Influence of different substrates on bacterial communities in coral reefs and surrounding environments of a coastal bay

Abstract

Substrate types are diverse in coastal coral reefs, which can determine the distribution pattern of marine benthic organisms. Coastal coral reefs are also increasingly influenced by activities from the intertidal zone. However, the variation of bacterial communities on different substrates from the intertidal zone to coastal coral reefs have been seldom discussed. Here, we collected 12 samples of different substrate (rock, sand, live coral, and dead coral) from three environments (i.e., intertidal zone, coral distribution area, and no-coral distribution area) in Daya Bay of the South China Sea, and investigated the influence of substrates on bacterial communities. The results showed that the bacterial diversity (Shannon and Chao 1 index) in sand substrates was higher than those in stone/hard substrates. However, a more complex co-occurrence network of bacterial communities were observed in intertidal sand samples than sand samples from the coral area. Principal coordinate analysis and taxonomic analyses of bacterial composition showed that substrate type can shape the variations in bacterial communities from different environments in the Daya Bay region. Bacteroidetes and Chloroflexi were more abundant in sand substrates, while Cyanobacteria and Planctomycetes were more abundant in rock substrates. Redundancy analysis revealed that environmental factors, such as gravel, heavy metals, salinity, and pH regulated the bacterial community in the coastal region. Furthermore, the shared operational taxonomic units (OTUs) from different substrates in the coral distribution area were identified, and most of the top 20 shared OTUs (core bacteria) were identical to the bacteria associated with coral reef ecosystems in previous studies; thus, indicating that core bacteria exist in coral reefs from Daya Bay. This study broadens the understanding of the effect of substrates on bacterial distributions in coral reefs and surrounding environments from a coastal bay.