Species-specific differences in thermal tolerance may define susceptibility to intracellular acidosis in reef corals

Numerous assays are used to quantify thermal tolerance of arthropods including dynamic ramping and static knockdown assays. The dynamic assay measures a critical temperature while the animal is gradually heated, whereas the static assay measures the time to knockdown at a constant temperature. Previous studies indicate that heat tolerance measured by both assays can be reconciled using the time × temperature interaction from “thermal tolerance landscapes” (TTLs) in unhardened animals. To investigate if this relationship remains true within hardened animals, we use a static assay to assess the effect of heat hardening treatments on heat tolerance in 10 Drosophila species. Using this TTL approach and data from the static heat knockdown experiments, we model the expected change in dynamic heat knockdown temperature (CTmax: temperature at which flies enter coma) and compare these predictions to empirical measurements of CTmax. We find that heat tolerance and hardening capacity are highly species specific and that the two assays report similar and consistent responses to heat hardening. Tested assays are therefore likely to measure the same underlying physiological trait and provide directly comparable estimates of heat tolerance. Regardless of this compliance, we discuss why and when static or dynamic assays may be more appropriate to investigate ectotherm heat tolerance.

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Reduced thermal tolerance of massive coral species in a highly variable environment

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2020.1379 ◽

2020 ◽

Vol 287 (1933) ◽

pp. 20201379 ◽

Cited By ~ 3

Author(s):

C. N. Klepac ◽

D. J. Barshis

Keyword(s):

Heat Stress ◽

Thermal Tolerance ◽

Coral Cover ◽

Thermal Anomaly ◽

American Samoa ◽

Variable Environment ◽

Thermal Anomalies ◽

Thermal Environments ◽

Acute Heat Stress ◽

Species Specific

Coral bleaching events are increasing in frequency and severity, resulting in widespread losses in coral cover. However, branching corals native to highly variable (HV) thermal environments can have higher bleaching resistance than corals from more moderate habitats. Here, we investigated the response of two massive corals, Porites lobata and Goniastrea retiformis , from a moderately variable (MV) and a low variability (LV) pool transplanted into a HV pool on Ofu Island in American Samoa. Paired transplant and native ramets were exposed to an acute thermal stress after 6 and 12 months of exposure to the HV pool to evaluate changes in thermal tolerance limits. For both species, photosynthetic efficiency and chlorophyll loss following acute heat stress did not differ between ramets transplanted into the HV pool and respective native pool. Moreover, HV native P. lobata exhibited the greatest bleaching susceptibility compared to MV and LV natives and there was no effect of acute heat stress on MV P. lobata . There was also a thermal anomaly during the study, where Ofu's backreef thermal regime surpassed historical records—2015 had 8 degree heating weeks (DHW) and 2016 had up to 5 DHW (in comparison to less than or equal to 3 over the last 10 years)—which may have exceeded the upper thermal limits of HV native P. lobata . These results strongly contrast with other research on coral tolerance in variable environments, potentially underscoring species-specific mechanisms and regional thermal anomalies that may be equally important in shaping coral responses to extreme temperatures.

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Divergent symbiont communities determine the physiology and nutrition of a reef coral across a light-availability gradient

The ISME Journal ◽

10.1038/s41396-019-0570-1 ◽

2020 ◽

Vol 14 (4) ◽

pp. 945-958 ◽

Cited By ~ 5

Author(s):

Christopher B. Wall ◽

Mario Kaluhiokalani ◽

Brian N. Popp ◽

Megan J. Donahue ◽

Ruth D. Gates

Keyword(s):

Photosynthetically Active Radiation ◽

Light Availability ◽

Reef Coral ◽

Carbon Assimilation ◽

Montipora Capitata ◽

Active Radiation ◽

Reef Corals ◽

Species Specific ◽

First Time ◽

Symbiont Species

AbstractReef corals are mixotrophic organisms relying on symbiont-derived photoautotrophy and water column heterotrophy. Coral endosymbionts (Family: Symbiodiniaceae), while typically considered mutualists, display a range of species-specific and environmentally mediated opportunism in their interactions with coral hosts, potentially requiring corals to rely more on heterotrophy to avoid declines in performance. To test the influence of symbiont communities on coral physiology (tissue biomass, symbiont density, photopigmentation) and nutrition (δ13C, δ15N), we sampled Montipora capitata colonies dominated by a specialist symbiont Cladocopium spp. or a putative opportunist Durusdinium glynnii (hereafter, C- or D-colonies) from Kāne‘ohe Bay, Hawai‘i, across gradients in photosynthetically active radiation (PAR) during summer and winter. We report for the first time that isotope values of reef corals are influenced by Symbiodiniaceae communities, indicative of different autotrophic capacities among symbiont species. D-colonies had on average 56% higher symbiont densities, but lower photopigments per symbiont cell and consistently lower δ13C values in host and symbiont tissues; this pattern in isotope values is consistent with lower symbiont carbon assimilation and translocation to the host. Neither C- nor D-colonies showed signs of greater heterotrophy or nutritional plasticity; instead changes in δ13C values were driven by PAR availability and photoacclimation attributes that differed between symbiont communities. Together, these results reveal Symbiodiniaceae functional diversity produces distinct holobionts with different capacities for autotrophic nutrition, and energy tradeoffs from associating with opportunist symbionts are not met with increased heterotrophy.

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Scope for latitudinal extension of reef corals is species specific

Frontiers of Biogeography ◽

10.21425/f58129328 ◽

2016 ◽

Vol 8 (1) ◽

Cited By ~ 9

Author(s):

Joshua Madin ◽

Andrew Allen ◽

Andrew Baird ◽

John Pandolfi ◽

Brigitte Sommer

Keyword(s):

Reef Corals ◽

Species Specific

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EFFECTS OF ELEVATED TEMPERATURE ON THE MORTALITY AND METABOLISM OF PACIFIC REEF CORALS

Marine Research in Indonesia ◽

10.14203/mri.v17i0.465 ◽

1970 ◽

Vol 17 ◽

pp. 71-72

Author(s):

Stephen L. Coles

Keyword(s):

Thermal Tolerance ◽

Elevated Temperatures ◽

Reef Coral ◽

Temperature Tolerance ◽

Temperature Adaptation ◽

Critical Temperatures ◽

Reef Corals ◽

Annual Water ◽

Physiological Tests ◽

Upper Thermal Tolerance

The upper thermal tolerance limits of subtropical (Hawaiian) and tropical (Enewetak) reef corals were determined both in the field and under laboratory conditions. Enewetak corals routinely withstand temperatures up to 34°C whereas similar exposure time at 32°C kill their Hawaiian congeners. These differing upper thermal limits correspond to increases of + 4 - 5°C above the annual water temperature maxima at each location. Reef coral temperature tolerance is therefore closely adapted to the ambient ocean temperature conditions of a geographic location.Studies of temperature effect on reef coral photosynthesis (P) and respiration (R) also showed different patterns between locations. Same species shower greater autotrophic capability at elevated temperatures in Enewetak than Hawaii. Critical temperatures estimated as coinciding with P:R ratio values minimal to support long term functional autotrophy were 2-5°C higher for Enewetak than Hawaiian specimens, closely corresponding to observed differences in upper thermal tolerance. Results support a hypothesis of temperature adaptation capability for reef corals and suggest that short term physiological tests can predict relative differences in temperature tolerance among coral species.

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Using naturally occurring climate resilient corals to construct bleaching-resistant nurseries

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1721415116 ◽

2019 ◽

Vol 116 (21) ◽

pp. 10586-10591 ◽

Cited By ~ 30

Author(s):

Megan K. Morikawa ◽

Stephen R. Palumbi

Keyword(s):

Heat Tolerance ◽

Thermal Tolerance ◽

American Samoa ◽

Bleaching Event ◽

Lower Growth ◽

Experimental Heat ◽

Naturally Occurring ◽

Nursery Stock ◽

Heat Tolerant ◽

Species Specific

Ecological restoration of forests, meadows, reefs, or other foundational ecosystems during climate change depends on the discovery and use of individuals able to withstand future conditions. For coral reefs, climate-tolerant corals might not remain tolerant in different environments because of widespread environmental adjustment of coral physiology and symbionts. Here, we test if parent corals retain their heat tolerance in nursery settings, if simple proxies predict successful colonies, and if heat-tolerant corals suffer lower growth or survival in normal settings. Before the 2015 natural bleaching event in American Samoa, we set out 800 coral fragments from 80 colonies of four species selected by prior tests to have a range of intraspecific natural heat tolerance. After the event, nursery stock from heat-tolerant parents showed two to three times less bleaching across species than nursery stock from less tolerant parents. They also retained higher individual genetic diversity through the bleaching event than did less heat-tolerant corals. The three best proxies for thermal tolerance were response to experimental heat stress, location on the reef, and thermal microclimate. Molecular biomarkers were also predictive but were highly species specific. Colony genotype and symbiont genus played a similarly strong role in predicting bleaching. Combined, our results show that selecting for host and symbiont resilience produced a multispecies coral nursery that withstood multiple bleaching events, that proxies for thermal tolerance in restoration can work across species and be inexpensive, and that different coral clones within species reacted very differently to bleaching.

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Homogenization of Endosymbiont Communities Hosted by Equatorial Corals during the 2016 Mass Bleaching Event

Microorganisms ◽

10.3390/microorganisms8091370 ◽

2020 ◽

Vol 8 (9) ◽

pp. 1370

Author(s):

Sudhanshi S. Jain ◽

Lutfi Afiq-Rosli ◽

Bar Feldman ◽

Oren Levy ◽

Jun Wei Phua ◽

...

Keyword(s):

Thermal Tolerance ◽

High Throughput Sequencing ◽

Quantitative Polymerase Chain Reaction ◽

Global Scale ◽

Bleaching Event ◽

Reef Corals ◽

Qpcr Method ◽

Polymerase Chain ◽

Limited Change

Thermal stress drives the bleaching of reef corals, during which the endosymbiotic relationship between Symbiodiniaceae microalgae and the host breaks down. The endosymbiont communities are known to shift in response to environmental disturbances, but how they respond within and between colonies during and following bleaching events remains unclear. In 2016, a major global-scale bleaching event hit countless tropical reefs. Here, we investigate the relative abundances of Cladocopium LaJeunesse & H.J.Jeong, 2018 and Durusdinium LaJeunesse, 2018 within and among Pachyseris speciosa colonies in equatorial Singapore that are known to host both these Symbiodiniaceae clades. Bleached and unbleached tissues from bleaching colonies, as well as healthy colonies, during and following the bleaching event were sampled and analyzed for comparison. The nuclear ribosomal internal transcribed spacer (ITS) regions were separately amplified and quantified using a SYBR Green-based quantitative polymerase chain reaction (qPCR) method and Illumina high-throughput sequencing. We found Cladocopium to be highly abundant relative to Durusdinium. The relative abundance of Durusdinium, known to be thermally tolerant, was highest in post-bleaching healthy colonies, while bleached and unbleached tissues from bleaching colonies as well as tissue from healthy colonies during the event had depressed proportions of Durusdinium. Given the importance of Durusdinium for thermal tolerance and stress response, it is surprising that bleached tissue showed limited change over healthy tissue during the bleaching event. Moreover, colonies were invariably dominated by Cladocopium during bleaching, but a minority of colonies were Durusdinium-dominant during non-bleaching times. The detailed characterization of Symbiodiniaceae in specific colonies during stress and recovery will provide insights into this crucial symbiosis, with implications for their responses during major bleaching events.

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Scope for latitudinal extension of reef corals is species specific

Frontiers of Biogeography ◽

10.21425/f5fbg29328 ◽

2016 ◽

Vol 8 (1) ◽

Cited By ~ 1

Author(s):

Joshua Madin ◽

Andrew Allen ◽

Andrew Baird ◽

John Pandolfi ◽

Brigitte Sommer

Keyword(s):

Reef Corals ◽

Species Specific

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Utility of Photochemical Traits as Diagnostics of Thermal Tolerance amongst Great Barrier Reef Corals

Frontiers in Marine Science ◽

10.3389/fmars.2018.00045 ◽

2018 ◽

Vol 5 ◽

Cited By ~ 11

Author(s):

Matthew R. Nitschke ◽

Stephanie G. Gardner ◽

Samantha Goyen ◽

Lisa Fujise ◽

Emma F. Camp ◽

...

Keyword(s):

Great Barrier Reef ◽

Thermal Tolerance ◽

Barrier Reef ◽

Reef Corals

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Competitive traits of coral symbionts may alter the structure and function of the microbiome

The ISME Journal ◽

10.1038/s41396-020-0697-0 ◽

2020 ◽

Vol 14 (10) ◽

pp. 2424-2432

Author(s):

Shelby E. McIlroy ◽

Jane C. Y. Wong ◽

David M. Baker

Keyword(s):

Temperature Stress ◽

Thermal Tolerance ◽

Niche Partitioning ◽

Cell Replication ◽

Algal Symbionts ◽

Nutrient Assimilation ◽

The Face ◽

Increased Sensitivity ◽

Species Specific ◽

And Function

Abstract In the face of global warming and unprecedented coral bleaching, a new avenue of research is focused on relatively rare algal symbionts and their ability to confer thermal tolerance to their host by association. Yet, thermal tolerance is just one of many physiological attributes inherent to the diversity of symbiodinians, a result of millions of years of competition and niche partitioning. Here, we revealed that competition among cocultured symbiodinians alters nutrient assimilation and compound production with species-specific responses. For Cladocopium goreaui, a species ubiquitous within stable coral associations, temperature stress increased sensitivity to competition eliciting a shift toward investment in cell replication, i.e., putative niche exploitation. Meanwhile, competition led Durusdinium trenchii, a thermally tolerant “background” symbiodinian, to divert resources from immediate growth to storage. As such, competition may be driving the dominance of C. goreaui outside of temperature stress, the destabilization of symbioses under thermal stress, the repopulation of coral tissues by D. trenchii following bleaching, and ultimately undermine the efficacy of symbiont turnover as an adaptive mechanism.

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