Studies On Water Quality And Microbiological Diversity Of Xiaolangdi Reservoir

In China,water consumption in the urban construction,domestic water system and scenic environment increases drastically with the rapid development of economy and urbanization.Reservoir has become a major source of the urban water in our country due to the shortage of unpolluted fresh water resources.Xiaolangdi Reservoir is the largest canyon reservoir in the middle and lower reaches of the Yellow River with a total area of 278 square kilometers and control drainage area of 694,200 square kilometers.It accounts for 92.3%of the Yellow River basin area and belongs to the National Key Water Conservancy Project.In this paper,the Xiaolangdi Reservoir was selected as the research area to determine the annual changing regularity of water quality by monitoring and analyzing changes of physicochemical parameters from Apr.2012 to Oct.2013.Additionally,total bacteria of nine monitoring points(i.e.left of Fengshi River,right of Fengshi River,Shijing River,Zhen River,Daxia River,left of Shawo,right of Shawo,area in front of the dam and below the dam)were investigated to explore the relationship between physicochemical parameters and water quality.Availability of phytoplankton diversity in monitoring water quality was conducted by counting the phytoplankton and calculating the Shannon-Weiner index.PCR-DGGE was performed to reveal the changing trends of microbial diversity in the reservoir.Conclusion in this study could provide theoretical basis for water quality monitoring,microbial diversity conservation and prevention of eutrophication in Xiaolangdi Reservoir as well as the subsequent programs to control water pollution.The main characteristic parameters reflecting water quality,total bacteria,quantity and diversity of phytoplankton as well as microbial diversity have been monitored and determined.Conclusions are as follows:i)Totally,we monitored the surface water quality of the Xiaolangdi Reservoir for 54 times from Apr.2012 to Oct.2013,which could be categorized into ? class(ca.85.2%)and ? class(ca.14.8%)without any excessive pollutants.According to the nutritional status,medium nutrition and mild eutrophication accounted for 57.4%and 42.6%,respectively,suggesting that overall water quality in the reservoir was good.Physicochemical index of water in each monitoring cross-section changed with the sampling point and time.Phosphorus-nitrogen ratio of water was higher than 7:1,the value that was appropriate for the growth of phytoplankton.Phosphorus was a major eutrophication limiting factor in the Xiaolangdi Reservoir.And the water quality was greatly affected by permanganate index each season.ii)Total bacteria changed with the season significantly.Results indicated that total number of bacteria was higher in summer and autumn and was relatively lower in spring,which might be related with water temperature.Colonies increased with water temperature increased and reduced in accordance with the low temperature.Based on the Shannon-Weiner index,H value of phytoplankton diversity ranged between 2 and 3 for the light pollution(water quality in ? to ? class),between 1 and 2 for the moderate pollution(water quality in ? to V class)and lower than 1 for the heavy pollution(water quality in ? class),respectively.iii)Through the application of PCR-DGGE technique,prokaryotic microbial diversity in the reservoir changed remarkably with time and space,which was significantly higher in June than in April and October.And diversity in Zhen River was more significant than other monitoring points,probably because of higher nutrient levels and algae in the water that was favorable for bacteria to multiply.Microbial diversity changed with the water flow velocity and monitoring points.This shows that exchange capacity of the reservoir and dam blocking have affected the microbial diversity greatly.