A photochemical fuel cell system using Anabaena N-7363

Summary A blue-green algae, Anabaena N-7363, was immobilized in 2% agar gel. The hydrogen productivity of the immobilized algae was three times higher than that of free algae. The maximum hydrogen production rate by the immobilized blue-green algae was 0.52 moles h^–1 g^–1 (of wet gel) in the medium without nitrogen sources under illumination (10,000 lux). The oxygen evolved was then removed by a reactor containing aerobic bacteria. A photo-current of 15–20 mA was continuously produced for 7 days by the photochemical fuel cell system consisting of the immobilized Anabaena reactor, the oxygen-removing reactor and the hydrogen-oxygen fuel cell. The conversion ratio of hydrogen to current was from 80% to 100%.     

Paleobiological Perspectives on Early Microbial Evolution

Microfossils, stromatolites, and chemical biosignatures indicate that Earth became a biological planet more than 3.5 billion years ago, making most of life''s history microbial. Proterozoic rocks preserve a rich record of cyanobacteria, including derived forms that differentiate multiple cell types. Stromatolites, in turn, show that microbial communities covered the seafloor from tidal flats to the base of the photic zone. The Archean record is more challenging to interpret, particularly on the question of cyanobacterial antiquity, which remains to be resolved. In the late Neoproterozoic Era, increasing oxygen and radiating eukaryotes altered the biosphere, with planktonic algae gaining ecological prominence in the water column, whereas seaweeds and, eventually, animals spread across shallow seafloors. From a microbial perspective, however, animals, algae, and, later, plants simply provided new opportunities for diversification, and, to this day, microbial metabolisms remain the only essential components of biogeochemical cycles.We live on a planet that records its own history, encrypted in the physical and chemical features of sedimentary rocks (Knoll 2003). Part of this history is biological; as appreciated by every child who has visited a natural history museum, bones and shells furnish a remarkable chronicle of animal evolution, complete with dinosaurs, trilobites, and other evocative taxa. The fossil record of animals extends nearly 600 million years into the past, but comparative biology makes it clear that diverse microorganisms populated our planet long before animals first evolved. The Earth itself is >4.5 billion years old, and the known sedimentary record begins with highly metamorphosed sedimentary rocks deposited ∼3.8 billion years ago. To what extent do Earth''s older sedimentary rocks provide a direct and informative record of our planet''s deep evolutionary history?     

Photobehaviour of Paramecium bursaria infected with different symbiotic and aposymbiotic species of Chlorella

The endosymbiotic unit of Paramecium bursaria and Chlorella spec. shows two types of photobehaviour: 1) A step-up photophobic response which possibly depends on photosensitive agents in the ciliate cell itself — as is also shown by alga-free Paramecium bursaria - and can be drastically enhanced by photosynthetic activity of symbiotic algae; and 2) a step-down photophobic response. The step-down response leads to photoaccumulation of green paramecia. Both types of photobehaviour in Paramecium bursaria do not depend on any special kind of algal partners: The infection of alga-free Paramecium bursaria with different Chlorella species results in new ciliatealgae-associations. They are formed not only by combination of the original symbiotic algae with their host, but also by infection with other symbiotic or free-living (aposymbiotic) chlorellae, respecitively. Systems with other than the original algae are not permanently stable — algae are lost under stress conditions — but show the same types of photobehaviour. Photoaccumulation in general requires algal photosynthesis and occurs only with ciliates containing more than fifty algae/cell. It is not mediated by a chemotactic response to oxygen in the medium, since it occurs at light fluence rates not sufficient for a release of oxygen by the symbiotic system, e.g., below its photosynthetic compensation point. Photoresponses can be inhibited by 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU). Sensory transduction does not depend on any special symbiotic features of the algae, e.g., sugar excretion. The participation of oxygen in the Paramecium cell, of its cytoplasmic pH and of ions released or taken up by endosymbiotic algae in sensory transduction is discussed.     

A laboratory investigation of the filtration and ingestion rates of the tilapia,Oreochromis niloticus,feeding on two species of blue-green algae

Synopsis Quantitative aspects of the filter-feeding of the tilapia,Oreochromis niloticus, on two species of the blue-green algae —Anabaena cylindrica andMicrocystis aeruginosa — were investigated in the laboratory. The ingestion rate of 85 mm SLO. niloticus was best fitted using a linear regression over the range of biovolume concentrations studied (3 × 10⁶ – 3 × 10⁸ m³ ml^–1). The ingestion rate of 40 mm SL fish gave a curvilinear relationship and was best fitted using a logarithmic regression. For each size class of fish, ingestion rates were higher when fed the largerAnabaena thanMicrocystis. The results of ingestion and filtration rates are comparable to work on other aquatic suspension feeders and tend to substantiate a universality in the fundamental regulatory mechanism of filter feeding.     

The effect of sulfide on the blue-green algae of hot springs II. Yellowstone National Park

In the Mammoth Springs (Yellowstone National Park) waters with near neutral pH and soluble sulfide (H₂S, HS^–, S^2–) of over 1–2 mg/liter (30–60M) are characterized by substrate covers of phototrophic bacteria (Chloroflexus and aChlorobium-like unicell) above 50C and by a blue-green alga (Spirulina labyrinthiformis) below this temperature.Synechococcus. Mastigocladus, and other blue-green algae typical of most hot springs of western North America are excluded, apparently by sulfide. The sulfide-adaptedSpirulina photosynthesized at maximum rates at 45C and at approximately 300 to 700Ein/m²/sec of visible radiation. Sulfide (0.6–1.2 mM) severely poisoned photosynthesis of nonadapted populations, but those continuously exposed to over 30M tolerated at least 1 mM without inhibition. A normal¹⁴C-HCO₃ photoincorporation rate was sustained with 0.6–1 mM sulfide in the presence of DCMU (7M) or NH₂OH (0.2 mM), although both of these photosystem II inhibitors prevented photoincorporation without sulfide. Other sulfur-containing compounds (S₂O₃ ^2– SO₃ ^2–, S₂O₄ ^2– thioglycolic acid cysteine) were unable to relieve DCMU inhibition. The lowering of the photoincorporation rate by preferentially irradiating photosystem I was also relieved by sulfide. The most tenable explanation of these results is that sulfide is used as a photo-reductant of CO₂, at least when photosystem II is inhibited. It is suggested that in some blue-green algae photosystem II is poisoned by a low sulfide concentration, thus making these algae sulfidedependent if they are to continue photosynthesizing in a sulfide environment. Presumably a sulfidecytochrome reductase enzyme system must be synthesized for sulfide to be used as a photo-reductant.     

State 1/State 2 changes in higher plants and algae

Current ideas regarding the molecular basis of State 1/State 2 transitions in higher plants and green algae are mainly centered around the view that excitation energy distribution is controlled by phosphorylation of the light-harvesting complex of photosystem II (LHC-II). The evidence supporting this view is examined and the relationship of the transitions occurring in these systems to the corresponding transitions seen in red and blue-green algae is explored.Abbreviations CCCP carbonylcyanide-m-chlorophenylhydrazone - Chl a chlorophyll a - Chl b chlorophyll b - DAD diaminodurene - DBMIB 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone - DCCD N,N-dicyclohexyl carbodiimide - DCMU 3-(3,4-dichlorophenyl)-l,l-dimethylurea (also called diuron) - FCCP carbonylcyanide-p-trifluoromethoxyphenylhydrazone - FSBA 5-fluorosulphonylbenzoyl adenosine - kDa kilodalton - LHC-II light-harvesting Chl a/Chl b protein - PMS phenazine methosulfate - PS I photosystem I - PS II photosystem II - SDS sodium dodecyl sulfate - TPTC triphenyl tin chloride This paper follows our new instructions for citation of references—authors are requested to follow Photosynth Res 10: 519–526 (1986)—editors.     

Structures of biogenic origin from Early Precambrian rocks of Euro-Asia

Spheroidal microfossils mainly 20 to 100 μm in diameter and exhibiting granular surface textures have been recovered from Early Precambrian rocks by applying a new method of water separation in combination with thin chemical preparation. In contrast to the Acritarcha, these microfossils are characterized by a relatively low specific weight (close to one) and considerable fragility due to impregnation by mineral matter. They occur in Archean sediments of Hindustan, in rocks of the Baltic and Aldan Shields with ages of 3.0 to 3.5 billion (10⁹) years, and in Proterozoic deposits in many regions of Euro-Asia. They commonly occur in great number in Precambrian sediments of West Africa. Australia and North America. These forms are here regarded asMenneria Lopuchin and are considered to be bluegreen algae.Menneria resembles alga-like forms reported by Engel, Nagy and their co-workers from the Onverwacht Series and microfossils reported by Schopf and Barghoorn from the Fig Tree Series, both of the Swaziland System of southern Africa. In addition to spheroidalmicrofossils, ribbon-like and filiform microstructures are here reported from Archean deposits. The biogenic structures here described from the Early Precambrian of Euro-Asia are considered to have been photosynthetic and planktonic. Their progressive evolution, intensive production of organic matter, and biogeochemical role in concentration of rare elements is discussed.     

Control of eutrophication by silver carp (Hypophthalmichthys molitrix) in the tropical Paranoá Reservoir (Brasília,Brazil): a mesocosm experiment

A mesocosm experiment was conducted to assess the impact of moderate silver carp (Hypophthalmichthys molitrix) biomass (41 g m^–3 or 850 kg ha^–1) on the plankton community and water quality of eutrophic Paranoá Reservoir (Brasília, Brazil). Microzooplankton (copepod nauplii and rotifers <200 m), netphytoplankton (> 20 m), total phytoplankton biomass (expressed as chlorophyll-a) and net primary productivity were significantly reduced by silver carp. Apart from increased nitrogen in the sediment, nutrients and chemical properties of the water were not affected by fish presence. The observed improvements in water quality suggest that stocking silver carp in Paranoá Reservoir to control blue-green algae is a promising biomanipulation practice.     

Mixed populations of marine microalgae in continuous culture: Factors affecting species dominance and biomass productivity

Marine microalgae were grown in multispecies continuous cultures. Under carbon dioxide limitation, blue-green algae dominated. Under nitrate and light limitation, species dominance depended on the initial conditions. When the inoculum consisted primarily of blue-green algae with smaller amounts of other species, blue-green algae and pennate diatoms dominated. When the inoculum consisted of equal amounts of all species, green flagellates and pennate diatoms dominated. Green flagellates and blue-green algae were incompatible and never shared dominance. When nutrient limitations were overcome, the productivity of seawater was increased 100-fold before light limitation occurred. The productivity could be further increased by reducing photorespiration in the culture. The dilution rates studied (0.1, 0.2, and 0.4 day(-1)) had no effect on species dominance, nor did the higher dilution rates select for smaller cells. The maximum productivity occurred at a dilution rate of 0.2 day(-1). Temperature had the greatest effect on species dominance, with green flagellates, pennate diatoms, and blue-green algae dominating at 20 degrees C and only blue-green algae dominating at 35 degrees C. The productivity at 35 degrees C was lower than that at 20 degrees C because of the lower solubility of carbon dioxide at higher temperatures. At 10% salinity, green flagellates and pennate diatoms dominated. The productivity at this salinity was 50% that obtained at the salinity of seawater (3.5%). At 25% salinity, only the green flagellate, Dunaliella salina, survived at a productivity of 1% that obtained at the salinity of seawater.     

Blue-green algae (cyanobacteria): prospects and perspectives

Summary Photosynthetic, prokaryotic blue-green algae (cyanobacteria) occur in a wide range of natural habitats of diverse ionic composition and as such, represent an important source of biological material for biosolar energy conversion programs using saline water. The gasvacuolate, filamentous Spirulina is grown in seminatural culture in Lake Texcoco, Mexico, as a major source of single-cell protein for animal nutrition. Pilot-scale trials in other areas of the world have also demonstrated the suitability of blue-green algae, including Spirulina, for growth under brackish conditions. The carbohydrate accumulation profiles of blue-green algae differ in isolates from freshwater, marine and hypersaline habitats, with a trend towards sucrose or trehalose accumulation in stenohaline freshwater strains grown in media containing NaCl, while euryhaline and marine forms frequently accumulate glucosylglycerol. Many halotolerant isolates from hypersaline habitats accumulate glycinebetaine in response to osmotic stress. This knowledge may provide scope for future improvement in the N₂ fixation rates of blue-green algae in saline media, using betaine-accumulating N₂-fixing strains in preference to other, saltsensitive isolates.     

Marine biodiversification in response to evolving phytoplankton stoichiometry

Diversification of the marine biosphere is intimately linked to the evolution of the biogeochemical cycles of carbon, nutrients, and primary productivity. A meta-analysis of the ratio of carbon-to-phosphorus buried in sedimentary rocks during the past 3 billion years indicates that both food quantity and, critically, food quality increased through time as a result of the evolving stoichiometry (nutrient content) of eukaryotic phytoplankton. Evolving food quantity and quality was primarily a function of broad tectonic cycles that influenced not just carbon burial, but also nutrient availability and primary productivity. Increasing nutrient availability during the middle-to-Late Proterozoic culminated in the production of food (phytoplankton biomass and fresh dead organic matter) with C:P Redfield ratios sufficient to finally promote geologically-rapid biodiversification during the Proterozoic–Phanerozoic transition. This resulted in further, massive nutrient sequestration into biomass that triggered positive feedback via nutrient recycling (bioturbation, mesozooplankton grazing) on phytoplankton productivity. Increasing rates and depths of bioturbation through the Phanerozoic suggest that nutrient recycling continued to increase. Increasing bioturbation and nutrient cycling appear to have been necessary to sustain the primary productivity and “energetics” (biomass, metabolic rates, and physical activity such as predation) of the marine biosphere because of the geologically-slow input of macronutrients like phosphorus from land and the continued sequestration of nutrients into marine and terrestrial biomass.     

Variation in some photosynthetic characteristics of microalgae cultured in outdoor thin-layered sloping reactors

In outdoor thin-layer sloping reactors algae are batch cultured and harvested at biomass concentrations of about 15 g (dw) I^-1 whereafter a portion is used as inoculum for the next cycle. Light saturation curves of the oxygen evolution (PII curves) of the algae were measured using diluted aliquots of suspension taken from the reactors. The maximum specific photosynthetic rates (P ^B _max) and the light intensity at the onset of saturated photosynthesis (I _k ) decreased whilst the maximum specific photosynthetic efficiency ( ^B ) increased with an increase in the biomass concentration, during the production cycle. These differences reflect transition from light- to dark-acclimated state of the algae that occurs as a result of an increase of the suspension concentration during the production cycle. During these experiments the thin-layered smooth sloping cultures (TLSS, culture depth 5–7 mm) had higher photosynthetic rates per volume than the thin-layered baffled sloping cultures (TLBS, culture depth 5–15 mm). This was ascribed to the higherP ^B _max values of the algae grown in the TLSS cultures, allowing them to utilise high incident irradiancies more effectively. However, the areal productivity of the TLBS was higher than the TLSS indicating a higher photosynthetic efficiency of the TLBS reactors. The specific productivity decreased rapidly with an increase in the biomass concentration, but the yield remained linear during the batch production cycle, even at high areal densities.     

Seasonal variation in size spectra of phytoplankton assemblages in Loch Leven,Scotland

Greatest axial dimensions (GALD) of phytoplankton cells, colonies and filaments etc, are used to describe the size structure of whole assemblages of species in the shallow eutrophic Loch Leven (S.E. Scotland). Two-weekly samples over the period 1979–1982 have been analysed to determine whether variation in size spectra show seasonal trends. Size frequency distributions are displayed using — for the first time in studies of phytoplankton assemblages — the graphical method based on rankits. The paper describes how individuals to be measured were chosen without bias towards any particular type. Seasonal variation in temperature and nutrient concentrations are discussed in relation to algal size structure.In spite of irregular shifts in species composition and abundance, phytoplankton assemblage size spectra (PASS) exhibit seasonal patterns. Early in the year, when temperatures are low and herbivorous zooplankton sparse, small algae ( 15 µm) predominate. The winter-early spring assemblages often exhibit a normal size frequency distribution. Later in the year larger algae occasionally become relatively more numerous, and skewed or polymodal frequency distributions are recorded. Increases in large algae are usually associated with Daphnia population maxima; the inter-relationship is clearly demonstrated in time-series plots of GALD isopleths and Daphnia numbers.The potential of the PASS method to further knowledge on ecological controls of phytoplankton is discussed. The investigator is compelled to include all species in a sample. The rankit-dimension graphs retain all the data, so the position of each algal measurement and its influence on the size distribution can be observed. This approach may help to identify size ranges of algae removed by a wide variety of grazing zooplankton.     

Does N2 fixation meet the nitrogen requirements of heterocystous blue-green algae in shallow eutrophic lakes?

Summary Phytoplankton net carbon uptake and nitrogen fixation were studied in two shallow, eutrophic lakes in South Sweden. Ranges of diurnal net carbon uptake were estimated by subtracting 24-h respiration rates corresponding to 5–20% of P _max, respectively, from daytime carbon uptake values. total nitrogen requirement of the phytoplankton assemblage was determined from the diurnal net carbon uptake, assuming a phytoplankton C:N ratio of 9.5:1. Nitrogen supplied by nitrogen fixation only occasionally corresponded to the demands of the total phytoplankton assemblage. When heterocystous algae made up a substantial proportion (10%) of the total phytoplankton biomass, nitrogen fixation could meet the requirements of heterocystous blue-green algae on c. 50% of the sampling occasions. Nitrogen deficiencies in heterocystous algae were most probably balanced by the simultaneous or sequential assimilation of dissolved inorganic nitrogen. It was concluded that uptake of ammonium or nitrate, regenerated from lake seston and sediment, is the main process by which growth of phytoplankton is maintained during summer in the lake ecosystems studied.     

Multiple amounts of DNA related to the size of chloroplasts

Summary Plants containing genetically small or large plastids appear in some euploid and trisomic types of Beta vulgaris.Small tissue samples of the first 6–10 leaves of nearly 30 euploid plants from 7 different generations were incubated in a solution containing ³H-thymidine in dark/light cycles, for up to 72 hr. For semiquantitative autoradiography the chloroplasts were then prepared on the slides with various kinds of isolation media, and fixed with OsO₄, glutaraldehyde, formaldehyde, or ethanol. The specifity of incorporation was tested by observing the extractability of label after differential treatment with acid or nucleases.Chloroplasts in leaves 2–11 cm long preferentially incorporate ³H-thymidine. The silver grains over plastids appear to be in clusters (centres). A relationship between the number of grains and also between the number of centres on the one hand, and the chloroplast size on the other could be found.It is concluded that chloroplasts occur in various degrees of polyenergide organization, as has been described, for example, for blue-green algae. Regarding the presence and degree of polyploidy—the other form of genetic polyvalency —the experiments provided no information. A remarkable variation in chloroplast size (and number of labelled centres) was observed, not only between different plants or between different leaves of a plants, but also within small tissue samples.     

Some effects of light on algal respiration and the validity of the light and dark hottle technique for measuring primary productivity

SUMMARY. Measurements of the rate of oxygen uptake in a number of blue-green algae and diatoms were carried out under both field and laboratory conditions to determine the effects of light on such rates. The light history of algal cells was an important controlling factor of oxygen uptake. When measured in the light, with dichlorophenyl-dimethylurea (DCMU), oxygen uptake was sometimes different from uptake measured in the dark. The results cast some doubt on the validity of the light and dark bottle method for determining primary productivity. It is suggested that oxygen uptake measurements should be made in the presence of DCMU.     

Territorial behavior of threespot damselfish (Eupomacentrus planifrons) increases reef algal biomass and productivity

Synopsis Algal growth and damselfish (Eupomacentrus planifrons) territories were studied in two reef habitats at Discovery Bay, Jamaica. Damselfish territories were contiguous in the reef flat (0 to 2.5 m), where the algal composition and biomass varied from territory to territory. In contrast, on the lower reef terrace (22 m), damselfish territories were often spatially segregated. While the algal composition of the territories was more uniform on the reef terrace, the total algal biomass was lower than in the territories on the reef flat. Damselfish are largely herbivorous, and they defend their territories against most intruding fish, including a number of herbivorous species. Areas of the reef terrace outside of damselfish territories were heavily grazed by herbivorous fishes and contained only small quantities of non-crustose algae.The reef terrace territories were characterized by a multispecific turf of algae (greens, blue-greens, and reds) covering the Acropora cervicornis framework and by the leafy, brown alga, Lobophora variegata. A rapid reduction in the biomass of brown algae and filamentous algae was noted when damselfish were permanently removed from their territories. Only calcified, encrusting algae — plants apparently somewhat undesirable as fish food sources — would be common on the terrace zone of this reef if damselfish territories were absent. Damselfish territoriality may significantly influence the dynamics of some reefs by increasing the biomass of the algal turf thereby increasing; reef productivity. Since blue-green algae, potential nitrogen fixers, occur in these algal turfs, the fish may also be indirectly affecting reef nutrition.     

Characterization of the ribosomal ribonucleic acids of blue-green algae

Summary The ribosomal RNA components of 12 species of blue-green algae have been characterized. The 23S RNA of most species is labile and discrete cleavage products were detected by polyacrylamide gel electrophoresis. In contrast, the 23S and 16S RNA's of three species, Anacystis nidulans, Nostoc sp. and Oscillatoria tenuis were essentially undegraded (apart from a hidden break in some of the 23S RNA molecules) and these are the most suitable species for further study. The undegraded 23S and 16S RNA's have similar molecular weights (1.07×10⁶ and 0.53–0.54×10⁶ respectively) to the corresponding molecules from bacteria and eukaryote chloroplasts. The nucleotide base compositions of separated, intact, 23S and 16S RNA's from blue-green algae are also of the prokaryotic type. For instance, the (G+C) content of each RNA is approximately 52 moles % and the (G-C)+(A-U) values are high (16–24 moles %). Blue-green algae, like other organisms, contain a 5S ribosomal RNA. Its electrophoretic mobility in polyacrylamide gels and its behaviour on methylated-albumen-kieselguhr-columns relative to E. coli, plant cytoplasmic and plant chloroplast 5S RNA's, are described.     

Cultural eutrophication of West Point Lake — a 10-year study

Urban development, primarily in the Atlanta, Georgia, metropolitan area, caused a significant rise in the volume of treated wastewater discharged into the Chattahoochee River from 1976 to 1985. West Point Lake, 109 km downstream from Atlanta, responded to the increased nutrient loading with an increase in mean annual phytoplankton primary productivity of from 550 mg C m^–2 day^–1 in 1976 to 1580 mg C m^–2 day^–1 in 1985, a move from mesotrophic to eutrophic status. Monthly water quality measurements in the lake headwaters failed to detect the trend of increasing enrichment. Phytoplankton chlorophyll a concentrations did not indicate a trend of increasing algal biomass. Increased productivity was caused by improved photosynthetic efficiency that resulted from a shift in the size distribution of algae comprising the phytoplankton community. Larger centric diatoms with relatively slow turnover rates that were dominant during the early years (1976–1980) of impoundment were replaced by smaller green and blue-green algal taxa with faster turnover rates during later years (1981–1985).     

Effect of Temperature on Blue-Green Algae (Cyanobacteria) in Lake Mendota

The temperature optimum for photosynthesis of natural populations of blue-green algae (cyanobacteria) from Lake Mendota was determined during the period of June to November 1976. In the spring, when temperatures ranged from 0 to 20°C, there were insignificant amounts of blue-green algae in the lake (less than 1% of the biomass). During the summer and fall, when the dominant phytoplankton was blue-green algae, the optimum temperature for photosynthesis was usually between 20 and 30°C, whereas the environmental temperatures during this period ranged from 24°C in August to 12°C in November. In general, the optimum temperature for photosynthesis was higher than the environmental temperature. More importantly, significant photosynthesis also occurred at low temperature in these samples, which suggests that the low temperature alone is not responsible for the absence of blue-green algae in Lake Mendota during the spring. Temperature optima for growth and photosynthesis of laboratory cultures of the three dominant blue-green algae in Lake Mendota were determined. The responses of the two parameters to changes in temperature were similar; thus, photosynthesis appears to be a valid index of growth. However, there was little photosynthesis by laboratory cultures at low temperatures, in contrast to the natural samples. Evidence for an interaction between temperature and low light intensities in their effect on photosynthesis of natural samples is presented.