Program

Estuaries are responsible for the transport and transformation of nutrients and organic matters from the continent to the adjacent coastal zone, and therefore play critical roles in global biogeochemical cycles. They are under increasing stress from human activities, especially in China, yet we still know little about the responses of microbial communities that mediate biogeochemical processes. Here, we investigated planktonic and benthic prokaryotic communities (Bacteria and Archaea) in the human-perturbed Jiulong River estuary (JRE), China by using 16S rRNA amplicon Miseq sequencing. The results of taxonomic assignments indicated that Beta- (23.32%), Alpha- (22.21%), Gammaproteobacteria (14.83%), Actinobacteria (8.67%), and Flavobacteria (7.56%) were the five most abundant classes in estuarine surface waters, while benthic prokaryotic communities were dominated by Gamma- (20.09%), Delta- (14.68%), Beta- (9.82%), Alphaproteobacteria (7.63%), and Anaerolineae (7.25%). Archaea accounted for minor proportion of total communities either in water or sediment samples. The results of Adnois tests confirmed that the compositions of prokaryotic communities from waters and sediments of the JRE were significantly different from each other, and then salinity may be the primary factor controlling spatial distributions of planktonic and benthic prokaryotic communities in this estuary. At the temporal scale, planktonic communities showed a more clear variation pattern. Remarkably, the ratios of Thaumarchaeota (putative ammonia-oxidizing archaea) to Nitrosomonadales (ammonia-oxidizing bacteria) either in water or sediments of the JRE increased to marine end, suggesting that bacterial and archaeal nitrifiers occupy low-salinity and high-salinity niches, respectively. The nutrient concentrations and salinity might be the most important factors which are responsible for this niche diversification. The influence of riverine communities to estuarine counterpart was also evaluated. Overall, this study shed light on our understanding of the biogeographic patterns and its ecological drivers of estuarine prokaryotic communities.