scholarly journals Bio-optical properties and radiative energy budgets in fed and starved scleractinian corals (Pocillopora damicornis) during thermal bleaching

2018 ◽  
Author(s):  
Niclas Heidelberg Lyndby ◽  
Jacob Boiesen Holm ◽  
Daniel Wangpraseurt ◽  
Christine Ferrier-Pagès ◽  
Michael Kühl
Keyword(s):  
Energy Efficiency ◽  
Thermal Stress ◽  
Photosynthetic Efficiency ◽  
Light Exposure ◽  
Radiative Energy ◽  
Energy Budgets ◽  
Pocillopora Damicornis ◽  
Thermal Bleaching ◽  
Active Feeding ◽  
Coral Health

AbstractCorals achieve outstanding photosynthetic quantum efficiencies approaching theoretical limits (i.e. 0.125 O2 photon-1) and it is unknown how such photosynthetic efficiency varies with environmental stress. In this study, we investigated the combined effects of thermal stress and active feeding on the radiative energy budget and photosynthetic efficiency of the symbiont-bearing coral Pocillopora damicornis by using fiber-optic and electrochemical microsensors in combination with variable chlorophyll fluorescence imaging. At normal temperature (25°C), the percentage of absorbed light energy used for photosynthesis was higher for fed (~5-6% under low light exposure) compared to unfed corals (4%). Corals from both feeding treatments responded equally to stress from high light exposure (2400 μmol photons m-2 s-1), exhibiting a decrease in photosynthetic energy efficiency down to 0.5-0.6%. Fed corals showed increased resilience against thermal bleaching compared to unfed corals, as fed corals were able to uphold their high photosynthetic energy efficiency for 5 days longer during thermal stress, as compared to unfed corals, which decreased their photosynthetic energy efficiency almost immediately when exposed to thermal stress. We conclude that active feeding is beneficial to corals by prolonging coral health and resilience during thermal stress as a result of an overall healthier symbiont population.

scholarly journals Radiative energy budgets of phototrophic surface-associated microbial communities and their photosynthetic efficiency under diffuse and collimated light

2017 ◽  
Author(s):  
Mads Lichtenberg ◽  
Kasper Elgetti Brodersen ◽  
Michael Kühl
Keyword(s):  
Energy Conservation ◽  
Photosynthetic Efficiency ◽  
Heat Dissipation ◽  
Incident Light ◽  
Energy Conversion Efficiency ◽  
Light Energy ◽  
Radiative Energy ◽  
Energy Budgets ◽  
Gross Photosynthesis ◽  
Light Regimes

AbstractWe investigated the radiative energy budgets of a heterogeneous photosynthetic coral reef sediment and a compact uniform cyanobacterial biofilm on top of coastal sediment. By combining electrochemical, thermocouple and fiber-optic microsensor measurements of O2, temperature and light, we could calculate the proportion of the absorbed light energy that was either dissipated as heat or conserved by photosynthesis. We show, across a range of different incident light regimes, that such radiative energy budgets are highly dominated by heat dissipation constituting up to 99.5% of the absorbed light energy. Highest photosynthetic energy conservation efficiency was found in the coral sediment under light-limiting conditions and amounted to ~13% of the absorbed light energy. Additionally, the effect of light directionality, i.e., diffuse or collimated light, on energy conversion efficiency was tested on the two surface-associated systems. The effects of light directionality on the radiative energy budgets of these phototrophic communities were not unanimous but, resulted in local spatial differences in heat-transfer, gross photosynthesis and light distribution. The light acclimation index, Ekwas >2 times higher in the coral sediment compared to the biofilm and changed the pattern of photosynthetic energy conservation under light-limiting conditions. At moderate to high incident 45 irradiances, the photosynthetic conservation of absorbed energy was highest in collimated light; a tendency that changed in the biofilm under sub-saturating incident irradiances, where higher photosynthetic efficiencies were observed under diffuse light. Our results suggest that the optical properties and the structural organization of phytoelements are important traits affecting the photosynthetic efficiency of biofilms and sediments.

scholarly journals Thermal stress reduces pocilloporid coral resilience to ocean acidification by impairing control over calcifying fluid chemistry

2021 ◽  
Vol 7 (2) ◽  
pp. eaba9958
Author(s):  
Maxence Guillermic ◽  
Louise P. Cameron ◽  
Ilian De Corte ◽  
Sambuddha Misra ◽  
Jelle Bijma ◽  
...  
Keyword(s):  
Thermal Stress ◽  
Ocean Acidification ◽  
Pocillopora Damicornis ◽  
Carbonate Chemistry ◽  
Negative Interaction ◽  
Saturation State ◽  
Stylophora Pistillata ◽  
Coral Calcification ◽  
Influence Of Temperature On ◽  
Different Time Scales

The combination of thermal stress and ocean acidification (OA) can more negatively affect coral calcification than an individual stressors, but the mechanism behind this interaction is unknown. We used two independent methods (microelectrode and boron geochemistry) to measure calcifying fluid pH (pHcf) and carbonate chemistry of the corals Pocillopora damicornis and Stylophora pistillata grown under various temperature and pCO2 conditions. Although these approaches demonstrate that they record pHcf over different time scales, they reveal that both species can cope with OA under optimal temperatures (28°C) by elevating pHcf and aragonite saturation state (Ωcf) in support of calcification. At 31°C, neither species elevated these parameters as they did at 28°C and, likewise, could not maintain substantially positive calcification rates under any pH treatment. These results reveal a previously uncharacterized influence of temperature on coral pHcf regulation—the apparent mechanism behind the negative interaction between thermal stress and OA on coral calcification.

scholarly journals Long-term changes in the susceptibility of corals to thermal stress around Phuket, Thailand

2017 ◽  
Author(s):  
Lalita Putchim ◽  
Niphon Phongsuwan ◽  
Chaimongkol Yaemarunpattana ◽  
Nalinee Thongtham ◽  
Claudio Richter
Keyword(s):  
Thermal Stress ◽  
Life History Traits ◽  
Sea Water ◽  
Species Level ◽  
Pocillopora Damicornis ◽  
Rapid Adaptation ◽  
Long Term Changes ◽  
Belt Transect ◽  
Line Intercept

The bleaching susceptibility of 28 coral taxa around southern Phuket was examined in four natural major bleaching events, in 1991, 1995, 2010, and 2016. Surveys were conducted by line intercept and belt transect methods. All coral colonies were identified to genus or species-level and their pigmentation status was assessed as: (1) fully pigmented (i.e. no bleaching), (2) pale (loss of colour), (3) fully bleached, and (4) recently dead as a result of bleaching-induced mortality. Bleaching and mortality indices were calculated to compare bleaching susceptibility among coral taxa. In 2016 some of the formerly bleaching susceptible coral taxa (e.g. Acropora, Montipora, Echinopora, and Pocillopora damicornis) showed far greater tolerance to elevated sea water temperature than in previous years. In P. damicornis the higher bleaching resistance encompassed all sizes from juveniles (<5cm) to adults (>30cm). In contrast, some of the formerly bleaching-resistant corals (e.g. the massive Porites, Goniastrea, Dipsastraea, and Favites) became more susceptible to bleaching over repeated thermal stress events. Our results support the hypothesis that some of the fast-growing branching corals (Acropora, Montipora, and Pocillopora) may have life-history traits that lead to more rapid adaptation to a changed environment than certain growing massive species.

scholarly journals The Global Radiative Energy Budget in MERRA and MERRA-2: Evaluation with Respect to CERES EBAF Data

2019 ◽  
Vol 32 (6) ◽  
pp. 1973-1994 ◽  
Author(s):  
Laura M. Hinkelman
Keyword(s):  
Radiative Energy ◽  
Energy Budgets ◽  
Polar Regions ◽  
Marine Stratocumulus ◽  
Radiative Fluxes ◽  
Clear Sky ◽  
Tropical Oceans ◽  
Net Flux ◽  
Errors Analysis

The representation of the long-term radiative energy budgets in NASA’s MERRA and MERRA-2 reanalyses has been evaluated, emphasizing changes associated with the reanalysis system update. Data from the CERES EBAF Edition 2.8 satellite product over 2001–15 were used as a reference. For both MERRA and MERRA-2, the climatological global means of most TOA radiative flux terms agree to within ~3 W m−2 of EBAF. However, MERRA-2’s all-sky reflected shortwave flux is ~7 W m−2 higher than either MERRA or EBAF’s, resulting in a net TOA flux imbalance of −4 W m−2. At the surface, all-sky downward longwave fluxes are problematic for both reanalyses, while high clear-sky downward shortwave fluxes indicate that their atmospheres are too transmissive. Although MERRA-2’s individual all-sky flux terms agree better with EBAF, its net flux agreement is worse (−8.3 vs −3.3 W m−2 for MERRA) because MERRA benefits from cancellation of errors. Analysis by region and surface type gives mixed outcomes. The results consistently indicate that clouds are overrepresented over the tropical oceans in both reanalyses, particularly MERRA-2, and somewhat underrepresented in marine stratocumulus areas. MERRA-2 also exhibits signs of excess cloudiness in the Southern Ocean. Notable discrepancies occur in the polar regions, where the effects of snow and ice cover are important. In most cases, MERRA-2 better represents variability and trends in the global mean radiative fluxes over the period of analysis. Overall, the performance of MERRA-2 relative to MERRA is mixed; there is still room for improvement in the radiative fluxes in this family of reanalysis products.

Effect of Temperature on Photoinhibition and Recovery in Actinidia deliciosa

1988 ◽  
Vol 15 (2) ◽  
pp. 195 ◽  
Author(s):  
DH Greer
Keyword(s):  
Light Exposure ◽  
Photochemical Reactions ◽  
High Light ◽  
Actinidia Deliciosa ◽  
Radiative Energy ◽  
Effect Of Temperature ◽  
Photoinhibition Of Photosynthesis ◽  
Temperature Dependent ◽  
Protection Mechanism ◽  
Kinetics Of

Photoinhibition of photosynthesis was induced in intact leaves of kiwifruit (Actinidia deliciosa) grown in natural light not exceeding a photon irradiance (PI) of 300 �mol m-2 s-1 by exposing them to a PI of 1500 �mol m-2 s-1. The temperature was held constant during the high-light exposure between 5 and 35°C. Recovery was followed at temperatures between 10 and 35°C, after photoinhibition was induced by a 240 min exposure to high light. The kinetics of photoinhibition and recovery were followed by chlorophyll fluorescence at 692 nm and 77K. Photoinhibition occurred at all temperatures but was greatest at low temperatures. Temperature affected the severity of photoinhibitory damage but not the kinetics of photoinhibition. Recovery was also temperature-dependent with little or no recovery occurring below about 20°C and rapid recovery at 30-35°C. The extent of photoinhibition also affected the rates of recovery which were reduced as the severity of photoinhibition increased. An analysis of the rate constants for energy transfer within photosystem II indicated that kiwifruit leaves have some capacity to prevent photoinhibition by increasing the amount of non-radiative energy dissipation. However, the analysis also indicates that this protection mechanism was not wholly effective since the primary photochemical reactions apparently become inactivated during exposure of these leaves to high light.

scholarly journals Radiative energy budget reveals high photosynthetic efficiency in symbiont-bearing corals

2014 ◽  
Vol 11 (93) ◽  
pp. 20130997 ◽  
Author(s):  
Kasper Elgetti Brodersen ◽  
Mads Lichtenberg ◽  
Peter J. Ralph ◽  
Michael Kühl ◽  
Daniel Wangpraseurt
Keyword(s):  
Energy Budget ◽  
Photosynthetic Efficiency ◽  
Light Field ◽  
Heat Dissipation ◽  
Spectral Composition ◽  
Light Energy ◽  
Low Energy ◽  
Radiative Energy ◽  
Gross Photosynthesis ◽  
Light Utilization

The light field on coral reefs varies in intensity and spectral composition, and is the key regulating factor for phototrophic reef organisms, for example scleractinian corals harbouring microalgal symbionts. However, the actual efficiency of light utilization in corals and the mechanisms affecting the radiative energy budget of corals are underexplored. We present the first balanced light energy budget for a symbiont-bearing coral based on a fine-scale study of the microenvironmental photobiology of the massive coral Montastrea curta . The majority (more than 96%) of the absorbed light energy was dissipated as heat, whereas the proportion of the absorbed light energy used in photosynthesis was approximately 4.0% under an irradiance of 640 µmol photons m −2 s −1 . With increasing irradiance, the proportion of heat dissipation increased at the expense of photosynthesis. Despite such low energy efficiency, we found a high photosynthetic efficiency of the microalgal symbionts showing high gross photosynthesis rates and quantum efficiencies (QEs) of approximately 0.1 O 2 photon −1 approaching theoretical limits under moderate irradiance levels. Corals thus appear as highly efficient light collectors with optical properties enabling light distribution over the corallite/tissue microstructural canopy that enables a high photosynthetic QE of their photosynthetic microalgae in hospite .

scholarly journals Effect of feeding and thermal stress on photosynthesis, respiration and the carbon budget of the scleractinian coral Pocillopora damicornis

2018 ◽  
Author(s):  
Niclas Heidelberg Lyndby ◽  
Jacob Boiesen Holm ◽  
Daniel Wangpraseurt ◽  
Renaud Grover ◽  
Cécile Rottier ◽  
...  
Keyword(s):  
Thermal Stress ◽  
High Temperature ◽  
Carbon Budget ◽  
Limiting Factor ◽  
Coral Host ◽  
Symbiotic Association ◽  
Pocillopora Damicornis ◽  
Fixed Carbon ◽  
Heterogeneous Distribution ◽  
Macro Scale

AbstractStudying carbon dynamics in the coral holobiont provides essential knowledge of nutritional strategies and is thus central to understanding coral ecophysiology. In this study, the first aim was to investigate the effect of daily feeding and thermal stress on oxygen (O2) rates measured at polyp-scale with microsensors and at whole fragment scale using incubation methods. The second aim was to assess the carbon budget of the symbiotic association using H13CO3, under the different conditions. Micro- and macro-scale measurements revealed enhanced O2 evolution rates for fed compared to unfed corals. However, gross O2 production in fed corals was increased at high temperature on a macroscale but not on a microscale basis, likely due to a heterogeneous distribution of photosynthesis over the coral surface. Starved corals always exhibited reduced photosynthetic activity at high temperature, which suggests that the nutritional status of the coral host is a key limiting factor for coral productivity under thermal stress. Quantification of photosynthate translocation and carbon budgets showed very low incorporation rates, for both symbionts and host (0.03 - 0.6 μg C cm-2 h-1) equivalent to only 0.008 - 0.6 %, of the photosynthetically fixed carbon for P. damicornis, in all treatments. Carbon loss (via respiration and/or mucus release) was about 41 - 47 % and 52 - 76% of the fixed carbon for starved and fed corals, respectively. Such high loss of translocated carbon suggests that P. damicornis is nitrogen and/or phosphorus limited. Heterotrophy might thus cover a larger portion of the nutritional demand for P. damicornis than previously assumed. Our results suggest that active feeding plays a fundamental role in metabolic dynamics and bleaching susceptibility of corals.

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