Showing papers on "Chlorococcum published in 1995"
TL;DR: In this article, the precipitation of calcite from a calcium bicarbonate solution, similar in ionic strength to natural hardwaters, was observed in a series of experiments utilizing an automated culture apparatus.
Abstract: The precipitation of calcite from a calcium bicarbonate solution, similar in ionic strength to natural hardwaters, was observed in a series of experiments utilizing an automated culture apparatus. Seeded growth experiments, using calcite seed crystals, were performed at a range of phosphate concentrations to observe inhibitory effects. These experiments demonstrated a linear relationship of increasing inhibition with increasing initial phosphate concentration. A further series of experiments was performed in which an actively photosynthesizing culture of a unicellular green alga (Chlorococcum sp.) was added to the culture vessel in order to initiate precipitation. Experiments to observe spontaneous precipitation, occurring in the absence of both seed and alga additions, were carried out to compare with precipitation rates in the algal experiments. A control experiment was also performed to investigate whether precipitation occurrred in algal cultures maintained in darkness. The carbonate site mechanistic model, developed for calcite precipitation in abiotic conditions, was used to analyse the results of the algal experiments and found to be applicable.
42 citations
TL;DR: Several blue-green algae, including Calothrix sp., Chroococcus sp., Oscillatoria sp., Gloeocapsa sp., Lyngbya sp, and the green alga Chlorococcum sp., were identified in a green and black accretion on a rock art site at Petroglyphs Provincial Park, Ontario, Canada as discussed by the authors.
Abstract: Several blue-green algae, including Calothrix sp., Chroococcus sp., Oscillatoria sp., Gloeocapsa sp., Lyngbya sp., and the green alga Chlorococcum sp., were identified in a green and black accretion on a rock art site at Petroglyphs Provincial Park, Ontario, Canada. The accretion covered several hundred petroglyphs of Algonkian origin which were pecked into a gently sloping marble outcrop. The algae promoted frost weathering of the marble by retaining water, and caused pitting and colouring of the rock surface. An enclosed, protective structure, with a fully glazed southeast wall, was constructed over the site to exclude atmospheric precipitation and groundwater run-off, while allowing maximum natural ventilation and passive solar heating of the rock surface. In laboratory tests, the algae showed a high tolerance to dryness, and algae viability within the protective structure was expected to drop only slowly. The algicidal and algistatic effectiveness of ethanol, silver nitrate and five commercial...
13 citations
TL;DR: The rationale of studying salinity tolerance of algae under nutrient limited conditions seems to be more appropriate in the bioassay method because it is established that the susceptibility / resistance characteristic of an algal species to external stress is nutritionally determined.
Abstract: Due to climatic changes in tropics, saline water bodies are often subject to natural fluctuations of salinity through precipitation, dessication, drought conditions or anthropogenic interference. Growth and persistence of algae under these conditions require physiological tolerance and/or resistant stages in the life cycle. Salinity, which ranges from 95.9-174.7 mg/L as NaCI, is considered as an important parameter for the Indradyumna pond (485 x 396 sq ft, maximum depth 5 m) of Puri, Orissa for it is located at a distance of 1 km from the Bay of Bengal. The fluctuation of salinity level of the pond has been observed during 1988-1991 mostly due to excessive use by innumerable number of pilgrims all over the year (Dash 1992). Increased salinity favors growth of cyanobacteria because this is the only group of photoautotrophic plankton taxa requiring Na + for growth (Allen and Arnon 1955). Green algal species like halotolerant planktonic algae (Hellebust and Le Gresley 1985), Chlorella, Ankistrodesmus and Scenedesmus (Kessler 1980) have also been found to be favored by increased salinity. However, the rationale of studying salinity tolerance of algae under nutrient limited conditions seems to be more appropriate in the bioassay method because it is established that the susceptibility / resistance characteristic of an algal species to external stress is nutritionally determined (Herbert and Bradley 1989; Mohapatra and Mohanty 1992). Accordingly, it was decided to see the effects of salinity stress on two indigenous phytoplankton species viz., Chlorococcum humicolo (Nag) Rabenh. and Scenedem~us bijugatus KUtz. in culture with differential nutrient enrichment using the sterile pond water as medium.
6 citations
TL;DR: The initial rates of photohydrogen evolution were at least double those of O2 evolution, demonstrating the higher affinity of the hydrogenase than the NADP-reductase to the electrons provided by the photosynthetic electron transport chain.
Abstract: The relationship between photosynthesis and photohydrogen evolution was investigated in a highly CO2-tolerant strain of Chlorococcum littorale. Concentrations of 0.03% to 40% CO2 were applied during growth of the cells. A concentraction of 5% CO2 is the most favourable condition for growth, pigment formation and carbohydrate formation, all of which tail off towards a concentration of 40% CO2. The same pattern was observed for oxygen evolution and photohydrogen evolution. The reason for the decline at high CO2 concentrations was found in the partial inhibition of photosystem II (PS II). The initial rates of photohydrogen evolution were at least double those of O2 evolution, demonstrating the higher affinity of the hydrogenase than the NADP-reductase to the electrons provided by the photosynthetic electron transport chain. CO2 concentration had no influence on the in vitro activity of the hydrogenase.
6 citations