Many metals present in trace concentrations the oceans are sensitive to reduction and oxidation reactions (termed redox-sensitive or RSTMs) can therefore be affected during intervals of expanded oceanic anoxia euxinia (anoxic sulfidic waters). These RSTMs important micronutrients; their availability plays a significant role controlling metabolic pathways ecosystem structure. Understanding links...

Ocean anoxic events (OAE) are characterized by increased organic content of marine sediment on a global scale with accompanying positive excursions in sedimentary and inorganic δ 13C values. To sustain the C exports burial required to explain isotope excursion, supplies nutrients oceans often invoked during ocean events. The potential source these is investigated this study for Oceanic Anoxic E...

This paper describes experimental research to directly quantify the ordinary heterotrophic organism (OHO) cell yield coefficient under anoxic and aerobic conditions with real wastewater as substrate. Until recently these two values were assumed equal in activated sludge models, despite theoretical predictions that the anoxic yield should be reduced relative to its aerobic value. In this study, ...

ability to survive hypoxic conditions. Abstract It is generally considered that animal life was triggered by the rise of oxygen levels. Based on experiments evaluating the minimum range of oxygen levels at which sponges can survive, Mills et al. [1] defend the opposite view. However, the authors do not demonstrate that 'animal life was not triggered by the oxygen rise' is the only possible and ...

The atmosphere–ocean system experienced a progressive change from anoxic to more oxidizing conditions through time. This oxidation is traditionally envisaged to have occurred as two stepwise increases in atmospheric oxygen at the beginning and end of the Proterozoic Eon. Here, we present a study of the redox-sensitive element, uranium, in organic-rich shales to track the history of Earth's enri...

Microbial methane consumption in anoxic sediments significantly impacts the global environment by reducing the flux of greenhouse gases from ocean to atmosphere. Despite its significance, the biological mechanisms controlling anaerobic methane oxidation are not well characterized. One current model suggests that relatives of methane-producing Archaea developed the capacity to reverse methanogen...

The largest mass extinction of biota in the Earth's history occurred during the Permian-Triassic transition and included two extinctions, one each at the latest Permian (first phase) and earliest Triassic (second phase). High seawater temperature in the surface water accompanied by euxinic deep-intermediate water, intrusion of the euxinic water to the surface water, a decrease in pH, and hyperc...

a r t i c l e i n f o Keywords: paleoceanography carbonate sedimentology aqueous geochemistry Observed changes in the source of CaCO 3 sediments since Archean time suggest a first order pattern of decreasing abundance of carbonate cements precipitated directly on the seafloor. We propose that the observed reduction in CaCO 3 precipitation on the seafloor is caused by a decrease in CaCO 3 satura...

The cycles of carbon and oxygen at the Earth surface are intimately linked, where the burial of organic carbon into sediments represents a source of oxygen to the surface environment. This coupling is typically quantified through the isotope records of organic and inorganic carbon. Yet, the late Neoproterozoic Eon, the time when animals first evolved, experienced wild isotope fluctuations which...

Earth's surface chemical environment has evolved from an early anoxic condition to the oxic state we have today. Transitional between an earlier Proterozoic world with widespread deep-water anoxia and a Phanerozoic world with large oxygen-utilizing animals, the Neoproterozoic Era [1000 to 542 million years ago (Ma)] plays a key role in this history. The details of Neoproterozoic Earth surface o...