Study Of The Aquatic Plant Application Status And Optical Characteristics In Urban Landscape Water Bodies

The near-natural treatment has gradually become a new concept to improve the water environment, which mostly ties in the reconstruction of the aquatic vegetation with application of aquatic plants. Light is one of the most important factors for aquatic plants, especially for submerged macrophytes. The underwater light conditions will be the limited factors for the living of aquatic plants due to the low water transparency. By taking 107 water bodies in 90 parks and public spaces of Shanghai as research objects, the aquatic plant application status was investigated and the problems exist were analyzed in this paper. Besides, the optical characteristics of landscape water bodies in Shanghai were studied with their influencing factors as well. Therefore the relationship between the aquatic plant application status and the optical characteristics in landscape water bodies was discussed in this study, which will provide the theoretical and scientific basis for the water near-natural treatments and managements in urban artificial landscape water. The results showed that:1. There were 26.2% of water bodies carrying no aquatic plants coverage, with the rest water bodies enjoying 27 families,42 generas and 53 species (including varieties) of aquatic plants. The applied aquatic plant life forms in these water bodies were dominated by the emergent plants, taking 63.5% of the total 52 species (without algae), floating plants secondly and submerged plants last.17 growth forms were covered in the applied aquatic plants, in which graminids carried the most species. The 17 growth form combination could be manifested as 6 groups:Lemnid-Hydrocharid, Vallisnerid-Isoetid, Potamid-Myriophyllid, Utricularid-Certophyllid, Trapid-Nymphoid and Graminid-Herbid.46 species of the applied aquatic plants were the introduced cultivated species, with 29 species of native aquatic plants, taking 15.6% of native aquatic plant resources. The results showed the poor application status of submerged macrophyte and native aquatic plants in Shanghai artificial landscape water bodies.2. The influencing factors of water transparency in landscape water of Shanghai included suspended matter, phytoplankton, TN and NH3-N. Suspended matters were the main influencing factors, phytoplankton secondly. TN and NH3-N indirectly affected water transparency by controlling the nutrients of phytoplankton. The influencing factors of Kd (PAR) were TP, TN, TDP and CODCr.TP carried the most influencing weight among all factors. The way TP affected Kd (PAR) was considered by controlling phytoplankton as well.3. Based on the investigation results and optical characteristics in objective water bodies, the optical characteristics were not considered as the limiting factors for the distribution of aquatic plants in Shanghai, whereas the interaction relationships existed indeed. The results showed that there was no significant correlation between the distribution of aquatic plants and the optical characteristics. The optical characteristics varied under different life froms combination, in which submerged macrophyte communities and "emergent-floating-submerged" plant communites showed the well optical characteristic status. The two aquatic plant combinations are recommended for the application of aquatic plants in urban artificial landscape water bodies.