scholarly journals Radiative Energy Budgets of Phototrophic Surface-Associated Microbial Communities and their Photosynthetic Efficiency Under Diffuse and Collimated Light

2017 ◽  
Vol 8 ◽  
Author(s):  
Mads Lichtenberg ◽  
Kasper E. Brodersen ◽  
Michael Kühl
Keyword(s):  
Microbial Communities ◽  
Photosynthetic Efficiency ◽  
Radiative Energy ◽  
Energy Budgets

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 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.

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 .

Satellite remote sensing of fires, smoke, and regional radiative energy budgets over South America and Africa

1999 ◽  
Author(s):  
Xiang Li ◽  
Jianglong Zhang ◽  
Sundar A. Christopher ◽  
Joyce Chou ◽  
Ronald M. Welch
Keyword(s):  
Remote Sensing ◽  
South America ◽  
Satellite Remote Sensing ◽  
Radiative Energy ◽  
Energy Budgets

scholarly journals Radiative Energy Budgets in a Microbial Mat Under Different Irradiance and Tidal Conditions

2019 ◽  
Vol 77 (4) ◽  
pp. 852-865 ◽  
Author(s):  
S. Haro ◽  
K. E. Brodersen ◽  
J. Bohórquez ◽  
S. Papaspyrou ◽  
A. Corzo ◽  
...  
Keyword(s):  
Microbial Mat ◽  
Radiative Energy ◽  
Energy Budgets
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