Exhibition of bleaching resistance via adaptive bleaching pattern by coral reefs of the Gulf of Mannar during massive bleaching event 2019

Coral reefs in the Gulf of Mannar (GoM) and Palk Bay regions are facing potential threats from climate change, sedimentation and anthropogenic activities. Considerably, coral reefs in these two regions are highly damaged due to frequent bleaching events caused by increased sea surface temperature (SST) recorded over the past two decades. Recently, during February to May 2019, mass bleaching event of corals was documented again in GoM and Palk Bay regions due to increased sea surface temperatures ranged between 32°C to 36°C. Despite of completely bleached corals, some coral colonies of the same bleached coral species have displayed adaptive bleaching pattern (ABP) for survival. This incidence is displayed by the symbiotic zooxanthellae to protect coral polyps from environmental stress such as elevated temperatures. These observations infer that coral colonies with preferential bleaching pattern ability would serve as environmental stress resisting coral colonies which can be used for restoration activities and cryopreservation. Further studies are needed to explain the potential mechanisms or specific environmental drivers responsible for ABP.

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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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Production of Novel Bioactive Compounds by the Bacteria Associated with Some Marine Sponges of Gulf of Mannar and Palk Bay, Southeast Coast of India

International Journal of Emerging Research in Management and Technology ◽

10.23956/ijermt.v6i8.136 ◽

2018 ◽

Vol 6 (8) ◽

pp. 183

Author(s):

V. Ramadas ◽

G. Chandralega

Keyword(s):

Bioactive Compounds ◽

Bacterial Species ◽

Marine Sponges ◽

Marine Organisms ◽

Gulf Of Mannar ◽

Bacterial Symbionts ◽

Palk Bay ◽

Excellent Source

Sponges, exclusively are aquatic and mostly marine, are found from the deepest oceans to the edge of the sea. There are approximately 15,000 species of sponges in the world, of which, 150 occur in freshwater, but only about 17 are of commercial value. A total of 486 species of sponges have been identified in India. In the Gulf of Mannar and Palk Bay a maximum of 319 species of sponges have been recorded. It has been proved that marine organisms are excellent source of bioactive secondary metabolites and number of compounds of originated from marine organisms had been reported to possess in-vitro and in-vivo immuno stimulatory activity. Extracts from 20 sponge species were tested for bacterial symbionts and bioactive compounds were isolated from such associated bacterial species in the present study.

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Nitrogen enrichment in macroalgae following mass coral mortality

Coral Reefs ◽

10.1007/s00338-021-02079-w ◽

2021 ◽

Author(s):

Eleanor J. Vaughan ◽

Shaun K. Wilson ◽

Samantha J. Howlett ◽

Valeriano Parravicini ◽

Gareth J. Williams ◽

...

Keyword(s):

Coral Reefs ◽

Coral Cover ◽

Strong Association ◽

French Polynesia ◽

Mass Mortality ◽

Transplant Experiment ◽

Bleaching Event ◽

Coral Mortality ◽

Absolute Increase ◽

Inorganic Matter

AbstractScleractinian corals are engineers on coral reefs that provide both structural complexity as habitat and sustenance for other reef-associated organisms via the release of organic and inorganic matter. However, coral reefs are facing multiple pressures from climate change and other stressors, which can result in mass coral bleaching and mortality events. Mass mortality of corals results in enhanced release of organic matter, which can cause significant alterations to reef biochemical and recycling processes. There is little known about how long these nutrients are retained within the system, for instance, within the tissues of other benthic organisms. We investigated changes in nitrogen isotopic signatures (δ15N) of macroalgal tissues (a) ~ 1 year after a bleaching event in the Seychelles and (b) ~ 3 months after the peak of a bleaching event in Mo’orea, French Polynesia. In the Seychelles, there was a strong association between absolute loss in both total coral cover and branching coral cover and absolute increase in macroalgal δ15N between 2014 and 2017 (adjusted r2 = 0.79, p = 0.004 and adjusted r2 = 0.86, p = 0.002, respectively). In Mo’orea, a short-term transplant experiment found a significant increase in δ15N in Sargassum mangarevense after specimens were deployed on a reef with high coral mortality for ~ 3 weeks (p < 0.05). We suggest that coral-derived nutrients can be retained within reef nutrient cycles, and that this can affect other reef-associated organisms over both short- and long-term periods, especially opportunistic species such as macroalgae. These species could therefore proliferate on reefs that have experienced mass mortality events, because they have been provided with both space and nutrient subsidies by the death and decay of corals.

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Multi-domain probiotic consortium as an alternative to chemical remediation of oil spills at coral reefs and adjacent sites

Microbiome ◽

10.1186/s40168-021-01041-w ◽

2021 ◽

Vol 9 (1) ◽

Author(s):

Denise P. Silva ◽

Helena D. M. Villela ◽

Henrique F. Santos ◽

Gustavo A. S. Duarte ◽

José Roberto Ribeiro ◽

...

Keyword(s):

Microbial Community ◽

Coral Reefs ◽

Environmental Changes ◽

Oil Spills ◽

Anthropogenic Activities ◽

Oil Contamination ◽

Negative Effects ◽

Corexit 9500 ◽

Coral Health ◽

The Impact

Abstract Background Beginning in the last century, coral reefs have suffered the consequences of anthropogenic activities, including oil contamination. Chemical remediation methods, such as dispersants, can cause substantial harm to corals and reduce their resilience to stressors. To evaluate the impacts of oil contamination and find potential alternative solutions to chemical dispersants, we conducted a mesocosm experiment with the fire coral Millepora alcicornis, which is sensitive to environmental changes. We exposed M. alcicornis to a realistic oil-spill scenario in which we applied an innovative multi-domain bioremediator consortium (bacteria, filamentous fungi, and yeast) and a chemical dispersant (Corexit® 9500, one of the most widely used dispersants), to assess the effects on host health and host-associated microbial communities. Results The selected multi-domain microbial consortium helped to mitigate the impacts of the oil, substantially degrading the polycyclic aromatic and n-alkane fractions and maintaining the physiological integrity of the corals. Exposure to Corexit 9500 negatively impacted the host physiology and altered the coral-associated microbial community. After exposure, the abundances of certain bacterial genera such as Rugeria and Roseovarius increased, as previously reported in stressed or diseased corals. We also identified several bioindicators of Corexit 9500 in the microbiome. The impact of Corexit 9500 on the coral health and microbial community was far greater than oil alone, killing corals after only 4 days of exposure in the flow-through system. In the treatments with Corexit 9500, the action of the bioremediator consortium could not be observed directly because of the extreme toxicity of the dispersant to M. alcicornis and its associated microbiome. Conclusions Our results emphasize the importance of investigating the host-associated microbiome in order to detect and mitigate the effects of oil contamination on corals and the potential role of microbial mitigation and bioindicators as conservation tools. Chemical dispersants were far more damaging to corals and their associated microbiome than oil, and should not be used close to coral reefs. This study can aid in decision-making to minimize the negative effects of oil and dispersants on coral reefs.

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Potential of increasing intensity of tropical cyclones due to sea surface temperature and impact on coral reefs in the context of climate change

Disaster Advances ◽

10.25303/149da0107 ◽

2021 ◽

Vol 14 (9) ◽

pp. 1-7

Author(s):

N.D. Hung ◽

L.T.H. Thuy ◽

T.V. Hang ◽

T.N. Luan

Keyword(s):

Climate Change ◽

Coral Reefs ◽

Surface Temperature ◽

Sea Surface Temperature ◽

Tropical Cyclones ◽

Coral Cover ◽

Central Zone ◽

Biosphere Reserve ◽

Sea Surface ◽

Strong Winds

The coral reef ecosystem in Cu Lao Cham, Vietnam is part of the central zone of the Cu Lao Cham -Hoi An, a biosphere reserve and it is strictly protected. However, the impacts of natural disasters - tropical cyclones (TCs) go beyond human protection. The characteristic feature of TCs is strong winds and the consequences of strong winds are high waves. High waves caused by strong TCs (i.e. level 13 or more) cause decline in coral cover in the seas around Cu Lao Cham. Based on the relationship between sea surface temperature (SST) and the maximum potential intensity (MPI) of TCs, this research determines the number of strong TCs in Cu Lao Cham in the future. Using results from a regional climate change model, the risk is that the number of strong TCs in the period 2021-2060 under the RCP4.5 scenario, will be 3.7 times greater than in the period 1980-2019 and under the RCP 8.5 scenario it will be 5.2 times greater than in the period 1980-2019. We conclude that increases in SST in the context of climate change risks will increase the number and intensity of TCs and so the risk of their mechanical impact on coral reefs will be higher leading to degradation of this internationally important site.

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Assessing the impact of exceptional inter-annual climatic variability on rates of net ecosystem carbon dioxide exchange at Clara bog.

10.5194/egusphere-egu21-13414 ◽

2021 ◽

Author(s):

Matthew Saunders ◽

Ruchita Ingle ◽

Shane Regan

Keyword(s):

Water Table ◽

Elevated Temperatures ◽

Ecosystem Respiration ◽

Anthropogenic Activities ◽

Climatic Variability ◽

Growing Season ◽

Carbon Dioxide Exchange ◽

Mean Annual Temperature ◽

Monitoring Networks ◽

The Impact

Peatland ecosystems are integral to the mitigation of climate change as they represent significant terrestrial carbon sinks. In Ireland, peatlands cover ~20% of the land area but hold up to 75% of the soil organic carbon stock however many of these ecosystems (~85% of the total area) have been degraded due to anthropogenic activities such as agriculture, forestry and extraction for horticulture or energy. Furthermore, the carbon stocks that remain in these systems are vulnerable to inter-annual variation in climate, such as changes in precipitation and temperature, which can alter the hydrological status of these systems leading to changes in key biogeochemical processes and carbon and greenhouse gas exchange.&#160; During 2018 exceptional drought and heatwave conditions were reported across Northwestern Europe, where reductions in precipitation coupled with elevated temperatures were observed. Exceptional inter-annual climatic variability was also observed at Clara bog, a near natural raised bog in the Irish midlands when data from 2018 and 2019 were compared. Precipitation in 2018 was ~300 mm lower than 2019 while the average mean annual temperature was 0.5&#176;C higher. The reduction in precipitation, particularly during the growing season in 2018, consistently lowered the water table where ~150 consecutive days where the water table was >5cm below the surface of the bog were observed at the central ecotope location. The differing hydrological conditions between years resulted in the study area, as determined by the flux footprint of the eddy covariance tower, acting as a net source of carbon of 53.5 g C m-2 in 2018 and a net sink of 125.2 g C m-2 in 2019. The differences in the carbon dynamics between years were primarily driven by enhanced ecosystem respiration (Reco) and lower rates of Gross Primary Productivity (GPP) in the drier year, where the maximum monthly ratio of GPP:Reco during the growing season was 0.96 g C m-2 month in 2018 and 1.14 g C m-2 month in 2019. This study highlights both the vulnerability and resilience of these ecosystems to exceptional inter-annual climatic variability and emphasises the need for long-term monitoring networks to enhance our understanding of the impacts of these events when they occur.

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Rapid coral mortality following unusually calm and hot conditions on Iriomote, Japan

F1000Research ◽

10.12688/f1000research.12660.2 ◽

2018 ◽

Vol 6 ◽

pp. 1728 ◽

Cited By ~ 2

Author(s):

Andrew H Baird ◽

Sally A. Keith ◽

Erika Woolsey ◽

Ryuta Yoshida ◽

Tohru Naruse

Keyword(s):

Water Movement ◽

Sea Surface ◽

Bleaching Event ◽

Coral Mortality ◽

Average Wind Speed ◽

Common Cause ◽

Wind Speeds ◽

Average Wind ◽

The Mean ◽

Low Wind Speeds

Coral bleaching can be induced by many different stressors, however, the most common cause of mass bleaching in the field is higher than average sea surface temperatures (SST). Here, we describe an unusual bleaching event that followed very calm sea conditions combined with higher than average SST. Patterns of mortality differed from typical bleaching in four ways: 1) mortality was very rapid; 2) a different suite of species were most affected; 3) tissue mortality in Acropora spp. was often restricted to the center of the colony; 4) the event occurred early in summer. The two weeks prior to the event included 8 days where the average wind speed was less than 3 ms-1. In addition, SSTs in the weeks preceding and during the event were 1.0-1.5°C higher than the mean for the last 30 years. We hypothesize that this unusual bleaching event was caused by anoxia resulting from a lack of water movement induced by low wind speeds combined with high SST.

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Blue carbon stock of the seagrass meadows of Gulf of Mannar and Palk Bay off Coromandel Coast, south India

Indian Journal of Fisheries ◽

10.21077/ijf.2020.67.4.98101-18 ◽

2020 ◽

Vol 67 (4) ◽

Author(s):

P. Kaladharan ◽

P.U. Zacharia ◽

S. Thirumalaiselvan ◽

A. Anasukoya ◽

Lavanya Ratheesh ◽

...

Keyword(s):

Carbon Stock ◽

South India ◽

Blue Carbon ◽

Gulf Of Mannar ◽

Organic Carbon Content ◽

Seagrass Meadows ◽

Soil Carbon Density ◽

Palk Bay ◽

Syringodium Isoetifolium ◽

Coromandel Coast

Blue carbon stock of the seagrass meadows of Gulf of Mannar and Palk Bay, off Coromandel Coast, south India, were computed from the organic carbon content and dry bulk densities of sediment core taken from the seagrass meadows of these two ecosystems. The Gulf of Mannar (GoM) and Palk Bay (PB) harbour 13 seagrass species dominated by Cymodocea serrulata and Syringodium isoetifolium. The soil carbon density of both GoM and PB were higher in subsurface cores. The blue carbon stock of seagrass meadows of the GoM was estimated as 0.001782 Tg and that of PB as 0.043996 Tg. The estimated value of blue carbon stored in seagrass meadows of GoM was 17820 US$ and that of PB was 43,99,682 US$. The results of this study are discussed in the light of climate change mitigation, emphasising the need to conserve these underwater meadows.

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Multi-model seascape genomics identifies distinct environmental drivers of selection among sympatric marine species

10.21203/rs.3.rs-35039/v3 ◽

2020 ◽

Author(s):

Erica Nielsen ◽

Romina Henriques ◽

Maria Beger ◽

Robert Toonen ◽

Sophie von der Heyden

Keyword(s):

Global Change ◽

Outlier Detection ◽

Genomic Variation ◽

Sea Surface ◽

Environmental Drivers ◽

Comparative Approach ◽

Evolutionary Potential ◽

Environmental Selection ◽

Outlier Loci ◽

Isolation By Environment

Abstract Background: As global change and anthropogenic pressures continue to increase, conservation and management increasingly needs to consider species’ potential to adapt to novel environmental conditions. Therefore, it is imperative to characterise the main selective forces acting on ecosystems, and how these may influence the evolutionary potential of populations and species. Using a multi-model seascape genomics approach, we compare putative environmental drivers of selection in three sympatric southern African marine invertebrates with contrasting ecology and life histories: Cape urchin (Parechinus angulosus), Common shore crab (Cyclograpsus punctatus), and Granular limpet (Scutellastra granularis). Results: Using pooled (Pool-seq), restriction-site associated DNA sequencing (RAD-seq), and seven outlier detection methods, we characterise genomic variation between populations along a strong biogeographical gradient. Of the three species, only S. granularis showed significant isolation-by-distance, and isolation-by-environment driven by sea surface temperatures (SST). In contrast, sea surface salinity (SSS) and range in air temperature correlated more strongly with genomic variation in C. punctatus and P. angulosus. Differences were also found in genomic structuring between the three species, with outlier loci contributing to two clusters in the East and West Coasts for S. granularis and P. angulosus, but not for C. punctatus. Conclusion: The findings illustrate distinct evolutionary potential across species, suggesting that species-specific habitat requirements and responses to environmental stresses may be better predictors of evolutionary patterns than the strong environmental gradients within the region. We also found large discrepancies between outlier detection methodologies, and thus offer a novel multi-model approach to identifying the principal environmental selection forces acting on species. Overall, this work highlights how adding a comparative approach to seascape genomics (both with multiple models and species) can elucidate the intricate evolutionary responses of ecosystems to global change.

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Multi-model seascape genomics identifies distinct environmental drivers of selection among sympatric marine species

10.21203/rs.3.rs-35039/v1 ◽

2020 ◽

Author(s):

Erica Nielsen ◽

Romina Henriques ◽

Maria Beger ◽

Robert Toonen ◽

Sophie von der Heyden

Keyword(s):

Global Change ◽

Outlier Detection ◽

Genomic Variation ◽

Sea Surface ◽

Environmental Drivers ◽

Comparative Approach ◽

Evolutionary Potential ◽

Environmental Selection ◽

Outlier Loci ◽

Isolation By Environment

Abstract Background: As global change and anthropogenic pressures continue to increase, conservation and management increasingly needs to consider species’ potential to adapt to novel environmental conditions. Therefore, it is imperative to characterise the main selective forces acting on ecosystems, and how these may influence the evolutionary potential of populations and species. Using a multi-model seascape genomics approach, we compare the dominant environmental drivers of selection in three sympatric southern African marine invertebrates with contrasting ecology and life histories: Cape urchin ( Parechinus angulosus ), Common shore crab ( Cyclograpsus punctatu s), and Granular limpet ( Scutellastra granularis ). Results: Using pooled (Pool-seq), restriction-site associated DNA sequencing (RAD-seq), and seven outlier detection methods, we characterise genomic variation between populations along a strong biogeographical gradient. Of the three species, only S. granularis showed significant isolation-by-distance, and isolation-by-environment driven by sea surface temperatures (SST). In contrast, sea surface salinity (SSS) and range in air temperature correlated more strongly with genomic variation in C. punctatus and P. angulosus . Differences were also found in genomic structuring between the three species, with outlier loci contributing to two clusters in the East and West Coasts for S. granularis and P. angulosus , but not for C. punctatus . Conclusion: The findings illustrate distinct evolutionary potential across species, suggesting that species-specific habitat requirements and responses to environmental stresses better predict evolutionary patterns than the strong environmental gradients within the region. We also found large discrepancies between outlier detection methodologies, and thus offer a novel multi-model approach to identifying the principal environmental selection forces acting on species. Overall, this work highlights how adding a comparative approach to seascape genomics (both with multiple models and species) can elucidate the intricate evolutionary responses of ecosystems to global change.

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