Woods Hole Oceanographic Institution

About: Woods Hole Oceanographic Institution is a nonprofit organization based out in Falmouth, Massachusetts, United States. It is known for research contribution in the topics: Population & Mantle (geology). The organization has 5685 authors who have published 18396 publications receiving 1202050 citations. The organization is also known as: WHOI.

Corrugated slip surfaces formed at ridge–transform intersections on the Mid-Atlantic Ridge

Abstract: The strips of ocean crust formed at the inside corners of both transform and non-transform offsets on the Mid-Atlantic Ridge are punctuated by topographic highs—the 'inside-corner highs'1–3—where plutonic rocks (including gabbros and peridotites) are frequently found4,5. Current tectonic models consider the inside-corner highs to be lower-crust and upper-mantle materials that have been exhumed by low-angle detachment faults dipping away from the inside corner to beneath the ridge axis3,6–8. But much of the evidence for the existence of such faults has hitherto been circumstantial. Here we present sonar images of two ridge–transform intersections on the Mid-Atlantic Ridge (near 30° N), which show that both active and 'fossil' inside-corner highs are capped by planar, dipping surfaces marked by corrugations and striations oriented parallel to the plate spreading direction. Although these surfaces may be the low-angle detachment faults envisaged by the models, they dip at much shallower angles than expected. This could be explained by the lubricating presence of serpentinized peridotite, fragments of which have been dredged from both surfaces. Alternatively, these slip surfaces may instead represent failure surfaces in serpentine-lubricated landslide zones.

An assessment of the use of sediment traps for estimating upper ocean particle fluxes

Abstract: This review provides an assessment of sediment trap accuracy issues by gathering data to address trap hydrodynamics, the problem of zooplankton “swimmers,” and the solubilization of material after collection. For each topic, the problem is identified, its magnitude and causes reviewed using selected examples, and an update on methods to correct for the potential bias or minimize the problem using new technologies is presented. To minimize hydrodynamic biases due to flow over the trap mouth, the use of neutrally buoyant sediment traps is encouraged. The influence of swimmers is best minimized using traps that limit zooplankton access to the sample collection chamber. New data on the impact of different swimmer removal protocols at the US time-series sites HOT and BATS are compared and shown to be important. Recent data on solubilization are compiled and assessed suggesting selective losses from sinking particles to the trap supernatant after collection, which may alter both fluxes and ratios of elements in long term and typically deeper trap deployments. Different methods are needed to assess shallow and short- term trap solubilization effects, but thus far new incubation experiments suggest these impacts to be small for most elements. A discussion of trap calibration methods reviews independent assessments of flux, including elemental budgets, particle abundance and flux modeling, and emphasizes the utility of U-Th radionuclide calibration methods.

Heteroduplexes in mixed-template amplifications: formation, consequence and elimination by ‘reconditioning PCR’

Abstract: Although it has been recognized that PCR amplification of mixed templates may generate sequence artifacts, the mechanisms of their formation, frequency and potential elimination have not been fully elucidated. Here evidence is presented for heteroduplexes as a major source of artifacts in mixed-template PCR. Nearly equal proportions of homoduplexes and heteroduplexes were observed after co-amplifying 16S rDNA from three bacterial genomes and analyzing products by constant denaturing capillary electrophoresis (CDCE). Heteroduplexes became increasingly prevalent as primers became limiting and/or template diversity was increased. A model exploring the fate of cloned heteroduplexes during MutHLS-mediated mismatch repair in the Escherichia coli host demonstrates that the diversity of artifactual sequences increases exponentially with the number of both variable nucleotides and of original sequence variants. Our model illustrates how minimization of heteroduplex molecules before cloning may reduce artificial genetic diversity detected during sequence analysis by clone screening. Thus, we developed a method to eliminate heteroduplexes from mixed-template PCR products by subjecting them to 'reconditioning PCR', a low cycle number re-amplification of a 10-fold diluted mixed-template PCR product. This simple modification to the protocol may ensure that sequence richness encountered in clone libraries more closely reflects genetic diversity in the original sample.