Spatial And Seasonal Diversity Of Bacterioplankton Communities In Lake Dongping

Lake Dongping is a typical shallow temperate lake. It receives large amount of waters and nutrient inputs from Dawen River and also discharges its freshwater into the low course of the Yellow River. Additionally, its ecosystem has seriously been impacted by noticeable amount of nutrient and pollutant inputs from seasonal starch factory and aquaculture activities on its shoreline or littoral zone. The unique environmental features of Lake Dongping make it an ideal natural habitat to study how different environmental inputs drive the spatial variation of bacterioplankton communities in freshwater lakes.This study examined the spatial and time variability of bacterioplankton community diversity and composition in a shallow eutrophic lake, and the relationship between biogeochemical features and bacterioplankton communities was also explored. Samples were collected from 5 sites in March, July, and October representing differences in environmental impacts (e.g., temperature, water level, aquaculture, river water inputs, and industrial waste). Major biogeochemical features of water samples were determined and bacterioplankton communities characterized using terminal restriction fragment length polymorphism (T-RFLP),DGGE and 16S rRNA gene clone library.Physiochemcial features displayed significant difference among samples. The 16S rRNA gene clone library result is that diverse bacterioplankton phylotypes were detected in water samples, including members of 10 described phyla: Proteobacteria (Alpha-, Beta- Gamma-, Delta-, and Epsilonproteobacteria), Cyanobacteria, Bacteroidetes, Actinobacteria, Verrucomicrobia, Firmicutes, Planctomycetes, Gemmatimonadetes, Chlamydiae and unclassified bacteria. Diversity and composition of bacterioplankton exhibited significant differences among 5 sites, with much less diverse bacterioplankton communities found at two sites with industrial pollutants (site A) and near the entrance of river water (site E).The result of T-RFLP was that the samples have different peaks, but samples that at the same sampling time existed the same peaks, so bacterioplankton communities displayed noticeable temporal variability in their diversity and composition. Shannon index H and species evenness E Calculated by the software Bio-dap showed samples with industrial pollutants had the least diverse bacterioplankton communities. DGGE results showed that samples had significant differences of the bands, bacterioplankton communities displayed noticeable variability in their diversity and composition in Lake Dongping.In our study,Betaproteobacteria, Bacteroidetes, Actinobacteria, and Cyanobacteria were found to be significantly correlated with some of the physiochemical features. The abundance of Betaproteobacteria was significantly correlated with chlorophyll, total phosphorus, and total potassium. The abundance of the Bacteroidetes and Actinobacteria was only correlated with total potassium and total phosphorus. Additionally, richness of Cyanobacteria was correlated with the concentration of NO3-+NO2- and total phosphorus. Canonical Correspondence Analysis (CCA) suggested that total phosphorus, potassium, chlorophyll and NO3-+NO2- concentration statistically best explained the differences in frequencies of bacterioplankton among different samples.Our results suggest that different environmental stressors such as nutrient and pollutant inputs, aquaculture activities and so on, contribute to spatial and temporal variations in physiochemical features and bacterioplankton communities of Lake Dongping.