Abstract: In order to study the relationship between phytoplankton community structure and water environment factors in the source region of the Yangtze River, we carried out surveys in the source region of the Yangtze River in May, August, September in the year 2017 and May, July and September in the year 2018. Besides, we conducted Pearson correlation analysis and Canonical ranking analysis between phytoplankton and water environmental factors. Results unveiled a total of 6 phyla 79 species of phytoplankton, mainly belongs to Bacillariophyta and Cyanophyta. The average density of phytoplankton at each sampling point was 71.66×10⁴ ind./L. Canonical analysis indicated that temperature, chemical oxygen demand, permanganate index, ammonia nitrogen, total nitrogen and dissolved oxygen were major factors affecting the phytoplankton community structure in the source region of the Yangtze River.

Key words: source region of the Yangtze River, phytoplankton, water environmental factor, canonical correspondence analysis, density, diversity index