Characteristics of dissolved organic matter during the cyanobacterial degradation in Chaohu Lake, China

The actual dissolved organic matter (DOM) in Chaohu Lake was used to feed cyanobacteria to explore the changes in microbial communities, fluorescence spectral characteristics, and molecular composition of DOM during the degradation of cyanobacteria. It is found that cyanobacteria grow periodically depending on the concentration of nutrients with the decreasing concentration of nutrient salts. Both Bacteroidetes and Actinobacteria have strong correlation with algae growth. Bacteroidetes has a positive correlation with algae growth, while Actinobacteria has a negative relationship. The humus-like components in the four groups are similar, but the protein-like component (C3) shows periodic changes with the life process of cyanobacteria. The average molecular weight of each sample detected by Orbitrap high-resolution mass spectrometer increases slightly and the DOM increases aromaticity in the end. In this study, the molecule of CRAM is difficult to be done by photodegradation and biodegradation in the early periods, but some molecules of CRAM are selectively degraded by microorganisms in the final period. The growth of cyanobacteria lead to increasing the concentration of protein-like and carbohydrate-like molecule of DOM in the water. In the final stage, the molecule group of CHO disappears significantly and the molecule group of heteroatomic group increases.