Vallisnerian natans tolerance and response of microbial community in wetlands to excess nutrients loading

Abstract Submerged macrophytes-biofilm symbionts are sensitive to water pollution and can be possibly used as the bio-indicators of aquatic ecosystems. However, the physiological responses of submersed macrophyte and microbial community to environmental pollution remain unclear. In this study, impacts of three kinds of treated or without treated sewage (JP, EP and CP) on Vallisnerian natans and microbial community were investigated. Compared with control, chlorophyll(a), carbohydrates and relative electrical conductivity (REC) in V. natans leaves and dissolved oxygen in overlaying water decreased in three treatments within 21 days. Microbial α-diversity values in three media were in sequence: surface sediments > epiphytic biofilm > overlying water. Cluster analyses showed that microbial community were more similar to each other within the same media regardless of nutrients. The species losses and replacements almost contributed equally to β-diversity among three media, suggesting these organisms can be potential microbial indicators. Several typical bacterioplankton Actinobacteria, Flavobacteriia, zooplankton Arthropoda and algae Cryptomonadales were dominant in water samples, while Firmicutes and Chloroflexi as well as protozoa Rhizaria and Amoebozoa had higher abundances in surface sediments than other two media. Genera conferring to biofilm formation or pollutant removal (Cellvibrio, Chitinophaga, Ohtaekwangia and Uliginosibacterium) were detected in epiphytic biofilm. Network analysis results showed that there were more complex interactions among microbes in epiphytic biofilm than overlying water and surface sediment. Our results highlighted that REC can be a good stress indicator of submersed macrophyte, while nutrients level and spatial variations caused differences in microbial community might be used as microbial indicators of water quality in submersed macrophyte-dominated water column. These data will provide useful information for the best management practice to protect aquatic ecosystems.