Estuarine Tidal Flat Wetland Sediment Extracellular Enzyme Research

The paper studied three aspects of extracelluar enzymes in sediments of the tidal flat wetland, namely 1) the distibution of five sorts of extracellular enzymes in sediments in the East End of Chongming Island along the elevation gradient or community succession series, the relationships between the activities of enzymes and the ecological factors, and functions of extracellular enzymes in the process of community succession; 2) the effects of the heavy metal ions and EDTA on the activity of alkaline phosphatase in sediments of the East End of Chongming Island by adding and removing of heavy metal ions, discussing whether the activities of extracellular enzymes could be taken as the indicators for the environmental status; 3) the variations of the activities of extracellular enzymes in sediments in the East End of Hengsha Island after the discarding clay. These studies would enrich the knowledge of the extracellular enzymes, help us to understud the ecological processes of wetland ecosystem and be important practice to direct the conservation and development of the estuarine tidal flat wetlands.The major conclusions drew on this studies are:1 . The activities of extracellular enzymes in sediment in the east end of Chongming island changed regularly along the elevation gradient, the physical and chemical factors affected the activities of extracellular enzymes.Along the elevation gradient or succession series, the activity of alkaline phosphatase increased gradually. Besides the surface sediments* alkaline phosphatase of sediments in every vegetation area has higher peak activity and Vmax,but a lower Km at the depth of 20-30cm.lt was proved that there was a remarkably active zone of the alkaline phosphatase in the sediments besides the surface layer. The activity of alkaline phosphatase was significantly correlated to the particle size and dissolved inorganic phosphorus negatively but opposite to organic matters and total nitrogen. Vmax had a same trend as activity of alkaline phosphatase, but opposite to Km. Theresults suggested that organic matter and total nitrogen could increase the activity of alkaline phosphatase, and that the activity of alkaline phosphatase was activated or inhibited by substrate and product due to co-existence. This mechanism was reported poorly in the wetland sediments or soils.With succession of community, the activity of catalase increased gradually, and the vertical variation of the activity was affected by environmental factors and didn't show identical rule. No matter what kinds of sample, including the horizontal and vertical, the activity of catalase was correlated to organic matter, total nitrogen and total phosphorus positively, but opposite to dissolved inorganic phosphorus and particle size of sediments. It suggested that the fertility of sediment and biological oxidation was improved with succession.The activity of proteinase decreased from bare flat to reed zone, and the activity in deeper sediment was lower than surface sediment. The activity of proteinase was correlated to organic matters and total nitrogen negatively, but opposite to dissolved inorganic phosphorus. From bare flat to reed zone, theconcentration of protein declined with diatom quantity which influenced the activity of proteinase. It suggested that proteinase in the sediments was probably produced by diatom, and the activity of proteinase was decided by the types of organic matter but not the concentration of organic matter.From bare flat to reed zone, the activity of sucrase changed insignificantly. There was a higher activity in triangle sulbush(5c/rp? mariquetef) zone than other vegetation zones. To the vertical distribution, there was higher activity at 10-3 Ocm depth. The activity of sucrase had insignificant correlation to the environmental factors. It may mainly depend on the composition of organic matter more than the organic matter.The activity of urease is too low to detect nearly and it had no correlation with environmental factors.2. The experiment of heavy m...