Correlation Between Water Purification Capacity and Bacterial Community Composition of Different Submerged Macrophytes

Abstract

Eight submerged macrophytes are commonly found in subtropical areas, including Vallisneria natans, Vallisneria denseserrulata, Hydrilla verticillata, Elodea canadensis, Ceratophyllum demersum, Potamogeton malaianus, Potamogeton pectinatus, and Potamogeton maackianus, and these eight macrophytes were selected as research objects. The absorption capacity of nitrogen and phosphorus and water purification ability of submerged macrophytes were compared under indoor static water conditions. Furthermore, combining the bacterial community composition of submerged macrophytes, which was determined by 16S rRNA gene sequencing, the correlation between the water purification ability and the bacterial community of submerged macrophytes was determined. The results showed that all of the submerged macrophytes had obvious purification effects on nitrogen and phosphorus in water. The removal of nitrogen and phosphorus by submerged macrophytes was mainly through plant synergism, and the removal rate of plant absorption and enrichment was low. Among them, the removal rate of nitrogen and phosphorus was the highest in Vallisneria denseserrulata, reaching 91.58% and 96.81%. The self-absorption ability of nitrogen and phosphorus from water of Elodea canadensis and Ceratophyllum demersum was higher than other groups. The plant synergistic purification ability of Vallisneria denseserrulata and Vallisneria natans was the highest. The absolute dominant phyla of eight submerged macrophyte-associated bacteria were Proteobacteria (abundance values were more than 40%). At the genus level, Cupriavidus, Rhodobacter, and Gemmatimonas were the dominant genera for different submerged macrophytes. Most of these bacterial groups were degradable, which may be the main reason for the strong ability of eight submerged macrophytes to purify nitrogen and phosphorus in the water. The LEfSe analysis showed that Vallisneria denseserrulata and Vallisneria natans had the highest number of bacteria with significant differences. Among them, Rhizobiales, Burkholderiales, Flavobacteriales, Alcaligenaceae, Cupriavidus, and Bacillales may be the dominant bacteria to enhance the efficiency of plant purification of the water by Vallisneria denseserrulata. The bacteria of Deinococci, Comamonadaceae, Saprospiraceae, and Hyphomicrobium may be the dominant bacteria to enhance the efficiency of plant purification of the water by Vallisneria natans.