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The seasonal dynamics of picophytoplankton communities in shallow turbid alkaline pans in Hungary was studied between July 2006 and May 2007. Similarly to other aquatic environments in the temperate zone, dominance of picocyanobacteria was observed in summer and that of picoeukaryotes in winter. The mild winter in 2006-2007, with midday water temperatures of 5-10°C, resulted in large winter phytoplankton blooms (maximum chlorophyll a concentration 800 lg l -1 ) in the shallow pans. The phytoplankton was composed of single-celled picoeukaryotes and had a maximum of 108 9 10 6 cells ml -1 in Büdös-szék pan, 50 9 10 6 cells ml -1 in Kelemen-szék pan in April 2007, and 47 9 10 6 cells ml -1 in Zab-szék pan in March 2007. In order to explain the winter dominance of picoeukaryotes, we isolated picoeukaryotic and picocyanobacterial strains and determined the temperature and light dependence of their photosynthesis. Under temperatures\15°C, the photosynthetic activity of the picoeukaryotic strain was higher and their light utilization was better than those of the picocyanobacterial strain. The results indicate that low temperature and light intensity in winter provide a competitive advantage to picoeukaryotes, while higher temperatures and light intensity are more favorable for picocyanobacteria.

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Microalgae are photosynthetic microorganisms that can produce lipids, proteins and carbohydrates in large amounts and within short periods of time and these can be processed into both biofuels and other useful commercial products. Due to this reason microalgae are considered as a potential source of renewable energy; and one of the most important decisions in obtaining oil from microalgae is the choice of species. In this study, the potential of Chlorophyceae species isolated from freshwater and soda lakes in Hungary and Romania (Central Europe) were characterized and evaluated by determining their biomass accumulation, lipid productivity, fatty acid profiles, and biodiesel properties besides protein and carbohydrate productivity. Out of nine strains tested, three accumulated more than 40% dry weight of protein, four accumulated more than 30% dry weight of carbohydrate and the strain Chlorella vulgaris LC8 accumulated high lipid content (42.1% ± 2.6%) with a favorable C16-C18 fatty acid profile (77.4%) as well as suitable biodiesel properties of high cetane number (57.3), low viscosity (4.7 mm 2 /s), lower iodine number (75.18 g I2/100 g), relative cloud point (8.8 °C) and negative cold filter plugging point (−6.5 °C). Hence the OPEN ACCESSEnergies 2015, 8 7503 new strain, Chlorella vulgaris LC8 has potential as a feedstock for the production of excellent quality biodiesel.