Water flow promotes nutrient release and microbial community assembly during Hydrilla verticillata decomposition

Abstract

The macrophytes decomposition is an important process in global freshwater ecosystems. However, the differences and dynamics in nutrient biogeochemical cycles are far from clear in lotic and lentic environment during autochthonous macrophytes decomposition. In this study, the nutrient transfer and microbial community shift during submerged macrophyte Hydrillaverticillata decomposition were investigated in lotic (flowing water) and lentic (static water) environments for 206 days. We found the changes in litter debris biomass can be modeled by exponential decay models (R2 = 0.979–0.984) in two system. Water flow stimulated cellulase activity and disturbed nutrients transfer between water and surface sediments in lotic environment compared to lentic environment. Turnover affected the microbial beta-diversity and stochastic processes enhanced bacterial and eukaryotic community assembly in plant debris and surface sediments with decomposition progresses. Contrary to surface sediments, water flow increased dispersal limitation but decreased heterogenous selection in plant debris. There were more Alveolata and Metazoans in plant debris and Metazoan in surface sediments in lotic environment than lentic environment. Co-occurrence networks revealed that water flow improved plant debris microbial community stability and changed microbial food web. Dissolved oxygen and macrophyte nutrition have important effects on microbial community composition and diversity. Our results showed heterotrophic bacteria, fungus, protozoa and metazoan played important role in H.verticillata decomposition. These provides deep insight into the mechanisms of macrophyte decomposition on biogeochemical cycle in lentic and lotic environment.