Dissimilatory iron reduction causes lead release from iron-oxyhydroxides.

Iron oxyhydroxides have strong chemical affinities for many trace metals including Pb, in aquatic systems where they often comprise several weight percent of the sediments. During diagenesis, Fe-oxyhydroxides may be reductively dissolved during anaerobic respiration. In freshwater sediments, where sulphate concentrations are low, most Fe reduction is microbially catalyzed. In this enzymatic process termed Dissimilatory Iron Reduction (DIR), Fe (III) minerals are used as terminal electron acceptors coupled to organic matter oxidation. In this study we examine the fate of Pb associated with Fe-oxyhydroxides during DIR in the presence of Shewanella putrefaciens 200R and lactate as the sole electron donor. The extent of Fe reduction, determined from the amount Fe(II) extractible from the mineral slurry by 0.5 mol L -1 HCl, was equivalent for both Pb bearing and pure Fe-oxyhydroxides. In contrast, aqueous Fe(II) concentrations in Pb-bearing Fe-oxyhydroxides reactors were significantly higher than those in reactors without Pb. (Abstract shortened by UMI.) Source: Masters Abstracts International, Volume: 45-01, page: 0252. Thesis (M.Sc.)--University of Windsor (Canada), 2006

Carbon cycling: The role of Methane and Copper in an early ocean analogue Lake Matano

This dissertation examines the carbon cycle of a modern ferruginous environment (Lake Matano, Indonesia), with a primary focus on the critical role of methane in carbon redistribution in this system. In addition, the mobility and availability of copper (Cu) (an essential component of microbial enzymatic systems related to methane oxidation) was evaluated in this iron-dominated, aquatic ecosystem. Fieldwork was conducted over several years to acquire the necessary samples and measurements that were used for constraining and modeling the lakes water budget, carbon cycle and copper mobility. It was determined that microbial methane oxidation was unusually high in the water column of this lake, providing possibly the highest anaerobic oxidation rates for this important greenhouse gas reported in freshwater or marine settings. Furthermore because of the nutrient limitations of the lake and its minimal photosynthetic activity it was shown that methane plays a key role in this carbon cycle and as a substrate for organic matter production, which in turn can be used as an energy source, and for cell growth. Ultimately some of this organic matter produced from methane will be buried and subsequently lithified. The availability of copper is intimately tied to this carbon cycle by its link to methanotrophy, as copper is a central part of the pMMO enzyme, which regulates enzyme expression and increases methanotrophic efficiency, and is therefore of paramount importance for the rates of methanotrophy occurring. Unexpectedly Cu is not entirely removed through sorption and co-precipitation by Fe and Mn oxides as often presumed in ferruginous and manganous environments where a lot of Fe(oxy)hydroxides and Mn oxides are present. It was found instead to be largely associated with organic matter and undergoing significant redistribution under microbial respiration between a variety of solid phases, including sulfide minerals. These discoveries deliver important insights into both the bioenergetics and microbial enzymatic evolution in the ferruginous basins of Precambrian Eons, through the continued study of one of their best modern analogue systems

Pliocene mixed-layer oceanography for Site 1241, using combined Mg/Ca and δ¹⁸O analyses of Globigerinoides sacculifer

To reconstruct changes in tropical Pacific surface hydrography, we used samples from Site 1241 (5°50′N, 86°26′W; 2027-m water depth) to establish high-resolution records of Mg/Ca and δ18O for the mixed-layer dwelling planktonic foraminifer Globigerinoides sacculifer for the Pliocene time interval from 4.8 to 2.4 Ma. An increase in average seasurface temperatures (SSTs) (24.5°–25.5°C) between 4.8 and 3.7 Ma can probably be explained by a southward shift of the Intertropical Convergence Zone, thereby increasing the influence of the warmer North Equatorial Countercurrent. The general global cooling trend, a response to intensification of Northern Hemisphere glaciation (NHG), started at ~3.2 Ma (shown by the δ18Obenthic record) and is paralleled by tropical east Pacific cooling (indicated by SSTMg/Ca). Tropical east Pacific cooling, however, had already commenced by ~3.7 Ma, suggesting that global cooling, probably related to decreasing atmospheric CO2 concentrations, might have started well before intensification of NHG. Relative changes in local sea-surface salinity (indicated by δ18Osalinity) show a decoupling from global high-latitude processes (shown by the δ18Obenthic record). Long-term regional freshening started with decreasing SSTMg/Ca at ~3.7 Ma, suggesting that changes in the tropical wind field combined with latitudinal shifts of the tropical rainbelt were related to general decreases in tropical east Pacific SST-controlled δ18Osalinity. The similarity of Pliocene SSTMg/Ca for G. sacculifer with modern SSTs in the east Pacific, in combination with the early development of a shallow thermocline at Site 1241, gives no direct support to the idea that a permanent El Niño-like Pliocene climate might have existed during the early Pliocene

Biogeochemistry of manganese in ferruginous Lake Matano, Indonesia

This study explores Mn biogeochemistry in a stratified, ferruginous lake, a modern analogue to ferruginous oceans. Intense Mn cycling occurs in the chemocline where Mn is recycled at least 15 times before sedimentation. The product of biologically catalyzed Mn oxidation in Lake Matano is birnessite. Although there is evidence for abiotic Mn reduction with Fe(II), Mn reduction likely occurs through a variety of pathways. The flux of Fe(II) is insufficient to balance the reduction of Mn at 125 m depth in the water column, and Mn reduction could be a significant contributor to CH<sub>4</sub> oxidation. By combining results from synchrotron-based X-ray fluorescence and X-ray spectroscopy, extractions of sinking particles, and reaction transport modeling, we find the kinetics of Mn reduction in the lake's reducing waters are sufficiently rapid to preclude the deposition of Mn oxides from the water column to the sediments underlying ferruginous water. This has strong implications for the interpretation of the sedimentary Mn record

Astronomically calibrated timescales from 6 to 2.5 Ma and Benthic Isotope Stratigraphies, sites 1236, 1237, 1239, and 1241

We present benthic isotope stratigraphies for Sites 1236, 1237, 1239, and 1241 that span the late Miocene–Pliocene time interval from 6 to 2.4 Ma. Orbitally tuned timescales were generated for Sites 1237 and 1241 by correlating the high-frequency variations in gamma ray attenuation density, percent sand of the carbonate fraction, and benthic δ¹³C to variations in Earth’s orbital parameters. The astronomical timescales for Sites 1237 and 1241 are in agreement with the one from Atlantic Site 925/926 (Ocean Drilling Program Leg 154). The comparison of benthic δ¹⁸O and δ¹³C records from the east Pacific sites and Atlantic Site 925/926 revealed a surprising clarity of the “41-k.y. signal” in δ¹³C records and a remarkably good correlation between their δ¹³C records. This suggests that the late Miocene–Pliocene amplitudes of obliquityrelated δ¹³C cycles reflect a magnitude of global response often larger than that provided by obliquity-related δ¹⁸O cycles. At Site 1237, the orbitally derived ages of Pliocene magnetic reversal boundaries between the base of Réunion and the top of Thvera confirm astronomical datings of the generally accepted ATNTS2004 timescale, except for the top of Kaena and the base of Sidufjall. Our astronomical age for the top of Kaena is about one obliquity cycle older. The base of Sidufjall appears to be about one precession cycle younger. The age models of Sites 1236 and 1239 were established by correlating their benthic δ¹⁸O and δ¹³C records directly to the orbitally tuned isotope record of Site 1241

Genetic fingerprinting of salmon louse (Lepeophtheirus salmonis) populations in the North-East Atlantic using a random forest classification approach

Caligid sea lice represent a significant threat to salmonid aquaculture worldwide. Population genetic analyses have consistently shown minimal population genetic structure in North Atlantic Lepeophtheirus salmonis, frustrating efforts to track louse populations and improve targeted control measures. The aim of this study was to test the power of reduced representation library sequencing (IIb-RAD sequencing) coupled with random forest machine learning algorithms to define markers for fine-scale discrimination of louse populations. We identified 1286 robustly supported SNPs among four L. salmonis populations from Ireland, Scotland and Northern Norway. Only weak global structure was observed based on the full SNP dataset. The application of a random forest machine-learning algorithm identified 98 discriminatory SNPs that dramatically improved population assignment, increased global genetic structure and resulted in significant genetic population differentiation. A large proportion of SNPs found to be under directional selection were also identified to be highly discriminatory. Our data suggest that it is possible to discriminate between nearby L. salmonis populations given suitable marker selection approaches, and that such differences might have an adaptive basis. We discuss these data in light of sea lice adaption to anthropogenic and environmental pressures as well as novel approaches to track and predict sea louse dispersal

Unexpected high frequency of neurofibroma in the celiac ganglion of German cattle

In a study originally designed to find potential risk factors for bovine spongiform encephalopathy (BSE) we examined tissues from 403 Holstein Frisian cattle in total. These included 20 BSE cattle and their 236 birth- and feeding cohort animals plus 32 offspring, 103 age, breed and district-matched control cattle and further twelve cattle with neurological signs. In addition to the obex, we examined the celiac ganglion, cervical cranial ganglion, trigeminal ganglion and proximal ganglion of the vagus nerve using histological techniques. Unexpectedly, we found a high number of neurofibroma, a benign peripheral nerve sheath tumor consisting of Schwann cells, fibroblasts and perineural cells. The neurofibroma were present only in the celiac ganglion and found during histologic examination. With a frequency of 9.91% in BSE cattle and their cohorts (case animals) and 9.09% in the age, breed and district matched control animals there seems to be no correlation between the occurrence of BSE and neurofibroma. Benign peripheral nerve sheath tumors have been described more often in cattle than in other domestic animals. Usually, they are incidental macroscopic findings in the thoracic ganglia during meat inspection. To our knowledge, there are no previous systematic histologic studies including bovine celiac ganglia at all. The high incidence of celiac ganglia neurofibroma may play a role in the frequently occurring abomasal displacements in Holstein Frisian cattle as the tumors might cause a gastrointestinal motility disorder. At present a genetic predisposition for these neoplasms cannot be ruled out.Grants ZN 1294 and ZN 2168, Volkswagen Stiftung financed the first years of sample collection, i.e. material from BSE and cohort animals regarding staff and material expenses Project number: 38028266, Deutsche Forschungsgemeinschaft (DFG), was granted for the original study design to identify risk factors for BSE in the cohort animals of BSE animalsSaarland University within the funding programme Open Access Publishing

GISCOME – Genetics of Ischaemic Stroke Functional Outcome network: A protocol for an international multicentre genetic association study

© 2017, © European Stroke Organisation 2017. Introduction: Genome-wide association studies have identified several novel genetic loci associated with stroke risk, but how genetic factors influence stroke outcome is less studied. The Genetics of Ischaemic Stroke Functional outcome network aims at performing genetic studies of stroke outcome. We here describe the study protocol and methods basis of Genetics of Ischaemic Stroke Functional outcome. Methods: The Genetics of Ischaemic Stroke Functional outcome network has assembled patients from 12 ischaemic stroke projects with genome-wide genotypic and outcome data from the International Stroke Genetics Consortium and the National Institute of Neurological Diseases Stroke Genetics Network initiatives. We have assessed the availability of baseline variables, outcome metrics and time-points for collection of outcome data. Results: We have collected 8831 ischaemic stroke cases with genotypic and outcome data. Modified Rankin score was the outcome metric most readily available. We detected heterogeneity between cohorts for age and initial stroke severity (according to the NIH Stroke Scale), and will take this into account in analyses. We intend to conduct a first phase genome-wide association outcome study on ischaemic stroke cases with data on initial stroke severity and modified Rankin score within 60–190 days. To date, we have assembled 5762 such cases and are currently seeking additional cases meeting these criteria for second phase analyses. Conclusion: Genetics of Ischaemic Stroke Functional outcome is a unique collection of ischaemic stroke cases with detailed genetic and outcome data providing an opportunity for discovery of genetic loci influencing functional outcome. Genetics of Ischaemic Stroke Functional outcome will serve as an exploratory study where the results as well as the methodological observations will provide a basis for future studies on functional outcome. Genetics of Ischaemic Stroke Functional outcome can also be used for candidate gene replication or assessing stroke outcome non-genetic association hypotheses