Environmental and Spatial Factors Shaping Bacterial Communities in Eelgrass Sediments Along the Japanese Coast

Zostera marina , commonly referred to as eelgrass, is a marine flowering plant frequently growing in some water‐saturated sediments along the coastal regions of Japan. We examined the bacterial communities in the sediment of three eelgrass areas to compare the bacterial composition of vegetated sediments (eelgrass sediments) with that of nearby unvegetated sediments. We also revealed the core bacterial groups commonly detected in all eelgrass beds examined. The bacterial communities varied between the eelgrass sediment and the surrounding unvegetated sediment. Deltaproteobacteria and Epsilonproteobacteria were showed significantly higher relative abundance in eelgrass sediment compared to the unvegetated sediment. As core taxa, 38 OTUs/phylotypes consistently appeared across the three eelgrass sediments and are considered unique to the eelgrass beds, indicating potential specific interactions with Z. marina . The most prevalent core taxa in eelgrass sediment were Gammaproteobacteria , Deltaproteobacteria , and Flavobacteriia , which include members involved in key biogeochemical processes. Additionally, environmental variables such as temperature, salinity, pH, DO, and total organic carbon (TOC), emerged as the key drivers of variation within the bacterial community. This study contributes to the understanding of bacterial diversity associated with Z. marina sediments and highlights differences in microbial community composition between eelgrass and adjacent unvegetated sediments. Deeper sequencing in future studies will further improve the resolution of rare bacterial diversity associated with eelgrass sediments.