Photosynthesis In Algae Research Articles

Effects of UV on carbon assimilation of phytoplankton in a mixed water column

Carbon assimilation is usually measured at fairly constant light intensities. Under natural conditions, however, planktonic algae are moved through the water column and experience light of fluctuating intensity and spectral composition. They may cope with strong UV for a short residence in the upper water layer. In order to estimate the effects of UV on primary production of phytoplankton under conditions of turbulent mixing, we compared carbon assimilation and exudation of algae incubated in UV-transparent quartz and in UV-absorbing glass bottles which were moved through different water layers. Computer-controlled elevators were used to simulate mixing depths between 2 and 14 meters. Compared to the glass bottles, particulate C assimilation in the quartz bottles was reduced by 20-30 % at mixing depths between 2 and 10 m. There was no significant difference between both types of incubation bottles at a mixing depth of 14 m. Exudation was enhanced by UV near the water surface (mixing depth up to 4 m) but not in the deep-mixed samples. Our results indicate serious damage of planktonic algae by UV even under conditions of vertical mixing if the euphotic zone exceeds the mixing depth. Depression was low for circulation through the whole euphotic zone and may disappear at even deeper mixing. Our results indicate lower photoinhibition per UV dosage at fluctuating than at constant light intensities. A model predicting inhibition as function of weighted irradiance spectra was adapted to describe wavelength dependent photoinhibition occurring at different mixing depths. The model results agreed very well with the inhibition rates measured under fluctuating light. These preliminary results are used to discuss the importance of UV on photosynthesis of planktonic algae in aquatic environments of different mixing depths and stabilities of stratification.

Benthic algal response to pulsed versus distributed inputs of sediments and nutrients in a Mackenzie Delta lake

The Mackenzie Delta is a lake-rich region where the distribution and abundance of phytoplankton, macrophytes, and benthic algae among lakes may be controlled by an interaction between nutrient supply and sediment in the water column, and episodic reduction in light availability associated with river flooding. To simulate the effects of episodic river inflow on benthic algae, limnocorrals (depth = 3 m) were either not manipulated (control), or received high or low weekly additions of nutrients (N and P) and sediments, delivered as a pulse (1/wk: high-pulsed, low-pulsed) or distributed incrementally through each week (⅓ of high or low load × 3 d/wk: high-distributed, low-distributed) in a balanced triplicated design (15 limnocorrals). Artificial substrates, enriched to mimic the supply of nutrients at the sediment/water interface, were suspended in the limnocorrals at 2 m depth for 6 wk beginning in mid-July 1995. Maximum average levels of phytoplankton biomass (inferred from chlorophyll) occurred in the treatment where light attenuation was highest (high-distributed), and lowest levels occurred where light attenuation was lowest (control). By contrast, maximum average accrual of benthic algal biomass on the artificial substrates occurred in the control, whereas lowest accrual occurred in the high-distributed treatment. Chlorophyll content per unit biovolume of benthic algae increased modestly in treatments experiencing low light relative to treatments with higher light, but was insufficient to explain the 3-fold difference in inferred biomass between the control and high-distributed treatment in the case of benthic algae, or the 4-fold difference in the case of phytoplankton. Under equivalent in situ light conditions, areal net photosynthesis of benthic algae was highest in the control and lowest in the high-pulsed treatment. Net photosynthetic rate per unit benthic algal chlorophyll was not significantly different among the control and treatments. Last, biomass accrual rates among treatments showed a strong inverse relation with average light attenuation among the limnocorrals over the duration of the experiment. These results indicate that light availability was primarily responsible for maximum biomass accrual in the control and was the dominant factor affecting accrual rates among treatments. Overall, this study suggests that the abundance of benthic algae among Mackenzie Delta lakes may progressively increase as flood frequency decreases and light availability becomes greater, whereas phytoplankton abundance may peak in lakes with intermediate transparencies by responding to nutrient additions despite interruption of the light environment by suspended sediments.

A high-performance instrumentation system to measure the fluorescence kinetics of plants for in vivo photosynthesis research

This paper presents the design and application of a new type of pulse amplitude modulated fluorimeter (PAM) that uses an optical system based on an integrating sphere to improve the rapid assessment of in vivo photosynthesis in green plants and algae. The lightweight instrument was designed for rechargeable battery operation and can easily be transported for field measurements. Its integrating sphere can accept whole plants in order to reduce plant stress due to cutting before measurements. Also, the excitation light is focused outside of the sphere and brought in by an optical fiber, allowing the use of high light intensities to saturate the photosynthesis process. Finally, the integrating sphere is equipped with an airflow device for the circulation of air pollutants inside the sphere, thus allowing the study of continuous air pollution in green plants via fluorescence emission. The paper concludes by presenting the results of measuring the fluorescence parameters of barley, a plant of interest for agricultural and environmental studies.

Activation by blue light of inorganic carbon acquisition for photosynthesis in Ectocarpus siliculosus: organic acid pools and short-term carbon fixation

Blue light stimulates photosynthesis in brown algae by activating a mechanism for carbon acquisition. As this is connected with liberation of CO2 from an internal pool, it had previously been suggested that a C4 pathway might operate, with CO2 mobilization from an intermediate mediated by the action of blue light. The possibility that such a C4 mechanism functions was tested in Ectocarpus siliculosus by investigating metabolite pools and carbon fixation products. Extracts were analysed by HPLC with an ion exchange column. With the exception of citrate/isocitrate all metabolite levels were far too low to serve as the intermediate pool. No changes in the concentrations of any of the metabolites were found after activation by blue light following red light pre-irradiation. During short-term incubations with 14C inorganic carbon, the major label was found in phosphoglycerate. There was also clear labelling of peaks containing malate plus pyruvate and in citrate/isocitrate. In addition, glycerate contained hig...

Activation by blue light of inorganic carbon acquisition for photosynthesis in Ectocarpus siliculosus: organic acid pools and short-term carbon fixation

Blue light stimulates photosynthesis in brown algae by activating a mechanism for carbon acquisition. As this is connected with liberation of CO2 from an internal pool, it had previously been suggested that a C4 pathway might operate, with CO2 mobilization from an intermediate mediated by the action of blue light. The possibility that such a C4 mechanism functions was tested in Ectocarpus siliculosus by investigating metabolite pools and carbon fixation products. Extracts were analysed by HPLC with an ion exchange column. With the exception of citrate/isocitrate all metabolite levels were far too low to serve as the intermediate pool. No changes in the concentrations of any of the metabolites were found after activation by blue light following red light pre-irradiation. During short-term incubations with 14C inorganic carbon, the major label was found in phosphoglycerate. There was also clear labelling of peaks containing malate plus pyruvate and in citrate/isocitrate. In addition, glycerate contained high levels of radioactivity in some culture strains of Ectocarpus siliculosus. In chase experiments, the radioactivity of all metabolites continued to increase, indicating the presence of considerable amounts of intracellular inorganic carbon. Transient labelling was not observed for any of the fixation products. When Ectocarpus was pre-irradiated with red light and then stimulated by blue light, fixation rates increased with a time course that correlated with the activation of oxygen evolution. Photosynthetic oxygen evolution was investigated in vivo after the addition of possible intermediates to carbon-free seawater. Most of the exogenous applied substrates did not enhance photosynthesis, either in red light or after blue light stimulation. A strong enhancement seen after the addition of oxaloacetate was most likely due to release of CO2 during the breakdown of the metabolite in the medium. Taken together, the data argue strongly against the operation of a C4 pathway in Ectocarpus. It is suggested that the internal pool mobilized by blue light contains inorganic carbon.

Inhibition of algal photosynthesis by a symbiotic coral

When symbiotic dinoflagellate algae (Symbiodinium sp.), isolated from the scleractinian coral Plesiastrea versipora were incubated in homogenized host tissue, carbon fixation was usually lower than in seawater only (43 cases of of 54), and this inhibition occurred throughout the year. Algae incubated in homogenized host tissue fixed a mean of 78.84% ± 22.6% of the amount fixed by algae in seawater (n = 54, range 33–142%). The difference between rates of fixation in seawater (mean ± SD of 61.300 ± 22.71 nmol C/105 cells) and in homogenates (mean ± SD of 47.377 ± 21.42 nmol C/105 cells) in individual experiments, was highly significant (p<0.0001, paired t-test). Homogenized host tissue from populations of P. versipora separated by 4000 km inhibited photosynthesis in algae from both their own and the distant coral population. Inhibition of photosynthesis was not observed when isolated algae from the anemone, Aiptasia pulchella were incubated in homogenate from P. versipora. An inhibitor of photosynthesis was isolated from a low molecular weight fraction of homogenized host tissue of P.versipora by cation-exchange chromatography and further purified by HPLC. This is the first natural inhibitor of photosynthesis that has been found in an invertebrate with symbiotic algae.

TEMPERATURE INDUCED PHOTOINHIBITION IN OUTDOOR CULTURES OF MONODUS SUBTERRANEUS

Outdoor algal cultures are continuously exposed to changes in environmental conditions, particularly irradiance and temperature. While the changes in light intensity take place in a range of one to two hours, the increase in temperature is a slower process and takes about four to five hours. This de‐synchronization between the two important environmental factors governing photosynthesis and growth of algae results in a unique stress condition where photoinhibition can be induced at relatively low light intensity. Outdoors the early morning culture temperature was found to be about 12 to 14° C, and reaches 25 to 28° C at mid‐day. In an experiment, such a natural temperature regime was compared to another one in which the morning temperature of the culture was increased to 20° C by using a heating system. A fast decline in the maximal photochemical efficiency of PSII (Fv/Fm) was observed starting as soon as sunrise. The decline was faster in the non‐heated culture and was to a lower value. The diurnal changes in the electron transfer rate (ETR) and in the non‐photochemical quenching (NPQ) of the cultures, indicated that the early morning exposure of cells to sub‐optimal temperature results in a fast inactivation of PSII activity which was reflected in an inhibition of the photosynthetic activity even when the two cultures finally reached the same temperature at mid‐day. Thus, under the same light and temperature mid‐day conditions the ETR was higher and the NPQ was significantly lower in the heated culture. Significant changes in productivity of the cultures also were observed.

ALGAE AND PROGRESS IN PHOTOSYNTHESIS RESEARCH III- PHOTOPRODUCTION OF HYDROGEN: MECHANISM AND PROBLEMS

ALGAE AND PROGRESS IN PHOTOSYNTHESIS RESEARCH III- PHOTOPRODUCTION OF HYDROGEN: MECHANISM AND PROBLEMS

The effect of environmental conditions on faecal coliform decay in post-treatment of UASB reactor effluent

The removal of faecal coliforms (FC) in waste stabilization ponds is partly caused by natural decay processes. This work distinguishes between light mediated and light independent processes, since only the upper layer of a stabilization pond receives solar radiation. Light attenuation by algae matter or other particles causes darkness in the rest of the pond. The purpose of this work was to investigate the decay processes in stabilization ponds in order to yield improved design of pond systems. Experiments were carried out with buffered effluents from an Upflow Anaerobic Sludge Blanket (UASB) reactor, treating domestic wastewater. The FC decay rate was determined and compared for light and dark conditions, in aerated bottles and beakers, respectively. The effective environmental factors were also investigated and mathematical expressions were derived for their effect on the FC decay rate. Special attention was given to the effect of light attenuation by algae matter. It was found that light independent FC decay in aerated UASB effluent is caused by a shortage in carbon sources, since glucose addition prevented decay for over ten days. The nutrient content of UASB effluent was satisfactory for a long-term survival. The FC decay in the dark parts of stabilization ponds is therefore under conditions of carbon and nutrient sufficiency expected to be negligible. Under conditions of carbon shortage, the light independent FC decay was found to be temperature dependent, but not pH dependent (in the range 7.2 - 9.1). The FC decay in beakers exposed to solar radiation was much faster then under dark conditions. The light mediated decay was affected by the pH, DO concentration and the solar radiation intensity, but not by the temperature. The addition of autoclaved algae matter strongly reduced the FC decay in the beakers, due to light attenuation. It is therefore expected that the light attenuation by algae matter in stabilization ponds also reduces the FC decay. This could partly offset the stimulating effects of algae photosynthesis (i.e. increased pH and DO concentrations) on FC decay. It seems therefore that there is an optimum algae concentration for maximum FC decay. This can lead to a new design approach, based on regulation of algae growth in stabilization pond systems.

Significance of a Two-Domain Structure in Subunits of Phycobiliproteins Revealed by the Normal Mode Analysis

Phycobiliproteins are basic building blocks of phycobilisomes, a supra-molecular assembly for the light-capturing function of photosynthesis in cyanobacteria and red algae. One functional form of phycobiliproteins is a trimeric form consisting of three identical units having C 3 symmetry, with each unit composed of two kinds of subunits, the α-subunit and β-subunit. These subunits have similar chain folds and can be divided into either globin-like or X-Y helices domains. We studied the significance of this two-domain structure for their assembled structures and biological function (light-absorption) using a normal mode analysis to investigate dynamic aspects of their three-dimensional structures. We used C-phycocyanin (C-PC) as an example, and focused on the interactions between the two domains. The normal mode analysis was carried out for the following two cases: 1) the whole subunit, including the two domains; and 2) the globin-like domain alone. By comparing the dynamic properties, such as correlative movements between residues and the fluctuations of individual residues, we found that the X-Y helices domain plays an important role not only in the C 3 symmetry assemblies of the subunits in phycobiliproteins, but also in stabilizing the light absorption property by suppressing the fluctuation of the specific Asp residues near the chromophore. Interestingly, the conformation of the X-Y helices domain corresponds to that of a module in pyruvate phosphate dikinase (PPDK). The module in PPDK is involved in the interactions of two domains, just as the X-Y helices domain is involved in the interactions of two subunits. Finally, we discuss the mechanical construction of the C-PC subunits based on the normal mode analysis.

Photosynthetic water oxidation: a simplex-scheme of its partial reactions

Photosynthesis of green plants, algae and cyanobacteria is powered by sunlight. It uses water as ultimate donor of electrons for the reduction of CO2 to yield carbohydrates. Photosystem II (PS II), a water^ plastoquinone oxidoreductase, is the key enzyme of oxygenic photosynthesis. It is an integral protein of the thylakoid membrane. PS II is functionally bipartite, its photosynthetic reaction centre (RC II) which mediates the primary charge separation is linked to the oxygen evolving complex (OEC) [1,2] which reacts with bound water (see Fig. 1). The net reaction of water oxidation: 2H2O34e ! O2 ‡ 4H‡ 1†

The metabolites of dietary chlorophylls

Abstract Chlorophylls, the green pigments responsible for photosynthesis in plants, algae and bacteria, are also part of the daily diet of herbivorous feeders. Numerous metabolic derivatives of the major green pigment, chlorophyll-a, have been found in a wide variety of organisms during the last decade. Studies of these metabolites show that some are antioxidants or cellular signaling mediators in vivo. The metabolites of bacteriochlorophylls-c and d, recently found in the deep-sea dragon fish, Malacosteus niger, function as a visual photosensitizer, enabling the fish to seek their prey in `the dark'. Discovery of these metabolites as well as their interesting biological functions raises questions as to the roles of chlorophyll derivatives in the chemical ecology of herbivorous life forms.

Cyanobacterial metabolites with bioactivity against photosynthesis in cyanobacteria, algae and higher plants

Cyanobacteria produce a large number and variety of bioactive allelochemical substances, with a diverse range of biological activities and chemical structures, and with effects on many biochemical processes within cells. An increasing number of such metabolites is being found to be directed against oxygenic photosynthetic processes, which, in the microbial world, are unique to algae and cyanobacteria. Such chemicals are likely to be involved in regulating natural populations, and are potentially useful as biochemical tools, and as herbicidal or biocontrol agents.

PHOTOSYNTHETIC CYTOCHROMES c IN CYANOBACTERIA, ALGAE, AND PLANTS.

The cytochromes that function in photosynthesis in cyanobacteria, algae, and higher plants have, like the other photosynthetic catalysts, been largely conserved in their structure and function during evolution. Cyanobacteria and algae contain cytochrome c6, which is not found in higher plants and which may enhance survival in their planktonic mode of life. Cyanobacteria and algae contain another cytochrome, low-potential c549, which is not found in higher plants. This cytochrome has a structural role in PSII and may contribute to anaerobic survival. There is a third unique cytochrome, cytochrome M, in the planktonic photosynthesizers, and its function is unknown. New evidence is appearing to indicate evolution of cytochrome interaction mechanisms during the evolution of photosynthesis. The ease of cytochrome gene manipulation in cyanobacteria and in Chlamydomonas reinhardtii now provides great advantages in understanding of photosynthesis. The solution of tertiary and quaternary structures of cytochromes and cytochrome complexes will provide structural and functional detail at atomic resolution.

ChlorophyllaFluorescence: A Tool for the Investigation of Toxic Effects in the Photosynthetic Apparatus

The effects of environmental pollutants, such as triazines, urea herbicides, phenols, nitro aromatic compounds, aldehydes, hydrogen sulfide, volatile halogenated aliphatic and aromatic compounds, and alkylbenzenes, the photosynthesis of green algae were investigated by using detailed analysis of chlorophyllafluorescence. Application of quenching analysis by means of a pulse amplitude-modulated fluorometer allows the discrimination of different modes of action. Blocks of the electron-transport chain, the action of uncouplers, and fluorescence quenching by nitroaormatic compounds could be distinguished. Hydrogen sulfide and short-chain aldehydes seem to react in the same way, probably by reaction with components of the electron-transport chain. Nonreactive volatile compounds affect chlorophyll fluorescence in a strictly hydrophobicity-dependent manner. The quenching analysis suggests an inhibition of utilization of proton-motive force for ATP synthesis. Detailed analysis of fluorescence patterns may be of great help for identification of toxic pollutants and their sources.

Sensitivity of Macrophyte-Dominated Freshwater Microcosms to Chronic Levels of the Herbicide Linuron

Effects of a chronic application of the herbicide Afalon (active ingredient linuron) on physicochemical conditions, decomposition of plant litter, and densities of zooplankton and macroinvertebrates were studied in indoor microcosms intended to model drainage ditches. For 28 days, concentrations of 0, 0.5, 5, 15, 50, and 150 μg/L linuron were maintained, each in two replicates. The microcosms were dominated by the macrophyteElodea nuttallii.The functional response of the ecosystem is discussed in relation to shifts in community structure. Treatment effects of linuron on community metabolism, as a direct effect of the inhibition of the photosynthesis of macrophytes and algae, resulted in a decrease in dissolved oxygen and pH, and an increase in alkalinity and conductivity (NOEC 0.5 μg/L). During the posttreatment period, differences between controls and highest dose fell gradually, but were still significant 7 weeks after the start of linuron application. Decomposition of particulate organic material in litter bags was not affected, despite decreases in DO. The negative effect of linuron on several algae (cryptophytes, diatoms) and the positive effect on the green algaChlamydomonasresulted in a decrease of several Rotatoria and an increase in Copepoda, and, to a lesser extent, Cladocera. The complete disappearance of the macrophyteE. nuttalliiin the 150 μg/L microcosms and a 50% reduction of its biomass in the 50 μg/L microcosms reduced the numbers of the snailPhysella acuta,which normally inhabits macrophytes. Artificial substrates indicated a significant increase in the isopodAsellus aquaticusin the 50 and 150 μg/L microcosms during the posttreatment period. This, however, was counteracted by a significant decrease inA. aquaticusat the final harvest. Changes in the ecosystem structure (decline in macrophyte biomass) made the artificial substrates more attractive.

Progress in the study on structure and function of the antenna of algae

IN the evolution series, algae possess a position between green plants and photosynthetic bacteria. The photosynthetic apparatus of algae and plants are very similar because both of them contain the two photosynthetic reaction centers of PSⅡ and PSⅠ and have the same photosynthetic function. Therefore, study of the photosynthesis of algae has a common significance. On the other hand, the light-harvesting antennae of plants are chlorophyll a/b-protein complex in thylakoids while those of algae are the phycobilisomes. A phycobilisome is a large super-......

Effects of 2,4-dichlorophenoxyacetic acid on Kentucky algae: simultaneous laboratory and field toxicity testings.

2,4-D was applied to a cove in Kentucky Lake which was highly infested with Myriophllum spicatum (Eurasian watermilfoil). Effects of 2,4-D on nontarget algal communities were monitored concurrently in the field and in laboratory microcosms for eight days. Results indicated that indirect effects of water temperature and increased nutrient concentrations due to lysis in milfoil plants may be more important in the field community dominated by Chlorophyta, Pyrrhophyta, and Bacillariophyta. 2,4-D applied at the label-recommended rate of 2 mg/L or less stimulated total community growth in both laboratory and field indicating a possible hormonal effect of 2,4-D on algae. Reduced community growth and metabolism at high laboratory concentrations of 100 mg/L and 1000 mg/L may indicate an inhibitory effect on photosynthesis and/or respiration in algae. 2,4-D altered the laboratory community structure and function in all concentrations tested. Heterotrophic taxa such as Nitzschia, Euglena, Chlamydomonas, Mallomonas, Anabaena, and Oscillatoria appeared to be least affected by 2,4-D at high concentrations. Scenedesmus, Pediastrum, Characiosiphon, Navicula, Melosira, and Fragilaria appeared to be more sensitive, even in the lowest concentrations.

Thermodynamic stability analysis of the carbon biogeochemical cycle in aquatic shallow environments

We carry out the thermodynamic stability analysis of the carbon cycle in a lagoon. Our approach differs from linear stability analysis, and is based on the excess entropy production. The coupled biogeochemical processes in the lagoon include gas transfer, photosynthesis, respiration, decomposition, sedimentation, and oxidation of algae. The thermodynamic stability criterion derived from this analysis indicates that, in addition to known limiting factors of biomass production such as temperature, light, and nitrogen and phosphorous concentrations, the rate of carbon dioxide delivery from the air reservoir to the water can be also a limiting factor. For the Venice lagoon, the criterion obtained predicts that a doubling of the CO 2 partial pressure in the atmosphere can render the system unstable, driving it to dramatic biomass production and degradation.

PHOTOSYNTHETIC RESPONSE OF THE GIANT KELP MACROCYSTIS PYRIFERA (PHAEOPHYCEAE) TO ULTRAVIOLET RADIATION1

ABSTRACTSolar ultraviolet radiation (UVA + UVB) impairs photosynthesis in marine algae. Canopy blades of the giant kelp Macrocystis pyrifera (L.) C. Agardh are exposed to high levels of solar UV in the field. To determine the effects of UV radiation on photosynthesis in the giant kelp and to identify sites of UV damage, O2 evolution, reaction center organization, light harvesting, and energy transfer efficiency were measured in canopy blades that had been exposed to elevated levels of UV in the laboratory. UV treatment reduced both the light‐saturated rate and the light‐limited rate of photosynthesis by 50% but produced no significant change in the rate of dark respiration. A significant impairment of photosystem II (PSII) reaction center function was observed, suggesting that PSII is a major site of damage in chromophytes. Reduced quantum efficiency of photosynthesis and loss of energy transfer from light‐harvesting pigments (fucoxanthin, chlorophyll a, and chlorophyll c) to PSII indicate that the major light‐harvesting complex of M. pyrifera, the fucoxanthin‐chlorophyll protein complex (FCPC), was another site of UV damage. These measures provide the first evidence of a direct effect of UV radiation on specific sites in the photosynthetic apparatus of chromophytes and indicate that in situ fluorescence excitation analysis may be a simple means to detect UV stress in algae.