Removal mechanisms of suspended solids in water bodies by Vallisneria spinulosa Yan microecosystem

Presence of suspended solids (SS) in water bodies reduce the intensity of underwater light, thus inhibiting the growth of submerged plants. However, practice of water ecological engineering shows that some submerged plants can effectively remove SS from water, resisting the negative influence of weak underwater light. This study selected the common submerged plant ( Vallisneria spinulosa Yan, V. spinulosa Yan) in surface water bodies to discuss the removal mechanisms of SS by its growth system. The results demonstrated that V.spinulosa Yan significantly enhanced the removal efficiency and velocity of SS in water. Analysis of particle size and zeta potential revealed that smaller particles were more easily migrated onto the leaf surfaces of V.spinulosa Yan for effective removal, which did not rely on the electrostatic adsorption effect. Microstructure characterization indicated that increase of water turbidity promoted the secretion of proteins and extracellular polymeric substances (EPS) by the microorganisms attached on V.spinulosa Yan leaf surfaces. Flocculation effect of the two components may be the main mechanism for SS removal in water by V.spinulosa Yan. Metagenomic analysis showed a significant increase in the abundance of bacteria, fungi, and actinomycetes, which could secrete microbial flocculants in the growth system of V.spinulosa Yan when the water turbidity was enhanced. This study provides valuable theoretical support for the ecological restoration by submerged plants in aquatic environments.