Unveiling associations between heavy metals and bacterial functional assembly under the impact of Spartina alterniflora invasion in the Yellow River Delta wetland

Heavy metal accumulation plays a paramount role in determining microbial-driven processes in ecosystems. However, the importance of sediment microbial functional assembly shaped by Spartina alterniflora invasion under the impact of heavy metals is still far from adequately understood. Here, 16S rRNA gene sequencing and sediment physicochemical properties analysis were used to determine the characteristics of bacterial assembly and functional profiles with seasonal variation across rhizosphere area of S. alterniflora (RS), non-rhizosphere area (NRS) and non-invaded area (NIA) near the Yellow River Delta wetland. Results indicated that sediment bacterial diversity was much higher near the RS area than it in the other area during summer, and this high diversity was correlated with elevated carbon-nitrogen levels near the RS area. In summer, heavy metals were primarily concentrated in the rhizosphere region but exhibited variability during winter. Sediment bacterial communities are governed primarily by homogeneous selection throughout the seasons, and they vary greatly in summer and winter in response to S. alterniflora invasion. Moreover, the functional profiles revealed that carbon metabolism and sulfur metabolism were predominant in both summer and winter, and the proportion of sulfur metabolism clearly increased near the rhizosphere region. The variation in carbon and nitrogen caused by the invasion of S. alterniflora under the influence of heavy metals was closely related to the characteristics of bacterial groups. Overall, this study elucidated the significant seasonal variability in diverse sediment microbial communities within plant-invaded wetlands. Furthermore, a linkage between heavy metals, bacterial assembly and bacterial functions amid plant invasions was proposed. • S. alterniflora shaped microbial communities and assembly under the impact of heavy metals. • Sediment bacterial communities were primarily governed by homogeneous selection throughout the seasons. • The variation of carbon and nitrogen content in soil caused by the invasion of S. alterniflora was tightly related to the characteristics of bacterial groups. • Carbon metabolism and sulfur metabolism were predominant in both summer and winter, the proportion of sulfur metabolism increased evidently near the rhizosphere region.