The production of biomass by microalgae is considered a clean alternative compared to other plant crops that require large areas for cultivation and that generate environmental impacts. This study evaluated the influence of temperature and nutrients on lipid contents of cultured species of freshwater microalgae, with a view toward using these lipids for biodiesel production. Two strains of Monoraphidium contortum, a culture containing Chlorella vulgaris and Desmodesmus quadricauda and another strain of Microcystis aeruginosa were maintained in the laboratory for six days, in five culture media: modified ASM-1 (control, with high concentrations of phosphate and nitrate; phosphorus-deficient; non-limiting phosphate; nitrogendeficient; and non-limiting nitrate). The cultures were then exposed to temperatures of 13°C, 25°C (control) and 37°C for eight days (n=3). Lipids were extracted by the cold-solvent (methanol and chloroform) method. On average, the highest total lipid yields were observed when the strains were maintained at 13°C and in the non-limiting nitrate medium. The lipid percentage varied depending on the concentration of algal biomass. This study showed that manipulation of controlling factors can increase the lipid concentration, optimizing the total production in order to use this raw material for biodiesel.

In this study we measured the relative contribution of two components of β-diversity, turnover and nestedness, of bacterioplankton among 25 shallow lakes in southern Brazil and tested their relationship with local (environment, chlorophyll-a and biomass of phytoplanktonic classes) and landscape variables, as well as geographical distance. We predicted that turnover would be the largest share of total β-diversity due to the variation of local characteristics among lakes. Further, we expected nestedness to increase at the expense of turnover with increasing geographical distance among lakes due to dispersal limitation. The results indicated a higher contribution of turnover than nestedness to total β-diversity, which was driven by local factors. When the relationship between β-diversity components and the spatial extent between each lake and all other lakes was considered, turnover was replaced by nestedness with increasing geographical distance for 8 (the furthermost lakes) of the 25 lakes likely because of a combination of decreasing dispersal due to distance and richness differences due to wind-driven mass effects. The results of this study suggest a role for nestedness as an indicator of dispersal limitation owing to geographical distance and wind dispersal, and for turnover as an indicator of species sorting because of environmental filters for these freshwater bacterial communities.

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