Author(s): S. Nakada; M. Umeda; T. Shimada; Y. Fujimoto
Linked Author(s):
Keywords: Quatic macrophyte; Biomass; Nutrient stock; Shallow lake
Abstract: Lake Izunuma is a shallow lake located in the northern part of Miyagi Prefecture in Japan, and eutrophication in the lake is a serious problem. Moreover, lotus (Nelumbo nucifera) has become the dominant species of aquatic macrophyte in the lake, the coverage area of which community has been expanding rapidly in recent years. Accumulation of fragmented dead body of the vegetation into the sediment is considered one of the major causes of eutrophication and water quality deterioration. The purpose of this study is to evaluate the effects of the lotus community on the water environment in Lake Izunuma. Measurements were conducted on the condition of the lotus community and sediment from June-2013 to March-2014. The storage of nutrients was calculated from the data of the observations (biomass and nutrient content rate of lotus). In the growing season, lotus appears to have an ability to remove the nutrient load from the lake by saving it in the stems and leaves mainly. On the other hand, nutrient stock is large in dead body from late autumn to spring. It is possible that water pollution is caused by decompositon of the dead plant. Nutrient content rate in sediment reduced because the lotus has absorbed nutrients and carbon content rate in sediment increased because the dead body of lotus decomposed from summer to winter. Therefore, it is considered lotus community affects the sediment composition.
Year: 2014