Abstract: From August 2012 to July 2013, phytoplankton communities and the main aquatic environmental factors were investigated in four landscape lakes (Jiangjun Lake, Long Lake, Luling Lake and Yicui Lake) in Ji’an, Jiangxi Province. The water quality was evaluated by using biodiversity indexes (Shannon index H, Margalef index D and Pielou index J), and the water environmental factors were analyzed by principal components analysis (PCA). The results indicated that a total of 163 species of phytoplankton were identified, which belonged to 7 phyla and 82 genera. Phytoplankton species in four landscape lakes were mainly composed of Bacillariophyta and Chlorophyta. Phytoplankton cell abundance varied seasonally with values ranging from 25.45×10⁶ to 54.04×10⁶ cells·L^-1, which were high in summer and autumn but low in winter and spring. In Jiangjun Lake, Long Lake, Luling Lake and Yicui Lake, the H value of phytoplankton was 1.26-2.08, 1.82-2.61, 2.27-2.62 and 1.10-2.32, respectively; the D value was 2.03-3.51, 2.36-3.71, 2.48-3.93 and 3.12-3.96, respectively; the J value was 0.45-0.69, 0.59-0.80, 0.67-0.77 and 0.50-0.84, respectively. Based on this investigation, it was considered that the four lakes were under eutrophic situation and at moderate pollution level. According to PCA of Luling Lake with relatively serious pollution, water temperature (WT), dissolved oxygen (DO) and total nitrogen (TN) were the most important environmental factors influencing the distribution of phytoplankton in small enclosed landscape water body. It is suggested that some necessary management and ecological remediation should be strengthened for the small closed landscape water.

Key words: forest litter, dissolved organic carbon (DOC), dissolved organic matter (DOM)