Effects of low nitrogen-phosphorus ratios in the phytoplankton community in Laguna de Bay, a shallow eutrophic lake in the Philippines
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The effects of low nitrogen-phosphorus ratios on microalgae from a large eutrophic freshwater lake in the Philippines were investigated. Natural microalgal populations from Laguna de Bay, the largest lake in the Philippines, were cultured using three different nitrogen-phosphorus weight ratios (2N:1P; 6N:1P and 12N:1P) at two phosphorus concentrations (0.25 and 0.5 mg l–1) in each case. The growth and genera composition of the cultures under the different treatments were followed for a 12-week period. Community level responses were assessed based on species richness (s), Shannon-Wiener Index (H’), Simpson Index (λ) and Evenness (J’). Among the different microalgal groups, only the chlorophytes showed a significantly higher density in response to the 12N:1P treatment at the higher P concentration, indicating that the nutrient ratio had a significant interaction with the nutrient levels used in the experiments. The genera found in the different treatments were generally similar; however, the degree of dominance of some varied with treatment during the experiment. The succession of dominant genera also differed among the N:P treatments. The diatoms like Fragilaria, Aulacoseira (= Melosira) and Nitzschia dominated the lowest N:P. On the other hand, chlorophytes (Kirchneriella and Scenedesmus) dominated the highest N:P treatment, particularly from the second to the seventh week of the experiments with the diatoms becoming co-dominant only towards the eighth week until the end of the experimental. The 6N:1P treatment showed a mixed dominance between the diatoms and the chlorophyte genera. The various indices of diversity indicate significantly lower diversity only in the 12N:1P at 0.5 mg l–1 P and not in 12N:1P at 0.25 mg l–1 P.
CitationCuvin-Aralar, M. L., Focken, U., Becker, K., & Aralar, E. V. (2004). Effects of low nitrogen-phosphorus ratios in the phytoplankton community in Laguna de Bay, a shallow eutrophic lake in the Philippines.
Chlorophylls; Community composition; Eutrophic lakes; Freshwater lakes; Genetic diversity; Growth; Nitrogen; Nutrients (mineral); Phosphorus; Phytoplankton; Species diversity; Hydrobiology; Phytoplankton; Aulacoseira; Fragilaria; Kirchneriella; Melosira; Nitzschia; Scenedesmus; Philippines, Luzon I., Laguna de Bay; Nutrient ratios
This study was part the doctoral dissertation of the senior author at Hohenheim University, Germany. Funds for the study was provided in part by the European Union STDIII Program as component of the project ‘Laguna de Bay, Philippines: An Ecosystem Approach for Sustainable Management’ under contract CT 94-0334. Additional funds were provided by SEAFDEC/AQD under project code FS-03-F97B. The Deutschen Akademischen Austauschdienstes DAAD supported the senior author’s stay in Germany. Mr F. Reyes assisted in the culture and field collection of the samples. Dr. SF Baldia assisted in the identification of the samples.
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