The bacterial community structure in epiphytic biofilm on submerged macrophyte Potamogetom crispus L. and its contribution to heavy metal accumulation in an urban industrial area in Hangzhou

Submerged macrophytes and their epiphytic biofilms are important media for metal transport/transformation in aquatic environment. However, the bacterial community structure and the contribution of the epiphytic biofilm to the heavy metal accumulation remain unclear. Therefore, in this study, water, sediment, submerged macrophyte (Potamogeton crispus L.) and its epiphytic biofilm samples in three sites of the moat in the industrial area of Hangzhou were collected for analyzing. The bacterial community structure was significantly impacted by the TN concentrations, and Genus Aeromonas (24.5-41.8%), Acinetobacter (16.2-29.8%) and Pseudomonas (12.6-23.6%) dominated in all epiphytic biofilm samples, which had the heavy metal pollutant resistibility. The contents of Cr in biofilms (7.4-8.3 mg/kg, DW) were significantly higher than those in leaves (1.0-2.4 mg/kg, DW), while the contents of Cu (11.0-13.9 mg/kg, DW) in leaves were significantly higher than those in biofilms (0.7-3.9 mg/kg, DW) in all the three sites. The BCF values of metals in the biofilm were followed the order of YF < IC < ETS. The results indicated that the epiphytic biofilm had positive effects on the metal bioaccumulation, and the metal accumulation ability increased with the hydrodynamic forces. Bioaccumulation by the epiphytic biofilm may be an effective way for metal (especially Cr) remediation.

Automated summary

Submerged macrophytes and their epiphytic biofilms play important roles in metal transport and transformation in aquatic environments. This study collected samples from the moat in the industrial area of Hangzhou to analyze the bacterial community structure and the contribution of epiphytic biofilms to heavy metal accumulation. The results showed that the bacterial community structure was significantly influenced by TN concentrations and that the epiphytic biofilms were dominated by heavy metal pollutant-resistant bacteria such as Aeromonas, Acinetobacter, and Pseudomonas. The study also found that the epiphytic biofilms had higher Cr accumulation compared to leaves, while leaves had higher Cu accumulation than the biofilms. The findings suggest that the epiphytic biofilms can effectively accumulate metals, particularly Cr, and can be a potential method for metal remediation.