Evaluation of growth rate, protein content and some physiological characteristics from two salt water phytoplanktonic species, microalga Dunaliella, under different environmental conditions

Abstract

Regarding the importance and selection of phytoplankton culturing for feeding marine zooplankton and fishes, under simple and practical conditions, two species of an unicellular green alga, Dunaliella sp. (isolated from Iran) and D.bardawil-UTEX 2538, were cultured and their growth characteristics were studied under different environmental light intensities (50µE and 150µE) and salt concentrations (0.1,0.5,1,1.5, 2 and 3M NaCl).Dunaliella sp. was different from D.bardawil because of having the longer logarithmic growth phase, higher number of cells (19×106 cells.ml-1 ) in 0.1M and 0.5M at light intensities of 150µE and 50µE respectively, higher chlorophyll and carotenoid contents, bigger size of cells (307.16±87.95µm 3 ) and higher dry weight at 0.5M on 8 th day from the beginning of experiment under 150µE, than those in D.bardawil. Protein content from the cells increased in both strains on 8 th day but the maximum amount was belonged to D.bardawil under 150µE. The highest specific growth rate (SGR) and the lowest doubling time (DT) were seen under 50µE at 0.1 M and 0.5 M (Iranin species and D.bardawil, respectively) and under 150µE in 0.5M (Iranian species) and 1M and 1.5M (D.bardawil). The highest SGR and the lowest DT of D.bardawil was at 50µE and for Dunaliella sp. was at 150µE (both at 0.5M). Increasing in light intensity from 50 µE to150µE, caused decrease in chlorophyll and carotenoid contents and conversely increase in protein content (also the highest amount of fresh weight on 8 thday) in most of the samples. Overall, Iranian species at lower salt concentrations showed better growth and higher efficiency.