Research on the Dissolved Organic Matter (DOM) and Microbial Community Diversity of Submerged Macrophyte Decomposition under Different Temperature

The characteristics of DOM, the variation of bacteria and fungi in the decomposed process of H. verticillata and P. wrightii Morong were studied under four temperatures (5℃、10℃、20℃ and 35℃). DO, conductivity, TOC, N, P, fluorescence spectra, and the diversity of bacterial and fungal community structure were tested from 0d to 68d. The results showed that the ratio of dry remaining biomass of H. verticillata to initial was 59.13%, 43.91%, 32.61% and 29.57% at 5℃, 10℃, 20℃ and 35℃ respectively. The ratio for P. wrightii Morong was 3%, 51.3%, 30.87% and 29.57%. The initial composition of C, N and P in the two submerged plants was different. Temperature had significant effect on the release of organic carbon and total nitrogen from plant decomposition (P<0.05), but it had no significant effect on total phosphorus release (P>0.05). By parallel factor analysis, Two humic acid-like components (C1 and C2) and one protein-like component (C3) was found in H. verticillata . In P. wrightii Morong, threef humic acid-like components were identified (C1, C2 and C3). The temperature increase caused more rapid changes in DO and conductivity in water body. By and large, the DO of two plants showed a trend of decrease-then-increase at all temperatures. By 16S rRNA and 18S rRNA molecular biotechnology, the abundance of microbial species in the decomposition process was higher at 20℃ and 35℃, than 0℃ and 10℃.The main bacteria were Phylum Firmicutes and Proteobacteria when two plants decomposed at 68d, and Ascomycetes was the most active fungi under 10℃ and 20℃.