关键词: 氮素运转, 氮素分配, 甜瓜, 氮素吸收利用率

Abstract: In order to investigate the relationship between phytoplankton community structure and environmental factors in Sanbanxi Reservoir, a nitrogenlimited deep reservoir of Guizhou Plateau, phytoplankton and water were sampled in December (wet season) 2012, and in April (normal season) and August (dry season) 2013. There existed 87 genera and 6 phyla phytoplankton in the samples, which were mainly composed of the Chlorophyta, Bacillariophyta and Cyanobacteria. In wet, normal and dry seasons, the phytoplankton abundance ranged from 0.064×10⁴ to 1.17×10⁴ cells·L^-1, from 8.21×10⁴ to 422.47×10⁴ cells·L^-1, and from 9.08×10⁴ to 2903.33×10⁴ cells·L^-1 respectively. The phytoplankton abundance of dry and wet seasons peaked in Jiachi and was minimized in Nanjia, and that of normal season peaked in Daba and was minimized in Nanjia. The dominant species were Melosira granulata, Fragilaria capucina and Microcystis marginata in dry, normal and wet seasons, respectively. The phytoplankton mainly distributed at the surface of 0 to 10 m, and its abundance decreased with water depth. The concentrations of total phosphorus averaged at 0.403 mg·L^-1 in Sanbanxi Reservoir, ranging from 0.281 to 1.139 mg·L^-1 in dry season, from 0.394 to 0.639 mg·L^-1 in normal season, and from 0.054 to 0.736 mg·L^-1 in wet season. The mean concentration of total nitrogen was 1.38 mg·L^-1. The N/P ratio (3.7:1) was lower than the most appropriate ratio 7:1 of phytoplankton, indicating that nitrogen is the limiting factor in Sanbanxi Reservoir. RDA analysis and Pearson analysis showed that water temperature was the key environmental factor, and N/P ratio was the important factor, regulating the phytoplankton community composition in the Sanbanxi Reservoir. Nutritive salt can affect phytoplankton community composition via improving the growth of Bacillariophyta and limiting the growth of Cyanobacteria.

Key words: nitrogen distribution, melon, nitrogen utilization rate, nitrogen transfer