Distribution of bacterial communities across plateau freshwater lake and upslope soils

Microorganisms are involved in a variety of biogeochemical processes in natural environments.The differences between bacterial communities in freshwaters and upslope soils remain unclear. The present study investigated the bacterial distribution in a plateau freshwater lake,Erhai Lake（southwestern China）, and its upslope soils. Illumina MiS eq sequencing illustrated high bacterial diversity in lake sediments and soils. Sediment and soil bacterial communities were mainly composed of Proteobacteria, Acidobacteria, Actinobacteria,Bacteroidetes, Chloroflexi and Planctomycetes. However, a distinctive difference in bacterial community structure was found between soil and sediment ecosystems. Water content, nitrogen and p H affected the distribution of the bacterial community across Erhai Lake and its upslope soils. Moreover, the soil bacterial community might also be shaped by plant types. This work could provide some new insights into plateau aquatic and terrestrial microbial ecology.

Seasonal and spatial distributions of euphotic zone and longterm variations in water transparency in a clear oligotrophic Lake Fuxian, China

To assess the seasonal and spatial variations and long-term trends in water optical properties in Lake Fuxian, investigations based on field work in four seasons and a long-term analysis of data from 1980 to 2014 were conducted. The results show that there was no significant variation in the euphotic depth（Z（eu）） across the four seasons, and no significant correlations between Z（eu） and potential influencing factors in seasons other than summer, suggesting that the water itself may be a major factor regulating the Z（eu）in general. Nevertheless, significant differences in Z（eu） between the north region（NR） and the south region（SR） were observed in all seasonal tests except spring. This finding relates to a higher abundance of chromophoric dissolved organic matter（CDOM） in the NR due to runoff, especially in the rainy seasons（summer and autumn）.CDOM and its terrigenous component had an important impact on Z（eu）in summer, with the highest precipitation, and impacts from suspended solids and non-algal particles were also found in the NR in summer. The Secchi disk depth in the lake decreased clearly over the years,with significantly negative correlations with the increasing permanganate index and air temperature, implying that organic contaminants（CDOM and/or phytoplankton） are important regulators of water transparency. We estimate that the combined effects of climate warming and changes in land use and land cover are also indirect regulating factors. These findings should be considered in the protection of Lake Fuxian, owing to the importance of light penetration in aquatic ecosystems.