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.

Changes in the Synechococcus Assemblage Composition at the Surface of the East China Sea Due to Flooding of the Changjiang River

“…The reaction mixture contained Phusion High-Fidelity DNA Polymerase (New England Biolabs, Massachusetts, USA), 1× Phusion HF buffer, 200 μM deoxynucleotide solution mixture, and 0.5 μM each of forward (16S-909F, 5′-ACTCAAAKGAATWGACGG-3′) and reverse (16S-1492R, 5′-NTACCTTGTTACGACT-3′) primers. The primer pair used in the reactions specifically amplified the hypervariable V6-V9 region of the 16S rRNA gene [27]. PCR was conducted in a thermocycler (Model 9700, Applied Biosystems, New York, USA) under the following conditions: 1 cycle of 98°C for 30 s, followed by 30 cycles of 98°C for 10 s, 52°C for 10 s and 72°C for 20 s, and 1 final cycle of 72°C for 10 min.…”

Homogeneity of coral reef communities across 8 degrees of latitude in the Saudi Arabian Red Sea

“…However, across this long and narrow body of water, 56 which spans 17 degrees of latitude, the Red Sea is not homogenous. Sea surface 57 temperatures (SST), salinity, and nutrient concentrations exhibit latitudinal gradients and 58 fluctuate seasonally (Acker et al, 2008;Ngugi et al, 2012;Raitsos et al, 2013). Average 59 temperatures increase southward and range from 20-28 °C (north to south) in the winter 60 conducted on the southern ends of the reefs).…”

Reconstruction of Novel Cyanobacterial Siphovirus Genomes from Mediterranean Metagenomic Fosmids

“…Phage DNA containing fosmids have been found to be particularly abundant in deep chlorophyll maximum (DCM) cellular fractions that have been analyzed worldwide (8)(9)(10). The DCM is the zone of maximal photosynthetic activity in the marine habitat (11).…”