ABSTRACT
Objective: To study the combined effect of temperature, nitrate and silicate on the growth, of the marine diatom, Chaetoceros simplex (Ostenfeld, 1901). Methods: Samples were analysed for the effect of temperature, nitrate and silicate on the growth, chlorophyll ‘a’, protein and carbohydrate contents. Totally fifteen experiments were conducted for 12 days under three different temperature (20, 25 and 29 ℃), 68 μmol photon m-2 s-1 light intensity and at five concentrations of nitrate: silicate propositions (882 μM [NO3-] -106 μM [SiO32-], 1323 μM [NO3] -159 μM [SiO32-], 1764 μM [NO3-] -212 μM [SiO32-], 2205 μM [NO3-]-265 μM [SiO32-] and 2646 μM [NO3-]-318 μM [SiO32-] respectively). Result:The maximum cell density reached 23.5 × 105 cells ml-1 with 1764 μM [NO3-] and 212 μM [SiO32-] concentrations at 29 ℃, in 10th day of culture. The high chlorophyll ‘a’ content of 1.57 ± 0.05 pg/cell at 20℃ and 2205 μM [NO3-]-265 μM [SiO32-]. The high protein content of 4.48 ± 0.17 pg/cell was found in 2205 μM [NO3-]-265 μM [SiO32-] at 25℃. The high carbohydrate contents of 0.78 ± 0.03 pg/cell were found in 1764 μM [NO3-]-212 μM [SiO32-] at the temperature of 25oC. Conclusions: The growth rate was directly proportional to nutrient concentration and temperature whereas chlorophyll ‘a’ and biochemical concentration was directly proportional to nutrient concentration. Based on the present results, furture work on growth optimization with the other physical and nutritional factors will yield noteworthy information on the mass cultivation of C. simplex for aquaculture purposes.