Dynamics of macrozoobenthos assemblages in the Fubao Bay of Lake Dianchi and their relation to organic pollutants
A two-year-long investigation on the dynamics of the structure and biodiversity of macrozoobenthos was conducted in the Fubao Bay of Dianchi Lake, Southwest China. A high level of organic pollution has been detected in this Bay for the last 10 years. In all, 31 benthic taxa belonging to eight families and 20 genera were identified. Oligochaeta dominated this ecosystem, comprising 53 to 99% of the total abundance and 75 to 99% of the total wet biomass. The standing crop of the solely dominant species Limnodrilus hoffmeisteri rose sharply in the two-year period: It increased from 46% of the total abundance to 73% and from 73% of the wet biomass to 99% in second year. One-way analysis of variance (ANOVA) revealed that there was no significant difference (p > 0.05) in the richness value for all and the most predominant groups between the two years. However, significant differences were detected between the total and oligochaete abundances (p < 0.05). The standing crop was the lowest (188.72 ind/m2 and 0.20 g/m2) in October, 2006 and the highest (14931.7 ind/m2 and 39.33 g/m2) in January, 2008. The annual mean standing crop increased nearly 10 times in density and eight times in wet biomass between the two years, and this increase was mainly contributed by oligochaetes. Analyses of three diversity indices and the K-dominance curve revealed that there was a significant difference between the two years. Multiple regression analysis indicated that the dynamics of the biomass of macrozoobenthos could be largely attributed to nitrate nitrogen.
Key words: Macrozoobenthos, structure, biodiversity, Dianchi Lake, organic pollution.