Impact of oyster culture on coral reef bacterioplankton community composition and function in Daya Bay, China

Subtropical coral reefs along the coast are facing multiple pressures. Mariculture is one of the main sources of such pressure. Oyster culture has become a worldwide phenomenon in coastal ecosystems. Due to the high filtration efficiency of oysters, their culture has helped to purify some coastal waters. However, high-density oyster culture has also had negative effects on coastal ecosystems, including the loss of natural habitat, changes in hydrology, cross infection of corals with pathogenic bacteria, and changes to the structure and function of bacterioplankton communities. In this study, the effect of oyster culture on coral reefs was characterized based on variability in the structure and function of bacterioplankton communities. Using 16S rRNA gene sequencing, a comprehensive bacterioplankton reference database was constructed for coral reef habitats associated with oyster culture and subjected to different disturbance gradients. Small shifts in the surrounding coral reef environment caused by oyster culture disturbance were detected by comparing the structure and function of bacterioplankton communities with biogeochemical parameters. The measured chemical dynamics explained 71.15% of the bacterioplankton community variability between habitats. Oyster culture increased the richness and diversity of bacterioplankton communities. Species composition similarity was highest between the oyster culture area and the nearest coral reef habitat. The spatial turnover in the bacterioplankton community was characterized by less uniform community assembly patterns. The bacterioplankton function of reefs relatively far from anthropogenic disturbance differed from that of those closer to such disturbances. Our results also show that the variability in structure and function of bacterioplankton communities between oyster culture areas and coral reef areas was mainly driven by salinity and ammonium. Oyster culture can impact bacterioplankton community composition and dynamics around coral reef habitats. The results provide an important context for developing frameworks for managing ecological interactions among oyster cultures and coral reef habitats of concern.