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.

Comparative Genomic Analysis of the Class Epsilonproteobacteria and Proposed Reclassification to Epsilonbacteraeota (phyl. nov.)

Abstract: The Epsilonproteobacteria is the fifth validly described class of the phylum Proteobacteria, known primarily for clinical relevance and for chemolithotrophy in various terrestrial and marine environments, including deep-sea hydrothermal vents. As 16S rRNA gene repositories have expanded and protein marker analysis become more common, the phylogenetic placement of this class has become less certain. A number of recent analyses of the bacterial tree of life using both 16S rRNA and concatenated marker gene analyses have failed to recover the Epsilonproteobacteria as monophyletic with all other classes of Proteobacteria. In order to address this issue, we investigated the phylogenetic placement of this class in the bacterial domain using 16S and 23S rRNA genes, as well as 120 single-copy marker proteins. Single- and concatenated-marker trees were created using a data set of 4,170 bacterial representatives, including 98 Epsilonproteobacteria. Phylogenies were inferred under a variety of tree building methods, with sequential jackknifing of outgroup phyla to ensure robustness of phylogenetic affiliations under differing combinations of bacterial genomes. Based on the assessment of nearly 300 phylogenetic tree topologies, we conclude that the continued inclusion of Epsilonproteobacteria within the Proteobacteria is not warranted, and that this group should be reassigned to a novel phylum for which we propose the name Epsilonbacteraeota (phyl. nov.). We further recommend the reclassification of the order Desulfurellales (Deltaproteobacteria) to a novel class within this phylum and a number of subordinate changes to ensure consistency with the genome-based phylogeny. Phylogenomic analysis of 658 genomes belonging to the newly proposed Epsilonbacteraeota suggests that the ancestor of this phylum was an autotrophic, motile, thermophilic chemolithotroph that likely assimilated nitrogen from ammonium taken up from the environment or generated from environmental nitrate and nitrite by employing a variety of functional redox modules. The emergence of chemoorganoheterotrophic lifestyles in several Epsilonbacteraeota families is the result of multiple independent losses of various ancestral chemolithoautotrophic pathways. Our proposed reclassification of this group resolves an important anomaly in bacterial systematics and ensures that the taxonomy of Proteobacteria remains robust, specifically as genome-based taxonomies become more common.

Multi-model mean nitrogen and sulfur deposition from the Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP): evaluation of historical and projected future changes

Abstract: . We present multi-model global datasets of nitrogen and sulfate deposition covering time periods from 1850 to 2100, calculated within the Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP). The computed deposition fluxes are compared to surface wet deposition and ice core measurements. We use a new dataset of wet deposition for 2000–2002 based on critical assessment of the quality of existing regional network data. We show that for present day (year 2000 ACCMIP time slice), the ACCMIP results perform similarly to previously published multi-model assessments. For this time slice, we find a multi-model mean deposition of approximately 50 Tg(N) yr−1 from nitrogen oxide emissions, 60 Tg(N) yr−1 from ammonia emissions, and 83 Tg(S) yr−1 from sulfur emissions. The analysis of changes between 1980 and 2000 indicates significant differences between model and measurements over the United States but less so over Europe. This difference points towards a potential misrepresentation of 1980 NH3 emissions over North America. Based on ice core records, the 1850 deposition fluxes agree well with Greenland ice cores, but the change between 1850 and 2000 seems to be overestimated in the Northern Hemisphere for both nitrogen and sulfur species. Using the Representative Concentration Pathways (RCPs) to define the projected climate and atmospheric chemistry related emissions and concentrations, we find large regional nitrogen deposition increases in 2100 in Latin America, Africa and parts of Asia under some of the scenarios considered. Increases in South Asia are especially large, and are seen in all scenarios, with 2100 values more than double their 2000 counterpart in some scenarios and reaching > 1300 mg(N) m−2 yr−1 averaged over regional to continental-scale regions in RCP 2.6 and 8.5, ~ 30–50% larger than the values in any region currently (circa 2000). However, sulfur deposition rates in 2100 are in all regions lower than in 2000 in all the RCPs. The new ACCMIP multi-model deposition dataset provides state-of-the-science, consistent and evaluated time slice (spanning 1850–2100) global gridded deposition fields for use in a wide range of climate and ecological studies.

Two Years in the Life of a Mediterranean Salt Lens

Abstract: A lens of Mediterranean water (Meddy) was tracked in the eastern North Atlantic for two years with SOFAR floats. The Meddy was first found between the Canary Islands and the Azores in October 1984. It center moved in an irregular pattern, at speeds of a few cm s−1, and translated 1100 km to the south in two years. This Meddy was surveyed four times by CTD and velocity profilers, and once with the microstructure profiler EPSONDE. When observed during the first two surveys the Meddy had a core that was stably and smoothly stratified in both salinity and temperature, nearly uniform in the horizontal, and was saltier than the surrounding ocean by 0.65 psu. The Meddy was eroded from its edges, top and bottom, and lost salt and hat with an e-folding time of about one year. The salinity at the center remained at its original value during the first year and decreased during the second year. Evidence was seen for mixing by lateral intrusions, double diffusion, and turbulence; the intrusions are thought to...

Tectonics of ridge-transform intersections at the Kane fracture zone

Abstract: The Kane Transform offsets spreading-center segments of the Mid-Atlantic Ridge by about 150 km at 24° N latitude In terms of its first-order morphological, geological, and geophysical characteristics it appears to be typical of long-offset (>100 km), slow-slipping (2 cm yr-1) ridge-ridge transform faults High-resolution geological observations were made from deep-towed ANGUS photographs and the manned submersible ALVIN at the ridge-transform intersections and indicate similar relationships in these two regions These data indicate that over a distance of about 20 km as the spreading axes approach the fracture zone, the two flanks of each ridge axis behave in very different ways Along the flanks that intersect the active transform zone the rift valley floor deepens and the surface expression of volcanism becomes increasingly narrow and eventually absent at the intersection where only a sediment-covered ‘nodal basin’ exists The adjacent median valley walls have structural trends that are oblique to both the ridge and the transform and have as much as 4 km of relief These are tectonically active regions that have only a thin (<200 m), highly fractured, and discontinuous carapace of volcanic rocks overlying a variably deformed and metamorphosed assemblage of gabbroic rocks Overprinting relationships reveal a complex history of crustal extension and rapid vertical uplift In contrast, the opposing flanks of the ridge axes, that intersect the non-transform zones appear to be similar in many respects to those examined elsewhere along slow-spreading ridges In general, a near-axial horst and graben terrain floored by relatively young volcanics passes laterally into median valley walls with a simple block-faulted character where only volcanic rocks have been found Along strike toward the fracture zone, the youngest volcanics form linear constructional volcanic ridges that transect the entire width of the fracture zone valley These volcanics are continuous with the older-looking, slightly faulted volcanic terrain that floors the non-transform fracture zone valleys These observations document the asymmetric nature of seafloor spreading near ridge-transform intersections An important implication is that the crust and lithosphere across different portions of the fracture zone will have different geological characteristics Across the active transform zone two lithosphere plate edges formed at ridge-transform corners are faulted against one another In the non-transform zones a relatively younger section of lithosphere that formed at a ridge-non-transform corner is welded to an older, deformed section that initially formed at a ridge-transform corner