title: Biogeography of pelagic bacterioplankton across an antagonistic temperature-salinity gradient in the Red Sea.
abstract: The Red Sea is a unique marine ecosystem with contrasting gradients of temperature and salinity along its north-to-south axis. It is an extremely oligotrophic environment that is characterized by perpetual year-round water column stratification, high annual solar irradiation, and negligible riverine and precipitation inputs. In this study, we investigated whether the contemporary environmental conditions shape community assemblages by pyrosequencing 16S rRNA genes of bacteria in surface water samples collected from the northeastern half of this water body. A combined total of 1855 operational taxonomic units (OTUs) were recovered from the 'small-cell' and 'large-cell' fractions. Here, a few major OTUs affiliated with Cyanobacteria and Proteobacteria accounted for ∼93% of all sequences, whereas a tail of 'rare' OTUs represented most of the diversity. OTUs allied to Surface 1a/b SAR11 clades and Prochlorococcus related to the high-light-adapted (HL2) ecotype were the most widespread and predominant sequence types. Interestingly, the frequency of taxa that are typically found in the upper mesopelagic zone was significantly elevated in the northern transects compared with those in the central, presumably as a direct effect of deep convective mixing in the Gulf of Aqaba and water exchange with the northern Red Sea. Although temperature was the best predictor of species richness across all major lineages, both spatial and environmental distances correlated strongly with phylogenetic distances. Our results suggest that the bacterial diversity of the Red Sea is as high as in other tropical seas and provide evidence for fundamental differences in the biogeography of pelagic communities between the northern and central regions.
authors: Red Sea Research Center, King Abdullah University of Science and Technology, 4700 KAUST, Thuwal 23955 6900, Saudi Arabia. david.ngugi@kaust.edu.sa
authors: David Kamanda
authors: DK
authors: Ngugi
authors: André
authors: A
authors: Antunes
authors: Andreas
authors: A
authors: Brune
authors: Ulrich
authors: U
authors: Stingl
mesh_terms: D044822:Biodiversity; D002980:Climate; D003001:Cloning, Molecular; D000458:Cyanobacteria / Q000145:classification / Q000235:genetics*; D004269:DNA, Bacterial / Q000235:genetics / Q000302:isolation & purification; D017753:Ecosystem; D060146:Ecotype; D014644:Genetic Variation; D019156:Indian Ocean; D010802:Phylogeny; D020560:Proteobacteria / Q000145:classification / Q000235:genetics*; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D054712:Salinity; D017422:Sequence Analysis, DNA; D013696:Temperature; D014871:Water Microbiology
chemical_list: D004269:DNA, Bacterial; D012336:RNA, Ribosomal, 16S