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.

Methanopyrus kandleri, gen. and sp. nov. represents a novel group of hyperthermophilic methanogens, growing at 110°C

Abstract: A novel group of hyperthermophilic rod-shaped motile methanogens was isolated from a hydrothermally heated deep sea sediment (Guaymas Basin, Gulf of California) and from a shallow marine hydrothermal system (Kolbeinsey ridge, Iceland). The grew between 84 and 110°C (opt: 98°C) and from 0.2% to 4% NaCl (opt. 2%) and pH 5.5 to 7 (opt: 6.5). The isolates were obligate chemolithoautotrophes using H2/CO2 as energy and carbon sources. In the presence of sulfur, H2S was formed and cells tended to lyse. The cell wall consisted of a new type of pseudomurein containing ornithin in addition to lysine and no N-acetylglucosamine. The pseudomurein layer was covered by a detergent-sensitive protein surface layer. The core lipid consisted exclusively of phytanyl diether. The GC content of the DNA was 60 mol%. By 16S rRNA comparisons the new organisms were not related to any of the three methanogenic lineages. Based on the physiological and molecular properties of the new isolates, we describe here a new genus, which we name Methanopyrus (the “methane fire”). The type species is Methanopyrus kandleri (type strain: AV19; DSM 6324).

The genomic landscape of rapid repeated evolutionary adaptation to toxic pollution in wild fish.

Abstract: Atlantic killifish populations have rapidly adapted to normally lethal levels of pollution in four urban estuaries. Through analysis of 384 whole killifish genome sequences and comparative transcriptomics in four pairs of sensitive and tolerant populations, we identify the aryl hydrocarbon receptor–based signaling pathway as a shared target of selection. This suggests evolutionary constraint on adaptive solutions to complex toxicant mixtures at each site. However, distinct molecular variants apparently contribute to adaptive pathway modification among tolerant populations. Selection also targets other toxicity-mediating genes and genes of connected signaling pathways; this indicates complex tolerance phenotypes and potentially compensatory adaptations. Molecular changes are consistent with selection on standing genetic variation. In killifish, high nucleotide diversity has likely been a crucial substrate for selective sweeps to propel rapid adaptation.

Some thoughts on the use of InSAR data to constrain models of surface deformation : noise structure and data downsampling

Abstract: Repeat-pass Interferometric Synthetic Aperture Radar (InSAR) provides spatially dense maps of surface deformation with potentially tens of millions of data points. Here we estimate the actual covariance structure of noise in InSAR data. We compare the results for several independent interferograms with a large ensemble of GPS observations of tropospheric delay and discuss how the common approaches used during processing of InSAR data affects the inferred covariance structure. Motivated by computational concerns associated with numerical modeling of deformation sources, we then combine the data-covariance information with the inherent resolution of an assumed source model to develop an efficient algorithm for spatially variable data resampling (or averaging). We illustrate these technical developments with two earthquake scenarios at different ends of the earthquake magnitude spectrum. For the larger events, our goal is to invert for the coseismic fault slip distribution. For smaller events, we infer the hypocenter location and moment. We compare the results of inversions using several different resampling algorithms, and we assess the importance of using the full noise covariance matrix.

Strength of slightly serpentinized peridotites: Implications for the tectonics of oceanic lithosphere

Abstract: We deformed cores of peridotite with ∼10%–15% lizardite and chrysotile serpentine to determine the influence of serpentine content on the strength and the style of deformation. The strength, the pressure dependence of strength, and the nominally nondilatant mode of brittle deformation of slightly serpentinized peridotites are comparable to those of pure serpentinites. These results indicate that deformation is accommodated primarily by serpentine, while olivine, despite being the more abundant component, remains nominally undeformed. On the basis of these data and previous work, we determine that the transition from a “strong,” dilatant dunite rheology to a “weak,” nondilatant serpentinite rheology is not a linear function of the degree of serpentinization. Instead, an abrupt transition in strength is observed at low degrees of serpentinization. The pressure of the transition from localized to distributed deformation also decreases abruptly, from >1000 MPa to 150–350 MPa. The change in rheological behavior occurs at a serpentine content of 10%–15% or less, which corresponds to published compressional seismic velocity of >7.8–7.5 km/s at a pressure of 200 MPa. The seismic velocity of the oceanic lithosphere, particularly of that formed at slow spreading ridges, can thus provide constraints on its mechanical properties at depth. Because slightly serpentinized peridotites have a rheology similar to that of pure serpentinite, significant lithospheric weakening may occur after the onset of alteration near or at the ridge axis.

The marine osmium isotope record

Abstract: Over the past decade the marine osmium isotope record has been developed into a new tracer in palaeoceanographic research. Several analytical developments, particularly in the past few years, have significantly increased our ability to study the behaviour of osmium in the surficial environment. The 187Os/188Os and osmium concentration of seawater, river water, rain, and hydrothermal vent fluids have been measured directly. Recently, the behaviour of osmium in estuaries–critical for estimating the marine residence time of osmium–has been studied. Our knowledge of the surficial osmium cycle has thus significantly improved. In addition, reconstructions of past variations in the marine 187Os/188Os recently have been extended back into the Mesozoic. This review attempts to summarize our current understanding of the marine osmium system–present and past. The 187Os/188Os of seawater during the Cenozoic to first order mimics the marine 87Sr/86Sr record. It is therefore tempting to interpret both records as reflecting increased input of radiogenic osmium and strontium resulting from enhanced continental weathering regulated by climatic/tectonic processes. However, the marine osmium isotope system differs fundamentally from the marine strontium isotope system. This review emphasizes three important differences. First, large impacts are capable of resetting the 187Os/188Os to unradiogenic values without significantly affecting the marine strontium system. Second, organic-rich sediments are characterized by high 187Re/188Os; resulting 187Os/188Os ingrowth-trajectories are similar to the average slope of the Cenozoic 187Os/188Os seawater record. Trends towards more radiogenic 187Os/188Os seawater therefore can be caused by weathering of organic-rich sediments at a constant rate. Third, the marine residence time of osmium is sufficiently short to capture short-periodic (glacial-interglacial) fluctuations that are inaccessible to the buffered marine strontium isotope system. This offers the opportunity to discriminate between high-frequency (climatic) and low-frequency (tectonic) forcing.