| According to the depth environmental governance and ecological restoration project progress of Lihu lake,sampling points were set in retreat fishing lake,environmental dredging areas and ecological reconstruction areas,Changguang Creek wetland flora in 2012 dry season,the 2013 normal season and the 2013 wet season.Using the laboratory culture method such as the specific medium plate culture and so on,investigating the ecological distribution of the microbial communities in the water and sediment and combining the physical and chemical monitoring indicators analyzed the distribution regularity of the microbial community in the water and sediment and discussed the relevance between the distribution of the microbial community and the physical and chemical indicators,hoping to provide scientific and technological support for the water ecological security assessment and the establishment of long-term management systems of Tai Hu New City.The main research results are as follows:(1)In the time distribution of microorganisms in the water,the microbial quantities of each sampling point showed a significant seasonal variation regularity that the largest and lowest number was showed in the wet and the dry season separately.It was consistent with the time distribution of TP,TN and COD in Lihu lake water that the content of TP,TN and COD are the highest in the wet season;at the level of distribution,analyzing the number of the total microbial communities in water of the whole year,the number of microorganisms in the project area(retreat fishing lake,environmental dredging areas and ecological reconstruction areas)sampling point was higher than the East Lihu lake ecological protection area control point,lower the Changguang Creek wetland sampling point.The manifestation of this distribution was most obvious especially in wet season;it was consistent with the regularity of TP,TN and COD in the water at the level of distribution that the content of TP,TN and COD are the highest Changguang Creek wetland sampling point.In the time distribution of microorganisms in the sediment,the microbial quantities of each sampling point showed a similar seasonal variation regularity that the largest and lowest number was showed in the wet and the dry season separately.TP in Lihu lake soil was consistent with the trend of the water,reaching the highest level in the wet season.The TN,ammonia and nitrate nitrogen distribution in time trends are inconsistent with the water,reaching the highest level in dry season;at the level of distribution,analyzing the number of the total microbial communities in sediment of the whole year,the number of microorganisms in the project area(retreat fishing lake,environmental dredging areas and ecological reconstruction areas)sampling point was higher than the East Lihu lake ecological protection area control point,lower the Changguang Creek wetland sampling point.TP in Lihu lake soil was consistent with the trend of the microorganisms in the soil at the level of distribution,reaching the higher level in the Changguang Creek wetland sampling point.The TN,ammonia and nitrate nitrogen distribution at the level of distribution trends are inconsistent with the microorganisms in time distribution,reaching the lower level in the Changguang Creek wetland sampling point.Through Amplicon sequence analysis of microbial 16SrDNA in water in the normal season we can get the result.Pseudomonas and Rheinheimera are the dominant bacteria which are important to the degradation organic matter in the environment in the samples of Changguang Creek plant control area sampling points where COD is higher and east of Lihu lake control area sampling points where COD is lower,they have 14.3 and 19.5 percents in the total samples respectively.Acinetobacter lwoffii is the dominant bacteria which is involved in phosphorus cycling in environment in the samples of Changguang Creek plant control area sampling points where TP content is higher and east of Lihu lake control area sampling points where TP content is lower,it have 3.0 and 5.4 percents in the total samples in different areas respectively.Acinetobacter is the dominant bacteria which is involved in nitrogen cycling in environment in the samples of Changguang Creek plant control area sampling points where N pollutant content is higher and east of Lihu lake control area sampling points where N pollutant content is lower,it have 38.4 and 19.6 percents in the total samples in different areas respectively.(2)Bacteria,Molds,Yeasts and Actinomycetes in water and sediment showed some positive correlation with organic pollutants,which is due to these organisms mostly belong to heterotrophic microorganisms that organic content had a greater influence on its growth and reproduction.PAO in water and sediments both showed a significant positive correlation with TP in water and sediments.PAO was a special facultative bacterium whose cells could uptake dissolved orthophosphate from water in nutrient-rich environments.Therefore,the number of PAO showed good correlation with TP.Ammoniated bacteria in water showed a significant positive correlation with TN and nitrate.Denitrifying bacteria in water showed a significant positive correlation with TN and nitrate,while denitrifying bacteria and nitrifying bacteria in sediment showed a significant negative correlation with TN,nitrate and TN.The nitrifying bacteria and nitrification bacteria in water and sediment were fewer for their slow growth and disadvantage in competition with other heterotrophic bacteria.(3)From the results of the single factor contaminants index method can be seen,the overall level of water contaminants at surface water quality standard between class III and class Ⅳ.The Lihu lake water in a moderately eutrophication status,the nutrient status range is 39.8～56.7,average value is 47.8.At the cell and molecular levels,the water microbial diversity index range are 0.785～2.499 and 3.387～3.753,it show that the lake in a health medium level after implementation engineering measures.At the molecular level,in sampling points of Changguang Creek wetland flora areas,the minimum microbial diversity index is 3.387 which have the highest contaminants.In sampling points of east of Lihu lake control area,the maximum microbial diversity index is 3.753 which have the lower contaminants.The result of water microbial diversity index analysis shows that Lihu lake water ecosystem health in better level.Microbial diversity index and contaminants in the water and soil have certain negative correlations,the higher contaminant concentration of the water and soil,the lower microbial diversity index and the worse quality of water and sediment.At the same time shows that microbial ecology and the ecosystem health of lake have strong correlations,microbial ecology indicator can be used as an important evaluation indicator for the ecosystem health of lake. |
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