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  • 11
    ISSN: 1573-5176
    Keywords: cyanobacteria ; blue-green algae ; biosynthesis ; growth ; gamma linolenic acid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The total lipid and fatty acid content ofSpirulina platensis UTEX 1928 was 7.2 and 2.2% respectively of cellular dry weight under controlled conditions supporting high growth rates. With increases in irradiance from 170 to 870 μmol photon m−2 s−1, growth rate increased, total lipid decreased, and fatty acid composition was unaffected. At 1411 μmol photon m−2 s−1, total lipid increased slightly and percent composition of the fatty acid gamma linolenic acid increased. Growth and total lipid content ofS. platensis were affected by changes in growth temperature from 25 to 38 °C. With increased growth rate, total lipid content increased. This suggests that the storage of carbon increases at temperatures supporting high growth rates. The degree of saturation increased with temperature. Although the percent composition of gamma linolenic acid was higher at lower growth temperature, production was still primarily a function of growth rate. The effect of temperature on fatty acid content and degree of saturation was of secondary importance. Nitrogen starvation increased total lipid content but decreased fatty acid content as a percentage of dry weight; composition of the fatty acids was unaffected. N-starvation appeared to suspend synthesis of long chain fatty acids inS. platensis, suggesting that some other compound stores fixed carbon when nitrogen is limiting. It was concluded that fatty acid production inS. platensis is maximized by optimizing culture conditions for growth.
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  • 12
    ISSN: 1573-5176
    Keywords: algal culture ; cell counting ; growth rate measurements ; image analysis ; microcomputer ; morphology ; video microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A largely unexplored area is the application of digital image processing to counting and sizing of microalgal cells from culture. Commercial systems are available, but have not been tested, nor necessarily optimized for high speed counting and sizing of phytoplankton. The present work describes the design, construction, specifications and comparative performance of an inexpensive system optimized for counting and sizing microalgal cells. This system has been tested with cells of the picoplankton to nanoplankton size ranges (1–20 μm). The hardware was a widely available standard microcomputer, an inexpensive video camera and monitor, and a video digitization board (frame grabber). A modifiable menu-driven program (PHYCOUNT) was written and provisions made to make this program available to other workers. The program is constructed such that it can be adapted to a variety of hardware setups Video digitization boards). Comparison of growth curves for microagae revealed there were no significant differences in division rate and cell yield as assessed by the image analysis method compared to manual counts with a hemacytometer. Several hundred cells were counted routinely within 10–15 s, far exceeding the counting rate achieved by hand tally. A variable transect feature allowed sampling every nth pixel and provided a substantial increase in execution speed. More than 1000 counts can be done per day. A protocol for the use of 96-well plates of polyvinyl chloride as counting chambers contributed to the processing of large numbers of samples rapidly. Other routines developed provided subtended area, defined the coordinates of cell perimeter, and derived cell length and width. The calculation of the latter two parameters was usually done off-line as data output is in standard numerical form accessible by other programs. Experience with daily use of the PHYCOUNT program and imaging hardware reveal that the system is reliable for cell counting and sizing. The presence of bacteria in the algal cultures does not affect cell counting or sizing.
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  • 13
    ISSN: 1573-5176
    Keywords: High Rate Algal Pond ; mathematical model ; quantum requirement ; light absorption ; attenuation ; productivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A model is presented to predict algal biomass concentration and productivity in a High Rate Algal Pond (HRAP) at all possible combinations of incident photon flux density (PFD), pond depth and hydraulic retention time (HRT). The total extinction coefficientk t and the absorption coefficient ka of algal biomass were measured at 1 nm intervals. Thek t values were used to calculate the underwater light climate, which included the spectral narrowing of the photon flux density with increasing depth. The number of quanta absorbed (QA) from the photosynthetic available radiation (PAR) was calculated using thek a /k t ratio and incident PFD at 1 nm intervals. Algal oxygen production is related to QA by the quantum requirement (QR), which was determined fromk a ,and the slope of the photosynthesis versus irradiance curve (α). Based on this calculation we propose a new concept: the compensating absorption rate (CAR), which represents the rate of photon absorption necessary to balance oxygen consuming processes. The model calculated productivities using literature data on HRT, pond depth and incident PFD, that compared well with the actual measured productivities. To achieve optimal HRAP productivities under fluctuating climatological conditions, we propose a pond management strategy based on model simulations.
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  • 14
    Electronic Resource
    Electronic Resource
    Springer
    Journal of applied phycology 1 (1989), S. 289-289 
    ISSN: 1573-5176
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
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  • 15
    ISSN: 1573-5176
    Keywords: Oscillatoria tenuis ; natural gas ; thermal degradation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cultures of the blue-green alga (cyanobacterium)Oscillatoria tenuis were used to simulate thermal degradation and gas formation by heating without oxygen at 250° and 350 °C for 100 h. Analysis through gas chromatography showed that the gases were mainly CH4, C2H6, C3H8, iC4 (isobutane), nC4 (normal butane), iC5 (isopentane), nC5 (normal pentane), H2, C02 and N2. The volume of gases per g dry weight of alga was 44 ml at 250 °C and 100 ml at 350 °C. Alkane gas comprised only 2.04% of the total at 250 °C and rising to 40.0% at 350 °C. The fraction of C02 decreased from 83.3% at 250 °C to 40.0% at 350 °C. The quantity of alkane in the soluble organic matter doubled with rising temperature but the H/C atomic ratio in the ‘kerogen’, insoluble organic matter, decreased sharply. Infrared spectra of the ‘kerogen’ showed that the peak of adipose radical at 2900 cm−1 disappeared gradually with rising temperature, which reflects the gradual break of CH4 or C2H6 from ‘kerogen’. This demonstrates that insoluble organic matter rather than soluble organic matter in blue-green algae are the main sources of the gas alkanes in the process of simulated thermal degradation.
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  • 16
    ISSN: 1573-5176
    Keywords: Anabaena doliolum ; ATP content ; 14CO2 uptake ; glutamine synthetase ; nitrogenase ; nitrate reductase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This study reports physiological features of a N2-fixing cyanobacteriumAnabaena doliolum in response to metal mixtures. Exposure of the cyanobacterium to Cu, Ni and Fe individually, as well as in combinations (Cu + Ni, Cu + Fe, Ni + Fe), showed marked differences in growth inhibition, nutrient uptake (NH4 + and NO3 −), photosynthesis, ATP content, nitrate reductase, glutamine synthetase and urease activities. The response to metal combinations was also dependent upon the order in which the metals were added. The Cu-Ni combination resulted in synergistic interaction, in contrast to the antagonism of Cu-Fe and Ni-Fe. Pre-addition of Fe protected the cyanobacterium against Cu and Ni toxicity. Statistically significant (P 〈 0.005) inhibition of all the processes following metal supplementation was observed. This study suggests that carbon fixation is the most suitable variable for assessing heavy metal toxicity.
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  • 17
    ISSN: 1573-5176
    Keywords: microalgae ; Spirulina ; phycocyanin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Spirulina biomass was separated into two fractions which may have various uses. A phycocyanin fraction may provide a food colourant and biomarkers, and a protein-rich leftover may be useful as aquaculture feed. Activated charcoal adsorption, ultrafiltration and spray drying were used effectively to produce a high quality colourant grade phycocyanin, while activated charcoal adsorption, ammonium sulphate precipitation, dialysis and chromatography were effective in preparing reagent grade phycocyanin.
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  • 18
    ISSN: 1573-5176
    Keywords: Ascophyllum nodosum ; commercial seaweed extract ; Arabidopsis thaliana ; root-knot nematode ; Meloidogyne javanica ; betaines ; biological control
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Treatment of Arabidopsis thaliana plants with a commercially-available, alkaline extract of the marine brown alga, Ascophyllum nodosum, resulted in a significant decrease in the number of females of the root-knot nematode, Meloidogyne javanica, which developed in the roots compared to those of plants grown in a water control medium. Significant reductions in egg recovery were also achieved from plants treated with the seaweed extract. Similar effects were produced when betaine components of the seaweed extract (γ-aminobutyric acid betaine, δ-aminovaleric acid betaine and glycinebetaine) were used in quantities equivalent to those applied in the seaweed extract treatment. As the experiments were conducted under monoxenic conditions, it can be concluded that the results obtained with the application of either the seaweed extract or betaines are indicative of their effects on the plants and are not dependent on microorganisms associated with the rhizosphere.
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  • 19
    ISSN: 1573-5176
    Keywords: Navicula saprophila ; eicosapentaenoicacid ; palmitoleic acid ; palmitic acid ; carbonate ; acetate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Changes in the eicosapentaenoic acid (EPA) content of Navicula saprophila grown photoautotrophically and mixotrophically with the addition of acetate were examined in terms of their growth progress. Among four conditions, mixotrophic conditions in CO2-enriched (about 2%) atmosphere gave a maximum EPA content. As sodium acetate was added to the growth medium, the EPA content increased and reached a maximum value of 34.6 mg EPA g-1 biomass in the early stationary growth phase. In contrast, under photoautotrophic conditions in CO2 enriched atmosphere, the EPA content decreased during this phase. EPA was localized as the fatty acid esters of monogalactosyl diacylglycerol, phosphatidylethanolamine and phosphatidylcholine, and the addition of acetate strongly enhanced production of the PC ester of EPA.
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  • 20
    ISSN: 1573-5176
    Keywords: community composition ; diversity ; epilithic cyanobacteria ; eutrophication ; monitoring ; species richness ; water quality
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Changes in epilithic cyanobacterial communities were determined in a river characterized by variations in nutrient content. The cyanobacterial community composition of the upstream sites was different from that of the downstream communities, where anthropogenic influences lead to an increase in nutrients (principally soluble reactive phosphate, SRP). There was a general trend in downstream sites towards a decrease in species richness, abundance, and diversity of cyanobacteria. The reduced cyanobacterial species richness in downstream locations was due largely to a marked decrease in the number of heterocystous species, although the number of non-heterocystous species also decreased. Epilithic phycobiliprotein content was positively correlated with the number of cyanobacterial cells, implying that this pigment provides information about the abundance of the cyanobacteria community in the epilithon. The lowest concentrations of phycobiliprotein in the epilithon were observed where concentrations of phosphate were highest. Similarly, the number of heterocystous and non-heterocystous species tended to decrease as the SRP increased, and as the DIN:SRP ratio decreased. However, no relation was found with dissolved inorganic nitrogen (DIN). The differences among cyanobacterial communities could be interpreted as being a consequence of variations in nutrient composition. Finally, the usefulness of cyanobacteria as an alternative tool for assessing changes in water quality is discussed.
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