Newly recognized turbidity current structure can explain prolonged flushing of submarine canyons

Seabed-hugging flows called turbidity currents are the volumetrically most important process transporting sediment across our planet and form its largest sediment accumulations. We seek to understand the internal structure and behavior of turbidity currents by reanalyzing the most detailed direct measurements yet of velocities and densities within oceanic turbidity currents, obtained from weeklong flows in the Congo Canyon. We provide a new model for turbidity current structure that can explain why these are far more prolonged than all previously monitored oceanic turbidity currents, which lasted for only hours or minutes at other locations. The observed Congo Canyon flows consist of a short-lived zone of fast and dense fluid at their front, which outruns the slower moving body of the flow. We propose that the sustained duration of these turbidity currents results from flow stretching and that this stretching is characteristic of mud-rich turbidity current systems. The lack of stretching in previously monitored flows is attributed to coarser sediment that settles out from the body more rapidly. These prolonged seafloor flows rival the discharge of the Congo River and carry ~2% of the terrestrial organic carbon buried globally in the oceans each year through a single submarine canyon. Thus, this new structure explains sustained flushing of globally important amounts of sediment, organic carbon, nutrients, and fresh water into the deep ocean

Co-Circulation of 72bp Duplication Group A and 60bp Duplication Group B Respiratory Syncytial Virus (RSV) Strains in Riyadh, Saudi Arabia during 2014 - Fig 3

<p><b>(A) Deduced amino acid alignment and mutations in the second variable region of G protein of the ON1 genotype.</b> The figure includes alignment of study ON1 strains with the prototype strain from Canada (JN257694). The amino acids sequence alignment corresponds to 227–321 amino acids of the prototype strain. Identical residues are indicated by dashes. The two copies of the duplicated 24-amino-acid region in group ON1 strains are indicated by rectangular boxes. Stop codons are indicated by asterisks. Potential N-glycosylation sites (NXT, where X is not proline) are indicated by grey shading. The potential sites for extensive O-glycosylation KPX - - - TTKX motifs are underlined. <b>(B) The amino acid sequence of ON1 genotype showing mutations in the study strains.</b> The sequence corresponds to the 227–321 amino acids of the ON1 prototype strain. The rectangular boxes represent the analogous 24 amino acid region followed by duplicated 24 amino acid region in ON1 strains. Changes at amino acid positions in study strains are shown by arrows.</p

Phylogenetic trees for hRSV group A (A) and group B (B).

<p>The nucleotide sequences from the second variable region of the G protein gene of the study RSVA strains are indicated by solid circles and RSVB by solid triangles. The nucleotide sequences were aligned with the CLUSTAL W program, and phylogenetic trees were constructed by Maximum Likelihood method using MEGA6 software. Bootstrap values greater than 70% are shown at the branch nodes.</p

Selection pressure analysis of the RSV NA1 genotype of the second hypervariable region of G protein gene using SLAC and FEL method.

<p>Selection pressure analysis of the RSV NA1 genotype of the second hypervariable region of G protein gene using SLAC and FEL method.</p

Shannon entropy plots of deduced amino acid sequences of the second hypervariable region of the G protein.

<p>The data set includes <b>(A)</b> RSV-A: NA1 genotype, n = 26 <b>(B)</b> ON1 genotype, n = 05 and <b>(C)</b> RSV-B: BA genotype, n = 11 of Saudi strains with their respective prototype strains. The entropy plots show the amino acid variability in the second hypervariable region of the G protein gene determined by BioEdit software. The threshold value was set at 0.2. Amino acid sites with entropy values <0.2 are considered conserved and values >0.2 are considered variable.</p

Age wise distribution of the RSV positive cases.

<p>Age wise distribution of the RSV positive cases.</p

Clinical manifestations of the study patients.

<p>Clinical manifestations of the study patients.</p