Responses of leaf-associated biofilms on the submerged macrophyte Vallisneria natans during harmful algal blooms

Abstract The present study investigated the physiological responses, photosynthetic activity, and microbial community structureof leaf-associated biofilms on the microphyte Vallisnerianatans during a harmful algal bloom. Results of the physiological and photosynthetic indices ( F v / F m ratios [maximum quantum yield of photosystem II(PSII)]; malondialdehyde content; total chlorophyll; and activities of superoxide dismutase, catalase and peroxidase) indicated that algal bloomscould cause inhibition of photosynthesis, oxidative stress and an antioxidant system stress response in Vallisnerianatans leaf-associated biofilms. Multifractal analysis suggested that allelochemicals or algal organic matter released by cyanobacteria could reduce the surface roughness of the leaf. Microbial diversity analysis of the biofilms showed that algal bloomsslightly altered the microbial community structurewhile the richness and evenness of the microbial composition remained stable. This study provided useful information to better understand the adverse effects of algal bloomson submerged macrophytes.