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14 results on '"WARTER VIOLA"'

1. Daily to seasonal environmental variability from giant clams revealed via spatially-resolved geochemical analyses and laboratory culture experiments : case studies from Recent and Miocene Indo-Pacific Tridacna shells

Author

Warter, Viola

Subjects
551.6
Abstract

This thesis presents high (weeks-months) and ultra-high (hours-days) resolution time-series proxy records obtained from Miocene, Recent and laboratory cultured giant clam (Tridacna spp.) shells. In order to evaluate the fidelity of two Late Miocene Tridacna shells from East Kalimantan (Indonesia) to preserve any palaeoenvironmental variability, a multi-method approach was applied to assess pristine aragonite preservation. Combined usage of XRD, SEM/CL imaging and LA-ICPMS trace elemental screening has proven effective at detecting diagenetic shell alteration. Seasonally-resolved palaeoproxy records obtained from pristine shell aragonite provide insight into tropical sea surface temperature (SST) variability of the Indo-Pacific region during the late Miocene. 18O time-series records from two fossil shells indicate an average SST variability of 2.7 ± 2.1 and 4.6 ± 1.7 °C, respectively, which exceeds the modern-day seasonality in the Makassar Strait two- to threefold. A novel methodological approach of ultra-high resolution LA-ICPMS analysis is introduced, which utilizes the combined capabilities of a rotating rectangular aperture (spot size 4 x 50 μm), the rapid signal washout of a Laurin two-volume laser ablation cell and slow compositional profiling (1.5 μm/s) and enables resolution of < 10 μm compositional variability in B/Ca, Mg/Ca, Sr/Ca and Ba/Ca preserved within microscopically visible growth increments of both Recent and Miocene Tridacna shells. In comparison to a lower-resolution, seasonally resolved Miocene record, the ~10-20 μm element/Ca cycles were determined to be daily in origin, and a further ~14-15 day cyclicity, interpreted to reflect tidal periodicity, is detected in long-term (annual) daily resolved proxy records. Laboratory culture experiments of Tridacna crocea, conducted under controlled environmental conditions including temperature, light level and seawater chemistry, allowed quantifying the temperature and light influence on shell growth rates. Corresponding ultra-high resolution LAICPMS analysis of the isotopically labelled cultured shell domains revealed that both temperature and light influence trace elemental incorporation into shell aragonite, yet biophysiology also controls trace element partitioning.

Published
2016

8. Microbial anaerobic Fe(II) oxidation - Ecology, mechanisms and environmental implications

Author

Bryce, Casey, Blackwell, Nia, Schmidt, Caroline, Otte, Julia, Huang, Yu-Ming, Kleindienst, Sara, Tomaszewski, Elizabeth, Schad, Manuel, Warter, Viola, Peng, Chao, Byrne, James M., and Kappler, Andreas

Subjects
FERROOXIDANS SP NOV, NITRATE-REDUCING BACTERIA, ACIDOVORAX SP BOFEN1, DEPENDENT IRON OXIDATION, NITROUS-OXIDE EMISSION, RHODOPSEUDOMONAS-PALUSTRIS TIE-1, PERIODICALLY HYPOXIC ESTUARY, FERROUS-IRON, RHODOBACTER-CAPSULATUS SB1003, FE(II)-OXIDIZING PHOTOAUTOTROPHIC BACTERIA
Abstract

Iron is the most abundant redox-active metal in the Earth's crust. The one electron transfer between the two most common redox states, Fe(II) and Fe(III), plays a role in a huge range of environmental processes from mineral formation and dissolution to contaminant remediation and global biogeochemical cycling. It has been appreciated for more than a century that microorganisms can harness the energy of this Fe redox transformation for their metabolic benefit. However, this is most widely understood for anaerobic Fe(III)-reducing or aerobic and microaerophilic Fe(II)-oxidizing bacteria. Only in the past few decades have we come to appreciate that bacteria also play a role in the anaerobic oxidation of ferrous iron, Fe(II), and thus can act to form Fe(III) minerals in anoxic settings. Since this discovery, our understanding of the ecology of these organisms, their mechanisms of Fe(II) oxidation and their role in environmental processes has been increasing rapidly. In this article, we bring these new discoveries together to review the current knowledge on these environmentally important bacteria, and reveal knowledge gaps for future research.

Published
2018

14. Using Zn and Ni behavior during magnetite precipitation in banded iron formations to determine its biological or abiotic origin.

Author

Han, Xiaohua, Tomaszewski, Elizabeth J., Schoenberg, Ronny, Konhauser, Kurt O., Amor, Matthieu, Pan, Yongxin, Warter, Viola, Kappler, Andreas, and Byrne, James M.

Subjects
*MAGNETITE, *BANDED iron formations, *MAGNETOTACTIC bacteria, *SHEWANELLA oneidensis, *TRACE elements, *SIDERITE
Abstract

• Magnetite is the dominant transformation product from Zn/Ni-ferrihydrite reduction. • Zn was more enriched in magnetite formed via abiogenic Fe(III) reduction. • Ni was more enriched in biogenic magnetite via microbial Fe(III) reduction. • Zn and Ni can potentially be used as biomarkers in ancient magnetite deposits. There is longstanding controversy about the genesis of magnetite in banded iron formations (BIFs), particularly concerning whether it is of abiogenic or biogenic origin. The composition of trace elements within magnetite produced by magnetotactic bacteria has been proposed as a promising marker for its biological origin; however further experimental evidence is required to investigate whether this also holds true for iron-metabolizing bacteria. Here, we compared the behavior of zinc (Zn) and nickel (Ni) in magnetite produced either abiogenically (ferrihydrite reacting with dissolved Fe2+) or biogenically (ferrihydrite reacting with dissolved Fe2+ generated via the dissimilatory iron-reducing bacterium - DIRB - Shewanella oneidensis MR-1). These abiotic and biotic incubations were applied for transforming three ferrihydrite (Fh) substrates: (1) Control Fh without added trace elements; (2) Zn-coprecipitated ferrihydrite (ZnFh); and (3) Ni-coprecipitated ferrihydrite (NiFh) in both NaHCO 3 and HEPES buffer. X-ray diffraction revealed magnetite as the dominant transformation product for all reaction conditions, while siderite was only detected in experiments containing NaHCO 3 as buffer. Based on similar initial dissolved Ni and Zn concentrations, we found opposing behavior of Zn and Ni where Zn showed enrichment in abiogenic magnetite, while Ni was more enriched in biogenic magnetite. Combining supposed Zn and Ni concentrations in Precambrian seawater and magnetite mineral grains from three formations deposited at different ages (i.e. 3.75 Ga Nuvvuagittuq Supracrustal Belt, 2.45 Ga Weeli Wolli Iron Formation, and 1.88 Ga Sokoman Iron Formation), we reconstructed potential Zn and Ni partition coefficients between Precambrian seawater and magnetite minerals. The reconstructed potential Zn and Ni partition coefficients suggested that these magnetite minerals from three formations were abiogenic. These differing behaviors suggest the possibility of using Zn and Ni partition coefficient ratios as a means of determining the presence or absence of DIRB in the formation of ancient magnetite deposits. [ABSTRACT FROM AUTHOR]

Published
2021
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