Overview and Degradation Reasons of Submerged Macrophytes of Gehu Lake

The submerged macrophytes is the important component of the shallow-water lake ecosystem,which could absorb and fix nutrients of nitrogen and phosphorous and purify the lake water.The eutrophication process and ecological restoration can be determined on the premise of better understanding of the distribution of submerged macrophytes of the shallow lakes.This paper collected the historical data and carried on field investigations,then came to a conclusion that the distribution area and biomass of the submerged macrophytes had sharply decreased and the speices had declined in the process of its eutrophication.The coverage of submerged macrophytes had decreased to less than 1% of the Gehu lake,the dominant species were Ceratophyllum demersum,Potamogeton cripus and Myriophyllum verticillatum with Hydrilla verticillata,Vallisneria natans and Potamogeton malaianus in 2009.The submerged macrophytes had been succeeded from clean-water type to stain-resistance type,while the Gehu lake had gradually shifted from stable state of clear water to turbid water during the succession of the dominant speices.Combined with the distribution area,biomass,dominant species and exsiting biomass of the submerged macrophytes in different periods of Gehu lake,the correlation between various envrionmental factors and human activities in the same period was also analyzed.Reasons on the degradation of the submerged macrophytes were discussed mainly based on load pollution into the lake,the size of fish farming and water quality.Finally it could give a guide on the restoration of the submerged macrophytes of Gehu lake.