Preprints
Filtering by Subject: Biogeochemistry
δ13C values of bacterial hopanoids and leaf waxes as tracers for methanotrophy in peatlands
Published: 2019-07-08
Subjects: Biogeochemistry, Earth Sciences, Geochemistry, Physical Sciences and Mathematics
Methane emissions from peatlands contribute significantly to atmospheric CH4 levels and play an essential role in the global carbon cycle. The stable carbon isotopic composition (δ13C) of bacterial and plant lipids has been used to study modern and past peatland biogeochemistry, especially methane cycling. However, the small number of recent peatlands that have been characterised and the lack of [...]
Probing the chemical transformation of seawater-soluble crude oil components during microbial oxidation
Published: 2019-06-18
Subjects: Biogeochemistry, Chemistry, Earth Sciences, Environmental Chemistry, Environmental Sciences, Life Sciences, Microbiology, Oceanography, Oceanography and Atmospheric Sciences and Meteorology, Oil, Gas, and Energy, Physical Sciences and Mathematics
Studies assessing the environmental impacts of oil spills focus primarily on the non-water-soluble components, leaving the fate of the water-soluble fraction (WSF) largely unexplored. We employed untargeted chemical analysis along with biological information to probe the transformation of crude oil WSF in seawater, in the absence of light, in a laboratory experiment. Over a 14-day incubation, [...]
The glacial express
Published: 2019-05-31
Subjects: Biogeochemistry, Earth Sciences, Physical Sciences and Mathematics
Glacial calcium carbonate (CaCO3) shells are larger than interglacial CaCO3 shells. My research explores the consequences of this size difference. Because larger CaCO3 shells sink faster and dissolve more slowly than smaller CaCO3 shells, larger glacial shells underwent less dissolution than smaller interglacial shells. The resulting CaCO3 transport efficiency increase, coupled with observations [...]
Marine biomarkers from ice cores reveal enhanced high-latitude Southern Ocean carbon sink during the Antarctic Cold Reversal
Published: 2019-05-31
Subjects: Biogeochemistry, Earth Sciences, Glaciology, Paleontology, Physical Sciences and Mathematics
Determining the feedbacks that modulate Southern Ocean carbon dynamics is key to understanding past and future climate. The global pause in rising atmospheric CO2 during the period of mid- to high-latitude southern surface cooling known as the Antarctic Cold Reversal (ACR, 14,700-12,700 years ago) provides an opportunity to disentangle competing influences. We present highly-resolved and [...]
Dark carbon fixation contributes to sedimentary organic carbon in the Arabian Sea oxygen minimum zone
Published: 2019-05-18
Subjects: Biogeochemistry, Earth Sciences, Environmental Microbiology and Microbial Ecology Life Sciences, Life Sciences, Microbiology, Oceanography and Atmospheric Sciences and Meteorology, Physical Sciences and Mathematics
In response to rising CO2 concentrations and increasing global sea surface temperatures, oxygen minimum zones (OMZ), or “dead zones”, are expected to expand. OMZs are fueled by high primary productivity, resulting in enhanced biological oxygen demand at depth, subsequent oxygen depletion, and attenuation of remineralization. This results in the deposition of organic carbon-rich sediments. Carbon [...]
A first look at dissolved Ge isotopes in marine sediments
Published: 2019-04-28
Subjects: Biogeochemistry, Earth Sciences, Physical Sciences and Mathematics
The removal of chemical species from seawater during the precipitation of authigenic minerals is difficult to constrain but may play a major role in the global biogeochemical cycles of some elements, including silicon (Si) and germanium (Ge). Here, we present Ge/Si, δ74Ge, and supporting chemical data of pore waters and core incubations at three continental margin sites in California and the Gulf [...]
Terrestrial environmental change across the onset of the PETM and the associated impact on biomarker proxies: a cautionary tale
Published: 2019-04-28
Subjects: Biogeochemistry, Earth Sciences, Geochemistry, Geology, Physical Sciences and Mathematics
The Paleocene-Eocene Thermal Maximum (PETM; ~ 56 million years ago (Ma) is the most severe carbon cycle perturbation event of the Cenozoic. Although the PETM is associated with warming in both the surface (~up to 8°C) and deep ocean (~up to 5°C), there are relatively few terrestrial temperature estimates from the onset of this interval. The associated response of the hydrological cycle during the [...]
A long-term, high-latitude record of Eocene hydrological change in the Greenland region
Published: 2019-04-26
Subjects: Biogeochemistry, Earth Sciences, Geochemistry, Geology, Physical Sciences and Mathematics
A range of proxy approaches have been used to reconstruct short-term changes to Earth’s hydrological cycle during the early Eocene hyperthermals. However, little is known about the response of Earth’s hydrological and biogeochemical systems to long-term Cenozoic cooling, which began following the Early Eocene Climatic Optimum (53.3 – 49.4 million years ago; Ma). Here, we use the molecular [...]
Separating isotopic impacts of karst and in-cave processes from climate variability using an integrated speleothem isotope-enabled forward model
Published: 2019-03-11
Subjects: Biogeochemistry, Earth Sciences, Hydrology, Physical Sciences and Mathematics, Speleology
Speleothem δ18O values are commonly used to infer past climate variability. However, both non-linear karst hydrological processes and in-cave disequilibrium isotope fractionation are recognised and hinder the interpretation of δ18O values. In recent years, proxy system models (PSMs) have emerged to quantitatively assess the confounding effects of these processes. This study presents the first [...]
Human-induced fire regime shifts during 19th century industrialization: a robust fire regime reconstruction using northern Polish lake sediments
Published: 2019-02-22
Subjects: Biogeochemistry, Earth Sciences, Environmental Sciences, Other Earth Sciences, Physical Sciences and Mathematics
Fire regime shifts are driven by climate and natural vegetation changes, but can be strongly affected by human land management. Yet, it is poorly known how exactly humans have influenced fire regimes prior to active wildfire suppression. Among the last 250 years, the human contribution to the global increase in fire occurrence during the mid-19th century is especially unclear, as data sources are [...]
Long Range Correlation in Redox Potential Fluctuations Signals Energetic Efficiency of Bacterial Fe(II) Oxidation
Published: 2019-02-21
Subjects: Biogeochemistry, Earth Sciences, Environmental Sciences, Physical Sciences and Mathematics
Differentiating biotic and abiotic processes in nature remains a persistent challenge, specifically in evaluating microbial contributions to geochemical processes through time. Building on previous work reporting that biologically-influenced systems exhibit stronger long-range correlation than abiotic systems, this study evaluated the relationship between long-range correlation of redox [...]
The organic component of the earliest sulfur cycling
Published: 2019-01-16
Subjects: Biogeochemistry, Earth Sciences, Physical Sciences and Mathematics
The chemistry of the Early Earth is widely inferred from the elemental and isotopic compositions of sulfidic sedimentary rocks, which are presumed to have formed globally through the reduction of seawater sulfate or locally from hydrothermally supplied sulfide. Here we argue that, in the sulfate-poor ferruginous oceans of the Archean eon, organic sulfur must have played an important and [...]
Critical Review of Polyphosphate and Polyphosphate Accumulating Organisms for Agricultural Water Quality Management
Published: 2018-12-03
Subjects: Agriculture, Biogeochemistry, Earth Sciences, Environmental Microbiology and Microbial Ecology Life Sciences, Environmental Sciences, Life Sciences, Microbiology, Natural Resources Management and Policy, Physical Sciences and Mathematics, Soil Science, Water Resource Management
Despite ongoing management efforts, phosphorus (P) loading from agricultural landscapes continues to impair water quality. Wastewater treatment research has enhanced our knowledge of microbial mechanisms influencing P cycling, especially regarding microbes known as polyphosphate accumulating organisms (PAOs) that store P as polyphosphate (polyP) under oxic conditions and release P under anoxic [...]
Geomorphology and Climate Interact to Control Organic Carbon Stock and Age in Mountain River Valley Bottoms
Published: 2018-10-08
Subjects: Biogeochemistry, Earth Sciences, Geomorphology, Physical Sciences and Mathematics
Organic carbon (OC) in valley bottom downed wood and soil that cycles over short to moderate timescales represents a large, dynamic, and poorly quantified pool of carbon whose distribution and residence time affects global climate. We compare four disparate mountain river basins to show that mountain river valley bottoms store substantial estimated OC stocks in floodplain soil and downed wood. [...]
Grand Challenges (and Great Opportunities) in Sedimentology, Stratigraphy, and Diagenesis Research
Published: 2018-09-23
Subjects: Biogeochemistry, Earth Sciences, Geomorphology, Physical Sciences and Mathematics, Sedimentology, Stratigraphy
Technological advances make these exciting times for geoscientists studying Earth surface processes, their depositional products, and interactions with the biosphere, hydrosphere, atmosphere, and lithosphere; from monitoring contemporary sediment transport processes to interpretation of sedimentary archives that record ancient environmental changes. We set out three research challenges: 1) [...]