scholarly journals Peroxynitrite Generation and Increased Heterotrophic Capacity Are Linked to the Disruption of the Coral–Dinoflagellate Symbiosis in a Scleractinian and Hydrocoral Species

2019 ◽  
Vol 7 (10) ◽  
pp. 426 ◽  
Author(s):  
Laura Fernandes de Barros Marangoni ◽  
Miguel Mies ◽  
Arthur Z. Güth ◽  
Thomás N. S. Banha ◽  
Alex Inague ◽  
...  
Keyword(s):  
Coral Bleaching ◽  
Elevated Temperatures ◽  
Time Lag ◽  
Scleractinian Corals ◽  
Warning Signs ◽  
Coral Tissue ◽  
Heterotrophic Activity ◽  
Trophic Plasticity ◽  
Coral Reef Ecosystems ◽  
Species Specific

Ocean warming is one of the greatest global threats to coral reef ecosystems; it leads to the disruption of the coral–dinoflagellate symbiosis (bleaching) and to nutrient starvation, because corals mostly rely on autotrophy (i.e., the supply of photosynthates from the dinoflagellate symbionts) for their energy requirements. Although coral bleaching has been well studied, the early warning signs of bleaching, as well as the capacity of corals to shift from autotrophy to heterotrophy, are still under investigation. In this study, we evaluated the bleaching occurrence of the scleractinian coral Mussismillia harttii and the hydrocoral Millepora alcicornis during a natural thermal stress event, under the 2015–2016 El Niño influence in three reef sites of the South Atlantic. We focused on the link between peroxynitrite (ONOO−) generation and coral bleaching, as ONOO− has been very poorly investigated in corals and never during a natural bleaching event. We also investigated the natural trophic plasticity of the two corals through the use of new lipid biomarkers. The results obtained first demonstrate that ONOO− is linked to the onset and intensity of bleaching in both scleractinian corals and hydrocorals. Indeed, ONOO− concentrations were correlated with bleaching intensity, with the highest levels preceding the highest bleaching intensity. The time lag between bleaching and ONOO− peak was, however, species-specific. In addition, we observed that elevated temperatures forced heterotrophy in scleractinian corals, as Mu. harttii presented high heterotrophic activity 15 to 30 days prior bleaching occurrence. On the contrary, a lower heterotrophic activity was monitored for the hydrocoral Mi. alicornis, which also experienced higher bleaching levels compared to Mu. hartii. Overall, we showed that the levels of ONOO− in coral tissue, combined to the heterotrophic capacity, are two good proxies explaining the intensity of coral bleaching.

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

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.

Predicting cold-water bleaching in corals: role of temperature, and potential integration of light exposure

2020 ◽  
Vol 642 ◽  
pp. 133-146
Author(s):  
PC González-Espinosa ◽  
SD Donner
Keyword(s):  
Coral Bleaching ◽  
Cold Water ◽  
Light Exposure ◽  
Light Attenuation ◽  
Florida Keys ◽  
Cold Temperature ◽  
Warm Water ◽  
Coral Tissue ◽  
Effect Of Temperature ◽  
Type I

Warm-water growth and survival of corals are constrained by a set of environmental conditions such as temperature, light, nutrient levels and salinity. Water temperatures of 1 to 2°C above the usual summer maximum can trigger a phenomenon known as coral bleaching, whereby disruption of the symbiosis between coral and dinoflagellate micro-algae, living within the coral tissue, reveals the white skeleton of coral. Anomalously cold water can also lead to coral bleaching but has been the subject of limited research. Although cold-water bleaching events are less common, they can produce similar impacts on coral reefs as warm-water events. In this study, we explored the effect of temperature and light on the likelihood of cold-water coral bleaching from 1998-2017 using available bleaching observations from the Eastern Tropical Pacific and the Florida Keys. Using satellite-derived sea surface temperature, photosynthetically available radiation and light attenuation data, cold temperature and light exposure metrics were developed and then tested against the bleaching observations using logistic regression. The results show that cold-water bleaching can be best predicted with an accumulated cold-temperature metric, i.e. ‘degree cooling weeks’, analogous to the heat stress metric ‘degree heating weeks’, with high accuracy (90%) and fewer Type I and Type II errors in comparison with other models. Although light, when also considered, improved prediction accuracy, we found that the most reliable framework for cold-water bleaching prediction may be based solely on cold-temperature exposure.

scholarly journals Community assessment of crustose calcifying red algae as coral recruitment substrates

2021 ◽  
Author(s):  
Mari E. Deinhart ◽  
Matthew S. Mills ◽  
Tom Schils
Keyword(s):  
Dna Sequences ◽  
Red Algae ◽  
Taxonomic Diversity ◽  
Coralline Algae ◽  
Crustose Coralline Algae ◽  
Coral Recruitment ◽  
Successful Recruitment ◽  
Ecological Roles ◽  
Coral Reef Ecosystems ◽  
Species Specific

AbstractSuccessful recruitment of invertebrate larvae to reef substrates is essential to the health of tropical coral reef ecosystems and their capacity to recover from disturbances. Crustose calcifying red algae (CCRA) have been identified as important recruitment substrates for scleractinian corals. As such, CCRA as a whole or subgroups (e.g., crustose coralline algae, CCA) are often used at the functional group level in experimental, ecological, and monitoring studies. Species of CCRA, however, differ in their ecological roles and their value as coral recruitment substrates. Here, we (1) investigate the species richness and community composition of CCRA on experimental coral recruitment tiles, and (2) assess if there is a recruitment preference of the coral Acropora surculosa for any of these CCRA species. 27 species of two orders of CCRA (Corallinales and Peyssonneliales) were identified from the recruit tiles. None of the DNA sequences of these species matched released sequences in GenBank or sequences of CCRA collected from natural reef systems in Guam. The similarity in CCRA communities between the recruitment tiles was high. Two species of CCRA were significantly preferred as recruitment substrates over the other CCRA species. Both of these species belonged to the subfamily of the Lithophylloideae. These two species are closely related to Pacific species that have been referred to as Titanoderma -but probably have to be assigned to another genus- and many of the latter have been attributed to be preferred coral recruitment substrates. Of all CCRA, Lithophylloideae sp. 1 had the highest benthic cover on the recruitment tiles and was the most preferred recruitment substrate. These findings highlight the high taxonomic diversity of CCRA communities and provide insight into species-specific ecological roles of CCRA that are often overlooked.

scholarly journals A hypothesis linking sub-optimal seawater <I>p</I>CO<sub>2</sub> conditions for cnidarian-<I>Symbiodinium</I> symbioses with the exceedence of the interglacial threshold (>260 ppmv)

2012 ◽  
Vol 9 (5) ◽  
pp. 1709-1723 ◽  
Author(s):  
S. A. Wooldridge
Keyword(s):  
Coral Reef ◽  
Elevated Temperatures ◽  
Evidence Base ◽  
Coral Reef Ecosystem ◽  
Coral Reef Ecosystems ◽  
Extinction Events ◽  
Response To Temperature ◽  
Host Metabolism ◽  
New Hypothesis ◽  
Seawater Pco2

Abstract. Most scleractinian corals and many other cnidarians host intracellular photosynthetic dinoflagellate symbionts ("zooxanthellae"). The zooxanthellae contribute to host metabolism and skeletogenesis to such an extent that this symbiosis is well recognised for its contribution in creating the coral reef ecosystem. The stable functioning of cnidarian symbioses is however dependent upon the host's ability to maintain demographic control of its algal partner. In this review, I explain how the modern envelope of seawater conditions found within many coral reef ecosystems (characterised by elevated temperatures, rising pCO2, and enriched nutrient levels) are antagonistic toward the dominant host processes that restrict excessive symbiont proliferation. Moreover, I outline a new hypothesis and initial evidence base, which support the suggestion that the additional "excess" zooxanthellae fraction permitted by seawater pCO2 levels beyond 260 ppmv significantly increases the propensity for symbiosis breakdown ("bleaching") in response to temperature and irradiance extremes. The relevance of this biological threshold is discussed in terms of historical reef extinction events, glacial-interglacial climate cycles and the modern decline of coral reef ecosystems.

Calcified macroalgae - critical to coastal ecosystems and vulnerable to change: a review

2009 ◽  
Vol 60 (8) ◽  
pp. 787 ◽  
Author(s):  
W. A. Nelson
Keyword(s):  
Anthropogenic Activities ◽  
Three Dimensional ◽  
Euphotic Zone ◽  
Coastal Development ◽  
Functional Ecology ◽  
Present Measurement ◽  
Marine Habitats ◽  
Run Off ◽  
Coral Reef Ecosystems ◽  
Species Specific

Calcified macroalgae are distributed in marine habitats from polar to tropical latitudes and from intertidal shores to the deepest reaches of the euphotic zone. These algae play critical ecological roles including being key to a range of invertebrate recruitment processes, functioning as autogenic ecosystem engineers through provision of three-dimensional habitat structure, as well as contributing critical structural strength in coral reef ecosystems. Calcified macroalgae contribute significantly to the deposition of carbonates in coastal environments. These organisms are vulnerable to human-induced changes resulting from land and coastal development, such as altered patterns of sedimentation, nutrient enrichment through sewage and agricultural run-off, and are affected by coastal dredging and aquaculture. The consequences of increasing sea surface temperatures and fundamental changes in the carbon chemistry of seawater due to CO2 emissions from anthropogenic activities will have serious impacts on calcifying macroalgae. It is not yet understood how interactions between a range of variables acting at local and global scales will influence the viability of calcifying macroalgae and associated ecosystems. Research is urgently needed on all aspects of the taxonomy, biology and functional ecology of calcifying macroalgae. Without an understanding of the species present, measurement of change and understanding species-specific responses will not be possible.

scholarly journals Where does it go? The fate of thiocyanate in the aquarium water and blood plasma of Amphiprion clarkii after exposure to cyanide

2020 ◽  
Author(s):  
J. Alexander Bonanno ◽  
Nancy E. Breen ◽  
Michael F. Tlusty ◽  
Lawrence J. Andrade ◽  
Andrew L. Rhyne
Keyword(s):  
Blood Plasma ◽  
Plasma Levels ◽  
Half Life ◽  
Compartment Model ◽  
Direct Exposure ◽  
Coral Reef Ecosystems ◽  
Aquarium Water ◽  
Acquity Uplc ◽  
Species Specific ◽  
Amphiprion Clarkii

ABSTRACTThe illegal practice of cyanide fishing continues to damage coral reef ecosystems throughout the Indo-Pacific. To combat this destructive fishing method, a simple, reliable test to detect whether or not a fish has been captured using cyanide (CN) is needed. This study analyzed the toxicokinetics of acute, pulsed CN exposure as well as chronic exposure to thiocyanate (SCN), the major metabolite of CN, in the clownfish species, Amphiprion clarkii. Fish were pulse exposed to 50 ppm CN for 20 or 45 seconds or chronically exposed to 100 ppm SCN for 12 days. Blood plasma levels of SCN were measured following derivatization to SCN-bimane using an Acquity UPLC I-Class and Q-Exactive hybrid Quadrupole-Orbitrap HRAM mass spectrometer or directly by HPLC-UV. After exposure to CN, depending on the duration of exposure, SCN plasma levels reached a maximum concentration (300–470 ppb) 0.13–0.17 days after exposure, had a 0.1 to 1.2 day half-life, and often did not return to baseline levels. The half-life of plasma SCN after direct exposure to SCN was found to be 0.13 days, similar to the CN exposure, and that SCN in the holding water would often drop below detection. Finally, we observed that when a fish, never exposed to SCN, was placed in aquarium water spiked with SCN, there was a steady decrease in aqueous SCN concentration over 24 hours until it could no longer be detected. This pattern was repeated with a second sequential dose. These results demonstrate that A. clarkii do not excrete SCN after CN exposure, but in fact can absorb low concentrations of SCN from water, refuting several publications. It appears that A. clarkii exhibit a classic two compartment model where SCN is rapidly eliminated from the blood plasma and is distributed throughout the tissue but not excreted in their urine. This study demonstrates that SCN may be used as a marker of CN exposure only if fish are tested shortly after exposure. There is species specific variability in response to CN, and studies of other taxa need to be performed before this test can be deployed in the field.

scholarly journals An algal symbiont (Breviolum psygmophilum) responds more strongly to chronic high temperatures than its facultatively symbiotic coral host (Astrangia poculata)

2021 ◽  
Author(s):  
Andrea N. Chan ◽  
Luis A. González-Guerrero ◽  
Roberto Iglesias-Prieto ◽  
Elizabeth M. Burmester ◽  
Randi D. Rotjan ◽  
...  
Keyword(s):  
Heat Stress ◽  
Thermal Stress ◽  
Stress Response ◽  
Coral Bleaching ◽  
Scleractinian Corals ◽  
Coral Host ◽  
Algal Symbionts ◽  
Algal Symbiont ◽  
Astrangia Poculata ◽  
And Control

AbstractScleractinian corals form the foundation of coral reefs by secreting skeletons of calcium carbonate. Their intracellular algal symbionts (Symbiodiniaceae) translocate a large proportion of photosynthate to the coral host, which is required to maintain high rates of calcification. Global warming is causing dissociation of coral host and algal symbiont, visibly presented as coral bleaching. Despite decades of study, the precise mechanisms of coral bleaching remain unknown. Separating the thermal stress response of the coral from the algal symbiont is key to understanding bleaching in tropical corals. The facultatively symbiotic northern star coral, Astrangia poculata, naturally occurs as both symbiotic and aposymbiotic (lacking algal symbionts) polyps – sometimes on the same coral colony. Thus, it is possible to separate the heat stress response of the coral host alone from the coral in symbiosis with its symbiont Breviolum psygmophilum. Using replicate symbiotic and aposymbiotic ramets of A. poculata, we conducted a chronic heat stress experiment to increase our understanding of the cellular mechanisms resulting in coral bleaching. Sustained high temperature stress resulted in photosynthetic dysfunction in B. psygmophilum, including a decline in maximum photosynthesis rate, maximum photochemical efficiency, and the absorbance peak of chlorophyll a. Interestingly, the metabolic rates of symbiotic and aposymbiotic corals were differentially impacted. RNAseq analysis revealed more differentially expressed genes between heat-stressed and control aposymbiotic colonies than heat-stressed and control symbiotic colonies. Notably, aposymbiotic colonies increased the expression of inflammation-associated genes such as nitric oxide synthases. Unexpectedly, the largest transcriptional response was observed between heat-stressed and control B. psygmophilum, including genes involved in photosynthesis, response to oxidative stress, and meiosis. Thus, it appears that the algal symbiont suppresses the immune response of the host, potentially increasing the vulnerability of the host to pathogens. The A. poculata-B. psygmophilum symbiosis provides a tractable model system for investigating thermal stress and immune challenge in scleractinian corals.

scholarly journals Detecting 2020 Coral Bleaching Event in the Northwest Hainan Island Using CoralTemp SST and Sentinel-2B MSI Imagery

2021 ◽  
Vol 13 (23) ◽  
pp. 4948
Author(s):  
Bailu Liu ◽  
Lei Guan ◽  
Hong Chen
Keyword(s):  
Coral Bleaching ◽  
Large Scale ◽  
Global Climate ◽  
Hainan Island ◽  
Threshold Value ◽  
Bleaching Event ◽  
Wide Range ◽  
Coral Reef Ecosystems ◽  
The Difference ◽  
Difference Images

In recent years, coral reef ecosystems have been affected by global climate change and human factors, resulting in frequent coral bleaching events. A severe coral bleaching event occurred in the northwest of Hainan Island, South China Sea, in 2020. In this study, we used the CoralTemp sea surface temperature (SST) and Sentinel-2B imagery to detect the coral bleaching event. From 31 May to 3 October, the average SST of the study area was 31.01 °C, which is higher than the local bleaching warning threshold value of 30.33 °C. In the difference images of 26 July and 4 September, a wide range of coral bleaching was found. According to the temporal variation in single band reflectance, the development process of bleaching is consistent with the changes in coral bleaching thermal alerts. The results show that the thermal stress level is an effective parameter for early warning of large-scale coral bleaching. High-resolution difference images can be used to detect the extent of coral bleaching. The combination of the two methods can provide better support for coral protection and research.

scholarly journals Warm seawater temperature promotes substrate colonization by the blue coral, Heliopora coerulea

PeerJ ◽  
2019 ◽  
Vol 7 ◽  
pp. e7785 ◽  
Author(s):  
Christine Guzman ◽  
Michael Atrigenio ◽  
Chuya Shinzato ◽  
Porfirio Aliño ◽  
Cecilia Conaco
Keyword(s):  
Gene Expression ◽  
Growth Rate ◽  
Extracellular Matrix ◽  
Expression Profiles ◽  
Seawater Temperature ◽  
Scleractinian Corals ◽  
Tissue Growth ◽  
Cellular Migration ◽  
Coral Tissue ◽  
Growth Margin

Background Heliopora coerulea, the blue coral, is a reef building octocoral that is reported to have a higher optimum temperature for growth compared to most scleractinian corals. This octocoral has been observed to grow over both live and dead scleractinians and to dominate certain reefs in the Indo-Pacific region. The molecular mechanisms underlying the ability of H. coerulea to tolerate warmer seawater temperatures and to effectively compete for space on the substrate remain to be elucidated. Methods In this study, we subjected H. coerulea colonies to various temperatures for up to 3 weeks. The growth and photosynthetic efficiency rates of the coral colonies were measured. We then conducted pairwise comparisons of gene expression among the different coral tissue regions to identify genes and pathways that are expressed under different temperature conditions. Results A horizontal growth rate of 1.13 ± 0.25 mm per week was observed for corals subjected to 28 or 31 °C. This growth rate was significantly higher compared to corals exposed at 26 °C. This new growth was characterized by the extension of whitish tissue at the edges of the colony and was enriched for a matrix metallopeptidase, a calcium and integrin binding protein, and other transcripts with unknown function. Tissues at the growth margin and the adjacent calcified encrusting region were enriched for transcripts related to proline and riboflavin metabolism, nitrogen utilization, and organic cation transport. The calcified digitate regions, on the other hand, were enriched for transcripts encoding proteins involved in cell-matrix adhesion, translation, receptor-mediated endocytosis, photosynthesis, and ion transport. Functions related to lipid biosynthesis, extracellular matrix formation, cell migration, and oxidation-reduction processes were enriched at the growth margin in corals subjected for 3 weeks to 28 or 31 °C relative to corals at 26 °C. In the digitate region of the coral, transcripts encoding proteins that protect against oxidative stress, modify cell membrane composition, and mediate intercellular signaling pathways were enriched after just 24 h of exposure to 31 °C compared to corals at 28 °C. The overall downregulation of gene expression observed after 3 weeks of sustained exposure to 31 °C is likely compensated by symbiont metabolism. Discussion These findings reveal that the different regions of H. coerulea have variable gene expression profiles and responses to temperature variation. Under warmer conditions, the blue coral invests cellular resources toward extracellular matrix formation and cellular migration at the colony margins, which may promote rapid tissue growth and extension. This mechanism enables the coral to colonize adjacent reef substrates and successfully overgrow slower growing scleractinian corals that may already be more vulnerable to warming ocean waters.

scholarly journals Heat-evolved microalgal symbionts increase coral bleaching tolerance

2020 ◽  
Vol 6 (20) ◽  
pp. eaba2498 ◽  
Author(s):  
P. Buerger ◽  
C. Alvarez-Roa ◽  
C. W. Coppin ◽  
S. L. Pearce ◽  
L. J. Chakravarti ◽  
...  
Keyword(s):  
Coral Bleaching ◽  
Thermal Tolerance ◽  
Carbon Fixation ◽  
Elevated Temperatures ◽  
Heat Waves ◽  
Constitutive Expression ◽  
Coral Host ◽  
Laboratory Evolution ◽  
Climate Resilience

Coral reefs worldwide are suffering mass mortalities from marine heat waves. With the aim of enhancing coral bleaching tolerance, we evolved 10 clonal strains of a common coral microalgal endosymbiont at elevated temperatures (31°C) for 4 years in the laboratory. All 10 heat-evolved strains had expanded their thermal tolerance in vitro following laboratory evolution. After reintroduction into coral host larvae, 3 of the 10 heat-evolved endosymbionts also increased the holobionts’ bleaching tolerance. Although lower levels of secreted reactive oxygen species (ROS) accompanied thermal tolerance of the heat-evolved algae, reduced ROS secretion alone did not predict thermal tolerance in symbiosis. The more tolerant symbiosis exhibited additional higher constitutive expression of algal carbon fixation genes and coral heat tolerance genes. These findings demonstrate that coral stock with enhanced climate resilience can be developed through ex hospite laboratory evolution of their microalgal endosymbionts.

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