The Influence of Oyster Farming on Sediment Bacterial Communities

Aquaculture currently provides half of all fish for human consumption, and this proportion is expected to increase to meet the growing global demand for protein. As aquaculture, including oyster farming, expands, it is increasingly important to understand effects on coastal ecosystems. The broad-scale ecological effects of oyster aquaculture are well documented; however, less is known regarding the influence of oyster aquaculture on sediment bacterial communities. To better understand this relationship, we compared three different oyster farming practices that varied in oyster biomass and proximity of oysters to the sediment. We used high-throughput sequencing and quantitative polymerase chain reaction to examine the effect of oyster farming on sediment bacterial communities. We examined the entire bacterial community and looked specifically at bacteria that support essential estuarine ecosystem services (denitrifiers), as well as bacteria that can be detrimental to human health (members of the Vibrio genus). We found that oyster biomass increased Vibrio richness and sediment carbon content, which influenced bacterial community composition. When compared to reference sites, the overall abundance of bacteria was increased by the bottom planting method, but the associated increases in denitrifiers and Vibrio were not significant. We were unable to detect V. parahaemolyticus, V. vulnificus, or V. cholera, the three most common Vibrio pathogens, in any sample, suggesting that oyster farming did not enhance these potential human pathogens in sediments at the time of sampling. These results highlight how differences in oyster farming practice can affect sediment bacterial communities, and the ecosystem services they provide.