Abstract:

Fuxian Lake is a representative deep plateau lake located in Yunnan Province, China. As human activities have increased since the 1980s, nutrients in the lake have been gradually rising, thereby changing the lake ecosystem. To describe the lake’s macrozoobenthic community and its response to ecological changes, we surveyed the macrozoobenthic community in Fuxian Lake from June to July in 2005. Twenty seven macrozoobenthic species belonging to 19 genera were collected in 110 sampling sites of 18 sections, and the community’s frequency of occurrence, average density, and average biomass were 97.3%, 855 ind./m², and 58.01 g/m², respectively. Mollusca was the dominant taxa in the lake (up to 50.3% of total density), followed by Chironomidae (32.3%), and Oligochaeta (17.4%). Procladius choreus, Alocinma longicornis and Bellamya quadrata were dominant species, accounting for 51.4% of total density. Oligochaeta and Chironomidae were distributed throughout the lake, while Mollusca were mainly found in the near-shore region. All dominant species showed an aggregated distributional pattern. Average macrobenthic biomass was significantly higher in the near-shore region than in the open-water region (P< 0.01), but average density did not differ between the two regions (P> 0.05). There were no differences in average density (P> 0.05) or biomass (P> 0.05) between the southern and northern portion of the lake. Correlation analyses indicated that total organic carbon in the sediment and dissolved oxygen were the key physical-chemical factors influencing macrozoobenthic density, while dissolved oxygen was the key factor influencing macrozoobenthic biomass. Macrozoobenthic diversity measured using Pielou, Margalef, Simpson, Shannon-Wiener, and modified Shannon-Wiener indices were 0.74, 2.88, 0.87, 2.40, and 20.84, respectively. Macrozoobenthic diversity was higher in the near-shore than in the open-water region, likely resulting from various submerged macrophytes in the near-shore region, which increased habitat heterogeneity. Compared to a 1980 survey, macrozoobenthic diversity in Fuxian Lake was higher in 2005, likely a result of increased nutrient levels and enlarged distribution of submerged macrophytes.

Key words: Mollusca, Oligochaeta, Chironomidae, community, Fuxian Lake