scholarly journals The role of zooxanthellae in the thermal tolerance of corals: a ‘nugget of hope’ for coral reefs in an era of climate change

2006 ◽  
Vol 273 (1599) ◽  
pp. 2305-2312 ◽  
Author(s):  
Ray Berkelmans ◽  
Madeleine J.H van Oppen
Keyword(s):  
Climate Change ◽  
Coral Reefs ◽  
Thermal Tolerance ◽  
Coral Species ◽  
Experimental Manipulation ◽  
Direct Result ◽  
Symbiont Type ◽  
Thermal Acclimatization ◽  
Highly Sensitive

The ability of coral reefs to survive the projected increases in temperature due to global warming will depend largely on the ability of corals to adapt or acclimatize to increased temperature extremes over the next few decades. Many coral species are highly sensitive to temperature stress and the number of stress (bleaching) episodes has increased in recent decades. We investigated the acclimatization potential of Acropora millepora , a common and widespread Indo-Pacific hard coral species, through transplantation and experimental manipulation. We show that adult corals, at least in some circumstances, are capable of acquiring increased thermal tolerance and that the increased tolerance is a direct result of a change in the symbiont type dominating their tissues from Symbiodinium type C to D. Our data suggest that the change in symbiont type in our experiment was due to a shuffling of existing types already present in coral tissues, not through exogenous uptake from the environment. The level of increased tolerance gained by the corals changing their dominant symbiont type to D (the most thermally resistant type known) is around 1–1.5 °C. This is the first study to show that thermal acclimatization is causally related to symbiont type and provides new insight into the ecological advantage of corals harbouring mixed algal populations. While this increase is of huge ecological significance for many coral species, in the absence of other mechanisms of thermal acclimatization/adaptation, it may not be sufficient to survive climate change under predicted sea surface temperature scenarios over the next 100 years. However, it may be enough to ‘buy time’ while greenhouse reduction measures are put in place.

scholarly journals Distribution and Diversity of Archaeal Ammonia Monooxygenase Genes Associated with Corals

2007 ◽  
Vol 73 (17) ◽  
pp. 5642-5647 ◽  
Author(s):  
J.Michael Beman ◽  
Kathryn J. Roberts ◽  
Linda Wegley ◽  
Forest Rohwer ◽  
Christopher A. Francis
Keyword(s):  
Coral Reefs ◽  
Microbial Communities ◽  
Coral Species ◽  
Estuarine Sediments ◽  
Ammonia Monooxygenase ◽  
Oceanic Water ◽  
Ecological Role ◽  
Bocas Del Toro ◽  
Water Columns

ABSTRACT Corals are known to harbor diverse microbial communities of Bacteria and Archaea, yet the ecological role of these microorganisms remains largely unknown. Here we report putative ammonia monooxygenase subunit A (amoA) genes of archaeal origin associated with corals. Multiple DNA samples drawn from nine coral species and four different reef locations were PCR screened for archaeal and bacterial amoA genes, and archaeal amoA gene sequences were obtained from five different species of coral collected in Bocas del Toro, Panama. The 210 coral-associated archaeal amoA sequences recovered in this study were broadly distributed phylogenetically, with most only distantly related to previously reported sequences from coastal/estuarine sediments and oceanic water columns. In contrast, the bacterial amoA gene could not be amplified from any of these samples. These results offer further evidence for the widespread presence of the archaeal amoA gene in marine ecosystems, including coral reefs.

scholarly journals Morphological stasis masks ecologically divergent coral species on tropical reefs

2020 ◽  
Author(s):  
P Bongaerts ◽  
IR Cooke ◽  
H Ying ◽  
D Wels ◽  
S Haan den ◽  
...  
Keyword(s):  
Coral Reefs ◽  
Coral Species ◽  
Common Garden ◽  
Genomic Signatures ◽  
Morphological Stasis ◽  
Sequencing Studies ◽  
Demographic Modelling ◽  
Whole Genome Resequencing ◽  
Taxonomic Framework

ABSTRACTCoral reefs are the epitome of species diversity, yet the number of described scleractinian coral species, the framework-builders of coral reefs, remains moderate by comparison. DNA sequencing studies are rapidly challenging this notion by exposing a wealth of undescribed diversity, but the evolutionary and ecological significance of this diversity remains largely unclear. Here, we present an annotated genome for one of the most ubiquitous corals in the Indo-Pacific (Pachyseris speciosa), and uncover through a comprehensive genomic and phenotypic assessment that it comprises morphologically indistinguishable, but ecologically divergent cryptic lineages. Demographic modelling based on whole-genome resequencing disproved that morphological crypsis was due to recent divergence, and instead indicated ancient morphological stasis. Although the lineages occur sympatrically across shallow and mesophotic habitats, extensive genotyping using a rapid diagnostic assay revealed differentiation of their ecological distributions. Leveraging “common garden” conditions facilitated by the overlapping distributions, we assessed physiological and quantitative skeletal traits and demonstrated concurrent phenotypic differentiation. Lastly, spawning observations of genotyped colonies highlighted the potential role of temporal reproductive isolation in the limited admixture, with consistent genomic signatures in genes related to morphogenesis and reproduction. Overall, our findings demonstrate how ecologically and phenotypically divergent coral species can evolve despite morphological stasis, and provide new leads into the potential mechanisms facilitating such divergence in sympatry. More broadly, they indicate that our current taxonomic framework for reef-building corals may be scratching the surface of the ecologically relevant diversity on coral reefs, consequently limiting our ability to protect or restore this diversity effectively.

scholarly journals Predicted Shifts in the Distributions of Atlantic Reef-Building Corals in the Face of Climate Change

2021 ◽  
Vol 8 ◽  
Author(s):  
Silas C. Principe ◽  
André L. Acosta ◽  
João E. Andrade ◽  
Tito M. C. Lotufo
Keyword(s):  
Climate Change ◽  
Coral Reefs ◽  
Coral Species ◽  
Relative Concentration ◽  
Structural Complexity ◽  
Brazilian Coast ◽  
Cascading Effects ◽  
Eastern Atlantic Ocean ◽  
The Future ◽  
The Face

Many species drive the diversity of ecosystems by adding structural complexity to the environment. In coral reefs, stony corals act as habitat-forming species, increasing niche availability for other organisms. Some coral species play key roles as reef builders due to their abundance or morpho-functional characteristics. Thus, changes in the distributions of these species can entail cascading effects in entire ecosystems. With climate change, many coral species are experiencing shifts in their distributions, threatening the preservation of coral reefs. Here, we projected the current and future distributions of three key reef builders of the Atlantic (Mussismilia hispida, Montastraea cavernosa, and the Siderastrea complex) under three relative concentration pathway scenarios: the most optimistic, the most pessimistic and one moderate scenario (RCP2.6, 4.5, and 8.5). Our models revealed that all the above species will undergo habitat loss in the future (2100) in the most pessimistic scenario, although new areas could become suitable, including regions in the eastern Atlantic Ocean. Additionally, when considering only its actual range of occurrence, M. hispida will lose habitats under all future scenarios. Moreover, in some regions of both the Tropical Northwestern Atlantic (TNA) and the Brazilian coast, these three species could disappear, with detrimental consequences for the associated communities. We highlight the need for an urgent change of course to guarantee functional reefs in the Atlantic in the future.

scholarly journals Foraminiferal holobiont thermal tolerance under climate change – Roommates problems or successful collaboration?

2020 ◽  
Author(s):  
Doron Pinko ◽  
Sigal Abramovich ◽  
Danna Titelboim
Keyword(s):  
Climate Change ◽  
Thermal Tolerance ◽  
Photosynthetic Activity ◽  
Extreme Temperature ◽  
Relative Contribution ◽  
Large Benthic Foraminifera ◽  
Algal Symbionts ◽  
Future Warming ◽  
Successful Collaboration

Abstract. Understanding the response of marine organisms to expected future warming is essential. Large Benthic Foraminifera (LBF) are symbiont bearing protists considered to be major carbonate producers and ecosystems engineers. We examined the thermal tolerance of two main types of LBF holobionts characterized by different algal symbionts and shell types (resulted from alternative biomineralization mechanisms): The hyaline diatom bearing, Amphistegina lobifera, and the porcelaneous dinoflagellate bearing, Sorites orbiculus. To assess the relative contribution of host and symbiont algae to the holobiont thermal tolerance we separately evaluated their response by measuring calcification rates and photosynthetic activity under present-day and future warming scenarios. Our results show that both holobionts exhibit thermal resilience up to 32 °C and sensitivity to 35 °C. This sensitivity differs in the magnitude of their response: calcification of A. lobifera was completely inhibited while it was only reduced in S. orbiculus. Thus, future warming will significantly shift the relative contribution of the two species as carbonate producers. Moreover, A. lobifera exhibited a synchronized response of the host and symbionts. In contrast, in S. orbiculus the symbionts responded prior to the host, possibly limiting its resilience. Our results also demonstrate the role of pre-exposure and acclimation processes of host, symbionts or both in mitigating future warming. It highlights the possibility that while pre-exposure to moderate temperatures benefits the holobiont, in cases of extreme temperature it might reduce its thermal tolerance.

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

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.

scholarly journals Reviews and syntheses: Marine biogenic aerosols and the ecophysiology of coral reefs

2019 ◽  
Author(s):  
Rebecca Jackson ◽  
Albert Gabric ◽  
Roger Cropp ◽  
Matthew Woodhouse
Keyword(s):  
Climate Change ◽  
Coral Reefs ◽  
Social Services ◽  
Radiative Forcing ◽  
Marine Boundary Layer ◽  
Global Climate ◽  
Aerosol Formation ◽  
Radiative Balance ◽  
Cloud Properties

Abstract. Coral reefs are being threatened by global climate change, with ocean warming and acidification, compounded by declining water quality in many coastal systems, adversely affecting coral health and cover. This is of great concern as coral reefs provide numerous ecosystem, economic and social services. Corals are also recognized as being amongst the strongest individual sources of natural atmospheric sulfur, through stress-induced emissions of dimethylsulfide (DMS). In the clean marine boundary layer, biogenic sulfates contribute to new aerosol formation and the growth of existing particles, with important implications for the radiative balance. Evidence suggests that DMS is not only directly involved in the coral stress response, alleviating oxidative stress, but may create an ocean thermostat which suppresses sea surface temperature (SST) through changes to aerosol and cloud properties. This review provides a summary of the current major threats facing coral reefs and describes the role of dimethylated sulfur compounds in coral physiology and climate. The role of coral reefs as a source of climatically important compounds is an emerging topic of research however, the window of opportunity to understand the complex biogeophysical processes involved is closing with ongoing degradation of the world's coral reefs. The greatest uncertainty in our estimates of radiative forcing and climate change are derived from natural aerosol sources, such as marine DMS, which constitutes the largest flux of oceanic reduced sulfur to the atmosphere. Gaining a better understanding of the role of coral reef DMS emissions is crucial to predicting the future climate of our planet.

scholarly journals Clarifying the concept of climate change refugia for coral reefs

2017 ◽  
Vol 75 (1) ◽  
pp. 43-49 ◽  
Author(s):  
Javid Kavousi ◽  
Gunnar Keppel
Keyword(s):  
Climate Change ◽  
Coral Reef ◽  
Coral Reefs ◽  
Environmental Conditions ◽  
Coral Species ◽  
High Capacity ◽  
Physiological Processes ◽  
In The Wild ◽  
Low Exposure

Abstract Refugia can facilitate the persistence of biodiversity under changing environmental conditions, such as anthropogenic climate change, and therefore constitute the best chance of survival for many coral species in the wild. Despite an increasing amount of literature, the concept of coral reef refugia remains poorly defined; so that climate change refugia have been confused with other phenomena, including temporal refuges, pristine habitats and physiological processes such as adaptation and acclimatization. We propose six criteria that determine the capacity of refugia to facilitate species persistence, including long-term buffering, protection from multiple climatic stressors, accessibility, microclimatic heterogeneity, size, and low exposure to non-climate disturbances. Any effective, high-capacity coral reef refugium should be characterized by long-term buffering of environmental conditions (for several decades) and multi-stressor buffering (provision of suitable environmental conditions with respect to climatic change, particularly ocean warming and acidification). Although not always essential, the remaining criteria are important for quantifying the capacity of potential refugia.

Cryobiology: principles, species conservation and benefits for coral reefs

2016 ◽  
Vol 28 (8) ◽  
pp. 1049 ◽  
Author(s):  
Mary Hagedorn ◽  
Virginia L. Carter
Keyword(s):  
Climate Change ◽  
Coral Reefs ◽  
Coral Species ◽  
Ex Situ Conservation ◽  
Species Conservation ◽  
Reproductive Period ◽  
Conservation Strategy ◽  
Ex Situ ◽  
Marine Life ◽  
Loss Of Genetic Diversity

Coral reefs are some of the oldest, most diverse and valuable ecosystems on Earth because they can support one-quarter of all marine life in our oceans. Despite their importance, the world’s coral reefs continue to be degraded at unprecedented rates by local and global threats that are warming and creating a more acidic ocean. This paper explores the reproductive challenges of coral for ex situ conservation, using IVF and cryopreservation, and our practical biobanking methods. Coral present challenges for cryopreservation because their reproductive period is often limited to a few nights yearly, they are mostly hermaphrodites with diverse modes of reproduction, including asexual reproduction (i.e. fragmentation and parthenogenesis) and sexual reproduction (i.e. self- and cross-fertilisation) and they express physiological toxins that can inhibit cryopreservation. We have banked spermatozoa from 12 coral species using the same field-hardy methods and have created new coral with thawed spermatozoa. In addition, we describe the cryopreservation of coral symbionts, whose physiology only permits the highest success seasonally. As part of a multidisciplinary conservation strategy, these collections may provide a major hedge against extinction for corals facing the damaging effects of climate change and loss of genetic diversity, and promise to help offset threats to our reefs worldwide.

scholarly journals Intrapopulation adaptive variance supports selective breeding in a reef-building coral

2021 ◽  
Author(s):  
Crawford Drury ◽  
Nina Bean ◽  
Casey Harris ◽  
Joshua Hancock ◽  
Joel Huckeba ◽  
...  
Keyword(s):  
Climate Change ◽  
Coral Reefs ◽  
Cell Signaling ◽  
Thermal Tolerance ◽  
Selective Breeding ◽  
Functional Differentiation ◽  
Small Scale ◽  
Acid Modification ◽  
Genomic Signatures ◽  
Gene Ontologies

The long-term persistence of coral reefs under climate change requires heritable drivers of thermal tolerance which support adaptation. The genomic basis of thermal tolerance has been evaluated across strong spatial and environmental gradients, but this variation also exists within populations due to neutral evolutionary processes. Small scale heterogeneity in coral bleaching is ubiquitous, so we used corals from a single reef to examine genomic signatures of bleaching performance, their biochemical correlates and the downstream consequences of selective breeding. In the absence of directional selection due to environmental differences, adult corals from a single population exhibit strong genomic patterns related to natural bleaching tolerance and symbiosis state, including functional differentiation in signaling pathways, protein and amino acid modification and metabolism. Conversely, growth, development and innate immune responses did not distinguish bleaching tolerance in adult corals. The genomic signatures of these gene ontologies influence biochemical patterns in healthy corals, primarily via cell-signaling pathway impacts on peptides and amino acids. Thermal tolerance in this population is highly heritable, with significantly higher survivorship under temperature stress in larvae and juveniles reared from thermally tolerant parents than those from sensitive parents. Using a select and re-sequence approach, certain gene ontologies were reproducibly impacted, while antioxidant activity and cell signaling ontologies were disproportionately selected in thermally tolerant corals, demonstrating the genomic drivers of successful selective breeding. These data show that intrapopulation variance in the absence of historical selection supports the adaptive capacity of coral reefs under climate change.

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