关键词: Frankia, 自然环境胁迫, 基因多样性

Abstract: From October 2007 to October 2008, a monthly investigation was conducted on the community structure of zoobenthos in four urban rivers, including Wuchaogang River, Henggang River, Chaoyang River, and Caoyanghuanbang River, in Shanghai. A total of 20 zoobenthos species were recorded, among which, 14 species were of Mollusc, and 3 species were of Annelida. The zoobenthos in the four rivers had a low diversity, with the maximum value of Shannon index being 0.602. The diversity index of macrobenthos could objectively reflect the environmental quality of river body. In the four rivers, the concentrations of Pb, As, and Zn in Mollusc were 1.15, 0.32, and 0.23 times higher than the China’s national standard, respectively, and the concentrations of Cd, Cu, Pb, and Zn in sediments were all beyond the national standard. No correlations were observed between the heavy metals concentrations in Mollusc and sediments. The toxic-response factor (Eⁱ_r) showed that the potential ecological risk of the heavy metals was in the order of Cd>Pb>Cu>As>Zn>Cr, and the potential ecological risk index showed that the heavy metals pollution of the sediments in the four rivers was moderate.

Key words: Frankia, Natural stress, Genetic diversity