Abstract:

Aims Our objectives were to 1) examine relationships between N and P contents in aquatic macrophytes, water and sediment in Taihu Lake, a eutrophic ecosystem, and 2) explore factors controlling N and P contents in plants in relation to plant characters, such as growth status and developmental stage.
Methods We selected 32 sampling sites in the emerging-plants-free water zone of Taihu Lake and collected plant samples twice with the quadrat method, sampled sediment with column-shaped samplers at different depths, and measured relevant parameters. Concentrations of total phosphorus and total nitrogen of sediment samples with and without macrophytes were measured with the Kjeldahl method and ICP-AES atomic absorption spectrometry, respectively, and those in tissues of aquatic plants were measured by Kjeldahl automatic N analyzer and molybdate-ascorbic colorimetric determination, respectively.
Important findings The N and P contents of tissues of submerged macrophytes were higher than floating-leaved macrophytes, and the nutrient contents were higher in May than in September. Significant correlations were found between the concentrations of N and P in plants and in water, but not in sediments. The N and P contents in plants were highly dependent on plant growth status and developmental stage. Our study provides the insight for the restoration of the eutrophic Taihu Lake ecosystem.

Key words: Taihu Lake, submerged macrophytes, floating-leaved macrophytes, contents of N and P, correlations