Seagrasses offer crucial ecosystem services and support high primary productivity; however, the meadow homeostasis is susceptible to human activities, including mariculture and restoration. While seagrass associated prokaryotes, eukaryotes and their functions have been reported, the fundamental question of how these activities govern community assembly remains unknown. In this study, we analyzed the bacterial, fungal, and other eukaryotic communities in seawater and rhizosphere of four seagrasses from natural, mariculture, and seagrass restoration areas. We found homogeneous selection processes played smaller roles in shaping the bacterial and fungal communities within the seagrass rhizosphere than in the surrounding seawater, but eukaryotes showed the opposite pattern. Bacterial, eukaryotic, and fungal communities associated with Zostera marina exhibited higher β diversity and a more deterministic assembly process compared to those of Phyllospadix iwatensis. This pattern was observed in both surrounding seawater and rhizosphere, and was particularly characterized by heterogeneous selection, where environmental heterogeneity promotes divergent community composition. Sea cucumber and kelp farming areas exhibited higher dispersal limitation (limited migration across space restricts community assembly) in bacterial and eukaryotic communities. Moreover, sea cucumber culture areas showed lower dispersal ability across all three communities. In seagrass restoration areas, the dominant environmental driver in the rhizosphere shifted from inorganic nitrogen to total carbon, with higher homogeneous selection (similar environmental conditions select for similar communities) in seawater and dispersal limitation in the rhizosphere for bacterial community assembly. Our findings elucidate how key seagrass species and mariculture/restoration activities reshape bacterial, eukaryotic, and fungal communities by shifting resource limitations and assembly processes, providing a mechanistic guide for optimizing mariculture and seagrass restoration.
Sun et al. (Thu,) studied this question.