by Darcy’s law in the porous bed, with derived matching conditions at the interface between the two layers. Both a horizontal and a novel vertical drift effect arise from the damping of the porous bed, which requires the use of a complex wavenumber k. This is in contrast to the purely horizontal second-order drift first derived by Stokes (Trans Camb Philos Soc 8:441–455, 1847) when working with solely a pure fluid layer. Our work provides a physical model for coral reefs in shallow seas, where fluid drift both above and within the reef is vitally important for maintaining a healthy reef ecosystem (Koehl et al. In: Proceedings of the 8th International Coral Reef Symposium, vol 2, pp 1087–1092, 1997; Monismith in Ann Rev Fluid Mech 39:37–55, 2007). We compare our model with field measurements by Koehl and Hadfield (J Mar Syst 49:75–88, 2004) and also explain the vertical drift effects as documented by Koehl et al. (Mar Ecol Prog Ser 335:1–18, 2007), who measured the exchange between a coral reef layer and the (relatively shallow) sea above.

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Status of Coral Reefs in the Water of Spermonde, Makassar, South Sulawesi

E3S Web of Conferences ◽

10.1051/e3sconf/202132403007 ◽

2021 ◽

Vol 324 ◽

pp. 03007

Author(s):

Ni Wayan Purnama Sari ◽

Rikoh Manogar Siringoringo ◽

Muhammad Abrar ◽

Risandi Dwirama Putra ◽

Raden Sutiadi ◽

...

Keyword(s):

Coral Reef ◽

Coral Reefs ◽

Coral Cover ◽

Public Awareness ◽

Live Coral ◽

Health Index ◽

Point Count ◽

Live Coral Cover ◽

Reef Health ◽

Index Value

Observations of the condition of coral reefs have been carried out in Spermonde waters from 2015 to 2018. The method used in this observation uses Underwater Photo Transect (UPT), and the data obtained is analyzed using CPCe (Coral Point Count with Excel Extensions) software. The results show that the percentage of coral cover has increased from year to year. The percentage of live coral cover in 2015 was 19.64%, 23.60 in 2016, 23.72% in 2017, and 27.83% in 2018. The increase in live coral cover from year to year is thought to occur due to the availability of nutrients. or increasing public awareness, considering this location is one of the most famous tourist attractions in Makassar. Coral reef health index values can be used to classify coral reef health. Through the analysis of the coral reef health index, an index value of 4 was obtained, which means that the condition of the coral reefs is in the “moderate” category.

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Analysis Condition of Coral Reef Covering in Pramuka Island Waters, Seribu Islands using Line Intercept Transect (LIT) Method

Jurnal Riset Biologi dan Aplikasinya ◽

10.26740/jrba.v2n2.p77-81 ◽

2020 ◽

Vol 2 (2) ◽

pp. 77

Author(s):

Rega Permana ◽

Nora Akbarsyah ◽

Pringgo KDNY Putra ◽

Aulia Andhikawati

Keyword(s):

Coral Reef ◽

Coral Reefs ◽

Coral Cover ◽

Life Forms ◽

Anthropogenic Factors ◽

Coral Reef Ecosystem ◽

Marine Tourism ◽

Tourist Destinations ◽

Line Intercept ◽

Reef Ecosystem

The coral reef ecosystem is one of the typical tropical ecosystems with high biodiversity which has an important role both biologically, ecologically, physically as well as socially and economically. Several coral reef areas in Indonesia were reported to have suffered damage, not only due to climate change which has an impact on rising sea surface temperatures and ocean acidification but also due to anthropogenic factors and irresponsible management of marine tourism. This study aimed to analyze the condition of coral reefs based on covering in Pramuka Island, which is one of the famous tourist destinations in the Seribu Islands. The study was conducted using Line Intercept Transect (LIT) method at predetermined coordinate points. The results showed that the dominant coral reef life form was Acropora Submassive (ACS), namely 18.9%, and Acropora Branching (ACB) as much as 12.48%. Besides, the types of life forms found were coral foliase (9.42%), Miliepora Coral (9.2%), Coral Massive (4.8%), Acropora Encrustring (4.24%), and so on. Based on the results of this study, it can be concluded that the condition of coral reefs in Pramuka Island is still relatively good with a total coral cover percentage of 72.38%. Efforts to protect the coral reef ecosystem in this area need to be considered so that its condition can be maintained.

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