Intermediate water circulation drives distribution of Pliocene Oxygen Minimum Zones
"Oxygen minimum zones (OMZs) play a critical role in global biogeochemical cycling and act as barriers to dispersal for marine organisms. OMZs are currently expanding and intensifying with climate change, however past distributions of OMZs are relatively unknown. Here we present evidence for widespread pelagic OMZs during the Pliocene (5.3-2.6 Ma), the most recent epoch with atmospheric CO2 analogous to modern (~400-450 ppm). The global distribution of OMZ-affiliated planktic foraminifer, Globorotaloides hexagonus, and Earth System and Species Distribution Models show [...]".
Authors: Catherine V. Davis et al.
Oceanic and atmospheric methane cycling in the cGENIE Earth system model
"The methane (CH4) cycle is a key component of the Earth system that links planetary climate, biological metabolism, and the global biogeochemical cycles of carbon, oxygen, sulfur, and hydrogen. However, currently lacking is a numerical model capable of simulating a diversity of environments in the ocean where CH4 can be produced and destroyed, and with the flexibility to be able to explore not only relatively recent perturbations to Earth’s CH4 cycle but also to probe CH4 cycling and associated climate impacts under the very low-O2 conditions characteristic of most of Earth history and likely widespread on other Earth-like planets. [...]"
Source: Geoscientific Model Development
Authors: Christopher T. Reinhard et al.
The control of hydrogen sulfide on benthic iron and cadmium fluxes in the oxygen minimum zone off Peru
"Sediments in oxygen-depleted marine environments can be an important sink or source of bio-essential trace metals in the ocean. However, the key mechanisms controlling the release from or burial of trace metals in sediments are not exactly understood. Here, we investigate the benthic biogeochemical cycling of Fe and Cd in the oxygen minimum zone off Peru. We combine bottom water profiles, pore water profiles, as well as benthic fluxes determined from pore water profiles and in-situ from benthic chamber incubations along a depth transect at 12° S. In agreement with previous studies, both concentration-depth profiles and in-situ benthic fluxes indicate a Fe release from sediments into bottom waters. [...]"
Source: Biogeosciences (Preprint)
Authors: Anna Plass et al.
Atmosphere–ocean oxygen and productivity dynamics during early animal radiations
"The proliferation of large, motile animals 540 to 520 Ma has been linked to both rising and declining O2 levels on Earth. To explore this conundrum, we reconstruct the global extent of seafloor oxygenation at approximately submillion-year resolution based on uranium isotope compositions of 187 marine carbonates samples from China, Siberia, and Morocco, and simulate O2 levels in the atmosphere and surface oceans using a mass balance model constrained by carbon, sulfur, and strontium isotopes in the same sedimentary successions. [...]"
Authors: Tais W. Dahl et al.
A New Characterization of the Upper Waters of the central Gulf of México based on Water Mass Hydrographic and Biogeochemical Characteristics
" In the Gulf of Mexico (GoM) at least three near-surface water masses are affected by mesoscale processes that modulate the biogeochemical cycles. Prior studies have presented different classifications of water masses where the greater emphasis was on deep waters and not on the surface waters (σθ < 26 kg m−3), as in this work. Here presents a new classification of water masses in the GoM, based on thermohaline properties and dissolved oxygen (DO) concentration using data from a total of five summer and winter cruises carried out primarily in the central GoM. [...]"
Authors: Gabriela Yareli Cervantes-Diaz et al.
The effect of marine aggregate parameterisations on nutrients and oxygen minimum zones in a global biogeochemical model
"Particle aggregation determines the particle flux length scale and affects the marine oxygen concentration and thus the volume of oxygen minimum zones (OMZs) that are of special relevance for ocean nutrient cycles and marine ecosystems and that have been found to expand faster than can be explained by current state-of-the-art models. [...]"
Author: Daniela Niemeyer et al.
Oxygen minimum zone-type biogeochemical cycling in the Cenomanian-Turonian Proto-North Atlantic across Oceanic Anoxic Event 2
"Oceanic Anoxic Events (OAEs) in Earth's history are regarded as analogues for current and future ocean deoxygenation, potentially providing information on its pacing and internal dynamics. In order to predict the Earth system's response to changes in greenhouse gas concentrations and radiative forcing, a sound understanding of how biogeochemical cycling differs in modern and ancient marine environments is required. [...]"
Source: Earth and Planetary Science Letters
Authors: Florian Scholz et al.
Isotopic evidence for complex biogeochemical cycling of Cd in the eastern tropical South Pacific
"Over the past decades, observations have confirmed decreasing oxygen levels and shoaling of oxygen minimum zones (OMZs) in the tropical oceans. Such changes impact the biogeochemical cycling of micronutrients such as Cd, but the potential consequences are only poorly constrained. Here, we present seawater Cd concentrations and isotope compositions for 12 depth profiles at coastal, nearshore and offshore stations from 4°S to 14°S in the eastern tropical South Pacific, where one of the world's strongest OMZs prevails. [...]"
Source: Earth and PLanetary Science Letters
Authors: Ruifang C. Xie et al.
The emergence of a globally productive biosphere
"A productive biosphere and oxygenated atmosphere are defining features of Earth and are fundamentally linked. Here I argue that cellular metabolism imposes central constraints on the historical trajectories of biopsheric productivity and atmospheric oxygenation. Photosynthesis depends on iron, but iron is highly insoluble under the aerobic conditions produced by oxygenic photosynthesis. [...]"
Source: PeerJ Preprints
Author: Rogier Braakman
Ecology and evolution of seafloor and subseafloor microbial communities
"Vast regions of the dark ocean have ultra-slow rates of organic matter sedimentation, and their sediments are oxygenated to great depths yet have low levels of organic matter and cells. Primary production in the oxic seabed is supported by ammonia-oxidizing archaea, whereas in anoxic sediments, novel, uncultivated groups have the potential to produce H2 and CH4, which fuel anaerobic carbon fixation. [...]"
Source: Nature Reviews Microbiology
Authors: William D. Orsi
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