scholarly journals Photosynthesis and Bio-Optical Properties of Fluorescent Mesophotic Corals

2021 ◽  
Vol 8 ◽  
Author(s):  
Or Ben-Zvi ◽  
Daniel Wangpraseurt ◽  
Omri Bronstein ◽  
Gal Eyal ◽  
Yossi Loya
Keyword(s):  
Optical Properties ◽  
Fluorescent Proteins ◽  
Light Attenuation ◽  
Coral Tissue ◽  
Coral Host ◽  
Natural Habitats ◽  
Algal Symbionts ◽  
Light Quantity ◽  
Photosynthetic Performances ◽  
The Relationship

Mesophotic coral ecosystems (MCEs) are light-dependent coral-associated communities found at 30–150 m depth. Corals inhabiting these deeper reefs are often acclimatized to a limited and blue-shifted light environment, enabling them to maintain the relationship with their photosynthetic algal symbionts (family Symbiodiniaceae) despite the seemingly suboptimal light conditions. Among others, fluorescent proteins produced by the coral host may play a role in the modulation of the quality and spectral distribution of irradiance within the coral tissue through wavelength transformation. Here we examined the bio-optical properties and photosynthetic performances of different fluorescence morphs of two mesophotic coral species Goniopora minor and Alveopora ocellata, in order to test the photosynthesis enhancement hypothesis proposed for coral fluorescence. The green morph of G. minor and the low fluorescence morph of A. ocellata exhibit, in their natural habitats, higher abundance. The morphs also presented different spectral reflectance and light attenuation within the tissue. Nevertheless, chlorophyll a fluorescence-based, and O2 evolution measurements, revealed only minor differences between the photosynthetic abilities of three fluorescence morphs of the coral G. minor and two fluorescence morphs of A. ocellata. The fluorescence morphs did not differ in their algal densities or chlorophyll concentrations and all corals harbored Symbiodiniaceae from the genus Cladocopium. Thus, despite the change in the internal light quantity and quality that corals and their symbionts experience, we found no evidence for the facilitation or enhancement of photosynthesis by wavelength transformation.

scholarly journals Measuring light scattering and absorption in corals with Inverse Spectroscopic Optical Coherence Tomography (ISOCT): a new tool for non-invasive monitoring

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
G. L. C. Spicer ◽  
A. Eid ◽  
D. Wangpraseurt ◽  
T. D. Swain ◽  
J. A. Winkelmann ◽  
...  
Keyword(s):  
Optical Coherence Tomography ◽  
Optical Properties ◽  
Light Scattering ◽  
Light Propagation ◽  
Coral Tissue ◽  
Coral Host ◽  
Invasive Monitoring ◽  
Optical Coherence ◽  
Invasive Approach ◽  
Non Invasive

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.

Optical Properties of Water Body in Xiaojiang River Backwater Area, Three Gorges Reservoir, 2008

2010 ◽  
Vol 113-116 ◽  
pp. 840-846
Author(s):  
Fang Fang ◽  
Hong Zhou ◽  
Jing Song Guo ◽  
Zhe Li ◽  
Yong Bo Chen ◽  
...  
Keyword(s):  
Optical Properties ◽  
Water Body ◽  
Three Gorges Reservoir ◽  
Light Attenuation ◽  
Particulate Matters ◽  
Three Gorges ◽  
Strong Correlations ◽  
Secchi Disc ◽  
The Impact ◽  
The Relationship

To discuss optical properties of water body in Xiaojiang river backwater area after the early impounding stage of the Three Gorges Reservoir (TGR), the correlations between visible light attenuation coefficients (Kd(PAR)) and Secchi Disc transparency (SD), total particulate matters (TPM), dissolved organic carbon (DOC) and chlorophyll-a (Chla) were investigated, and spatiotemporal variations of Kd(PAR) and its influencing factors were analyzed. In the study area, there are no significant spatial variations of Kd(PAR), but the seasonal changes are obvious, with the highest value in winter and the lowest value in summer. Statistics analysis suggests that there are strong correlations between Kd(PAR) and SD, TPM, TIM, the value of R2 are 0.7791, 0.7285, and 0.7637, respectively. The relationship between Kd(PAR) and DOC is less significant(R2=0.1289). However, the correlation between Kd(PAR) and Chla was weak (R2=0.006). Further study shows that, the impact of total particulate matters on the optical properties of water body is as a result of both seasonal impoundment of the TGR and particular hydrological condition of Xiaojiang river basin.

Optical properties of Gas-vacuolate cells and colonies of Microcystis in relation to light Attenuation in a Turbid, Stratified Reservoir (Mount Bold Reservoir, South Australia)

1989 ◽  
Vol 40 (6) ◽  
pp. 595 ◽  
Author(s):  
GG Ganf ◽  
RL Oliver ◽  
AE Walsby
Keyword(s):  
Optical Properties ◽  
Light Attenuation ◽  
Significant Proportion ◽  
Spectral Composition ◽  
General Rule ◽  
Slight Modification ◽  
Scattering Coefficient ◽  
Inherent Optical Properties ◽  
Gas Vacuoles ◽  
The Relationship

Profiles of downwelling and upwelling irradiance were measured in a stratified, turbid reservoir, when Microcystis aeruginosa formed a significant proportion of the phytoplankton community. The attenuation coefficient (Kd) was c. 2.1 m-1 and the reflectance (R) c. 0.03. Application of Kirk's simulation model relating apparent and inherent optical properties enabled calculation of coefficients of absorption (a; 1.3-1.6 m-') and scattering (6; 5-7 m-1). The asymptotic diffuse backscattering coefficient (0.2 m-1) was derived from the relationship b′b = 3.6 RaKd, a slight modification of Kirk's original equation. Turbidity measurements supported the general rule that nephelometric turbidity was numerically equivalent to the scattering coefficient. There was good agreement between the measured light profile and one reconstructed from inherent optical properties using the relationship between Kd, a and b. The optical properties of cells and colonies of Microcystis were investigated before and after the collapse of gas vacuoles. The Chla-specific absorption coefficient for cells (0.0138 m2 mg,-1 Chla) was higher than for colonies (0.0106 m2 mg,-1 Chla) at a depth equivalent to 0.2 m. Both coefficients decreased with increasing depth as the spectral composition changed. The Chla-specific scattering coefficient for vacuolate cells (0.14 m2 mg,-1 Chla) was greater than for colonies (0.11 m2 mg,-1 Chla), and a similar correspondence occurred for non-vacuolate cells and colonies (0.029 and 0.020 m2 mg,-1 Chla respectively). These measurements illustrate the package effect and also that c. 80% of light scattering is due to gas vacuoles. The relationship between pressure-sensitive turbidity and gas-vacuole volume suggested that 1 gL mL-1 was equivalent to a turbidity of 2 NTU. These optical characteristics, combined with the buoyant nature of Microcystis, suggest that it is a canopy species.

scholarly journals Multiphysics modelling of photon, mass and heat transfer in coral microenvironments

2021 ◽  
Vol 18 (182) ◽  
pp. 20210532
Author(s):  
Shannara Kayleigh Taylor Parkins ◽  
Swathi Murthy ◽  
Cristian Picioreanu ◽  
Michael Kühl
Keyword(s):  
Optical Properties ◽  
Heat Dissipation ◽  
Three Dimensional ◽  
Chemical Species ◽  
Basic Structure ◽  
Photon Absorption ◽  
Coral Tissue ◽  
Coral Host ◽  
Tissue Contraction ◽  
Multiphysics Modelling

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 O 2 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.

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

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

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

scholarly journals Physiological and ecological consequences of the water optical properties degradation on reef corals

Coral Reefs ◽  
2021 ◽  
Author(s):  
Tomás López-Londoño ◽  
Claudia T. Galindo-Martínez ◽  
Kelly Gómez-Campo ◽  
Luis A. González-Guerrero ◽  
Sofia Roitman ◽  
...  
Keyword(s):  
Optical Properties ◽  
Population Decline ◽  
Light Availability ◽  
Potential Effect ◽  
Optical Quality ◽  
Light Penetration ◽  
Reef Corals ◽  
Orbicella Faveolata ◽  
Light Quantity ◽  
Reduced Light

AbstractDegradation of water optical properties due to anthropogenic disturbances is a common phenomenon in coastal waters globally. Although this condition is associated with multiple drivers that affect corals health in multiple ways, its effect on light availability and photosynthetic energy acquisition has been largely neglected. Here, we describe how declining the water optical quality in a coastal reef exposed to a turbid plume of water originating from a man-made channel compromises the functionality of the keystone coral species Orbicella faveolata. We found highly variable water optical conditions with significant effects on the light quantity and quality available for corals. Low-light phenotypes close to theoretical limits of photoacclimation were found at shallow depths as a result of reduced light penetration. The estimated photosynthetically fixed energy depletion with increasing depth was associated with patterns of colony mortality and vertical habitat compression. A numerical model illustrates the potential effect of the progressive water quality degradation on coral mortality and population decline along the depth gradient. Collectively, our findings suggest that preserving the water properties seeking to maximize light penetration through the water column is essential for maintaining the coral reef structure and associated ecosystem services.

scholarly journals Changes in Optical Properties upon Dye–Clay Interaction: Experimental Evaluation and Applications

Nanomaterials ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 197
Author(s):  
Giorgia Giovannini ◽  
René M. Rossi ◽  
Luciano F. Boesel
Keyword(s):  
Optical Properties ◽  
Hybrid Materials ◽  
High Performance ◽  
Fluorescent Properties ◽  
Chemical Mechanisms ◽  
Strong Electrostatic Interaction ◽  
Potential Applications ◽  
Photochemical Properties ◽  
Physical And Chemical ◽  
The Relationship

The development of hybrid materials with unique optical properties has been a challenge for the creation of high-performance composites. The improved photophysical and photochemical properties observed when fluorophores interact with clay minerals, as well as the accessibility and easy handling of such natural materials, make these nanocomposites attractive for designing novel optical hybrid materials. Here, we present a method of promoting this interaction by conjugating dyes with chitosan. The fluorescent properties of conjugated dye–montmorillonite (MMT) hybrids were similar to those of free dye–MMT hybrids. Moreover, we analyzed the relationship between the changes in optical properties of the dye interacting with clay and its structure and defined the physical and chemical mechanisms that take place upon dye–MMT interactions leading to the optical changes. Conjugation to chitosan additionally ensures stable adsorption on clay nanoplatelets due to the strong electrostatic interaction between chitosan and clay. This work thus provides a method to facilitate the design of solid-state hybrid nanomaterials relevant for potential applications in bioimaging, sensing and optical purposes.

scholarly journals Spectral optical properties of long-range transport Asian dust and pollution aerosols over Northeast Asia in 2007 and 2008

2010 ◽  
Vol 10 (12) ◽  
pp. 5391-5408 ◽  
Author(s):  
J. Jung ◽  
Y. J. Kim ◽  
K. Y. Lee ◽  
M. G. -Cayetano ◽  
T. Batmunkh ◽  
...  
Keyword(s):  
Optical Properties ◽  
Long Range ◽  
Atmospheric Chemistry ◽  
Light Attenuation ◽  
Measurement Data ◽  
Absorption Efficiency ◽  
Asian Dust ◽  
Urban Site ◽  
Long Range Transport ◽  
Range Transport

Abstract. As a part of the IGAC (International Global Atmospheric Chemistry) Mega-cities program, aerosol physical and optical properties were continuously measured from March 2007 to March 2008 at an urban site (37.57° N, 126.94° E) in Seoul, Korea. Spectral optical properties of long-range transported Asian dust and pollution aerosols have been investigated based on the year long measurement data. Optically measured black carbon/thermally measured elemental carbon (BC/EC) ratio showed clear monthly variation with high values in summer and low values in winter mainly due to the enhancement of light attenuation by the internal mixing of EC. Novel approach has been suggested to retrieve the spectral light absorption coefficient (babs) from Aethalometer raw data by using BC/EC ratio. Mass absorption efficiency, σabs (=babs/EC) at 550 nm was determined to be 9.0±1.3, 8.9±1.5, 9.5±2.0, and 10.3±1.7 m2 g−1 in spring, summer, fall, and winter, respectively with an annual mean of 9.4±1.8 m2 g−1. Threshold values to classify severe haze events were suggested in this study. Increasing trend of aerosol single scattering albedo (SSA) with wavelength was observed during Asian dust events while little spectral dependence of SSA was observed during long-range transport pollution (LTP) events. Satellite aerosol optical thickness (AOT) and Hysplit air mass backward trajectory analyses as well as chemical analysis were performed to characterize the dependence of spectral optical properties on aerosol type. Results from this study can provide useful information for studies on regional air quality and aerosol's effects on climate change.

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