The Experts below are selected from a list of 37524 Experts worldwide ranked by ideXlab platform
Rene H Wijffels - One of the best experts on this subject based on the ideXlab platform.
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Photosynthetic Efficiency of chlamydomonas reinhardtii in flashing light
Biotechnology and Bioengineering, 2011Co-Authors: Carsten Vejrazka, Marcel Janssen, Mathieu Streefland, Rene H WijffelsAbstract:Efficient light to biomass conversion in photobioreactors is crucial for economically feasible microalgae production processes. It has been suggested that photosynthesis is enhanced in short light path photobioreactors by mixing-induced flashing light regimes. In this study, Photosynthetic Efficiency and growth of the green microalga Chlamydomonas reinhardtii were measured using LED light to simulate light/dark cycles ranging from 5 to 100?Hz at a light-dark ratio of 0.1 and a flash intensity of 1000?µmol?m-2?s-1. Light flashing at 100?Hz yielded the same Photosynthetic Efficiency and specific growth rate as cultivation under continuous illumination with the same time-averaged light intensity (i.e., 100?µmol?m-2?s-1). The Efficiency and growth rate decreased with decreasing flash frequency. Even at 5?Hz flashing, the rate of linear electron transport during the flash was still 2.5 times higher than during maximal growth under continuous light, suggesting storage of reducing equivalents during the flash which are available during the dark period. In this way the dark reaction of photosynthesis can continue during the dark time of a light/dark cycle. Understanding Photosynthetic growth in dynamic light regimes is crucial for model development to predict microalgal photobioreactor productivities. Biotechnol. Bioeng. 2011;108: 2905–2913. © 2011 Wiley Periodicals, Inc
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luminostat operation a tool to maximize microalgae Photosynthetic Efficiency in photobioreactors during the daily light cycle
Bioresource Technology, 2011Co-Authors: Maria Cuaresma, Carlos Vilchez, Marcel Janssen, Evert J Van Den End, Rene H WijffelsAbstract:Abstract The luminostat regime has been proposed as a way to maximize light absorption and thus to increase the microalgae Photosynthetic Efficiency within photobioreactors. In this study, simulated outdoor light conditions were applied to a lab-scale photobioreactor in order to evaluate the luminostat control under varying light conditions. The photon flux density leaving the reactor (PFD out ) was varied from 4 to 20 μmol photons m −2 s −1 and the productivity and Photosynthetic Efficiency of Chlorella sorokiniana were assessed. Maximal volumetric productivity (1.22 g kg −1 d −1 ) and biomass yield on PAR photons (400–700 nm) absorbed (1.27 g mol −1 ) were found when PFD out was maintained between 4 and 6 μmol photons m −2 s −1 . The resultant Photosynthetic Efficiency was comparable to that already reported in a chemostat-controlled reactor. A strict luminostat regime could not be maintained under varying light conditions. Further modifications to the luminostat control are required before application under outdoor conditions.
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Photosynthetic Efficiency of chlorella sorokiniana in a turbulently mixed short light path photobioreactor
Biotechnology Progress, 2010Co-Authors: Anna M J Kliphuis, Lenneke De Winte, Carste Vejrazka, Dirk E Martens, Marcel Jansse, Rene H WijffelsAbstract:To be able to study the effect of mixing as well as any other parameter on productivity of algal cultures, we designed a lab-scale photobioreactor in which a short light path (SLP) of (12 mm) is combined with controlled mixing and aeration. Mixing is provided by rotating an inner tube in the cylindrical cultivation vessel creating Taylor vortex flow and as such mixing can be uncoupled from aeration. Gas exchange is monitored on-line to gain insight in growth and productivity. The maximal productivity, hence Photosynthetic Efficiency, of Chlorella sorokiniana cultures at high light intensities (1,500 micromol m(-1) s(-1)) was investigated in this Taylor vortex flow SLP photobioreactor. We performed duplicate batch experiments at three different mixing rates: 70, 110, and 140 rpm, all in the turbulent Taylor vortex flow regime. For the mixing rate of 140 rpm, we calculated a quantum requirement for oxygen evolution of 21.2 mol PAR photons per mol O(2) and a yield of biomass on light energy of 0.8 g biomass per mol PAR photons. The maximal Photosynthetic Efficiency was found at relatively low biomass densities (2.3 g L(-1)) at which light was just attenuated before reaching the rear of the culture. When increasing the mixing rate twofold, we only found a small increase in productivity. On the basis of these results, we conclude that the maximal productivity and Photosynthetic Efficiency for C. sorokiniana can be found at that biomass concentration where no significant dark zone can develop and that the influence of mixing-induced light/dark fluctuations is marginal.
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enclosed outdoor photobioreactors light regime Photosynthetic Efficiency scale up and future prospects
Biotechnology and Bioengineering, 2003Co-Authors: Marcel Janssen, J Tramper, Luuc R Mur, Rene H WijffelsAbstract:Enclosed outdoor photobioreactors need to be developed and designed for large-scale production of phototrophic microorganisms. Both light regime and Photosynthetic Efficiency were analyzed in characteristic examples of state-of-the-art pilot-scale photobioreactors. In this study it is shown that productivity of photobioreactors is determined by the light regime inside the bioreactors. In addition to light regime, oxygen accumulation and shear stress limit productivity in certain designs. In short light-path systems, high efficiencies, 10% to 20% based on Photosynthetic active radiation (PAR 400 to 700 nm), can be reached at high biomass concentrations (>5 kg [dry weight] m(-3)). It is demonstrated, however, that these and other photobioreactor designs are poorly scalable (maximal unit size 0.1 to 10 m(3)), and/or not applicable for cultivation of monocultures. This is why a new photobioreactor design is proposed in which light capture is physically separated from photoautotrophic cultivation. This system can possibly be scaled to larger unit sizes, 10 to >100 m(3), and the reactor liquid as a whole is mixed and aerated. It is deduced that high Photosynthetic efficiencies, 15% on a PAR-basis, can be achieved. Future designs from optical engineers should be used to collect, concentrate, and transport sunlight, followed by redistribution in a large-scale photobioreactor.
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Photosynthetic Efficiency of dunaliella tertiolecta under short light dark cycles
Enzyme and Microbial Technology, 2001Co-Authors: Marcel Janssen, J Tramper, Luuc R Mur, Peter Slenders, Rene H WijffelsAbstract:Abstract Inside photobioreactors algae are exposed to light/dark fluctuations. In this study the marine green alga Dunaliella tertiolecta was cultivated under short light/dark cycles of 3/3 s, 94/94 ms and 31/156 ms as found in medium and short light-path reactors. The photon flux density (PFD) during the light period was 440–455 μmol m −2 s −1 and, under the 31/156 ms cycle only, 1025 μmol m −2 s −1 . The Photosynthetic Efficiency was determined and expressed as the biomass yield on light energy in gram protein produced per mol of photons absorbed. The yield under the 94/94 ms cycle was higher than the yield under continuous light of 440–455 μmol m −2 s −1 . Apparently a light integration effect occurs under the 94/94 ms cycle together with an increase of the Photosynthetic Efficiency. On the contrary, at the 3/3 s cycle the Efficiency decreased. Also under the 31/156 ms cycle, with 1025 μmol m −2 s −1 in the light period, the yield was lower than under continuous light. The results obtained under the 31/156 ms light/dark cycle are discussed with respect to the performance of short light-path flat panel photobioreactors operated at high biomass densities.
Luuc R Mur - One of the best experts on this subject based on the ideXlab platform.
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enclosed outdoor photobioreactors light regime Photosynthetic Efficiency scale up and future prospects
Biotechnology and Bioengineering, 2003Co-Authors: J Tramper, Luuc R MurAbstract:Enclosed outdoor photobioreactors need to be developed and designed for large-scale production of phototrophic microorganisms. Both light regime and Photosynthetic Efficiency were analyzed in characteristic examples of state-of-the-art pilot-scale photobioreactors. In this study it is shown that productivity of photobioreactors is determined by the light regime inside the bioreactors. In addition to light regime, oxygen accumulation and shear stress limit productivity in certain designs. In short light-path systems, high efficiencies, 10% to 20% based on Photosynthetic active radiation (PAR 400 to 700 nm), can be reached at high biomass concentrations (>5 kg [dry weight] m(-3)). It is demonstrated, however, that these and other photobioreactor designs are poorly scalable (maximal unit size 0.1 to 10 m(3)), and/or not applicable for cultivation of monocultures. This is why a new photobioreactor design is proposed in which light capture is physically separated from photoautotrophic cultivation. This system can possibly be scaled to larger unit sizes, 10 to >100 m(3), and the reactor liquid as a whole is mixed and aerated. It is deduced that high Photosynthetic efficiencies, 15% on a PAR-basis, can be achieved. Future designs from optical engineers should be used to collect, concentrate, and transport sunlight, followed by redistribution in a large-scale photobioreactor. (C) 2002 Wiley Periodicals, Inc.
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enclosed outdoor photobioreactors light regime Photosynthetic Efficiency scale up and future prospects
Biotechnology and Bioengineering, 2003Co-Authors: Marcel Janssen, J Tramper, Luuc R Mur, Rene H WijffelsAbstract:Enclosed outdoor photobioreactors need to be developed and designed for large-scale production of phototrophic microorganisms. Both light regime and Photosynthetic Efficiency were analyzed in characteristic examples of state-of-the-art pilot-scale photobioreactors. In this study it is shown that productivity of photobioreactors is determined by the light regime inside the bioreactors. In addition to light regime, oxygen accumulation and shear stress limit productivity in certain designs. In short light-path systems, high efficiencies, 10% to 20% based on Photosynthetic active radiation (PAR 400 to 700 nm), can be reached at high biomass concentrations (>5 kg [dry weight] m(-3)). It is demonstrated, however, that these and other photobioreactor designs are poorly scalable (maximal unit size 0.1 to 10 m(3)), and/or not applicable for cultivation of monocultures. This is why a new photobioreactor design is proposed in which light capture is physically separated from photoautotrophic cultivation. This system can possibly be scaled to larger unit sizes, 10 to >100 m(3), and the reactor liquid as a whole is mixed and aerated. It is deduced that high Photosynthetic efficiencies, 15% on a PAR-basis, can be achieved. Future designs from optical engineers should be used to collect, concentrate, and transport sunlight, followed by redistribution in a large-scale photobioreactor.
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Photosynthetic Efficiency of dunaliella tertiolecta under short light dark cycles
Enzyme and Microbial Technology, 2001Co-Authors: Marcel Janssen, J Tramper, Luuc R Mur, Peter Slenders, Rene H WijffelsAbstract:Abstract Inside photobioreactors algae are exposed to light/dark fluctuations. In this study the marine green alga Dunaliella tertiolecta was cultivated under short light/dark cycles of 3/3 s, 94/94 ms and 31/156 ms as found in medium and short light-path reactors. The photon flux density (PFD) during the light period was 440–455 μmol m −2 s −1 and, under the 31/156 ms cycle only, 1025 μmol m −2 s −1 . The Photosynthetic Efficiency was determined and expressed as the biomass yield on light energy in gram protein produced per mol of photons absorbed. The yield under the 94/94 ms cycle was higher than the yield under continuous light of 440–455 μmol m −2 s −1 . Apparently a light integration effect occurs under the 94/94 ms cycle together with an increase of the Photosynthetic Efficiency. On the contrary, at the 3/3 s cycle the Efficiency decreased. Also under the 31/156 ms cycle, with 1025 μmol m −2 s −1 in the light period, the yield was lower than under continuous light. The results obtained under the 31/156 ms light/dark cycle are discussed with respect to the performance of short light-path flat panel photobioreactors operated at high biomass densities.
Marcel Janssen - One of the best experts on this subject based on the ideXlab platform.
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Photosynthetic Efficiency of chlamydomonas reinhardtii in flashing light
Biotechnology and Bioengineering, 2011Co-Authors: Carsten Vejrazka, Marcel Janssen, Mathieu Streefland, Rene H WijffelsAbstract:Efficient light to biomass conversion in photobioreactors is crucial for economically feasible microalgae production processes. It has been suggested that photosynthesis is enhanced in short light path photobioreactors by mixing-induced flashing light regimes. In this study, Photosynthetic Efficiency and growth of the green microalga Chlamydomonas reinhardtii were measured using LED light to simulate light/dark cycles ranging from 5 to 100?Hz at a light-dark ratio of 0.1 and a flash intensity of 1000?µmol?m-2?s-1. Light flashing at 100?Hz yielded the same Photosynthetic Efficiency and specific growth rate as cultivation under continuous illumination with the same time-averaged light intensity (i.e., 100?µmol?m-2?s-1). The Efficiency and growth rate decreased with decreasing flash frequency. Even at 5?Hz flashing, the rate of linear electron transport during the flash was still 2.5 times higher than during maximal growth under continuous light, suggesting storage of reducing equivalents during the flash which are available during the dark period. In this way the dark reaction of photosynthesis can continue during the dark time of a light/dark cycle. Understanding Photosynthetic growth in dynamic light regimes is crucial for model development to predict microalgal photobioreactor productivities. Biotechnol. Bioeng. 2011;108: 2905–2913. © 2011 Wiley Periodicals, Inc
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luminostat operation a tool to maximize microalgae Photosynthetic Efficiency in photobioreactors during the daily light cycle
Bioresource Technology, 2011Co-Authors: Maria Cuaresma, Carlos Vilchez, Marcel Janssen, Evert J Van Den End, Rene H WijffelsAbstract:Abstract The luminostat regime has been proposed as a way to maximize light absorption and thus to increase the microalgae Photosynthetic Efficiency within photobioreactors. In this study, simulated outdoor light conditions were applied to a lab-scale photobioreactor in order to evaluate the luminostat control under varying light conditions. The photon flux density leaving the reactor (PFD out ) was varied from 4 to 20 μmol photons m −2 s −1 and the productivity and Photosynthetic Efficiency of Chlorella sorokiniana were assessed. Maximal volumetric productivity (1.22 g kg −1 d −1 ) and biomass yield on PAR photons (400–700 nm) absorbed (1.27 g mol −1 ) were found when PFD out was maintained between 4 and 6 μmol photons m −2 s −1 . The resultant Photosynthetic Efficiency was comparable to that already reported in a chemostat-controlled reactor. A strict luminostat regime could not be maintained under varying light conditions. Further modifications to the luminostat control are required before application under outdoor conditions.
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enclosed outdoor photobioreactors light regime Photosynthetic Efficiency scale up and future prospects
Biotechnology and Bioengineering, 2003Co-Authors: Marcel Janssen, J Tramper, Luuc R Mur, Rene H WijffelsAbstract:Enclosed outdoor photobioreactors need to be developed and designed for large-scale production of phototrophic microorganisms. Both light regime and Photosynthetic Efficiency were analyzed in characteristic examples of state-of-the-art pilot-scale photobioreactors. In this study it is shown that productivity of photobioreactors is determined by the light regime inside the bioreactors. In addition to light regime, oxygen accumulation and shear stress limit productivity in certain designs. In short light-path systems, high efficiencies, 10% to 20% based on Photosynthetic active radiation (PAR 400 to 700 nm), can be reached at high biomass concentrations (>5 kg [dry weight] m(-3)). It is demonstrated, however, that these and other photobioreactor designs are poorly scalable (maximal unit size 0.1 to 10 m(3)), and/or not applicable for cultivation of monocultures. This is why a new photobioreactor design is proposed in which light capture is physically separated from photoautotrophic cultivation. This system can possibly be scaled to larger unit sizes, 10 to >100 m(3), and the reactor liquid as a whole is mixed and aerated. It is deduced that high Photosynthetic efficiencies, 15% on a PAR-basis, can be achieved. Future designs from optical engineers should be used to collect, concentrate, and transport sunlight, followed by redistribution in a large-scale photobioreactor.
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Photosynthetic Efficiency of dunaliella tertiolecta under short light dark cycles
Enzyme and Microbial Technology, 2001Co-Authors: Marcel Janssen, J Tramper, Luuc R Mur, Peter Slenders, Rene H WijffelsAbstract:Abstract Inside photobioreactors algae are exposed to light/dark fluctuations. In this study the marine green alga Dunaliella tertiolecta was cultivated under short light/dark cycles of 3/3 s, 94/94 ms and 31/156 ms as found in medium and short light-path reactors. The photon flux density (PFD) during the light period was 440–455 μmol m −2 s −1 and, under the 31/156 ms cycle only, 1025 μmol m −2 s −1 . The Photosynthetic Efficiency was determined and expressed as the biomass yield on light energy in gram protein produced per mol of photons absorbed. The yield under the 94/94 ms cycle was higher than the yield under continuous light of 440–455 μmol m −2 s −1 . Apparently a light integration effect occurs under the 94/94 ms cycle together with an increase of the Photosynthetic Efficiency. On the contrary, at the 3/3 s cycle the Efficiency decreased. Also under the 31/156 ms cycle, with 1025 μmol m −2 s −1 in the light period, the yield was lower than under continuous light. The results obtained under the 31/156 ms light/dark cycle are discussed with respect to the performance of short light-path flat panel photobioreactors operated at high biomass densities.
J Tramper - One of the best experts on this subject based on the ideXlab platform.
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enclosed outdoor photobioreactors light regime Photosynthetic Efficiency scale up and future prospects
Biotechnology and Bioengineering, 2003Co-Authors: J Tramper, Luuc R MurAbstract:Enclosed outdoor photobioreactors need to be developed and designed for large-scale production of phototrophic microorganisms. Both light regime and Photosynthetic Efficiency were analyzed in characteristic examples of state-of-the-art pilot-scale photobioreactors. In this study it is shown that productivity of photobioreactors is determined by the light regime inside the bioreactors. In addition to light regime, oxygen accumulation and shear stress limit productivity in certain designs. In short light-path systems, high efficiencies, 10% to 20% based on Photosynthetic active radiation (PAR 400 to 700 nm), can be reached at high biomass concentrations (>5 kg [dry weight] m(-3)). It is demonstrated, however, that these and other photobioreactor designs are poorly scalable (maximal unit size 0.1 to 10 m(3)), and/or not applicable for cultivation of monocultures. This is why a new photobioreactor design is proposed in which light capture is physically separated from photoautotrophic cultivation. This system can possibly be scaled to larger unit sizes, 10 to >100 m(3), and the reactor liquid as a whole is mixed and aerated. It is deduced that high Photosynthetic efficiencies, 15% on a PAR-basis, can be achieved. Future designs from optical engineers should be used to collect, concentrate, and transport sunlight, followed by redistribution in a large-scale photobioreactor. (C) 2002 Wiley Periodicals, Inc.
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enclosed outdoor photobioreactors light regime Photosynthetic Efficiency scale up and future prospects
Biotechnology and Bioengineering, 2003Co-Authors: Marcel Janssen, J Tramper, Luuc R Mur, Rene H WijffelsAbstract:Enclosed outdoor photobioreactors need to be developed and designed for large-scale production of phototrophic microorganisms. Both light regime and Photosynthetic Efficiency were analyzed in characteristic examples of state-of-the-art pilot-scale photobioreactors. In this study it is shown that productivity of photobioreactors is determined by the light regime inside the bioreactors. In addition to light regime, oxygen accumulation and shear stress limit productivity in certain designs. In short light-path systems, high efficiencies, 10% to 20% based on Photosynthetic active radiation (PAR 400 to 700 nm), can be reached at high biomass concentrations (>5 kg [dry weight] m(-3)). It is demonstrated, however, that these and other photobioreactor designs are poorly scalable (maximal unit size 0.1 to 10 m(3)), and/or not applicable for cultivation of monocultures. This is why a new photobioreactor design is proposed in which light capture is physically separated from photoautotrophic cultivation. This system can possibly be scaled to larger unit sizes, 10 to >100 m(3), and the reactor liquid as a whole is mixed and aerated. It is deduced that high Photosynthetic efficiencies, 15% on a PAR-basis, can be achieved. Future designs from optical engineers should be used to collect, concentrate, and transport sunlight, followed by redistribution in a large-scale photobioreactor.
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Photosynthetic Efficiency of dunaliella tertiolecta under short light dark cycles
Enzyme and Microbial Technology, 2001Co-Authors: Marcel Janssen, J Tramper, Luuc R Mur, Peter Slenders, Rene H WijffelsAbstract:Abstract Inside photobioreactors algae are exposed to light/dark fluctuations. In this study the marine green alga Dunaliella tertiolecta was cultivated under short light/dark cycles of 3/3 s, 94/94 ms and 31/156 ms as found in medium and short light-path reactors. The photon flux density (PFD) during the light period was 440–455 μmol m −2 s −1 and, under the 31/156 ms cycle only, 1025 μmol m −2 s −1 . The Photosynthetic Efficiency was determined and expressed as the biomass yield on light energy in gram protein produced per mol of photons absorbed. The yield under the 94/94 ms cycle was higher than the yield under continuous light of 440–455 μmol m −2 s −1 . Apparently a light integration effect occurs under the 94/94 ms cycle together with an increase of the Photosynthetic Efficiency. On the contrary, at the 3/3 s cycle the Efficiency decreased. Also under the 31/156 ms cycle, with 1025 μmol m −2 s −1 in the light period, the yield was lower than under continuous light. The results obtained under the 31/156 ms light/dark cycle are discussed with respect to the performance of short light-path flat panel photobioreactors operated at high biomass densities.
Michael Kuhl - One of the best experts on this subject based on the ideXlab platform.
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radiative energy budgets of phototrophic surface associated microbial communities and their Photosynthetic Efficiency under diffuse and collimated light
Frontiers in Microbiology, 2017Co-Authors: Mads Lichtenberg, Kasper Elgetti Brodersen, Michael KuhlAbstract:We 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, Ek, i.e. the irradiance at the onset of saturation of photosynthesis, was >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 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. The aim was to investigate how the physical structure and light propagation affected energy budgets and light utilization efficiencies in loosely organized vs. compact phototrophic sediment under diffuse and collimated 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.
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radiative energy budgets of phototrophic surface associated microbial communities and their Photosynthetic Efficiency under diffuse and collimated light
bioRxiv, 2017Co-Authors: Mads Lichtenberg, Kasper Elgetti Brodersen, Michael KuhlAbstract:We 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 O 2 , 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, E k was >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 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.