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Methane oxidation in the waters of a humics-rich boreal lake stimulated by photosynthesis, nitrite, Fe(III) and humics

Abstract.

"Small boreal lakes are known to contribute significantly to global methane emissions. Lake Lovojärvi is a eutrophic lake in Southern Finland with bottom water methane concentrations up to 2 mM. However, the surface water concentration, and thus the diffusive emission potential, was low (< 0.5 μM). We studied the biogeochemical processes involved in methane removal by chemical profiling and through incubation experiments. δ13C-CH4 profiling of the water column revealed methane-oxidation hotspots just below the oxycline and within the anoxic water column. In incubation experiments involving the addition of light and/or oxygen, methane oxidation rates in the anoxic hypolimnion were enhanced 3-fold, suggesting a major role for photosynthetically fueled aerobic methane oxidation. A distinct peak in methane concentration was observed at the chlorophyll a maximum[...]"

Source: Biogeoscience
Authors: Sigrid van Grinsven et al.
DOI: https://doi.org/10.5194/bg-2021-3

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Effects of Experimental Ocean Acidification on the Larval Morphology and Metabolism of a Temperate Sparid, Chrysoblephus laticeps

Abstract.

"Ocean acidification is predicted to have widespread impacts on marine species. The early life stages of fishes, being particularly sensitive to environmental deviations, represent a critical bottleneck to recruitment. We investigated the effects of ocean acidification (∆pH = −0.4) on the oxygen consumption and morphometry during the early ontogeny of a commercially important seabream, Chrysoblephus laticeps, up until flexion. Hatchlings appeared to be tolerant to hypercapnic conditions, exhibiting no difference in oxygen consumption or morphometry between treatments, although the yolk reserves were marginally reduced in the low-pH treatment. The preflexion stages appeared[...]"

 

Source: MDPI
Authors: Cuen Muller et al.
DOI: https://doi.org/10.3390/oceans2010002

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A transient swing to higher oxygen levels in the atmosphere and oceans at ~1.4 Ga

Abstract.

"The mid-Proterozoic (1.8–0.8 Ga) may have witnessed persistent and predominant anoxia at the Earth’s surface. However, recent studies suggest that there was a period around ~1.4 Ga where oxygen levels might have been transiently elevated, both in the atmosphere and oceans. In order to shed light on this debated topic, we analyzed rare earth elements plus Y (REY) and Cr isotope profiles of the carbonate rocks from the ~1.44-Gyr-old Tieling Formation consisting of the lower Daizhuangzi (DZZ) and upper Laohuding (LHD) Members at the Jixian section, North China. The DZZ samples are characterized by middle REE enriched, hump-shaped REY distribution patterns, while those of the LHD Member display[...]"

 

Source: Science Direct
Authors: Wei Wei et al.
DOI: https://doi.org/10.1016/j.precamres.2020.106058

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Sea urchin chronicles. The effect of oxygen super-saturation and marine polluted sediments from Bagnoli-Goroglio Bay on different life stages of the

sea urchin Paracentrotus lividus

Abstract.

"In marinas and harbours, the accumulation of pollutants in sediments, combined with poor exchange of water with the open sea, poses a major environmental threat. The presence of photosynthetic organisms and the related oxygen production, however, may alleviate the negative effects of environmental contamination on heterotrophic organisms, enhancing their physiological defences. Furthermore, possible transgenerational buffer effects may increase the ability of natural populations to face environmental[...]"

 

Source: Science Direct
Authors: Antonia Chiarore et al.
DOI: https://doi.org/10.1016/j.marenvres.2020.104967

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Meiofauna improve oxygenation and accelerate sulfide removal in the seasonally hypoxic seabed

Abstract.

"Oxygen depleted areas are widespread in the marine realm. Unlike macrofauna, meiofauna are abundant in hypoxic sediments. We studied to what extent meiofauna affect oxygen availability, sulfide removal and microbial communities. Meiofauna were extracted alive and added to intact sediments simulating abundance gradients previously reported in the area. [...]"

Source: Marine Environmental Research
Authors: Stefano Bonaglia et al.
DOI: 10.1016/j.marenvres.2020.104968

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On the co‐evolution of surface oxygen levels and animals

Abstract.

"Few topics in geobiology have been as extensively debated as the role of Earth's oxygenation in controlling when and why animals emerged and diversified. All currently described animals require oxygen for at least a portion of their life cycle. Therefore, the transition to an oxygenated planet was a prerequisite for the emergence of animals. Yet, our understanding of Earth's oxygenation and the environmental requirements of animal habitability and ecological success is currently limited; estimates for the timing of the appearance of environments sufficiently oxygenated to support ecologically stable populations of animals span a wide range, from billions of years to only a few million years before animals appear in the fossil record. [...]"

Source: Geobiology
Authors: Devon B. Cole et al.
DOI: 10.1111/gbi.12382

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Millennial-scale variations in sedimentary oxygenation in the western subtropical North Pacific and its links to North Atlantic climate

Abstract.

"The deep-ocean carbon cycle, especially carbon sequestration and outgassing, is one of the mechanisms to explain variations in atmospheric CO2 concentrations on millennial and orbital timescales. However, the potential role of subtropical North Pacific subsurface waters in modulating atmospheric CO2 levels on millennial timescales is poorly constrained. An increase in the respired CO2 concentration in the glacial deep-ocean due to biological pump generally corresponds to deoxygenation in the ocean interior. [...]"

Source: Climate of the Past
Authors: Jianjun Zou et al.
DOI: 10.5194/cp-16-387-2020

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Post-depositional manganese mobilization during the last glacial period in sediments of the eastern Clarion-Clipperton Zone, Pacific Ocean

Abstract.

"Numerous studies have provided compelling evidence that the Pacific Ocean has experienced substantial glacial/interglacial changes in bottom-water oxygenation associated with enhanced carbon dioxide storage in the glacial deep ocean. Under postulated low glacial bottom-water oxygen concentrations (O2bw), redox zonation, biogeochemical processes and element fluxes in the sediments must have been distinctively different during the last glacial period (LGP) compared to current well-oxygenated conditions. [...]"

Source: Earth and Planetary Science Letters
Authors: Jessica B.Volz et al.
DOI: 10.1016/j.epsl.2019.116012

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Stepwise Earth oxygenation is an inherent property of global biogeochemical cycling

Abstract.

"Oxygenation of Earth’s atmosphere and oceans occurred across three major steps during the Paleoproterozoic, Neoproterozoic, and Paleozoic eras, with each increase having profound consequences for the biosphere. Biological or tectonic revolutions have been proposed to explain each of these stepwise increases in oxygen, but the principal driver of each event remains unclear. Here we show, using a theoretical model, that the observed oxygenation steps are a simple consequence of internal feedbacks in the long-term biogeochemical cycles of carbon, oxygen, and phosphorus, and that there is no requirement for a specific stepwise external forcing to explain the course of Earth surface oxygenation. [...]"

Source: Science
Authors: Lewis J. Alcott et al.
DOI: 10.1126/science.aax6459

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Anoxygenic photosynthesis and the delayed oxygenation of Earth’s atmosphere

Abstract.

"The emergence of oxygenic photosynthesis created a new niche with dramatic potential to transform energy flow through Earth’s biosphere. However, more primitive forms of photosynthesis that fix CO2 into biomass using electrons from reduced species like Fe(II) and H2 instead of water would have competed with Earth’s early oxygenic biosphere for essential nutrients. [...]"

Source: Nature Communications
Authors: Kazumi Ozaki et al.
DOI: 10.1038/s41467-019-10872-z

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