Diversity and potential function of bacterial communities in different upwelling systems

Upwelling is one of the most important processes in the marine ecosystem and plays an important role in nutrient transport. However, the bacterial community structure and function of upwelling areas in the South China Sea (SCS) have received little attention. This study provides a systematic insight into bacterial diversity and predicted metabolic functions related to upwelling areas using Illumina Miseq sequencing. The results suggest that bacterial communities exhibit different patterns of spatial distribution in different upwelling systems, and provides evidence for phylogenetic taxonomy shaped by ecological preferences. The bacterial community displayed a significant vertical gradient in upwelling systems. Oceanospirillales, Alteromonadales, Sphingomonadales, Flavobacteriales, Rhodobacterales, and Bacillales were dominant in areas of coastal upwelling, while Oceanospirillales, Alteromonadales, Rhodobacterales, and Lactobacillales were also abundant in areas of oceanic upwelling. Whereas, Lactobacillales, Pseudomonadales, and Alteromonadales were dominant in non-upwelling regions and displayed a uniform distribution among different depths. The predicted metagenome showed that functional metabolism shifts were consistent with taxon responses. Most of the gene families were significantly enriched and were more abundant in upwelling than non-upwelling regions, indicating that bacteria could increase their ability for metabolic exchange and nutrient transformation due to the upwelling effect. This study emphasized that upwelling induces a shift in the upwelling-driven microbe and metabolic functions, resulting in obvious impacts on material transformation.