Effects Of Environmental Conditions On Structure And Productivity Of Submerged Macrophyte Communities

Submerged macrophytes, the major component of aquatic plant communities, play a key role in restoration of aquatic ecosystems. They have relatively high sensitivity to their surrounding environments. Because submerged plant species may differ in the ability to respond to environment variability, changing environmental conditions may greatly alter their interactions and thus affect the structure and productivity of submerged macrophyte communities. In this thesis, three greenhouse experiments using constructed experimental communities with several common submerged macrophytes were conducted to examine the effects of environmental conditions on structure and productivity of submerged macrophyte communities.In most aquatic environments, light is a limiting factor for the growth and/or distribution of submerged macrophytes. The light availability received by submerged macrophytes is not homogeneous, because light is commonly distributed heterogeneously in the horizontal plane underwater. In one greenhouse experiment, the effects of light intensity and light heterogeneity on structure and productivity of submerged macrophyte communities were investigated. The results showed that light intensity significantly affected productivity and structure of submerged macrophyte communities, whereas light heterogeneity did not.Submerged macrophytes are easily disturbed by human activities, for example fishery activities. One experiment was conducted to investigate the effects of disturbance of rowing involved in fishery activities on structure and productivity of submerged macrophyte communities. Disturbance significantly increased the species diversity and evenness but decreased the growth of submerged macrophyte communities. It is, therefore, concluded that disturbance has significant influence on structure and productivity of submerged macrophyte communities.In another greenhouse experiment, we addressed the response of submerged macrophyte communities to fragmentation. The results indicated that fragmentation significantly decreased species diversity and evenness, but did not affect productivity of submerged macrophyte communities.