Abstract: To clarify the relationship between water physicochemical characteristics and phytoplankton community in Hongfeng Lake, water samples were monthly collected and analyzed at three sites (DB, HYD, and HW) in 2014. The trophic level index (TLI), algal abundance, and evaluation criteria for lake trophic type were used to evaluate the eutrophic level of Hongfeng Lake. The correlation between environmental factors and the abundance of phytoplankton were analyzed. The results showed that: (1) A total of 105 species (belonging to seven phyla) of phytoplankton were identified in the lake, dominated by cyanobacteria, green algae, and diatom. (2) Algae abundance peaked in spring and autumn, with Pseudanabaenasp. being the dominant specie in most months, followed by Scenedesmus bijugatus, Chlorella vulgaris and Cyclotella sp. (3) The eutrophic level of Hongfeng Lake ranged from mesotrophic to moderate eutrophication. (4) Results of correlation analysis showed that water temperature, dissolved oxygen, total nitrogen concentration, and water transparency were the major factors influencing the abundance of algae. Our results provide important scientific foundation for water environment protection and eutrophication control in Hongfeng Lake.

Key words: generalized Pareto model., limited density-size line, linear quantile regression, maximum density-size line, Larix olgensis plantation