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Geobiology

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https://www.readbyqxmd.com/read/28434198/eukaryotic-diversity-in-late-pleistocene-marine-sediments-around-a-shallow-methane-hydrate-deposit-in-the-japan-sea
#1
M Kouduka, A S Tanabe, S Yamamoto, K Yanagawa, Y Nakamura, F Akiba, H Tomaru, H Toju, Y Suzuki
Marine sediments contain eukaryotic DNA deposited from overlying water columns. However, a large proportion of deposited eukaryotic DNA is aerobically biodegraded in shallow marine sediments. Cold seep sediments are often anaerobic near the sediment-water interface, so eukaryotic DNA in such sediments is expected to be preserved. We investigated deeply buried marine sediments in the Japan Sea, where a methane hydrate deposit is associated with cold seeps. Quantitative PCR analysis revealed the reproducible recovery of eukaryotic DNA in marine sediments at depths up to 31...
April 23, 2017: Geobiology
https://www.readbyqxmd.com/read/28419718/shifting-microbial-communities-sustain-multiyear-iron-reduction-and-methanogenesis-in-ferruginous-sediment-incubations
#2
M S Bray, J Wu, B C Reed, C B Kretz, K M Belli, R L Simister, C Henny, F J Stewart, T J DiChristina, J A Brandes, D A Fowle, S A Crowe, J B Glass
Reactive Fe(III) minerals can influence methane (CH4 ) emissions by inhibiting microbial methanogenesis or by stimulating anaerobic CH4 oxidation. The balance between Fe(III) reduction, methanogenesis, and CH4 oxidation in ferruginous Archean and Paleoproterozoic oceans would have controlled CH4 fluxes to the atmosphere, thereby regulating the capacity for CH4 to warm the early Earth under the Faint Young Sun. We studied CH4 and Fe cycling in anoxic incubations of ferruginous sediment from the ancient ocean analogue Lake Matano, Indonesia, over three successive transfers (500 days in total)...
April 17, 2017: Geobiology
https://www.readbyqxmd.com/read/28397387/a-geochemical-study-of-the-ediacaran-discoidal-fossil-aspidella-preserved-in-limestones-implications-for-its-taphonomy-and-paleoecology
#3
N Bykova, B C Gill, D Grazhdankin, V Rogov, S Xiao
The Ediacara biota features the rise of macroscopic complex life immediately before the Cambrian explosion. One of the most abundant and widely distributed elements of the Ediacara biota is the discoidal fossil Aspidella, which is interpreted as a subsurface holdfast possibly anchoring a frondose epibenthic organism. It is a morphologically simple fossil preserved mainly in siliciclastic rocks, which are unsuitable for comprehensive stable isotope geochemical analyses to decipher its taphonomy and paleoecology...
April 11, 2017: Geobiology
https://www.readbyqxmd.com/read/28397335/proterozoic-microbial-mats-and-their-constraints-on-environments-of-silicification
#4
A R Manning-Berg, L C Kah
The occurrence of microfossiliferous, early diagenetic chert in Proterozoic successions is broadly restricted to peritidal marine environments. Such coastal environments are amongst the most environmentally variable of marine environments, experiencing both enhanced evaporation and potential influx of terrestrial freshwaters. To better understand potential conditions under which silicification occurs, we focus on microfossiliferous early diagenetic chert from the Mesoproterozoic Bylot Supergroup, northern Baffin Island...
April 11, 2017: Geobiology
https://www.readbyqxmd.com/read/28387043/controls-on-the-evolution-of-ediacaran-metazoan-ecosystems-a-redox-perspective
#5
F Bowyer, R A Wood, S W Poulton
A growing number of detailed geochemical studies of Ediacaran (635-541 Ma) marine successions have provided snapshots into the redox environments that played host to the earliest known metazoans. Whilst previous compilations have focused on the global evolution of Ediacaran water column redox chemistry, the inherent heterogeneity evident in palaeogeographically distinct environments demands a more dissected approach to better understand the nature, interactions and evolution of extrinsic controls on the development of early macrobenthic ecosystems...
April 7, 2017: Geobiology
https://www.readbyqxmd.com/read/28387009/paleoecology-and-paleoceanography-of-the-athel-silicilyte-ediacaran-cambrian-boundary-sultanate-of-oman
#6
D A Stolper, G D Love, S Bates, T W Lyons, E Young, A L Sessions, J P Grotzinger
The Athel silicilyte is an enigmatic, hundreds of meters thick, finely laminated quartz deposit, in which silica precipitated in deep water (>~100-200 m) at the Ediacaran-Cambrian boundary in the South Oman Salt Basin. In contrast, Meso-Neoproterozoic sinks for marine silica were dominantly restricted to peritidal settings. The silicilyte is known to contain sterane biomarkers for demosponges, which today are benthic, obligately aerobic organisms. However, the basin has previously been described as permanently sulfidic and time-equivalent shallow-water carbonate platform and evaporitic facies lack silica...
April 7, 2017: Geobiology
https://www.readbyqxmd.com/read/28383164/ferrous-iron-and-ammonium-rich-diffuse-vents-support-habitat-specific-communities-in-a-shallow-hydrothermal-field-off-the-basiluzzo-islet-aeolian-volcanic-archipelago
#7
G Bortoluzzi, T Romeo, V La Cono, G La Spada, F Smedile, V Esposito, G Sabatino, M Di Bella, S Canese, G Scotti, M Bo, L Giuliano, D Jones, P N Golyshin, M M Yakimov, F Andaloro
Ammonium- and Fe(II)-rich fluid flows, known from deep-sea hydrothermal systems, have been extensively studied in the last decades and are considered as sites with high microbial diversity and activity. Their shallow-submarine counterparts, despite their easier accessibility, have so far been under-investigated, and as a consequence, much less is known about microbial communities inhabiting these ecosystems. A field of shallow expulsion of hydrothermal fluids has been discovered at depths of 170-400 meters off the base of the Basiluzzo Islet (Aeolian Volcanic Archipelago, Southern Tyrrhenian Sea)...
April 6, 2017: Geobiology
https://www.readbyqxmd.com/read/28378894/a-theory-of-atmospheric-oxygen
#8
T A Laakso, D P Schrag
Geological records of atmospheric oxygen suggest that pO2 was less than 0.001% of present atmospheric levels (PAL) during the Archean, increasing abruptly to a Proterozoic value between 0.1% and 10% PAL, and rising quickly to modern levels in the Phanerozoic. Using a simple model of the biogeochemical cycles of carbon, oxygen, sulfur, hydrogen, iron, and phosphorous, we demonstrate that there are three stable states for atmospheric oxygen, roughly corresponding to levels observed in the geological record. These stable states arise from a series of specific positive and negative feedbacks, requiring a large geochemical perturbation to the redox state to transition from one to another...
April 5, 2017: Geobiology
https://www.readbyqxmd.com/read/28371135/climate-and-geochemistry-as-drivers-of-eucalypt-diversification-in-australia
#9
E N Bui, A H Thornhill, C E González-Orozco, N Knerr, J T Miller
Eucalypts cover most of Australia. Here, we investigate the relative contribution of climate and geochemistry to the distribution and diversity of eucalypts. Using geostatistics, we estimate major element concentrations, pH, and electrical conductivity at sites where eucalypts have been recorded. We compare the median predicted geochemistry and reported substrate for individual species that appear associated with extreme conditions; this provides a partial evaluation of the predictions. We generate a site-by-species matrix by aggregating observations to the centroids of 100-km-wide grid cells, calculate diversity indices, and use numerical ecology methods (ordination, variation partitioning) to investigate the ecology of eucalypts and their response to climatic and geochemical gradients...
April 3, 2017: Geobiology
https://www.readbyqxmd.com/read/28299862/the-neoarchaean-surficial-sulphur-cycle-an-alternative-hypothesis-based-on-analogies-with-20th-century-atmospheric-lead
#10
M Gallagher, M J Whitehouse, B S Kamber
We revisit the S-isotope systematics of sedimentary pyrite in a shaly limestone from the ca. 2.52 Ga Gamohaan Formation, Upper Campbellrand Subgroup, Transvaal, South Africa. The analysed rock is interpreted to have been deposited in a water depth of ca. 50-100 m, in a restricted sub-basin on a drowning platform. A previous study discovered that the pyrites define a nonzero intercept δ(34) SV-CDT -Δ(33) S data array. The present study carried out further quadruple S-isotope analyses of pyrite, confirming and expanding the linear δ(34) SV-CDT -Δ(33) S array with an δ(34) S zero intercept at ∆(33) S ca...
March 16, 2017: Geobiology
https://www.readbyqxmd.com/read/28256065/volcanic-ash-supports-a-diverse-bacterial-community-in-a-marine-mesocosm
#11
V Witt, P M Ayris, D E Damby, C Cimarelli, U Kueppers, D B Dingwell, G Wörheide
Shallow-water coral reef ecosystems, particularly those already impaired by anthropogenic pressures, may be highly sensitive to disturbances from natural catastrophic events, such as volcanic eruptions. Explosive volcanic eruptions expel large quantities of silicate ash particles into the atmosphere, which can disperse across millions of square kilometres and deposit into coral reef ecosystems. Following heavy ash deposition, mass mortality of reef biota is expected, but little is known about the recovery of post-burial reef ecosystems...
March 3, 2017: Geobiology
https://www.readbyqxmd.com/read/28188680/experimental-fossilization-of-mat-forming-cyanobacteria-in-coarse-grained-siliciclastic-sediments
#12
S A Newman, V Klepac-Ceraj, G Mariotti, S B Pruss, N Watson, T Bosak
Microbial fossils and textures are commonly preserved in Ediacaran and early Cambrian coarse-grained siliciclastic sediments that were deposited in tidal and intertidal marine settings. In contrast, the fossilization of micro-organisms in similar marine environments of post-Cambrian age is less frequently reported. Thus, temporal discrepancies in microbial preservation may have resulted from the opening and closing of a unique taphonomic window during the terminal Proterozoic and early Phanerozoic, respectively...
February 11, 2017: Geobiology
https://www.readbyqxmd.com/read/28158920/the-geobiological-nitrogen-cycle-from-microbes-to-the-mantle
#13
A L Zerkle, S Mikhail
Nitrogen forms an integral part of the main building blocks of life, including DNA, RNA, and proteins. N2 is the dominant gas in Earth's atmosphere, and nitrogen is stored in all of Earth's geological reservoirs, including the crust, the mantle, and the core. As such, nitrogen geochemistry is fundamental to the evolution of planet Earth and the life it supports. Despite the importance of nitrogen in the Earth system, large gaps remain in our knowledge of how the surface and deep nitrogen cycles have evolved over geologic time...
February 3, 2017: Geobiology
https://www.readbyqxmd.com/read/28130812/identification-distribution-and-quantification-of-biominerals-in-a-deciduous-forest
#14
C Krieger, C Calvaruso, C Morlot, S Uroz, L Salsi, M-P Turpault
Biomineralization is a common process in most vascular plants, but poorly investigated for trees. Although the presence of calcium oxalate and silica accumulation has been reported for some tree species, the chemical composition, abundance, and quantification of biominerals remain poorly documented. However, biominerals may play important physiological and structural roles in trees, especially in forest ecosystems, which are characterized by nutrient-poor soils. In this context, our study aimed at investigating the morphology, distribution, and relative abundance of biominerals in the different vegetative compartments (foliage, branch, trunk, and root) of Fagus sylvatica L...
January 28, 2017: Geobiology
https://www.readbyqxmd.com/read/28128527/sulphur-cycling-in-a-neoarchaean-microbial-mat
#15
N R Meyer, A L Zerkle, D A Fike
Multiple sulphur (S) isotope ratios are powerful proxies to understand the complexity of S biogeochemical cycling through Deep Time. The disappearance of a sulphur mass-independent fractionation (S-MIF) signal in rocks <~2.4 Ga has been used to date a dramatic rise in atmospheric oxygen levels. However, intricacies of the S-cycle before the Great Oxidation Event remain poorly understood. For example, the isotope composition of coeval atmospherically derived sulphur species is still debated. Furthermore, variation in Archaean pyrite δ(34) S values has been widely attributed to microbial sulphate reduction (MSR)...
January 27, 2017: Geobiology
https://www.readbyqxmd.com/read/27917584/primary-productivity-of-snow-algae-communities-on-stratovolcanoes-of-the-pacific-northwest
#16
T L Hamilton, J Havig
The majority of geomicrobiological research conducted on glacial systems to date has focused on glaciers that override primarily carbonate or granitic bedrock types, with little known of the processes that support microbial life in glacial systems overriding volcanic terrains (e.g., basalt or andesite). To better constrain the role of the supraglacial ecosystems in the carbon and nitrogen cycles, to gain insight into microbiome composition and function in alpine glacial systems overriding volcanic terrains, and to constrain potential elemental sequestration or release through weathering processes associated with snow algae communities, we examined the microbial community structure and primary productivity of snow algae communities on stratovolcanoes in the Cascade Range of the Pacific Northwest...
March 2017: Geobiology
https://www.readbyqxmd.com/read/28063184/biologically-agglutinated-eukaryotic-microfossil-from-cryogenian-cap-carbonates
#17
K R Moore, T Bosak, F A Macdonald, D J G Lahr, S Newman, C Settens, S B Pruss
Cryogenian cap carbonates that overlie Sturtian glacial deposits were formed during a post-glacial transgression. Here, we describe microfossils from the Kakontwe Formation of Zambia and the Taishir Formation of Mongolia-both Cryogenian age, post-Sturtian cap carbonates-and investigate processes involved in their formation and preservation. We compare microfossils from these two localities to an assemblage of well-documented microfossils previously described in the post-Sturtian Rasthof Formation of Namibia...
January 6, 2017: Geobiology
https://www.readbyqxmd.com/read/28063179/integrated-carbon-sulfur-and-nitrogen-isotope-chemostratigraphy-of-the-ediacaran-lantian-formation-in-south-china-spatial-gradient-ocean-redox-oscillation-and-fossil-distribution
#18
W Wang, C Guan, C Zhou, Y Peng, L M Pratt, X Chen, L Chen, Z Chen, X Yuan, S Xiao
The Ediacaran Doushantuo Formation in South China is a prime target for geobiological investigation because it offers opportunities to integrate chemostratigraphic and paleobiological data. Previous studies were mostly focused on successions in shallow-water shelf facies, but data from deep-water successions are needed to fully understand basinal redox structures. Here, we report δ(13) Ccarb , δ(13) Corg , δ(34) Spyr , δ(34) SCAS , and δ(15) Nsed data from a drill core of the fossiliferous Lantian Formation, which is a deep-water equivalent of the Doushantuo Formation...
January 6, 2017: Geobiology
https://www.readbyqxmd.com/read/28044397/selenium-iv-vi-reduction-and-tolerance-by-fungi-in-an-oxic-environment
#19
C E Rosenfeld, J A Kenyon, B R James, C M Santelli
Microbial processes are known to mediate selenium (Se) oxidation-reduction reactions, strongly influencing Se speciation, bioavailability, and transport throughout the environment. While these processes have commonly been studied in anaerobic bacteria, the role that aerobic fungi play in Se redox reactions could be important for Se-rich soil systems, dominated by microbial activity. We quantified fungal growth, aerobic Se(IV, VI) reduction, and Se immobilization and volatilization in the presence of six, metal-tolerant Ascomycete fungi...
January 2, 2017: Geobiology
https://www.readbyqxmd.com/read/28042698/geochemically-distinct-carbon-isotope-distributions-in-allochromatium-vinosum-dsm-180-t-grown-photoautotrophically-and-photoheterotrophically
#20
T Tang, W Mohr, S R Sattin, D R Rogers, P R Girguis, A Pearson
Anoxygenic, photosynthetic bacteria are common at redox boundaries. They are of interest in microbial ecology and geosciences through their role in linking the carbon, sulfur, and iron cycles, yet much remains unknown about how their flexible carbon metabolism-permitting either autotrophic or heterotrophic growth-is recorded in the bulk sedimentary and lipid biomarker records. Here, we investigated patterns of carbon isotope fractionation in a model photosynthetic sulfur-oxidizing bacterium, Allochromatium vinosum DSM180(T) ...
January 1, 2017: Geobiology
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