Growth responses of Spirulina platensis to some physico-chemical factors and the kinetics of phosphorus utilization
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CitationBaldia, S. F., Fukami, K., Nishijima, T., & Hata, Y. (1995). Growth responses of Spirulina platensis to some physico-chemical factors and the kinetics of phosphorus utilization.
PublisherJapanese Society of Fisheries Science
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Nitrogen and phosphorus utilization in the cyanobacterium Microcystis aeruginosa isolated from Laguna de Bay, Philippines SF Baldia, AD Evangelista, EV Aralar & AE Santiago -
Journal of Applied Phycology, 2007 - Springer VerlagPhytoplankton supports fisheries and aquaculture production. Its vital role as food for aquatic animals, like mollusks, shrimp, and fish cannot be overemphasized. Because of its contribution as a food source for fish, the growth kinetics of Microcystis aeruginosa, a dominant cyanobacterium in the lake, was studied. The regular occurrence of M. 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. M. aeruginosa was collected from Laguna de Bay, isolated, and established in axenic conditions. Data on the growth kinetic parameters for nitrate-nitrogen and phosphate-phosphorus utilization by M. aeruginosa gave the following values: half-saturation constant (Ks), 0.530 mg N. L−1 and 0.024 mg P. L−1 respectively; maximum growth rate (μmax), 0.671. d−1 and 0.668. d−1 respectively; maximum cell yield, 6.5 and 6.54 log, cells. ml−1 respectively; nutrient level for saturated growth yield, 8.71 mg N. L−1 and 0.22 mg P. L−1 respectively; and minimum cell quota (Q0), 2.82 pg N. cell−1 and 0.064 pg P. cell−1 respectively. The low Ks value and high maximum growth rate (μmax) for phosphorus by M. aeruginosa would suggest a high efficiency of phosphorus utilization. On the other hand, the high Ks value for nitrogen indicated a low rate of uptake for this nutrient.
Effects of low nitrogen-phosphorus ratios in the phytoplankton community in Laguna de Bay, a shallow eutrophic lake in the Philippines 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.
Utilization of feed and rice straw compost for milkfish, Chanos chanos, production in brackishwater ponds NS Sumagaysay -
Journal of Applied Ichthyology, 1991 - Blackwell PublishingThe study was undertaken to determine the effect of 0, 25, 50 and 75% replacement of organic matter in the feed with rice straw compost on milkfish (Chanos chanos) growth and production. Treatments have similar organic matter and nitrogen loads. Up to 50% substitution (Treatments 1 to 3) was possible without significantly affecting fish growth and yield (668–725 kg/ha). A significant reduction in growth and yield (456 kg/ha) with 75% substitution (Treatment 4) implies that organic matter from compost did not contribute much to fish growth. Low phosphorus content of compost and inadequate phosphorus load in spite of increasing mineral input from compost resulted in similar primary productivity in all treatments. It appeared that compost was not a satisfactory feed substitute and that the fish derived most of their nutrition from the feed. The results further suggest that yield could be economically increased by using a low protein diet (23.8%) given at a lower rate (1.75% of body weight). To further improve yield, feeding rate can be gradually increased as biomass increases, although the most cost-effective ration will depend on the fish capacity to grow under certain environmental conditions.