The Influences Of Light, Nutrition And Phytoplankton On Growth And Physiology Of Submerged Macrophytes In Eutrophic Waters

In order to study the mechanisms involved in the decline of submerged macrophytes in eutrophic lakes of the middle and lower reaches of the Yangtze River, and to further provide theoretic bases for their restoration, this study assessed the effects of nutrient enrichment, light limitation and dense phytoplankton on the growth and physiology of submerged macrophytes.The effects of light and nutrient availability, 3 (light)×3 (nutrient), on growth and N, P and C concentrations of Vallisneria natans were investigated in a microcosm experiment. Growth of V. natans decreased with increased light limitation. Inhibition of increased nutrient loading on the growth of V. natans was observed only in high light treatments, while in medium light treatments there was no significant effect of nutrient enrichment on growth, and the growth of V. natans increased with nutrient enrichment in low light treatments. Low light intensity increased tissue total nitrogen, total phosphorus, ammonia-N and free amino acid-N but lowered tissue soluble sugar and starch. The concentrations of total phosphorus, ammonia-N, free amino acid-N and starch increased with nutrient enrichments. The results suggested that both low light availability and high nutrient availability influenced the growth of V. natans significantly, and that there were interactions between them, indicating effects of...