SUN Tao1,2, WU Yanyou1, WU Yansheng1,2, FANG Lei1,2, ZHOU Ying1,2,
TONG Chengying1,2, ZHANG Kaiyan3
（1. State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry,
Chinese Academy of Sciences, Guiyang 550081, China；
2. University of Chinese Academy of Sciences, Beijing 100049, China；
3. School of Karst Science, Guizhou Normal University, Guiyang 550001, China）
Abstract：Carbon and nitrogen cycles have always been the focus of research in the field of global change. Aquatic organisms, as the main drivers of the material cycle in the water environment, play an important role in aquatic ecosystems. Microalgae are important photosynthetic units in the aquatic environment. The utilization mechanism of inorganic carbon and quantitative methods of inorganic carbon utilization pathway have been reported, but the response of HCO3- assimilation to different proportions of nitrogen sources is still unclear. Therefore, in this study, the response of HCO3- assimilation of Chlorella proteinosa to nitrogen sources in different proportions were investigated through culture experiments in the laboratory, combined with bidirectional isotope labeling method and stable carbon isotope technique. The results showed that: under the condition of certain nitrogen nutrition, different proportions of nitrogen sources had significant effects on the growth and reproduction of Chlorella proteinosa. When the nitrogen supply (in form of nitrate and ammonia) was constant at 18 mmol/L, a small proportion of ammonia produced the highest growth of Chlorella proteinosa, but when the ratio of ammonia nitrogen increased, the growth and reproduction of Chlorella proteinosa would be inhibited. However, a higher proportion of ammonia will inhibit the growth of Chlorella proteinosa. Different ratios of nitrogen sources also have significant effects on HCO3- assimilation of Chlorella proteinosa. With the increase of the proportion of ammonia nitrogen, the C/N ratio of Chlorella proteinosa decreased at first and then tended to be stable. Meanwhile, the utilizing share of HCO3- also decreased continuously. During the growth and reproduction of microalgae, the assimilation of carbon and nitrogen nutrients influenced each other with a complex conjugate relationship. This study can provide a theoretical basis for the study of carbon and nitrogen metabolism of microalgae in response to karst water environment changes.
Key words：microalgae; HCO3- assimilation; nitrogen source; ammonia nitrogen
EARTH AND ENVIRONMENT Vol.51, No.1, Tot No.351, 2023, Page 125
