Abstract: Chlorophyll a (Chla) and diatom community structure are two indicators of lake water quality. In this study, we investigated the environmental parameters, chlorophyll a, and diatom community of four small urban lakes in Kunming (Beitan, Beihu, Nanhu and Longtan lakes in the campus of Yunnan Normal University) between March 2017 and December 2019. The results showed that the concentrations of total nitrogen (TN), total phosphorus (TP), and Chla in the four lakes showed significant seasonal fluctuation. The Chla concentration in Nanhu Lake, which had the highest nutrient level among the four lakes, was significantly higher than that in the other three lakes and largely affected by TN. In comparison, water temperature significantly contributed to the increases in Chla concentration in the other three lakes. Water temperature and TN were significantly correlated with Chla across the four lakes. Diatom assemblages in Beitan, Nanhu, and Longtan lakes were dominated by planktonic diatoms, and benthic diatoms were dominant in the shallowest lake Beihu, suggesting that water depth significantly affected the proportion of planktonic diatoms and dominant taxa. Water depth, TN, TP, transparency, and water temperature affected the spatio-temporal changes of diatom community structure, with water temperature as the major factor in causing the seasonal variation in diatom community, and TN and TP as the major drivers for community variation among lakes within the same season.

Key words: urban lake, diatoms, chlorophyll a, spatio-temporal pattern, eutrophication