Community Diversity Of Aquatic Microbial Decomposition Process

Aquatic plant is one of the major primary producers in shallow lake ecosystems. The decomposition and mineralization of aquatic plants have significant effect on the nutrient cycle and the energy transfer in lake ecosystems. Planktonic microorganisms (including bacteria and fungi) play important roles in the process of the decomposition of aquatic plant litters. However, little is known about the biodiversity and composition of bacteria and fungi during the decomposition of aquatic plants.To study the bacterial and the fungal community diversity and composition during the decomposition of aquatic plants litter, different types of plant residues were separately added into plastic column systems containing local lake sediment and upper water in this study. We selected Phragmites communis, P. malaianus, Trapa spp. and Vallisneria which were respectively split into root, stem and leaf to carry out our decomposition experiments. Finally, decoposition system were composed of1-the root of Phragmites communis,2-the stem of Phragmites communis,3-the leaf of Phragmites communis.4-the root of P. malaianus,5-the stem of P. malaianus,6-the leaf of P. malaianus,7-the root of Trapa spp.,8-the stem of Trapa spp.,9-the leaf of Trapa spp.,10-the root of Vallisneria,11-the leaf of Vallisneria,12-Control. The culture of decomposition system lasted30days. Sampling was conducted at0days,10days,20days,30days.We applied terminal restriction fragment length polymorphism(T-RFLP) to analyze the community composition and diversity of bacteria in water column and upper sediment during the process of the decomposition of aquatic plants. The results showed that the decomposition of aquatic plants had significantly effect on the biodiversity and composition of bacteria. Different decomposition rates of root, stem and leaf have different influence on bacterial community, especially3-the leaf of Phragmites communis.We applied high-throughput sequencing to analyze the community composition and diversity of bacteria in upper sediment at30days during the process of the decomposition of aquatic plants. Results revealed that Proteobacteria is the major and important phylum, especially β-Proteobacteria. Besides, the phylum were also contained as follow:α-Proteobacteria, γ-Proteobacteria,δ-Proteobacteria, Chloroflexi, Acidobacteria, Actinobacteria, Bacteroidetes, Planctomycetes.Suitable primers that specifically amplify fungal18S rRNA gene was selected out. Clone libraries were conducted and positive clones were selected for sequencing. Results showed that the primer pairs nu-SSU-0817/nu-SSU-1536and nu-SSU-0817/nu-SSU-1196were suitable to amplify fungal18S rRNA gene in this work. Basidiomycota was the most common fungal taxa in water column, and Chytridiomycota in upper sediment.This research would give a further insight into fungal community functions and their niches differentiation during the process of the decomposition of aquatic plants.