The Growth of Vallisneria natans and Its Epiphytic Biofilm in Simulated Nutrient-Rich Flowing Water

Abstract

This paper investigates the effects of water flow on the growth and physiological indicators of the submerged macrophyte, Vallisneria natans, and the bacteria and algae community composition on its epiphytic biofilm-covered leaves. The authors set up a simulated flowing water laboratory experiment testing high nitrogen (N) and phosphorus (P) concentrations. Total chlorophyll and dissolved oxygen (DO) was significantly enhanced, and turbidity was reduced, thereby accelerating the growth of V. natans. These experiments were compared to another set of observations on a static group. The accumulation of malonaldehyde (MDA) in the dynamic groups was significantly higher than that in the static group. As an antioxidant stress response, the total superoxide dismutase (T-SOD) was also induced in plants exposed to nutrient-rich flowing water. The results of 16S rRNA high-throughput sequencing analyses showed that the water flow increased the bacteria community diversity of biofilm-producing bacteria with N and P removing bacteria, carbon cycle bacteria, and plant growth-promoting rhizobacteria on the epiphytic biofilm. This research determined that water flow alleviates the adverse effects of eutrophication when V. natans grows in water containing high N and P concentrations. Water flow also inhibits the growth of cyanobacteria (also referred to as blue-green algae) in epiphytic biofilm. The ecological factor of water flow, such as water disturbance and aeration measures, could alleviate the adverse effect of eutrophic water by providing a new way to restore submerged macrophytes, such as V. natans, in eutrophic water.