A STUDY ON THE RELATIONSHIP BETWEEN ALGAL COMMUNITY AND TROPHIC LEVEL FOUR IN LAKE SIHAI, BEIJING
北京4海藻类群落结构特征与水体营养水平的研究

The lake Liuhai is consisted of 6 small lakes located in central urban area of Beijing city (Fig.1)The investigation of algal community related to the trophic level in lake Liuhai was carried out monthly through Jan.to Dec.1987 The results obtained on the first 4 lakes are as follows.1. The algal species, density and diversity index in the lakes appeared obvious horizontal variations, and the number and diversity index of species in lake Shishahai, i. e., Lakes Xihai, Houhai and Qianhai, were remakbly higher than that in lake Beihai. On the contrary, the density of algae in lake Shishahai was remakbly lower than that in Beihai, Instead of cleanliness-loving species, the pollution-resisting species of algae are dominant species in Beihai. This results indicated that the trophic level of lake Beihai was much higher than that of lake Shishahai.2. It was found that the algal species and density in the four lakes exhibited obviously seasonal fluctuations. The highest content appeared in summer and autumn,and the lowest in winter.This phenomenon was light in lake Shishahai.3. The results from a correlation analysis of algal density with some ecoloogical factors in lakes indicated that the algal number increases as watertemperature, water colour, total phosphorus, total nitrogen, BOD5, COD, suspended solid increase but as water transparency decreases.4. The community successions of algae are well coincided with the variations of water quality. According to the date of algal communities,the water quality of the lake Shishahai belongs to mesoeutrophic lake, and lake Beihai is eutrophic.