Variation in susceptibility among three Caribbean coral species and their algal symbionts indicates the threatened staghorn coral, Acropora cervicornis, is particularly susceptible to elevated nutrients and heat stress

Coral cover is declining worldwide due to multiple interacting threats. We compared the effects of elevated nutrients and temperature on three Caribbean corals: Acropora cervicornis, Orbicella faveolata, and Siderastrea siderea. Colonies hosting different algal types were exposed to either ambient nutrients (A), elevated NH4 (N), or elevated NH4 + PO4 (N+P) at control temperatures (26 °C) for > 2 months, followed by a 3-week thermal challenge (31.5 °C). A. cervicornis hosted Symbiodinium (S. fitti) and was highly susceptible to the combination of elevated nutrients and temperature. During heat stress, A. cervicornis pre-exposed to elevated nutrients experienced 84%-100% mortality and photochemical efficiency (Fv/Fm) declines of 41-50%. In comparison, no mortality and lower Fv/Fm declines (11-20%) occurred in A. cervicornis that were heat-stressed but not pre-exposed to nutrients. O. faveolata and S. siderea response to heat stress was determined by their algal symbiont community and was not affected by nutrients. O. faveolata predominantly hosted Durusdinium trenchii or Breviolum, but only corals hosting Breviolum were susceptible to heat, experiencing 100% mortality, regardless of nutrient treatment. S. siderea colonies predominantly hosted Cladocopium C1 (C. goreaui), Cladocopium C3, D. trenchii, or variable proportions of Cladocopium C1 and D. trenchii. This species was resilient to elevated nutrients and temperature, with no significant mortality in any of the treatments. However, during heat stress, S. siderea hosting Cladocopium C3 suffered higher reductions in Fv/Fm (41-56%) compared to S. siderea hosting Cladocopium C1 and D. trenchii (17-26% and 10-16%, respectively). These differences in holobiont susceptibility to elevated nutrients and heat may help explain historical declines in A. cervicornis starting decades earlier than other Caribbean corals. Our results suggest that tackling only warming temperatures may be insufficient to ensure the continued persistence of Caribbean corals, especially A. cervicornis. Reducing nutrient inputs to reefs may also be necessary for these iconic coral species to survive.

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Seascape genomics reveals candidate molecular targets of heat stress adaptation in three coral species

10.1101/2020.05.12.090050 ◽

2020 ◽

Cited By ~ 2

Author(s):

Oliver Selmoni ◽

Gaël Lecellier ◽

Hélène Magalon ◽

Laurent Vigliola ◽

Francesca Benzoni ◽

...

Keyword(s):

Heat Stress ◽

Molecular Mechanisms ◽

Coral Species ◽

New Caledonia ◽

Heat Waves ◽

Molecular Targets ◽

Remote Sensing Data ◽

Stress Adaptation ◽

Nucleotide Polymorphisms ◽

Apoptotic Pathways

AbstractAnomalous heat waves are causing a major decline of hard corals around the world and threatening the persistence of coral reefs. There are, however, reefs that had been exposed to recurrent thermal stress over the years and whose corals appeared tolerant against heat. One of the mechanisms that could explain this phenomenon is local adaptation, but the underlying molecular mechanisms are poorly known.In this work, we applied a seascape genomics approach to study heat stress adaptation in three coral species of New Caledonia (southwestern Pacific) and to uncover molecular actors potentially involved. We used remote sensing data to characterize the environmental trends across the reef system, and sampled corals living at the most contrasted sites. These samples underwent next generation sequencing to reveal single-nucleotide-polymorphisms (SNPs) of which frequencies associated with heat stress gradients. As these SNPs might underpin an adaptive role, we characterized the functional roles of the genes located in their genomic neighborhood.In each of the studied species, we found heat stress associated SNPs notably located in proximity of genes coding for well-established actors of the cellular responses against heat. Among these, we can mention proteins involved in DNA damage-repair, protein folding, oxidative stress homeostasis, inflammatory and apoptotic pathways. In some cases, the same putative molecular targets of heat stress adaptation recurred among species.Together, these results underscore the relevance and the power of the seascape genomics approach for the discovery of adaptive traits that could allow corals to persist across wider thermal ranges.

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Density Dependence Drives Habitat Production and Survivorship of Acropora cervicornis Used for Restoration on a Caribbean Coral Reef

Frontiers in Marine Science ◽

10.3389/fmars.2016.00261 ◽

2016 ◽

Vol 3 ◽

Cited By ~ 18

Author(s):

Mark C. Ladd ◽

Andrew A. Shantz ◽

Ken Nedimyer ◽

Deron E. Burkepile

Keyword(s):

Coral Reef ◽

Density Dependence ◽

Acropora Cervicornis ◽

Caribbean Coral ◽

Caribbean Coral Reef

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An emerging coral disease outbreak decimated Caribbean coral populations and reshaped reef functionality

10.21203/rs.3.rs-734716/v1 ◽

2021 ◽

Author(s):

Lorenzo Alvarez-Filip ◽

F. González-Barrios ◽

Esmeralda Pérez-Cervantes ◽

Ana Molina-Hernandez ◽

Nuria Estrada-Saldívar

Keyword(s):

Coral Species ◽

Coral Disease ◽

Structural Features ◽

Caribbean Region ◽

Carbonate Production ◽

Coral Abundance ◽

Caribbean Coral ◽

Coral Communities ◽

The Caribbean ◽

Physical Functionality

Abstract Diseases are major drivers of the deterioration of coral reefs, linked to major declines in coral abundance, reef functionality, and reef-related ecosystems services1-3. An outbreak of a new disease is currently rampaging through the populations of the remaining reef-building corals across the Caribbean region. The outbreak was first reported in Florida in 2014 and reached the northern Mesoamerican reef by summer 2018, where it spread across the ~ 450-km reef system only in a few months4. Rapid infection was generalized across all sites and mortality rates ranged from 94% to < 10% among the 21 afflicted coral species. This single event further modified the coral communities across the region by increasing the relative dominance of weedy corals and reducing reef functionality, both in terms of functional diversity and calcium carbonate production. This emergent disease is likely to become the most lethal disturbance ever recorded in the Caribbean, and it will likely result in the onset of a new functional regime where key reef-building and complex branching acroporids (a genus apparently unaffected) will once again become conspicuous structural features in reef systems with yet even lower levels of physical functionality.

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Convergent mortality responses of Caribbean coral species to seawater warming

Ecosphere ◽

10.1890/es13-00107.1 ◽

2013 ◽

Vol 4 (7) ◽

pp. art87 ◽

Cited By ~ 36

Author(s):

T. B. Smith ◽

M. E. Brandt ◽

J. M. Calnan ◽

R. S. Nemeth ◽

J. Blondeau ◽

...

Keyword(s):

Coral Species ◽

Caribbean Coral

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The rise of a native sun coral species on southern Caribbean coral reefs

Ecosphere ◽

10.1002/ecs2.2942 ◽

2019 ◽

Vol 10 (11) ◽

Author(s):

Bert W. Hoeksema ◽

Auke‐Florian Hiemstra ◽

Mark J. A. Vermeij

Keyword(s):

Coral Reefs ◽

Coral Species ◽

Southern Caribbean ◽

Caribbean Coral ◽

Caribbean Coral Reefs

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An updated assessment of Symbiodinium that associate with common scleractinian corals from Moorea (French Polynesia) reveals high diversity among background symbionts and a novel finding of clade B.

10.7287/peerj.preprints.2607v1 ◽

2016 ◽

Author(s):

Héloïse Rouzé ◽

Gaël J Lecellier ◽

Denis Saulnier ◽

Serge Planes ◽

Yannick Gueguen ◽

...

Keyword(s):

Coral Species ◽

French Polynesia ◽

Molecular Tools ◽

Quantitative Real Time Pcr ◽

Algal Symbionts ◽

Clade B ◽

Highly Sensitive ◽

Low Levels ◽

First Time ◽

High Diversity

The adaptative bleaching hypothesis (ABH) states that depending on the symbiotic flexibility of coral hosts (i.e., the ability of corals to “switch” or “shuffle” their algal symbionts), coral bleaching can lead to a change in the composition of their associated Symbiodinium community, and, thus, contribute to the coral’s overall survival. In order to determine the flexibility of corals, molecular tools are required to provide accurate species delineations, and to detect low levels of coral-associated Symbiodinium. Here, we used highly sensitive quantitative (real-time) PCR (qPCR) technology to analyse five common coral species from Moorea (French Polynesia), previously screened using only traditional conventional molecular methods, to assess the presence of low-abundance (background) Symbiodinium. Similar to other studies, each coral species exhibited a strong specificity to a particular clade, irrespective of the environment. In addition, however, each of the five species harboured at least one additional Symbiodinium clade, among clades A-D, at background levels. Unexpectedly, and for the first time in French Polynesia, clade B was detected as a coral symbiont. These results increase the number of known coral-Symbiodinium associations from corals found in French Polynesia, and likely indicate an underestimation of the ability of the corals in this region to associate with and/or “shuffle” different Symbiodinium clades. Altogether our data suggest that corals from French Polynesia may manage a trade-off between optimizing symbioses with a specific Symbiodinium clade(s), and maintaining associations with particular background clades that may play a role in the ability of corals to respond to environmental change.

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

10.1101/2021.02.08.430325 ◽

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.

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