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 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 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.

Do changes in light direction affect absorption profiles in leaves?

2010 ◽  
Vol 37 (5) ◽  
pp. 403 ◽  
Author(s):  
Craig R. Brodersen ◽  
Thomas C. Vogelmann
Keyword(s):  
Cross Sections ◽  
Incident Light ◽  
Monochromatic Light ◽  
Diffuse Light ◽  
Spongy Mesophyll ◽  
Light Regimes ◽  
Direct Light ◽  
Direct Measurements ◽  
Leaf Level

Leaf anatomy plays a functional role in propagating light through the leaf; palisade mesophyll has been shown to facilitate the channelling of collimated light deeper into the spongy mesophyll. Direct measurements of the propagation of diffuse light into the leaf, however, are absent. Using chlorophyll fluorescence imaging of leaf cross-sections, we measured light absorption profiles in leaves under direct (collimated), diffuse and low-angle monochromatic light. Low-angle and diffuse light was absorbed closer to the irradiated surface than direct light perpendicular to the surface. The shapes of internal absorption profiles indicated that leaves were influenced by the directional quality of the incident light. In addition, absorption profiles revealed that leaves were not simple light absorbing objects and that cellular anatomy influences the direction of light travelling into the mesophyll. These findings also suggest a mechanism for previously measured differences in leaf level photosynthesis under opposing light regimes.

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 Relation between Changes in Photosynthetic Rate and Changes in Canopy Level Chlorophyll Fluorescence Generated by Light Excitation of Different Led Colours in Various Background Light

2019 ◽  
Vol 11 (4) ◽  
pp. 434 ◽  
Author(s):  
Linnéa Ahlman ◽  
Daniel Bånkestad ◽  
Torsten Wik
Keyword(s):  
Steady State ◽  
Light Quality ◽  
Incident Light ◽  
Red Light ◽  
Intensity Level ◽  
Potential Candidate ◽  
Light Emitting ◽  
Background Light ◽  
Light Regimes ◽  
The Difference

Using light emitting diodes (LEDs) for greenhouse illumination enables the use of automatic control, since both light quality and quantity can be tuned. Potential candidate signals when using biological feedback for light optimisation are steady-state chlorophyll a fluorescence gains at 740 nm, defined as the difference in steady-state fluorescence at 740 nm divided by the difference in incident light quanta caused by (a small) excitation of different LED colours. In this study, experiments were conducted under various background light (quality and quantity) to evaluate if these fluorescence gains change relative to each other. The light regimes investigated were intensities in the range 160–1000 μ mol   m − 2   s − 1 , and a spectral distribution ranging from 50% to 100% red light. No significant changes in the mutual relation of the fluorescence gains for the investigated LED colours (400, 420, 450, 530, 630 and 660 nm), could be observed when the background light quality was changed. However, changes were noticed as function of light quantity. When passing the photosynthesis saturate intensity level, no further changes in the mutual fluorescence gains could be observed.

New approaches for household energy conservation—In search of personal household energy budgets and energy reduction options

Energy Policy ◽  
2006 ◽  
Vol 34 (18) ◽  
pp. 3612-3622 ◽  
Author(s):  
René M.J. Benders ◽  
Rixt Kok ◽  
Henri C. Moll ◽  
Gerwin Wiersma ◽  
Klaas Jan Noorman
Keyword(s):  
Energy Conservation ◽  
Energy Reduction ◽  
Energy Budgets ◽  
Household Energy ◽  
New Approaches

Different strategies of acclimation of photosynthesis, electron transport and antioxidative activity in leaves of two cotton species to water deficit

2016 ◽  
Vol 43 (5) ◽  
pp. 448 ◽  
Author(s):  
Xiao-Ping Yi ◽  
Ya-Li Zhang ◽  
He-Sheng Yao ◽  
Hong-Hai Luo ◽  
Ling Gou ◽  
...  
Keyword(s):  
Electron Transport ◽  
Water Deficit ◽  
Heat Dissipation ◽  
Photosynthetic Apparatus ◽  
Light Energy ◽  
Photochemical Quenching ◽  
Antioxidant Systems ◽  
Mehler Reaction ◽  
Cotton Species ◽  
Excess Light

To better understand the adaptation mechanisms of the photosynthetic apparatus of cotton plants to water deficit conditions, the influence of water deficit on photosynthesis, chlorophyll a fluorescence and the activities of antioxidant systems were determined simultaneously in Gossypium hirsutum L. cv. Xinluzao 45 (upland cotton) and Gossypium barbadense L. cv. Xinhai 21 (pima cotton). Water deficit decreased photosynthesis in both cotton species, but did not decrease chlorophyll content or induce any sustained photoinhibition in either cotton species. Water deficit increased ETR/4 − AG, where ETR/4 estimates the linear photosynthetic electron flux and AG is the gross rate of carbon assimilation. The increase in ETR/4 − AG, which represents an increase in photorespiration and alternative electron fluxes, was particularly pronounced in Xinluzao 45. In Xinluzao 45, water deficit increased the activities of antioxidative enzymes, as well as the contents of reactive oxygen species (ROS), which are related to the Mehler reaction. In contrast, moderate water deficit particularly increased non-photochemical quenching (NPQ) in Xinhai 21. Our results suggest that Xinluzao 45 relied on enhanced electron transport such as photorespiration and the Mehler reaction to dissipate excess light energy under mild and moderate water deficit. Xinhai 21 used enhanced photorespiration for light energy utilisation under mild water deficit but, when subjected to moderate water deficit, possessed a high capacity for dissipating excess light energy via heat dissipation.

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