Worldwide, there are 80,000-130,000 recognized mollusk species, and approximately 5% of them live in freshwater. These extensively diversified invertebrate animals compose the large phylum Mollusca. Although the mollusks could be found in various habitats and have their own characteristic behaviors, but one thing them have in common is the sensitivities to environments. As an environmental indicator, the species and structures of freshwater mollusk populations could reflect how serious the water has been polluted. 　　　

Lake Er-hai. Lake Chenghai, Lake Lugu, and Lake Bita are important freshwater bodies in northwest Yunnan, China. As the irreplaceable local drinking water resources, it is of meaning to figure out the ecological situations of those lakes. So, from 2008 to 2010, Du Lina (Kunming Institute of Zoology, the CAS) and her colleagues undertook a survey of the mollusks composition there.

During the survey, an intensive sampling was carried out. 77 sample sites (including 23 stations in Lake Er-hai. Lake Chenghai and Lake Lugu, respectively and 8 sites in Lake Bita) were sampled using handnet and dredge. Lake Lugu is in good condition and 23 molluscan species and 1 subspecies were collected. 14 and 5 species were collected in Lake Er-hai and Lake Chenghai, respectively. According to DU, the decreasing of substrate species and the increasing of floating species in Lake Er-hai may relate with eutrophication. Meanwhile, maybe due to its high altitude geographic location, only 5 species were collected in Lake Bita.

Moreover, Simpson diversity index and Shannon-Wiener diversity index were compared among 4 lakes. These indexes indicated that the Lake Er-hai. Lake Chenghai, and Lake Bita are all lighted polluted.

This study was the first survey to the four plateau lakes, in which differences of mollusks compositions among these four plateau lakes were discussed. The main findings of this study have been published on Journal of Hydroecology (2012, 33:44-49).

(By Su-Qing Liu)