1,211 research outputs found

    Spatial variability in the diversity and structure of faunal assemblages associated with kelp holdfasts (<i>Laminaria hyperborea</i>) in the northeast Atlantic

    Get PDF
    <p>Map indicating the locations of the four study regions in the UK, northeast Atlantic: (A) northern Scotland, (B) western Scotland, (C) southwest Wales and (D) southwest England. Smaller panels show the positions of the 3 study sites within each region.</p

    Carbonate alteration of ophiolitic rocks in the Arabian–Nubian Shield of Egypt: sources and compositions of the carbonating fluid and implications for the formation of Au deposits

    Get PDF
    Ultramafic portions of ophiolitic fragments in the Arabian–Nubian Shield (ANS) show pervasive carbonate alteration forming various degrees of carbonated serpentinites and listvenitic rocks. Notwithstanding the extent of the alteration, little is known about the processes that caused it, the source of the CO2 or the conditions of alteration. This study investigates the mineralogy, stable (O, C) and radiogenic (Sr) isotope composition, and geochemistry of suites of variably carbonate altered ultramafics from the Meatiq area of the Central Eastern Desert (CED) of Egypt. The samples investigated include least-altered lizardite (Lz) serpentinites, antigorite (Atg) serpentinites and listvenitic rocks with associated carbonate and quartz veins. The C, O and Sr isotopes of the vein samples cluster between −8.1‰ and −6.8‰ for δ13C, +6.4‰ and +10.5‰ for δ18O, and 87Sr/86Sr of 0.7028–0.70344, and plot within the depleted mantle compositional field. The serpentinites isotopic compositions plot on a mixing trend between the depleted-mantle and sedimentary carbonate fields. The carbonate veins contain abundant carbonic (CO2±CH4±N2) and aqueous-carbonic (H2O-NaCl-CO2±CH4±N2) low salinity fluid, with trapping conditions of 270–300°C and 0.7–1.1 kbar. The serpentinites are enriched in Au, As, S and other fluid-mobile elements relative to primitive and depleted mantle. The extensively carbonated Atg-serpentinites contain significantly lower concentrations of these elements than the Lz-serpentinites suggesting that they were depleted during carbonate alteration. Fluid inclusion and stable isotope compositions of Au deposits in the CED are similar to those from the carbonate veins investigated in the study and we suggest that carbonation of ANS ophiolitic rocks due to influx of mantle-derived CO2-bearing fluids caused break down of Au-bearing minerals such as pentlandite, releasing Au and S to the hydrothermal fluids that later formed the Au-deposits. This is the first time that gold has been observed to be remobilized from rocks during the lizardite–antigorite transition

    The structure of biogenic habitat and epibiotic assemblages associated with the global invasive kelp Undaria pinnatifida in comparison to native macroalgae

    Get PDF
    Kelp forests dominate temperate and polar rocky coastlines and represent critical marine habitats because they support elevated rates of primary and secondary production and high biodiversity. A major threat to the stability of these ecosystems is the proliferation of non-native species, such as the Japanese kelp Undariapinnatifida (‘Wakame’), which has recently colonised natural habitats in the UK. We quantified the abundance and biomass of U. pinnatifida on a natural rocky reef habitat over 10 months to make comparisons with three native canopy-forming brown algae (Laminaria ochroleuca, Saccharina latissima, and Saccorhiza polyschides). We also examined the biogenic habitat structure provided by, and epibiotic assemblages associated with, U. pinnatifida in comparison to native macroalgae. Surveys conducted within the Plymouth Sound Special Area of Conservation indicated that U. pinnatifida is now a dominant and conspicuous member of kelp-dominated communities on natural substrata. Crucially, U. pinnatifida supported a structurally dissimilar and less diverse epibiotic assemblage than the native perennial kelp species. However, U. pinnatifida-associated assemblages were similar to those associated with Saccorhiza polyschides, which has a similar life history and growth strategy. Our results suggest that a shift towards U. pinnatifida dominated reefs could result in impoverished epibiotic assemblages and lower local biodiversity, although this could be offset, to some extent, by the climate-driven proliferation of L. ochroleuca at the poleward range edge, which provides complex biogenic habitat and harbours relatively high biodiversity. Clearly, greater understanding of the long-term dynamics and competitive interactions between these habitat-forming species is needed to accurately predict future biodiversity patterns

    Carbon dioxide generation and drawdown during active orogenesis of siliciclastic rocks in the Southern Alps, New Zealand

    Get PDF
    C.D.M. was supported by NERC CASE PhD studentship award NE/G524160/1 (GNS Science, NZ, CASE partner). D.A.H.T. acknowledges support from research grants NE/H012842/1 and NE/J022128/1 and a Royal Society Wolfson Research Merit Award (WM130051). S.C.C. was funded under GNS Science's “Impacts of Global Plate Tectonics in and around New Zealand Programme” (PGST Contract CO5X0203). J.C.A. was supported by NSF OCE1334758. We also thank Matthew Cooper, Andy Milton, Darryl Green and Lora Wingate for laboratory assistance. We thank Mike Bickle for editorial advice and comments, and reviews from two anonymous reviewers that improved this manuscript.Peer reviewedPublisher PD

    Objective Measures of Electrode Discrimination With Electrically Evoked Auditory Change Complex and Speech-Perception Abilities in Children With Auditory Neuropathy Spectrum Disorder

    Get PDF
    This study aimed to 1) determine the sensitivity of the electrically evoked auditory change complex (eACC) to changes in stimulating electrode position; and 2) investigate the association between results of eACC measures and behavioral electrode discrimination and their association with speech-perception performance in pediatric cochlear implant (CI) users who have auditory neuropathy spectrum disorder (ANSD)

    Uplift and exposure of serpentinized massifs: Modeling differential serpentinite diapirism and exhumation of the Troodos Mantle Sequence, Cyprus

    Get PDF
    Serpentinized mantle peridotites form prominent mountains, including the highest elevations of the Troodos ophiolite in Cyprus (Mount Olympus, 1,952 m), but to date, only qualitative mechanisms have been proposed to explain the uplift of mantle rocks to high altitudes. Serpentinization reactions between mantle rocks and water result in profound changes to the rheology and physical properties of peridotites including significant density reduction (∼900 kg/m3). Field observations, density measurements, and isostatic uplift and erosional modeling provide new constraints on the contribution of serpentinization to the uplift of the Troodos Mantle Sequence. Different serpentinization styles have resulted in two distinct serpentinite domains with contrasting densities. Our modeling shows that the Troodos Mountains can form within the geologically constrained uplift time frame (∼5.5 Myr) exclusively through partial serpentinization reactions. We interpret the serpentinite domains as two nested diapirs that formed due to different extents of serpentinization and density reduction. Differential uplift and exhumation have decoupled the two serpentinite diapirs from the originally overlying ocean crustal rocks. Once at high altitudes the incursion of meteoric water reinforced coupled deformation-alteration-recrystallization processes in the shallow subsurface producing a localized low density completely serpentinized diapir. A second decoupling between the contrasting serpentinite diapirs results in localized differential uplift and exhumation, extruding deep materials to the east of Mount Olympus. Application of our modeling to other serpentinite massifs (e.g., St. Peter and St. Paul Rocks, New Idria, California) highlights the contribution of isostasy to the uplift of serpentinized massifs

    Gap Detection Measured With Electrically Evoked Auditory Event–Related Potentials and Speech-Perception Abilities in Children With Auditory Neuropathy Spectrum Disorder

    Get PDF
    This study aimed 1) to investigate the feasibility of recording the electrically evoked auditory event-related potential (eERP), including the onset P1-N1-P2 complex and the electrically evoked auditory change complex (EACC) in response to temporal gaps, in children with auditory neuropathy spectrum disorder (ANSD); and 2) to evaluate the relationship between these measures and speech perception abilities in these subjects

    Acoustically Evoked Auditory Change Complex in Children With Auditory Neuropathy Spectrum Disorder: A Potential Objective Tool for Identifying Cochlear Implant Candidates

    Get PDF
    The overall aim of the study was to evaluate the feasibility of using electrophysiological measures of the auditory change complex (ACC) to identify candidates for cochlear implantation in children with auditory neuropathy spectrum disorder (ANSD). In order to achieve this overall aim, this study 1) assessed the feasibility of measuring the ACC evoked by temporal gaps in a group of children with ANSD across a wide age range; and 2) investigated the association between gap detection thresholds (GDTs) measured by the ACC recordings and open-set speech-perception performance in these subjects
    corecore