| The study of microbial carbon sources in aquatic ecosystems is very important because carbon content has become the main indicator for the study of aquatic ecosystem functions.When bacteria enter the river system through various channels,they will be widely distributed between water and sediment.Bacteria in the water settle into the sediment through the sorption particles and the bacteria in sediment can be substantially released into water greatly altering river hydrology,as well as aquatic ecosystem upstream and downstream of the dam,but how dam affects the spatial and temporal distribution of bacterial biomass is still unknown.The present study aims to determine the impact of Gongguoqiao dam on microbial biomass in water column and surface sediment at the middle reach of Lancang River during the wet,the normal and the dry seasons.The results in the study are as follows:?1?The average bacterial biomass in the water body of the upstream and downstream of the Gongguoqiao Dam during the dry season was 0.02±0.02?g·mL-1;the normal season was 0.02±0.02?g·mL-1;the wet period was:0.004±0.002?g·mL-1.The average bacterial biomass in sediments at the upstream and downstream of the Gongguoqiao Dam during the dry period was 0.96±0.61?g·mg-1;the normal season was 1.21±0.66?g·mg-1;the dry season was 0.40±0.14?g·mg-1.?2?On the time scale,bacterial biomass in the upstream and downstream of the Gongguoqiao dam exhibited the highest level at the normal season and the lowest at the wet season both in the water and sediment,but seasonal trends in bacterial abundance were not obvious.On the spatial scale,the bacterial biomass in water and surface sediment shows a V-shaped distribution trend between the upstream and downstream of the dam.This results supported the assumption that low water retention time and low nutrient levels caused by the operation of the dam and the stormwater floods will caused the the lowest bacterial biomass,and the dam interception will reduce bacterial biomass;?3?The concentration of microbial biomass in water and surface sediment varied significantly?ANOVA Tukey's Test,p<0.01?.Such differences were greatest in the wet season,followed by the dry and wet seasons.Floods in the rainy season,discharge of hydropower stations,power generation operations,and wind disturbances all contribute to the re-suspension of bacteria in sediment into the water.?4?Correlation analysis and PCA analysis of bacterial biomass and related environmental factors in water and sediments showed that in the different seasons,bacterial biomass in water mainly showed correlation with nutrient substances and Chla concentration.Bacterial biomass density in sediment has also a positive correlation with TN and TP concentrations.However,in the whole year,the bacterial biomass of the water mainly shows a positive correlation with TDS and EC.Water content and organic matter concentration are important environmental factors affecting sediment bacterial biomass.However,bacterial abundance may be more limited by temperature,local bacteria adaptation and grazing by zooplankton and zoobenthos,when nutrients are sufficient.This study drawn the distribution of bacterial biomass in the river water colum and sediment in the upstream and downstream of large-scale hydroelectric dams.By grasping the fluctuation of bacterial biomass in time and space,we discussed the interaction between the bacterial biomass and main environmental factors.The results of the present study reveal the current situation of watershed ecosystem under the influence of large hydropower stations.This study provides a preliminary contribution to the biological indexes of bacterial biomass as a function of the functional changes of aquatic ecosystems,and provides basic data for ecological protection and ecological restoration of seasonal natural river channels between reservoirs and reservoirs in cascade hydropower development. |
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