LI Haitao¹, WU Yanyou²
(1.Guizhou Vocational College of Agriculture, Guiyang 551400, China;
2.State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China)

Abstract: Chlamydomonas reinhardtii and Chlorella pyrenoidosa were treated under different concentrations of ammonium and nitrate with different δ15N. The characteristics of stable isotope fractionation were determined under different inorganic nitrogen treatments. The results showed that microalgae grew slowly and showed no stable nitrogen isotope fractionation when the organic nitrogen from the culture medium was the only available nitrogen source. In the case of low inorganic nitrogen concentration, the growth of microalgae and the stable nitrogen isotope fractionation increased when the inorganic nitrogen concentration was increased up to 2.0 mmol/L, in the case of high inorganic nitrogen concentration (>2.0 mmol/L), the growth of microalgae tended to be stable, the stable nitrogen isotope fractionation tended to increase during the utilization of ammonium, but decreased during the utilization of nitrate. These observations may be related to the decrease of nitrate reductase activity in microalgae.

Keyword: Chlamydomonas reinhardtii；Chlorella pyrenoidosa; ammonium; nitrate; nitrogen isotope composition

EARTH AND ENVIRONMENT Vol.47, No.6, Tot No.332, 2019, Page 839-843