Studying how natural phytoplankton adjust their photosynthetic properties to the quantity and qua... more Studying how natural phytoplankton adjust their photosynthetic properties to the quantity and quality of underwater light (i.e. light climate) is essential to understand primary production. A wavelength-dependent photoacclimation strategy was assessed using a multi-color pulse-amplitude-modulation chlorophyll fluorometer for phytoplankton samples collected in the spring at 19 locations across the English Channel. The functional absorption cross section of photosystem II, photosynthetic electron transport (PET λ) parameters and non-photochemical quenching were analyzed using an original approach with a sequence of three statistical analyses. Linear mixed-effects models using wavelength as a longitudinal variable were first applied to distinguish the fixed effect of the population from the random effect of individuals. Population and individual trends of wavelength-dependent PET λ parameters were consistent with photosynthesis and photoacclimation theories. The natural phytoplankton communities studied were in a photoprotective state for blue wavelengths (440 and 480 nm), but not for other wavelengths (green (540 nm), amber (590 nm) and light red (625 nm)). Populationdetrended PET λ values were then used in multivariate analyses (partial triadic analysis and redundancy analysis) to study ecological implications of PET λ dynamics among water masses. Two wavelength ratios based on the microalgae saturation parameter E k (in relative and absolute units), related to the hydrodynamic regime and underwater light climate, clearly confirmed the physiological state of microalgae. They also illustrate more accurately that natural phytoplankton communities can implement photoacclimation processes that are influenced by in situ light quality during the daylight cycle in temporarily and weakly stratified water. Ecological implications and consequences of PET λ are discussed in the context of turbulent coastal ecosystems.
Future atmospheric CO2 levels will most likely have complex consequences for marine organisms, pa... more Future atmospheric CO2 levels will most likely have complex consequences for marine organisms, particulary photosynthetic calcifying organisms. Corallina officinalis L. is an erect calcifying macroalga found in the inter- and subtidal regions of temperate rocky coastlines and provides important substrate and refugia for marine meiofauna. The main goal of the current study was to determine the physiological responses of C. officinalis to increased CO2 concentrations expected to occur within the next century and beyond. Our results show that growth and production of inorganic material decreased under high CO2 levels, while carbonic anhydrase activity was stimulated and negatively correlated to algal inorganic content. Photosynthetic efficiency based on oxygen evolution was also negatively affected by increased CO2. The results of this study indicate that C. officinalis may become less competitive under future CO2 levels, which could result in structural changes in future temperate intertidal communities.
Studying how natural phytoplankton adjust their photosynthetic properties to the quantity and qua... more Studying how natural phytoplankton adjust their photosynthetic properties to the quantity and quality of underwater light (i.e. light climate) is essential to understand primary production. A wavelength-dependent photoacclimation strategy was assessed using a multi-color pulse-amplitude-modulation chlorophyll fluorometer for phytoplankton samples collected in the spring at 19 locations across the English Channel. The functional absorption cross section of photosystem II, photosynthetic electron transport (PET λ) parameters and non-photochemical quenching were analyzed using an original approach with a sequence of three statistical analyses. Linear mixed-effects models using wavelength as a longitudinal variable were first applied to distinguish the fixed effect of the population from the random effect of individuals. Population and individual trends of wavelength-dependent PET λ parameters were consistent with photosynthesis and photoacclimation theories. The natural phytoplankton communities studied were in a photoprotective state for blue wavelengths (440 and 480 nm), but not for other wavelengths (green (540 nm), amber (590 nm) and light red (625 nm)). Populationdetrended PET λ values were then used in multivariate analyses (partial triadic analysis and redundancy analysis) to study ecological implications of PET λ dynamics among water masses. Two wavelength ratios based on the microalgae saturation parameter E k (in relative and absolute units), related to the hydrodynamic regime and underwater light climate, clearly confirmed the physiological state of microalgae. They also illustrate more accurately that natural phytoplankton communities can implement photoacclimation processes that are influenced by in situ light quality during the daylight cycle in temporarily and weakly stratified water. Ecological implications and consequences of PET λ are discussed in the context of turbulent coastal ecosystems.
An innovative, closed, ring-shaped cultivation vessel was developed by simplifying tumble movemen... more An innovative, closed, ring-shaped cultivation vessel was developed by simplifying tumble movement to a circular motion pattern. New cultivation vessel combines adaptability and manageability with growth rates similar or better than standard tank cultivation. New cultivation vessel distinctly reduces variable cost, facilitates control of the cultivation process and eliminates interferences with the environment. Title Development of an innovative ring-shaped cultivation system for a land-based cultivation of marine macroalgae.
Photoinhibition of photosynthesis and its recovery was investigated in the laboratory and in the ... more Photoinhibition of photosynthesis and its recovery was investigated in the laboratory and in the field with fluorescence and oxygen measuring devices. Photosynthetic efficiency measured at non-saturating fluence rates and the ratio of variable fluorescence to maximal fluorescence (FJF,) showed an approximately inverse course compared to the fluence rate of daylight measured continuously during the day. In the morning photosynthetic efficiency was high, but decreased with increasing fluence rate. Maximal photoinhibition of photosynthesis occurred around noon or in the early afternoon. During the afternoon photosynthetic efficiency increased again and full recovery was reached in the evening. These lunetics of recovery differ from those obtained in the laboratory under artificial conditions, where the red algae required up to 48 h to recover from a strong photoinhibition. Different species showed Mferent sensitivity to photoinhibition and different capability for recovery. The red alga Porphyra spp., living in the upper eulittoral, was able to cope with the high fluence rates at the water surface. The red alga Delesseria sanguinea, living in the subtidal zone, shows the highest sensitivity to photoinhibition. Thus, a relation between photoinhibitory sensitivity and the zonation of the algae in the littoral exists.
reference transcriptome. The pooling of various RNA samples from different treatments was conduct... more reference transcriptome. The pooling of various RNA samples from different treatments was conducted to ensure a high functional coverage of the reference transcriptome. Reference library sequencing was carried out with a genome sequencer Illumina HiSeq 2500 in rapid run 300 bp paired-end modus. Gene expression sequencing. The cDNA libraries for analysing differential gene expression in darkness were constructed in triplicates. Strand-specific cDNA libraries for analyzing differential gene expression were sequenced in HiSeq 2500 rapid run 100 bp single read modus. All library preparations and sequencing were carried out by GATC Biotech (Konstanz, Germany). The cleaned raw data were deposited in the European Nucleotide Archive (ENA) at the European Molecular Biological Laboratory-European Bioinformatics Institute under study accession number PRJEB30351.
Microalgae are one of the most dominant forms of life on earth that is tightly associated with a ... more Microalgae are one of the most dominant forms of life on earth that is tightly associated with a distinct and specialized microbiota. We have previously shown that the microbiota of Scenedesmus quadricauda harbors less than 10 distinct microbial species. Here, we provide evidence that dominant species are affiliated with the genera of Variovorax, Porphyrobacter, and Dyadobacter. Experimental and transcriptome-based evidence implies that within this multispecies interaction, Dyadobacter is a key to alga growth and fitness and is highly adapted to live in the phycosphere. While presumably under light conditions the alga provides the energy source to the bacteria, Dyadobacter produces and releases mainly a large variety of polysaccharides modifying enzymes. This is coherent with high-level expression of the T9SS in alga cocultures. The transcriptome data further imply that quorum-quenching proteins (QQ) and biosynthesis of vitamins B 1 , B 2 , B 5 , B 6 , and B 9 are expressed by Dyadobacter at high levels in comparison to Variovorax and Porphyrobacter. Notably, Dyadobacter produces a significant number of leucine-rich repeat (LRR) proteins and enzymes involved in bacterial reactive oxygen species (ROS) tolerance. Complementary to this, Variovorax expresses the genes of the biosynthesis of vitamins B 2 , B 5 , B 6 , B 7 , B 9 , and B 12 , and Porphyrobacter is specialized in the production of vitamins B 2 and B 6. Thus, the shared currency between partners are vitamins, microalgae growth-promoting substances, and dissolved carbon. This work significantly enlarges our knowledge on alga-bacteria interaction and demonstrates physiological investigations of microalgae and associated bacteria, using microscopy observations, photosynthetic activity measurements, and flow cytometry. IMPORTANCE The current study gives a detailed insight into mutualistic collaboration of microalgae and bacteria, including the involvement of competitive interplay between bacteria. We provide experimental evidence that Gram-negative bacteria belonging to the Dyadobacter, Porphyrobacter, and Variovorax are the key players in a Scenedesmus quadricauda alga-bacteria interaction. We impart strong evidence that Dyadobacter produces and releases polysaccharides degradation enzymes and leucine-rich repeat proteins; Variovorax supplies the consortium with auxins and vitamin B 12 , while Porphyrobacter produces a broad spectrum of B vitamins. We show not only that the microalgae collaborate with the bacteria and vice versa but also that the bacteria interact with each other via quorum-sensing and secretion system mechanisms. The shared currency between partners appears to be vitamins, microalgae growth-promoting substances, and dissolved carbon.
Epic311 Wissenschaftliche Tagung Der Sektion Phykologie in Der Dgb, 2006
Laminaria digitata is an abundant brown macroalgae on the upper sublittoral rocky shores of Helgo... more Laminaria digitata is an abundant brown macroalgae on the upper sublittoral rocky shores of Helgoland that is used as a habitat and food to a variety of organisms. The seasonal abundance of vagile herbivores and the respecive feeding pressures were monitored. Feeding experiments were conducted to investigate feeding preferences of four different snail species (Gibbula cineraria, Lacuna vincta, Littorina littorea and Littorina mariae/obtusata) and two species of isopods (Idotea granulosa and I. emarginata) in winter and spring. Results from the monitoring indicate that the abundance and the composition of herbivores on Laminaria digitata change seasonally - with Lacuna vincta as the most abundant grazer. In the feeding experiments, the six grazer species each showed preferences among the different tissue types of the alga.The results suggest that Laminaria digitata offers a non-uniform food quality to mesograzers and is a temporary habitat for vagile organisms.
The effects that ultraviolet radiation (UVR, 280 to 400 nm) and photosynthetically active radiati... more The effects that ultraviolet radiation (UVR, 280 to 400 nm) and photosynthetically active radiation (PAR, 400 to 700 nm) had on early life stages of Mastocarpus stellatus and Chondrus crispus were studied to determine if differences in UVR tolerance could influence their recruitment success on the upper eulittoral shores of Helgoland (North Sea). Photosynthesis, germination capacity, DNA damage and carpospore repair were measured after exposures to different time lengths and intensities of PAR + UV-A + UV-B, PAR + UV-A or PAR alone, and also after recovery in low white light. Germination and photosynthesis of the low light adapted carpospores of both species were inhibited as PAR was increased. Supplemental UV-A and UV-B had a small additional effect on the F v /F m of M. stellatus but this effect was more pronounced in C. crispus. However, photosynthesis of both species significantly recovered after 48 h. Carpospore viability in C. crispus was more sensitive than in M. stellatus to UVR, while a higher dose was needed to achieve 50% germination inhibition in M. stellatus. Furthermore, UV-B-induced DNA damage, measured as cyclobutane-pyrimidine dimers (CPDs), was less in M. stellatus spores, which also exhibited an efficient DNA repair mechanism compared with C. crispus. In contrast, growth and chlorophyll a contents in young gametophytes of both species were not affected by repeated UV exposures. Higher total carotenoid was measured in plants exposed to UVR, indicating a photoprotection role, because photosynthesis completely acclimated to UVR after 3 d. Furthermore, DNA damage was not detected on mature fronds of both species when exposed to the full solar spectrum. Therefore, the susceptibility of carpospores to UVR could influence species recruitment to the upper eulittoral zone.
With the rising demands for renewable fuels, there is growing interest in utilizing abundant and ... more With the rising demands for renewable fuels, there is growing interest in utilizing abundant and sustainable non-edible biomass as a feedstock for bioethanol production. Macroalgal biomass contains a high content of carbohydrates in the form of special polysaccharides like alginate, agar, and carrageenan that can be converted to fermentable sugars. In addition, using seagrass as a feedstock for bioethanol production can provide a sustainable and renewable energy source while addressing environmental concerns. It is a resource-rich plant that offers several advantages for bioethanol production, including its high cellulose content, rapid growth rates, and abundance in coastal regions. To reduce sugar content and support efficient microbial fermentation, co-fermentation of macroalgae with seagrass (marine biomass) can provide complementary sugars and nutrients to improve process yields and economics. This review comprehensively covers the current status and future potential of ferment...
In different marine red algae (Chondrus crispus, Delesseria sanguinea, Membranoptera alata, Phyco... more In different marine red algae (Chondrus crispus, Delesseria sanguinea, Membranoptera alata, Phycodrys rubens, Phyllophora truncata, Polyneura hilliae) photoinhibition of photosynthesis has been investigated by means of both fluorescence and oxygen measurements. Measurements of absolute oxygen production show that photoinhibition causes a decline in the initial slope and in the rate of bending of the fluence rate‐response curve (i.e. the photosynthetic efficiency at non‐saturating fluence rates), as well as a decline in the photosynthetic capacity (Pm) at saturating fluence rates. Fluorescence data (Fv/Fm) were consistent with the results of oxygen measurements. Under excessive light photoinhibition protects photosynthesis against photo‐damage in red algae. However, an increase in the initial fluorescence (Fo) after photoinhibitory treatment indicates that it could not prevent photodamage entirely.Action spectra of photoinhibition demonstrate that the main photoinhibition site in Polyneura hiliae is PS II, because far red light absorbed by PS I was ineffective. The strong increase of Fo in the blue wavelength range and the slight and partial recovery in weak blue light indicate that blue light especially causes photodamage.Recovery of photosynthesis requires dim white light conditions. Experiments with monochromatic light also show a wavelength dependence of recovery. Moreover, the recovery of photosynthesis after a photoinhibitory treatment is strongly temperature dependent, indicating participation of enzymatic processes. The comparison of fluorescence and oxygen measurement of the recovery shows different results in some species. The rate of oxygen production in red control light increased immediately after photoinhibited algae were exposed to weak light conditions. Surprisingly, the ratio of variable to maximum fluorescence (Fv/Fm) of Phyllophora truncata and the maximum fluorescence (Fm) of Polyneura hilliae show first a delay of the recovery under weak light conditions. Thus, in recovery experiments fluorescence and oxygen data are not quite consistent.
Studying how natural phytoplankton adjust their photosynthetic properties to the quantity and qua... more Studying how natural phytoplankton adjust their photosynthetic properties to the quantity and quality of underwater light (i.e. light climate) is essential to understand primary production. A wavelength-dependent photoacclimation strategy was assessed using a multi-color pulse-amplitude-modulation chlorophyll fluorometer for phytoplankton samples collected in the spring at 19 locations across the English Channel. The functional absorption cross section of photosystem II, photosynthetic electron transport (PET λ) parameters and non-photochemical quenching were analyzed using an original approach with a sequence of three statistical analyses. Linear mixed-effects models using wavelength as a longitudinal variable were first applied to distinguish the fixed effect of the population from the random effect of individuals. Population and individual trends of wavelength-dependent PET λ parameters were consistent with photosynthesis and photoacclimation theories. The natural phytoplankton communities studied were in a photoprotective state for blue wavelengths (440 and 480 nm), but not for other wavelengths (green (540 nm), amber (590 nm) and light red (625 nm)). Populationdetrended PET λ values were then used in multivariate analyses (partial triadic analysis and redundancy analysis) to study ecological implications of PET λ dynamics among water masses. Two wavelength ratios based on the microalgae saturation parameter E k (in relative and absolute units), related to the hydrodynamic regime and underwater light climate, clearly confirmed the physiological state of microalgae. They also illustrate more accurately that natural phytoplankton communities can implement photoacclimation processes that are influenced by in situ light quality during the daylight cycle in temporarily and weakly stratified water. Ecological implications and consequences of PET λ are discussed in the context of turbulent coastal ecosystems.
Future atmospheric CO2 levels will most likely have complex consequences for marine organisms, pa... more Future atmospheric CO2 levels will most likely have complex consequences for marine organisms, particulary photosynthetic calcifying organisms. Corallina officinalis L. is an erect calcifying macroalga found in the inter- and subtidal regions of temperate rocky coastlines and provides important substrate and refugia for marine meiofauna. The main goal of the current study was to determine the physiological responses of C. officinalis to increased CO2 concentrations expected to occur within the next century and beyond. Our results show that growth and production of inorganic material decreased under high CO2 levels, while carbonic anhydrase activity was stimulated and negatively correlated to algal inorganic content. Photosynthetic efficiency based on oxygen evolution was also negatively affected by increased CO2. The results of this study indicate that C. officinalis may become less competitive under future CO2 levels, which could result in structural changes in future temperate intertidal communities.
Studying how natural phytoplankton adjust their photosynthetic properties to the quantity and qua... more Studying how natural phytoplankton adjust their photosynthetic properties to the quantity and quality of underwater light (i.e. light climate) is essential to understand primary production. A wavelength-dependent photoacclimation strategy was assessed using a multi-color pulse-amplitude-modulation chlorophyll fluorometer for phytoplankton samples collected in the spring at 19 locations across the English Channel. The functional absorption cross section of photosystem II, photosynthetic electron transport (PET λ) parameters and non-photochemical quenching were analyzed using an original approach with a sequence of three statistical analyses. Linear mixed-effects models using wavelength as a longitudinal variable were first applied to distinguish the fixed effect of the population from the random effect of individuals. Population and individual trends of wavelength-dependent PET λ parameters were consistent with photosynthesis and photoacclimation theories. The natural phytoplankton communities studied were in a photoprotective state for blue wavelengths (440 and 480 nm), but not for other wavelengths (green (540 nm), amber (590 nm) and light red (625 nm)). Populationdetrended PET λ values were then used in multivariate analyses (partial triadic analysis and redundancy analysis) to study ecological implications of PET λ dynamics among water masses. Two wavelength ratios based on the microalgae saturation parameter E k (in relative and absolute units), related to the hydrodynamic regime and underwater light climate, clearly confirmed the physiological state of microalgae. They also illustrate more accurately that natural phytoplankton communities can implement photoacclimation processes that are influenced by in situ light quality during the daylight cycle in temporarily and weakly stratified water. Ecological implications and consequences of PET λ are discussed in the context of turbulent coastal ecosystems.
An innovative, closed, ring-shaped cultivation vessel was developed by simplifying tumble movemen... more An innovative, closed, ring-shaped cultivation vessel was developed by simplifying tumble movement to a circular motion pattern. New cultivation vessel combines adaptability and manageability with growth rates similar or better than standard tank cultivation. New cultivation vessel distinctly reduces variable cost, facilitates control of the cultivation process and eliminates interferences with the environment. Title Development of an innovative ring-shaped cultivation system for a land-based cultivation of marine macroalgae.
Photoinhibition of photosynthesis and its recovery was investigated in the laboratory and in the ... more Photoinhibition of photosynthesis and its recovery was investigated in the laboratory and in the field with fluorescence and oxygen measuring devices. Photosynthetic efficiency measured at non-saturating fluence rates and the ratio of variable fluorescence to maximal fluorescence (FJF,) showed an approximately inverse course compared to the fluence rate of daylight measured continuously during the day. In the morning photosynthetic efficiency was high, but decreased with increasing fluence rate. Maximal photoinhibition of photosynthesis occurred around noon or in the early afternoon. During the afternoon photosynthetic efficiency increased again and full recovery was reached in the evening. These lunetics of recovery differ from those obtained in the laboratory under artificial conditions, where the red algae required up to 48 h to recover from a strong photoinhibition. Different species showed Mferent sensitivity to photoinhibition and different capability for recovery. The red alga Porphyra spp., living in the upper eulittoral, was able to cope with the high fluence rates at the water surface. The red alga Delesseria sanguinea, living in the subtidal zone, shows the highest sensitivity to photoinhibition. Thus, a relation between photoinhibitory sensitivity and the zonation of the algae in the littoral exists.
reference transcriptome. The pooling of various RNA samples from different treatments was conduct... more reference transcriptome. The pooling of various RNA samples from different treatments was conducted to ensure a high functional coverage of the reference transcriptome. Reference library sequencing was carried out with a genome sequencer Illumina HiSeq 2500 in rapid run 300 bp paired-end modus. Gene expression sequencing. The cDNA libraries for analysing differential gene expression in darkness were constructed in triplicates. Strand-specific cDNA libraries for analyzing differential gene expression were sequenced in HiSeq 2500 rapid run 100 bp single read modus. All library preparations and sequencing were carried out by GATC Biotech (Konstanz, Germany). The cleaned raw data were deposited in the European Nucleotide Archive (ENA) at the European Molecular Biological Laboratory-European Bioinformatics Institute under study accession number PRJEB30351.
Microalgae are one of the most dominant forms of life on earth that is tightly associated with a ... more Microalgae are one of the most dominant forms of life on earth that is tightly associated with a distinct and specialized microbiota. We have previously shown that the microbiota of Scenedesmus quadricauda harbors less than 10 distinct microbial species. Here, we provide evidence that dominant species are affiliated with the genera of Variovorax, Porphyrobacter, and Dyadobacter. Experimental and transcriptome-based evidence implies that within this multispecies interaction, Dyadobacter is a key to alga growth and fitness and is highly adapted to live in the phycosphere. While presumably under light conditions the alga provides the energy source to the bacteria, Dyadobacter produces and releases mainly a large variety of polysaccharides modifying enzymes. This is coherent with high-level expression of the T9SS in alga cocultures. The transcriptome data further imply that quorum-quenching proteins (QQ) and biosynthesis of vitamins B 1 , B 2 , B 5 , B 6 , and B 9 are expressed by Dyadobacter at high levels in comparison to Variovorax and Porphyrobacter. Notably, Dyadobacter produces a significant number of leucine-rich repeat (LRR) proteins and enzymes involved in bacterial reactive oxygen species (ROS) tolerance. Complementary to this, Variovorax expresses the genes of the biosynthesis of vitamins B 2 , B 5 , B 6 , B 7 , B 9 , and B 12 , and Porphyrobacter is specialized in the production of vitamins B 2 and B 6. Thus, the shared currency between partners are vitamins, microalgae growth-promoting substances, and dissolved carbon. This work significantly enlarges our knowledge on alga-bacteria interaction and demonstrates physiological investigations of microalgae and associated bacteria, using microscopy observations, photosynthetic activity measurements, and flow cytometry. IMPORTANCE The current study gives a detailed insight into mutualistic collaboration of microalgae and bacteria, including the involvement of competitive interplay between bacteria. We provide experimental evidence that Gram-negative bacteria belonging to the Dyadobacter, Porphyrobacter, and Variovorax are the key players in a Scenedesmus quadricauda alga-bacteria interaction. We impart strong evidence that Dyadobacter produces and releases polysaccharides degradation enzymes and leucine-rich repeat proteins; Variovorax supplies the consortium with auxins and vitamin B 12 , while Porphyrobacter produces a broad spectrum of B vitamins. We show not only that the microalgae collaborate with the bacteria and vice versa but also that the bacteria interact with each other via quorum-sensing and secretion system mechanisms. The shared currency between partners appears to be vitamins, microalgae growth-promoting substances, and dissolved carbon.
Epic311 Wissenschaftliche Tagung Der Sektion Phykologie in Der Dgb, 2006
Laminaria digitata is an abundant brown macroalgae on the upper sublittoral rocky shores of Helgo... more Laminaria digitata is an abundant brown macroalgae on the upper sublittoral rocky shores of Helgoland that is used as a habitat and food to a variety of organisms. The seasonal abundance of vagile herbivores and the respecive feeding pressures were monitored. Feeding experiments were conducted to investigate feeding preferences of four different snail species (Gibbula cineraria, Lacuna vincta, Littorina littorea and Littorina mariae/obtusata) and two species of isopods (Idotea granulosa and I. emarginata) in winter and spring. Results from the monitoring indicate that the abundance and the composition of herbivores on Laminaria digitata change seasonally - with Lacuna vincta as the most abundant grazer. In the feeding experiments, the six grazer species each showed preferences among the different tissue types of the alga.The results suggest that Laminaria digitata offers a non-uniform food quality to mesograzers and is a temporary habitat for vagile organisms.
The effects that ultraviolet radiation (UVR, 280 to 400 nm) and photosynthetically active radiati... more The effects that ultraviolet radiation (UVR, 280 to 400 nm) and photosynthetically active radiation (PAR, 400 to 700 nm) had on early life stages of Mastocarpus stellatus and Chondrus crispus were studied to determine if differences in UVR tolerance could influence their recruitment success on the upper eulittoral shores of Helgoland (North Sea). Photosynthesis, germination capacity, DNA damage and carpospore repair were measured after exposures to different time lengths and intensities of PAR + UV-A + UV-B, PAR + UV-A or PAR alone, and also after recovery in low white light. Germination and photosynthesis of the low light adapted carpospores of both species were inhibited as PAR was increased. Supplemental UV-A and UV-B had a small additional effect on the F v /F m of M. stellatus but this effect was more pronounced in C. crispus. However, photosynthesis of both species significantly recovered after 48 h. Carpospore viability in C. crispus was more sensitive than in M. stellatus to UVR, while a higher dose was needed to achieve 50% germination inhibition in M. stellatus. Furthermore, UV-B-induced DNA damage, measured as cyclobutane-pyrimidine dimers (CPDs), was less in M. stellatus spores, which also exhibited an efficient DNA repair mechanism compared with C. crispus. In contrast, growth and chlorophyll a contents in young gametophytes of both species were not affected by repeated UV exposures. Higher total carotenoid was measured in plants exposed to UVR, indicating a photoprotection role, because photosynthesis completely acclimated to UVR after 3 d. Furthermore, DNA damage was not detected on mature fronds of both species when exposed to the full solar spectrum. Therefore, the susceptibility of carpospores to UVR could influence species recruitment to the upper eulittoral zone.
With the rising demands for renewable fuels, there is growing interest in utilizing abundant and ... more With the rising demands for renewable fuels, there is growing interest in utilizing abundant and sustainable non-edible biomass as a feedstock for bioethanol production. Macroalgal biomass contains a high content of carbohydrates in the form of special polysaccharides like alginate, agar, and carrageenan that can be converted to fermentable sugars. In addition, using seagrass as a feedstock for bioethanol production can provide a sustainable and renewable energy source while addressing environmental concerns. It is a resource-rich plant that offers several advantages for bioethanol production, including its high cellulose content, rapid growth rates, and abundance in coastal regions. To reduce sugar content and support efficient microbial fermentation, co-fermentation of macroalgae with seagrass (marine biomass) can provide complementary sugars and nutrients to improve process yields and economics. This review comprehensively covers the current status and future potential of ferment...
In different marine red algae (Chondrus crispus, Delesseria sanguinea, Membranoptera alata, Phyco... more In different marine red algae (Chondrus crispus, Delesseria sanguinea, Membranoptera alata, Phycodrys rubens, Phyllophora truncata, Polyneura hilliae) photoinhibition of photosynthesis has been investigated by means of both fluorescence and oxygen measurements. Measurements of absolute oxygen production show that photoinhibition causes a decline in the initial slope and in the rate of bending of the fluence rate‐response curve (i.e. the photosynthetic efficiency at non‐saturating fluence rates), as well as a decline in the photosynthetic capacity (Pm) at saturating fluence rates. Fluorescence data (Fv/Fm) were consistent with the results of oxygen measurements. Under excessive light photoinhibition protects photosynthesis against photo‐damage in red algae. However, an increase in the initial fluorescence (Fo) after photoinhibitory treatment indicates that it could not prevent photodamage entirely.Action spectra of photoinhibition demonstrate that the main photoinhibition site in Polyneura hiliae is PS II, because far red light absorbed by PS I was ineffective. The strong increase of Fo in the blue wavelength range and the slight and partial recovery in weak blue light indicate that blue light especially causes photodamage.Recovery of photosynthesis requires dim white light conditions. Experiments with monochromatic light also show a wavelength dependence of recovery. Moreover, the recovery of photosynthesis after a photoinhibitory treatment is strongly temperature dependent, indicating participation of enzymatic processes. The comparison of fluorescence and oxygen measurement of the recovery shows different results in some species. The rate of oxygen production in red control light increased immediately after photoinhibited algae were exposed to weak light conditions. Surprisingly, the ratio of variable to maximum fluorescence (Fv/Fm) of Phyllophora truncata and the maximum fluorescence (Fm) of Polyneura hilliae show first a delay of the recovery under weak light conditions. Thus, in recovery experiments fluorescence and oxygen data are not quite consistent.
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Papers by Dieter Hanelt