The study on uptake of nitrate and ammonium by Scendesmus obliquus based on 15N stable isotope technique
基于15N稳定同位素技术的斜生栅藻对硝氮和氨氮吸收的研究

Abstract: Nitrate (NO3 -N) and ammonium (NH4+-N) nitrogen are the main forms of inorganic nitrogen in waters. This paper studied the uptake characteristics of NO3 -N and NH4+-N by Scendesmus obliquus based on 15N stable isotope technique. The result shows that the NH4+-N uptake rate was significantly higher than NO3 -N uptake rate at the same nitrogen concentration; The NO3 -N uptake rate in the mixed nitrogen group in which both NO3 -N and NH4+-N presented was significantly lower than that in the single nitrogen group in which only NO3 -N presented, indicating that the presence of NH4+-N inhibits the uptake of NO3--N. The result also shows that when 15NO3--N and 14NO3--N existed simultaneously, Scendesmus obliquus took up 14NO3--N preferentially which produces isotope fractionation. However, the effect of different form of nitrogen source is far greater than the effect of isotope fractionation.