1
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Helgoe J, Davy SK, Weis VM, Rodriguez-Lanetty M. Triggers, cascades, and endpoints: connecting the dots of coral bleaching mechanisms. Biol Rev Camb Philos Soc 2024; 99:715-752. [PMID: 38217089 DOI: 10.1111/brv.13042] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2023] [Revised: 12/08/2023] [Accepted: 12/12/2023] [Indexed: 01/15/2024]
Abstract
The intracellular coral-dinoflagellate symbiosis is the engine that underpins the success of coral reefs, one of the most diverse ecosystems on the planet. However, the breakdown of the symbiosis and the loss of the microalgal symbiont (i.e. coral bleaching) due to environmental changes are resulting in the rapid degradation of coral reefs globally. There is an urgent need to understand the cellular physiology of coral bleaching at the mechanistic level to help develop solutions to mitigate the coral reef crisis. Here, at an unprecedented scope, we present novel models that integrate putative mechanisms of coral bleaching within a common framework according to the triggers (initiators of bleaching, e.g. heat, cold, light stress, hypoxia, hyposalinity), cascades (cellular pathways, e.g. photoinhibition, unfolded protein response, nitric oxide), and endpoints (mechanisms of symbiont loss, e.g. apoptosis, necrosis, exocytosis/vomocytosis). The models are supported by direct evidence from cnidarian systems, and indirectly through comparative evolutionary analyses from non-cnidarian systems. With this approach, new putative mechanisms have been established within and between cascades initiated by different bleaching triggers. In particular, the models provide new insights into the poorly understood connections between bleaching cascades and endpoints and highlight the role of a new mechanism of symbiont loss, i.e. 'symbiolysosomal digestion', which is different from symbiophagy. This review also increases the approachability of bleaching physiology for specialists and non-specialists by mapping the vast landscape of bleaching mechanisms in an atlas of comprehensible and detailed mechanistic models. We then discuss major knowledge gaps and how future research may improve the understanding of the connections between the diverse cascade of cellular pathways and the mechanisms of symbiont loss (endpoints).
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Affiliation(s)
- Joshua Helgoe
- Department of Biological Sciences, Institute of Environment, Florida International University, 11200 SW 8th Street, OE 167, Miami, FL, USA
| | - Simon K Davy
- School of Biological Sciences, Victoria University of Wellington, PO Box 600, Wellington, New Zealand
| | - Virginia M Weis
- Department of Integrative Biology, Oregon State University, 2701 SW Campus Way, 2403 Cordley Hall, Corvallis, OR, USA
| | - Mauricio Rodriguez-Lanetty
- Department of Biological Sciences, Institute of Environment, Florida International University, 11200 SW 8th Street, OE 167, Miami, FL, USA
- Department of Biological Sciences, Biomolecular Sciences Institute, Florida International University, 11200 SW 8th Street, Miami, FL, USA
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2
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Lyndby NH, Murthy S, Bessette S, Jakobsen SL, Meibom A, Kühl M. Non-invasive investigation of the morphology and optical properties of the upside-down jellyfish Cassiopea with optical coherence tomography. Proc Biol Sci 2023; 290:20230127. [PMID: 37752841 PMCID: PMC10523073 DOI: 10.1098/rspb.2023.0127] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2023] [Accepted: 08/30/2023] [Indexed: 09/28/2023] Open
Abstract
The jellyfish Cassiopea largely cover their carbon demand via photosynthates produced by microalgal endosymbionts, but how holobiont morphology and tissue optical properties affect the light microclimate and symbiont photosynthesis in Cassiopea remain unexplored. Here, we use optical coherence tomography (OCT) to study the morphology of Cassiopea medusae at high spatial resolution. We include detailed 3D reconstructions of external micromorphology, and show the spatial distribution of endosymbionts and white granules in the bell tissue. Furthermore, we use OCT data to extract inherent optical properties from light-scattering white granules in Cassiopea, and show that granules enhance local light-availability for symbionts in close proximity. Individual granules had a scattering coefficient of µs = 200-300 cm-1, and scattering anisotropy factor of g = 0.7, while large tissue-regions filled with white granules had a lower µs = 40-100 cm-1, and g = 0.8-0.9. We combined OCT information with isotopic labelling experiments to investigate the effect of enhanced light-availability in whitish tissue regions. Endosymbionts located in whitish tissue exhibited significantly higher carbon fixation compared to symbionts in anastomosing tissue (i.e. tissue without light-scattering white granules). Our findings support previous suggestions that white granules in Cassiopea play an important role in the host modulation of the light-microenvironment.
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Affiliation(s)
- Niclas Heidelberg Lyndby
- Laboratory for Biological Geochemistry, School of Architecture, Civil and Environmental Engineering, Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland
| | - Swathi Murthy
- Marine Biological Section, Department of Biology, University of Copenhagen, Strandpromenaden 5, 3000 Helsingør, Denmark
| | - Sandrine Bessette
- Laboratory for Biological Geochemistry, School of Architecture, Civil and Environmental Engineering, Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland
- Laboratoire MAPIEM, Université de Toulon, 4323 Toulon, France
| | - Sofie Lindegaard Jakobsen
- Marine Biological Section, Department of Biology, University of Copenhagen, Strandpromenaden 5, 3000 Helsingør, Denmark
| | - Anders Meibom
- Laboratory for Biological Geochemistry, School of Architecture, Civil and Environmental Engineering, Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland
- Center for Advanced Surface Analysis, Institute of Earth Science, University of Lausanne, 1015 Lausanne, Switzerland
| | - Michael Kühl
- Marine Biological Section, Department of Biology, University of Copenhagen, Strandpromenaden 5, 3000 Helsingør, Denmark
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3
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Hazraty-Kari S, Morita M, Tavakoli-Kolour P, Nakamura T, Harii S. Reactions of juvenile coral to three years of consecutive thermal stress. THE SCIENCE OF THE TOTAL ENVIRONMENT 2023; 863:161227. [PMID: 36586691 DOI: 10.1016/j.scitotenv.2022.161227] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/24/2022] [Revised: 12/06/2022] [Accepted: 12/23/2022] [Indexed: 06/17/2023]
Abstract
As global temperatures continue to rise, corals are being exposed to increasing heat stress throughout their early life stages; however, the impact of this phenomenon is poorly understood. We exposed the reef-building coral Acropora tenuis juveniles to ∼26-28 °C (control) and ∼ 31 °C (heat stress) for one week per year over three consecutive years. In the first year of heat stress, >96 % of juveniles survived despite symbiotic algal densities in juvenile corals declining. In comparison, survival rates in the third year of heat stress declined to 50 %. Survival rates under natural conditions after stress also gradually decreased in the stressed groups. The rate in the reduction of survivorship was prominent in the consecutive thermally stressed groups (juveniles stressed twice in two years). Symbiotic algal density and photosynthetic activity (Fv/Fm) also declined in stressed juvenile groups. However, heat stress did not significantly affect the growth of juveniles. In the third year of heat stress, temperature negatively affected the physiology of juveniles in terms of survivorship, brightness (an indicator of bleaching), symbiotic algal density, and photosynthetic efficiency. Stress across consecutive years appeared to cause the survivorship of juvenile corals to decline, with three years of stress contributing to the severe decline of a reef. In conclusion, A. tenuis juveniles are not able to acclimatize to heat stress, with successive heat waves of <7 days in the summer potentially negatively affecting resilience.
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Affiliation(s)
- Sanaz Hazraty-Kari
- Graduate School of Engineering and Science, University of the Ryukyus, Okinawa, Japan.
| | - Masaya Morita
- Sesoko Station, Tropical Biosphere Research Center, University of the Ryukyus, Okinawa, Japan
| | | | - Takashi Nakamura
- Graduate School of Engineering and Science, University of the Ryukyus, Okinawa, Japan; Sesoko Station, Tropical Biosphere Research Center, University of the Ryukyus, Okinawa, Japan
| | - Saki Harii
- Sesoko Station, Tropical Biosphere Research Center, University of the Ryukyus, Okinawa, Japan.
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4
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The role of the endolithic alga Ostreobium spp. during coral bleaching recovery. Sci Rep 2022; 12:2977. [PMID: 35194106 PMCID: PMC8863988 DOI: 10.1038/s41598-022-07017-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2021] [Accepted: 01/25/2022] [Indexed: 02/06/2023] Open
Abstract
In this study, we explore how the Caribbean coral Orbicella faveolata recovers after bleaching, using fragments from 13 coral colonies exposed to heat stress (32 °C) for ten days. Biological parameters and coral optical properties were monitored during and after the stress. Increases in both, the excitation pressure over photosystem II (Qm) and pigment specific absorption (a*Chla) were observed in the stressed corals, associated with reductions in light absorption at the chlorophyll a red peak (De675) and symbiont population density. All coral fragments exposed to heat stress bleached but a fraction of the stressed corals recovered after removing the stress, as indicated by the reductions in Qm and increases in De675 and the symbiont population observed. This subsample of the experimentally bleached corals also showed blooms of the endolithic algae Ostreobium spp. underneath the tissue. Using a numerical model, we quantified the amount of incident light reflected by the coral, and absorbed by the different pigmented components: symbionts, host-tissue and Ostreobium spp. Our study supports the key contribution of Ostreobium spp. blooms near the skeletal surface, to coral recovery after bleaching by reducing skeleton reflectance. Endolithic blooms can thus significantly alleviate the high light stress that affects the remaining symbionts during the stress or when the coral has achieved the bleached phenotype.
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5
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Kramer N, Tamir R, Ben‐Zvi O, Jacques SL, Loya Y, Wangpraseurt D. Efficient light‐harvesting of mesophotic corals is facilitated by coral optical traits. Funct Ecol 2021. [DOI: 10.1111/1365-2435.13948] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
| | - Raz Tamir
- School of Zoology Tel‐Aviv University Tel Aviv Israel
- The Interuniversity Institute for Marine Sciences of Eilat Eilat Israel
| | - Or Ben‐Zvi
- School of Zoology Tel‐Aviv University Tel Aviv Israel
- The Interuniversity Institute for Marine Sciences of Eilat Eilat Israel
| | - Steven L. Jacques
- Department of Bioengineering University of Washington Seattle WA USA
| | - Yossi Loya
- School of Zoology Tel‐Aviv University Tel Aviv Israel
| | - Daniel Wangpraseurt
- Department of Nanoengineering University of California San Diego San Diego CA USA
- Department of Chemistry University of Cambridge Cambridge UK
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6
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Taylor Parkins SK, Murthy S, Picioreanu C, Kühl M. Multiphysics modelling of photon, mass and heat transfer in coral microenvironments. J R Soc Interface 2021; 18:20210532. [PMID: 34465209 PMCID: PMC8437025 DOI: 10.1098/rsif.2021.0532] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Coral reefs are constructed by calcifying coral animals that engage in a symbiosis with dinoflagellate microalgae harboured in their tissue. The symbiosis takes place in the presence of steep and dynamic gradients of light, temperature and chemical species that are affected by the structural and optical properties of the coral and their interaction with incident irradiance and water flow. Microenvironmental analyses have enabled quantification of such gradients and bulk coral tissue and skeleton optical properties, but the multi-layered nature of corals and its implications for the optical, thermal and chemical microenvironment remains to be studied in more detail. Here, we present a multiphysics modelling approach, where three-dimensional Monte Carlo simulations of the light field in a simple coral slab morphology with multiple tissue layers were used as input for modelling the heat dissipation and photosynthetic oxygen production driven by photon absorption. By coupling photon, heat and mass transfer, the model predicts light, temperature and O2 gradients in the coral tissue and skeleton, under environmental conditions simulating, for example, tissue contraction/expansion, symbiont loss via coral bleaching or different distributions of coral host pigments. The model reveals basic structure-function mechanisms that shape the microenvironment and ecophysiology of the coral symbiosis in response to environmental change.
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Affiliation(s)
- Shannara Kayleigh Taylor Parkins
- Department of Biotechnology, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands.,The Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Kemitorvet 220, 2800 Kgs. Lyngby, Denmark
| | - Swathi Murthy
- Marine Biology Section, Department of Biology, University of Copenhagen, Strandpromenaden 5, 3000 Helsingør, Denmark
| | - Cristian Picioreanu
- Department of Biotechnology, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands.,Biological and Environmental Sciences and Engineering Division, Water Desalination and Reuse Center, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia
| | - Michael Kühl
- Marine Biology Section, Department of Biology, University of Copenhagen, Strandpromenaden 5, 3000 Helsingør, Denmark.,Climate Change Cluster, University of Technology Sydney, Ultimo, New South Wales 2007, Australia
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7
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Carturan BS, Pither J, Maréchal JP, Bradshaw CJA, Parrott L. Combining agent-based, trait-based and demographic approaches to model coral-community dynamics. eLife 2020; 9:e55993. [PMID: 32701058 PMCID: PMC7473774 DOI: 10.7554/elife.55993] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2020] [Accepted: 07/23/2020] [Indexed: 11/26/2022] Open
Abstract
The complexity of coral-reef ecosystems makes it challenging to predict their dynamics and resilience under future disturbance regimes. Models for coral-reef dynamics do not adequately account for the high functional diversity exhibited by corals. Models that are ecologically and mechanistically detailed are therefore required to simulate the ecological processes driving coral reef dynamics. Here, we describe a novel model that includes processes at different spatial scales, and the contribution of species' functional diversity to benthic-community dynamics. We calibrated and validated the model to reproduce observed dynamics using empirical data from Caribbean reefs. The model exhibits realistic community dynamics, and individual population dynamics are ecologically plausible. A global sensitivity analysis revealed that the number of larvae produced locally, and interaction-induced reductions in growth rate are the parameters with the largest influence on community dynamics. The model provides a platform for virtual experiments to explore diversity-functioning relationships in coral reefs.
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Affiliation(s)
| | - Jason Pither
- Department of Biology, University of British ColumbiaKelownaCanada
- Institute for Biodiversity, Resilience, and Ecosystem Services, University of British ColumbiaKelownaCanada
- Department of Earth, Environmental and Geographic Sciences, University of British ColumbiaKelownaCanada
| | | | - Corey JA Bradshaw
- Global Ecology, College of Science and Engineering, Flinders UniversityAdelaideAustralia
| | - Lael Parrott
- Department of Biology, University of British ColumbiaKelownaCanada
- Institute for Biodiversity, Resilience, and Ecosystem Services, University of British ColumbiaKelownaCanada
- Department of Earth, Environmental and Geographic Sciences, University of British ColumbiaKelownaCanada
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8
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Wangpraseurt D, Jacques S, Lyndby N, Holm JB, Pages CF, Kühl M. Microscale light management and inherent optical properties of intact corals studied with optical coherence tomography. J R Soc Interface 2020; 16:20180567. [PMID: 30958182 DOI: 10.1098/rsif.2018.0567] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Coral reefs are highly productive photosynthetic systems and coral optics studies suggest that such high efficiency is due to optimized light scattering by coral tissue and skeleton. Here, we characterize the inherent optical properties, i.e. the scattering coefficient, μs, and the anisotropy of scattering, g, of eight intact coral species using optical coherence tomography (OCT). Specifically, we describe light scattering by coral skeletons, coenoarc tissues, polyp tentacles and areas covered by fluorescent pigments (FP). Our results reveal that light scattering between coral species ranges from μs = 3 mm-1 ( Stylophora pistillata) to μs = 25 mm-1 ( Echinopora lamelosa) . For Platygyra pini, μs was 10-fold higher for tissue versus skeleton, while in other corals (e.g. Hydnophora pilosa) no difference was found between tissue and skeletal scattering. Tissue scattering was threefold enhanced in coenosarc tissues ( μs = 24.6 mm-1) versus polyp tentacles ( μs = 8.3 mm-1) in Turbinaria reniformis. FP scattering was almost isotropic when FP were organized in granule chromatophores ( g = 0.34) but was forward directed when FP were distributed diffusely in the tissue ( g = 0.96). Our study provides detailed measurements of coral scattering and establishes a rapid approach for characterizing optical properties of photosynthetic soft tissues via OCT in vivo.
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Affiliation(s)
- Daniel Wangpraseurt
- 1 Marine Biological Section, Department of Biology, University of Copenhagen , Strandpromenaden 5, 3000 Helsingør , Denmark.,2 Department of Chemistry, University of Cambridge , Lensfield Road, Cambridge , UK.,3 Scripps Institution of Oceanography, University of California , San Diego, CA , USA
| | - Steven Jacques
- 4 Department of Biomedical Engineering, Tufts University , Medford, MA , USA
| | - Niclas Lyndby
- 1 Marine Biological Section, Department of Biology, University of Copenhagen , Strandpromenaden 5, 3000 Helsingør , Denmark
| | - Jacob Boiesen Holm
- 1 Marine Biological Section, Department of Biology, University of Copenhagen , Strandpromenaden 5, 3000 Helsingør , Denmark
| | | | - Michael Kühl
- 1 Marine Biological Section, Department of Biology, University of Copenhagen , Strandpromenaden 5, 3000 Helsingør , Denmark.,6 Climate Change Cluster, University of Technology Sydney , Ultimo, New South Wales 2007 , Australia
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9
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Measuring light scattering and absorption in corals with Inverse Spectroscopic Optical Coherence Tomography (ISOCT): a new tool for non-invasive monitoring. Sci Rep 2019; 9:14148. [PMID: 31578438 PMCID: PMC6775107 DOI: 10.1038/s41598-019-50658-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2019] [Accepted: 09/17/2019] [Indexed: 12/12/2022] Open
Abstract
The success of reef-building corals for >200 million years has been dependent on the mutualistic interaction between the coral host and its photosynthetic endosymbiont dinoflagellates (family Symbiodiniaceae) that supply the coral host with nutrients and energy for growth and calcification. While multiple light scattering in coral tissue and skeleton significantly enhance the light microenvironment for Symbiodiniaceae, the mechanisms of light propagation in tissue and skeleton remain largely unknown due to a lack of technologies to measure the intrinsic optical properties of both compartments in live corals. Here we introduce ISOCT (inverse spectroscopic optical coherence tomography), a non-invasive approach to measure optical properties and three-dimensional morphology of living corals at micron- and nano-length scales, respectively, which are involved in the control of light propagation. ISOCT enables measurements of optical properties in the visible range and thus allows for characterization of the density of light harvesting pigments in coral. We used ISOCT to characterize the optical scattering coefficient (μs) of the coral skeleton and chlorophyll a concentration of live coral tissue. ISOCT further characterized the overall micro- and nano-morphology of live tissue by measuring differences in the sub-micron spatial mass density distribution (D) that vary throughout the tissue and skeleton and give rise to light scattering, and this enabled estimates of the spatial directionality of light scattering, i.e., the anisotropy coefficient, g. Thus, ISOCT enables imaging of coral nanoscale structures and allows for quantifying light scattering and pigment absorption in live corals. ISOCT could thus be developed into an important tool for rapid, non-invasive monitoring of coral health, growth and photophysiology with unprecedented spatial resolution.
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10
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Wangpraseurt D, Lichtenberg M, Jacques SL, Larkum AWD, Kühl M. Optical Properties of Corals Distort Variable Chlorophyll Fluorescence Measurements. PLANT PHYSIOLOGY 2019; 179:1608-1619. [PMID: 30692219 PMCID: PMC6446749 DOI: 10.1104/pp.18.01275] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/15/2018] [Accepted: 01/16/2019] [Indexed: 06/09/2023]
Abstract
Pulse-amplitude-modulated (PAM) fluorimetry is widely used in photobiological studies of corals, as it rapidly provides numerous photosynthetic parameters to assess coral ecophysiology. Coral optics studies have revealed the presence of light gradients in corals, which are strongly affected by light scattering in coral tissue and skeleton. We investigated whether coral optics affects variable chlorophyll (Chl) fluorescence measurements and derived photosynthetic parameters by developing planar hydrogel slabs with immobilized microalgae and with bulk optical properties similar to those of different types of corals. Our results show that PAM-based measurements of photosynthetic parameters differed substantially between hydrogels with different degrees of light scattering but identical microalgal density, yielding deviations in apparent maximal electron transport rates by a factor of 2. Furthermore, system settings such as the measuring light intensity affected F 0, Fm , and Fv /Fm in hydrogels with identical light absorption but different degrees of light scattering. Likewise, differences in microalgal density affected variable Chl fluorescence parameters, where higher algal densities led to greater Fv /Fm values and relative electron transport rates. These results have important implications for the use of variable Chl fluorimetry in ecophysiological studies of coral stress and photosynthesis, as well as other optically dense systems such as plant tissue and biofilms.
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Affiliation(s)
- Daniel Wangpraseurt
- Marine Biological Section, Department of Biology, University of Copenhagen, DK-3000 Helsingør, Denmark
- Department of Chemistry, University of Cambridge, Cambridge CB2 1EW, UK
- Scripps Institution of Oceanography, University of California San Diego, La Jolla, California 92037
| | - Mads Lichtenberg
- Marine Biological Section, Department of Biology, University of Copenhagen, DK-3000 Helsingør, Denmark
| | | | - Anthony W D Larkum
- Climate Change Cluster, University of Technology Sydney, Ultimo, New South Wales 2007, Australia
| | - Michael Kühl
- Marine Biological Section, Department of Biology, University of Copenhagen, DK-3000 Helsingør, Denmark
- Climate Change Cluster, University of Technology Sydney, Ultimo, New South Wales 2007, Australia
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11
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Morais J, Medeiros APM, Santos BA. Research gaps of coral ecology in a changing world. MARINE ENVIRONMENTAL RESEARCH 2018; 140:243-250. [PMID: 29970251 DOI: 10.1016/j.marenvres.2018.06.021] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2018] [Revised: 06/21/2018] [Accepted: 06/28/2018] [Indexed: 06/08/2023]
Abstract
Coral reefs have long inspired marine ecologists and conservationists around the world due to their ecological and socioeconomic importance. Much knowledge on the anthropogenic impacts on coral species has been accumulated, but relevant research gaps on coral ecology remain underappreciated in human-modified seascapes. In this review we assessed 110 studies on coral responses to five major human disturbances- acidification, climate change, overfishing, pollution and non-regulated tourism -to identify geographic and theoretical gaps in coral ecology and help to guide further researches on the topic. We searched for papers in Web of Science published from 2000 to 2016 and classified them according to the ocean, ecoregion, human threat, level of biological organization, study approach, method of data collection, depth of data collected, and type of coral response. Most studies were carried out in the Indo-Pacific and Caribbean (36.3 and 31.9%, respectively) and used observational approach (60%) with scuba diving (36.3%) to assess the impact of ocean warming (55.4%) on coral communities (58.2%). Only 37 of the 141 global ecoregions that contain coral reefs were studied. All studies were restricted to shallow waters (0.5-27 m depth) and reported negative responses of corals to human disturbance. Our results reinforce the notion that corals are sensitive to anthropogenic changes. They reveal the scarcity of information on coral responses to pollution, tourism, overfishing and acidification, particularly in mesophotic ecosystems (>30 m depth) and in ecoregions outside the Indo-Pacific and Caribbean. Experimental studies at the individual and population levels should be also encouraged.
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Affiliation(s)
- Juliano Morais
- Programa de Pós-Graduação em Ciências Biológicas, Universidade Federal da Paraíba, Cidade Universitária, Castelo Branco, 58051-900, João Pessoa, PB, Brazil
| | - Aline P M Medeiros
- Programa de Pós-Graduação em Ciências Biológicas, Universidade Federal da Paraíba, Cidade Universitária, Castelo Branco, 58051-900, João Pessoa, PB, Brazil
| | - Bráulio A Santos
- Universidade Federal da Paraíba, Centro de Ciências Exatas e da Natureza, Departamento de Sistemática e Ecologia, Cidade Universitária, Castelo Branco, 58051-900, João Pessoa, PB, Brazil.
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12
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Carturan BS, Parrott L, Pither J. A modified trait‐based framework for assessing the resilience of ecosystem services provided by coral reef communities. Ecosphere 2018. [DOI: 10.1002/ecs2.2214] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Affiliation(s)
- Bruno S. Carturan
- Department of Biology University of British Columbia Okanagan Campus, 1177 Research Road Kelowna British Columbia V1V 1V7 Canada
- Institute for Biodiversity, Resilience, and Ecosystem Services University of British Columbia Okanagan Campus, 1177 Research Road Kelowna British Columbia V1V 1V7 Canada
| | - Lael Parrott
- Department of Biology University of British Columbia Okanagan Campus, 1177 Research Road Kelowna British Columbia V1V 1V7 Canada
- Institute for Biodiversity, Resilience, and Ecosystem Services University of British Columbia Okanagan Campus, 1177 Research Road Kelowna British Columbia V1V 1V7 Canada
- Department of Earth, Environmental and Geographic Sciences University of British Columbia Okanagan Campus, 1177 Research Road Kelowna British Columbia V1V 1V7 Canada
| | - Jason Pither
- Department of Biology University of British Columbia Okanagan Campus, 1177 Research Road Kelowna British Columbia V1V 1V7 Canada
- Institute for Biodiversity, Resilience, and Ecosystem Services University of British Columbia Okanagan Campus, 1177 Research Road Kelowna British Columbia V1V 1V7 Canada
- Department of Earth, Environmental and Geographic Sciences University of British Columbia Okanagan Campus, 1177 Research Road Kelowna British Columbia V1V 1V7 Canada
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13
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Smith H, Epstein H, Torda G. The molecular basis of differential morphology and bleaching thresholds in two morphs of the coral Pocillopora acuta. Sci Rep 2017; 7:10066. [PMID: 28855618 PMCID: PMC5577224 DOI: 10.1038/s41598-017-10560-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2017] [Accepted: 08/10/2017] [Indexed: 11/24/2022] Open
Abstract
Processes of cnidarian evolution, including hybridization and phenotypic plasticity, have complicated the clear diagnosis of species boundaries within the phylum. Pocillopora acuta, a species of scleractinian coral that was recently split from the widespread Pocillopora damicornis species complex, occurs in at least two distinct morphs on the Great Barrier Reef. Contrasting morphology combined with evidence of differential bleaching thresholds among sympatrically distributed colonies suggest that the taxonomy of this recently described species is not fully resolved and may represent its own species complex. To examine the basis of sympatric differentiation between the two morphs, we combined analyses of micro- and macro-skeletal morphology with genome wide sequencing of the coral host, as well as ITS2 genotyping of the associated Symbiodinium communities. We found consistent differences between morphs on both the macro- and micro-skeletal scale. In addition, we identified 18 candidate functional genes that relate to skeletal formation and morphology that may explain how the two morphs regulate growth to achieve their distinct growth forms. With inconclusive results in endosymbiotic algal community diversity between the two morphs, we propose that colony morphology may be linked to bleaching susceptibility. We conclude that cryptic speciation may be in the early stages within the species P. acuta.
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Affiliation(s)
- Hillary Smith
- ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, Queensland 4811, Australia. .,Australian Institute of Marine Science, PMB 3, Townsville, Queensland 4810, Australia. .,College of Science and Engineering, James Cook University, Townsville, Queensland 4811, Australia. .,AIMS@JCU, James Cook University, Townsville, Queensland 4811, Australia.
| | - Hannah Epstein
- ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, Queensland 4811, Australia.,Australian Institute of Marine Science, PMB 3, Townsville, Queensland 4810, Australia.,College of Science and Engineering, James Cook University, Townsville, Queensland 4811, Australia.,AIMS@JCU, James Cook University, Townsville, Queensland 4811, Australia
| | - Gergely Torda
- ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, Queensland 4811, Australia.,Australian Institute of Marine Science, PMB 3, Townsville, Queensland 4810, Australia
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14
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Swain TD, DuBois E, Goldberg SJ, Backman V, Marcelino LA. Bleaching response of coral species in the context of assemblage response. CORAL REEFS (ONLINE) 2017; 36:395-400. [PMID: 29129968 PMCID: PMC5679474 DOI: 10.1007/s00338-017-1550-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/27/2023]
Abstract
Caribbean coral reefs are declining due to a mosaic of local and global stresses, including climate change-induced thermal stress. Species and assemblage responses differ due to factors that are not easily identifiable or quantifiable. We calculated a novel species-specific metric of coral bleaching response, taxon-α and -β, which relates the response of a species to that of its assemblages for 16 species over 18 assemblages. By contextualizing species responses within the response of their assemblages, the effects of environmental factors are removed and intrinsic differences among taxa are revealed. Most corals experience either a saturation response, overly-sensitive to weak stress (α > 0) but under-responsive compared to assemblage bleaching (β < 1), or a threshold response, insensitive to weak stress (α < 0) but over-responsive compared to assemblage bleaching (β > 1). This metric may help reveal key factors of bleaching susceptibility and identify species as targets for conservation.
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Affiliation(s)
- Timothy D. Swain
- Department of Civil and Environmental Engineering, Northwestern University, 2145 Sheridan Road, Evanston, Illinois, 60208, USA
- Integrative Research Center, Field Museum of Natural History, 1400 South Lake Shore Drive, Chicago, Illinois, 60605, USA
| | - Emily DuBois
- Department of Civil and Environmental Engineering, Northwestern University, 2145 Sheridan Road, Evanston, Illinois, 60208, USA
| | - Scott J. Goldberg
- Department of Civil and Environmental Engineering, Northwestern University, 2145 Sheridan Road, Evanston, Illinois, 60208, USA
| | - Vadim Backman
- Department of Biomedical Engineering, Northwestern University, 2145 Sheridan Road, Evanston, Illinois, 60208, USA
| | - Luisa A. Marcelino
- Department of Civil and Environmental Engineering, Northwestern University, 2145 Sheridan Road, Evanston, Illinois, 60208, USA
- Integrative Research Center, Field Museum of Natural History, 1400 South Lake Shore Drive, Chicago, Illinois, 60605, USA
- Corresponding author: Luisa Marcelino, Phone: (847) 491-4035, Fax: (847) 491-4011,
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15
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Wangpraseurt D, Wentzel C, Jacques SL, Wagner M, Kühl M. In vivo imaging of coral tissue and skeleton with optical coherence tomography. J R Soc Interface 2017; 14:20161003. [PMID: 28250104 PMCID: PMC5378135 DOI: 10.1098/rsif.2016.1003] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2016] [Accepted: 02/01/2017] [Indexed: 11/12/2022] Open
Abstract
Application of optical coherence tomography (OCT) for in vivo imaging of tissue and skeleton structure of intact living corals enabled the non-invasive visualization of coral tissue layers (endoderm versus ectoderm), skeletal cavities and special structures such as mesenterial filaments and mucus release from intact living corals. Coral host chromatophores containing green fluorescent protein-like pigment granules appeared hyper-reflective to near-infrared radiation allowing for excellent optical contrast in OCT and a rapid characterization of chromatophore size, distribution and abundance. In vivo tissue plasticity could be quantified by the linear contraction velocity of coral tissues upon illumination resulting in dynamic changes in the live coral tissue surface area, which varied by a factor of 2 between the contracted and expanded state of a coral. Our study provides a novel view on the in vivo organization of coral tissue and skeleton and highlights the importance of microstructural dynamics for coral ecophysiology.
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Affiliation(s)
- Daniel Wangpraseurt
- Marine Biological Section, Department of Biology, University of Copenhagen, Strandpromenaden 5, Helsingør 3000, Denmark
| | - Camilla Wentzel
- Marine Biological Section, Department of Biology, University of Copenhagen, Strandpromenaden 5, Helsingør 3000, Denmark
| | - Steven L Jacques
- Department of Biomedical Engineering, Oregon Health and Science University, 3303 SW Bond Avenue, Portland, OR 97239, USA
| | - Michael Wagner
- Engler-Bunte Institute, Chair of Water Chemistry and Water Technology, Karlsruhe Institute of Technology, Engler-Bunte-Ring 1, 76131 Karlsruhe, Germany
| | - Michael Kühl
- Marine Biological Section, Department of Biology, University of Copenhagen, Strandpromenaden 5, Helsingør 3000, Denmark
- Climate Change Cluster, University of Technology Sydney, PO Box 123, Broadway, Sydney, New South Wales 2007, Australia
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16
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Wangpraseurt D, Holm JB, Larkum AWD, Pernice M, Ralph PJ, Suggett DJ, Kühl M. In vivo Microscale Measurements of Light and Photosynthesis during Coral Bleaching: Evidence for the Optical Feedback Loop? Front Microbiol 2017; 8:59. [PMID: 28174567 PMCID: PMC5258690 DOI: 10.3389/fmicb.2017.00059] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2016] [Accepted: 01/09/2017] [Indexed: 12/21/2022] Open
Abstract
Climate change-related coral bleaching, i.e., the visible loss of zooxanthellae from the coral host, is increasing in frequency and extent and presents a major threat to coral reefs globally. Coral bleaching has been proposed to involve accelerating light stress of their microalgal endosymbionts via a positive feedback loop of photodamage, symbiont expulsion and excess in vivo light exposure. To test this hypothesis, we used light and O2 microsensors to characterize in vivo light exposure and photosynthesis of Symbiodinium during a thermal stress experiment. We created tissue areas with different densities of Symbiodinium cells in order to understand the optical properties and light microenvironment of corals during bleaching. Our results showed that in bleached Pocillopora damicornis corals, Symbiodinium light exposure was up to fivefold enhanced relative to healthy corals, and the relationship between symbiont loss and light enhancement was well-described by a power-law function. Cell-specific rates of Symbiodinium gross photosynthesis and light respiration were enhanced in bleached P. damicornis compared to healthy corals, while areal rates of net photosynthesis decreased. Symbiodinium light exposure in Favites sp. revealed the presence of low light microniches in bleached coral tissues, suggesting that light scattering in thick coral tissues can enable photoprotection of cryptic symbionts. Our study provides evidence for the acceleration of in vivo light exposure during coral bleaching but this optical feedback mechanism differs between coral hosts. Enhanced photosynthesis in relation to accelerating light exposure shows that coral microscale optics exerts a key role on coral photophysiology and the subsequent degree of radiative stress during coral bleaching.
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Affiliation(s)
- Daniel Wangpraseurt
- Marine Biological Section, Department of Biology, University of CopenhagenHelsingør, Denmark; Climate Change Cluster, Department of Environmental Sciences, University of Sydney, SydneyNSW, Australia
| | - Jacob B Holm
- Marine Biological Section, Department of Biology, University of Copenhagen Helsingør, Denmark
| | - Anthony W D Larkum
- Climate Change Cluster, Department of Environmental Sciences, University of Sydney, Sydney NSW, Australia
| | - Mathieu Pernice
- Climate Change Cluster, Department of Environmental Sciences, University of Sydney, Sydney NSW, Australia
| | - Peter J Ralph
- Climate Change Cluster, Department of Environmental Sciences, University of Sydney, Sydney NSW, Australia
| | - David J Suggett
- Climate Change Cluster, Department of Environmental Sciences, University of Sydney, Sydney NSW, Australia
| | - Michael Kühl
- Marine Biological Section, Department of Biology, University of CopenhagenHelsingør, Denmark; Climate Change Cluster, Department of Environmental Sciences, University of Sydney, SydneyNSW, Australia
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