Studies on the growth physiology of Microcystis aeruginosa (Cyanobacteria) isolated from Laguna de Bay, Philippines
2006
Baldia, S.F. | Evangelista, A.D. | Aralar, E.V. | Santiago, A.E.
Phytoplankton, one of the biological components of the aquatic environment, supports fisheries and aquaculture production. Its vital role as food for aquatic animals like molasses, shrimp and fish cannot be over emphasized. Because of the algal's contribution as a food source of fish, the growth kinetics of Microcystis, a dominant algal species in the lake, was studied. The regular occurrence of this blue-green alga, Microcystis aeruginosa, is experienced during the months of May to July or from September to November in Laguna de Bay, the largest freshwater lake in the Philippines. Microcystis aeruginosa was collected from Laguna de Bay, isolated, and establish in axenic condition. Results of the study on the effects of light intensity of M. aeruginosa showed that growth was optimum between 9-18 micromol m E-2 SE-1, suggesting its high growth efficiency at low irradiance. Data on the growth kinetic parameters for nitrate-nitrogen and phosphate-phosphorous utilization by M. aeruginosa gave the following values: half-saturation constant (Ks), 0.530 mg N/l and 0.024 mg P/l, maximum growth rate, 0.671 and 0.668/d, respectively, maximum cell yield, 6.5 and 6.54 log, cells/ml, respectively, nutrient level for saturated growth yield, 8.71 mg N/l and 0.22 mg P/l, and minimum cell quota, 2.82 pg N/cell and 0.064 pg P/cell. The lower Ks value and high maximum growth rate (micromax) for phosphorous by Microcystis would suggest its high efficiency in phosphorous utilization. Results of this study indicate that light and nutrient uptake kinetics by Microcystis aeruginosa is the combined factors contributing to its dominance in a eutrophic lake such as the Laguna de Bay.
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