PHYSIOLOGICAL AND BIOCHEMICAL RESPONSES OF SCENDESMUS OBLIQUUS TO PHOSPHORUS AND TURBULENCE STRESS

In order to explore the potential effect of changing hydrological regimes on the green algae blooms, the effect of different levels turbulences on the growth and phosphorus (P) strategy of Scendesmus obliquus were studied. This experiment, lasting for 3 weeks, was designed with 3 levels turbulences, no turbulence(0 r/min), light turbulence (90 r/min)and high turbulence (120 r/min), combined with P-limit condition (0.2 mg/L) and P-replete condition (2 mg/L). The parameters determined during the experiment were listed as follows: growth rate, alkaline phosphatase activity (APA), cellular Chlorophyll a (Chl. a) contents and P uptake kinetic parameters. Our result showed: (1) Compared with the standing condition, light and high turbulence could both affect the growth rates of S. obliquus markedly, however, there was no significant variation between the growth rates of P-limit and P-replete condition. (2) On the 21st day, APAs of S. obliquus under turbulence were significantly higher than that under standing condition, contrarily, the cellular P concentrations of S. obliquus under turbulence were much higher than that under standing condition. (3) Chl. a contents of S. obliquus under P-limit condition declined significantly while light and high turbulences both leaded to the de-creasing of Chl. a contents under P-replete condition. (4) Through P uptake kinetic parameters, the affinity for P in S. obliquus under standing condition was higher than that under turbulence. According to our results, S. obliquus adapt to the standing and P-rich condition. Once the P concentration in waters continue to increase, the standing and low flowing rate water will face the risks that Green algae like S. obliquus will bloom.