Study On Temporal And Spatial Variation, Influence Factors Of The Extracellular Enzymes Activity From Water Column And Sediment In Erhai Lake

Microbial cells are able to synthesis and secretion extracellular enzymes to catalyzed and hydrolysis the high molecular weight particulate organic substances into low molecular weight of dissolved substances,which could be directly utilized by microbial cells.In aquatic ecosystems, enzymatic are through to be the initial, rate-limiting step of decomposition and mineralization of organic matter. Study on the extracellular enzyme activity of sediment activity could help us to further understand the biogeochemical processes of the sediment.In this study, the water cloumn and sediment of the Erhai lake as the object of this research, aims to analyze the impact of the environment factors、physical and chemical factors on the extracellular enzymes activity of the Erhai water column and sediment,in order to provide a theoretical basis for the treatment of eutrophication in Erhai Lake:The main conclusions of this paper are as follows:(1) In the sediment of Erhai lake, invertase、 polyphenol oxidase、 peroxidase、 protease、 urease、 alkaline phosphatase activity was of significant seasonal variation, and their seasonal variation is very similar, the order are autumn (November)<winter (February)<spring (May)<summer (August).The seasonal variation of the sediment extracellular enzymes activity are controled by temperature,and the input of algae secretions and the allochthonous nutrients to the sediment have an important influence on the activity of the sediment extracellular enzymes activity;(2)The spatial distribution of the sediment extracellular enzymes activity are significantly different, the spatial distribution of the six enzymes are similar, normally the enzymes activity of EH2、EH4is the highest in Erhai Lake, followed by EH8、 EH9in southern platform of the lake, the enzymes activity of EH5、EH6are the lowest. And then sediment extracellular enzymes have a close relationship with physicochemical properties of the sediments, Among them, invertase, polyphenol oxidase,peroxidase was highly significantly correlated with sediment ω (OM);protease, urease, was highly significantly correlated with sediment ω (TN)；alkaline phosphatase is no obvious correlated with Sediments ω (TP) and ω (OP),but highly significantly correlated with (OP)/ω (TP).The nutritional status of the sediment has an important impact on the distribution of sediment extracellular enzymes activity,so the enzyme activity of the sediments can be used as a valid indicator factor to indicate the degree of pollution of sediment.(3) The all six extracellular enzymes activity of the sediment in Erhai Lake are significant correlated with TN, CODMn in water column, indicating that there is a certain contribution for the activity of the sediment extracellular enzymes to the release of endogenous nutrients from the sediment, higher enzyme activity may be aggravated the endogenous release process;(4) The alkaline phosphatase activity in Erhai Lake water column showed obvious seasonal changes, the alkaline phosphatase activity wolud decrease at first and then increased.The alkaline phosphatase show the highest activity with40.18μmolL·h-1at May,the lowest with12.30μmolL·h-1at September. Algae alkaline phosphatase is the main source of alkaline phosphatase in water column. The alkaline phosphatase activity is regulated by the concentration of orthophosphate:When the concentration of orthophosphate is low.Microbial cells and algae will be synthesis and secretion a large number of alkaline phosphatase, in order to improve the concentration of orthophosphate in water column;When the concentration of orthophosphate is high,the alkaline phosphatase activity will be inhibited;(5)Dissolved organic phosphorus play a important part in the algae growth and reproduction, it is the main source of Phosphorus for algae, before the algal blooms, the algae can synthesis and secrete alkaline phosphatase to hydrolysis dissolved organic phosphorus in water column.At the same time algae can utilize dissolved organic phosphorus in many ways besides through synthesis alkaline phosphatase.(6) In the simulation experiment, the trends of the alkaline phosphatase activity in overlying water are increased at first,and then decreased. It show the highest activity at pH8conditions,followed by the pH6conditions,alkaline phosphatase activity show the lowest activity at pH10.The adaptation of microorganism and the differences of the SRP concentration in overlying water is the major reasons to led that result.The alkaline phosphatase in overlying water show higher activity in aerobic treatment conditions than in anaerobic treatment conditions, indicating that bacterial will growth better under aerobic conditions;(7) In the simulation experiment,the sediment alkaline phosphatase activity show the highest activity at pH8conditions, followed by the pH6conditions, alkaline phosphatase activity show the lowest activity at pH10,this result is relevant with microbial composition of the sediment;The dissolved oxygen state of overlying water have litter impact on sediment alkaline phosphatase activity, the sediments alkaline phosphatase activity is slightly higher under anaerobic treatment than under aerobic treatment at pH8conditions, but alkaline phosphatase activity is almost show no difference between aerobic and anaerobic treatment at the rest of pH conditions.