Original paper

Persistence of clear water in a nutrient-impacted region of Lake Taihu: The role of periphyton grazing by snails

Li, Kuanyi; Liu, Zhengwen; Gu, Binhe

Abstract

Due to rapid loss of submerged macrophytes with increasing nutrient loading, a shift from a clear water state to a turbid water state has been observed in some areas of Lake Taihu, a large shallow eutrophic lake in China, while the East Bay of the lake remained clear. In order to explore the persistence mechanisms of the clear water ecosystem, two outdoor experiments were performed to examine the effects of nutrient additions and grazing activity of the snail Bellamya aeruginosa on the growth of the submerged plant Vallisneria spiralis from July to September 2006. Nutrient additions resulted in an increase of periphyton biomass and a reduction of relative growth rates of V. spiralis. B. aeruginosa grazing led to a decrease in periphyton biomass and a 6 to 8-fold increase in plant growth rate relative to the control experiment without snail presence. Our study suggests that the persistence of East Bay clear water state to increased nutrient loadings is related to the abundance of the grazing snails. Careful management of the snail population is important for maintaining the clear water state when nutrient inputs are not sufficiently reduced.

Keywords

persistenceeast baynutrientsnailsubmersed macrophytes