Abstract. 

"The Cenomanian-Turonian (Late Cretaceous) climate warming was closely coupled to profound perturbations of biogeochemical cycles and ecosystems. The occurrence of organic matter-rich sediments across various depositional environments of the proto-North Atlantic hereby marks severe oxygen-deficient conditions, culminating in Oceanic Anoxic Event (OAE 2) at the Cenomanian/Turonian boundary. Here we combine bulk, isotope and molecular geochemical techniques to characterize trends in organic matter accumulation and its relationship to biogeochemical cycling (nitrogen, carbon) and marine phytoplankton community shifts [...]". 

Source: Science Direct
Authors: Wolfgang Ruebsam & Lorenz Schwark
DOI: https://doi.org/10.1016/j.gloplacha.2023.104117

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Abstract. 

"Dissolved oxygen regulates microbial distribution and nitrogen cycling and, therefore, ocean productivity and Earth's climate. To date, the assembly of microbial communities in relation to oceanographic changes due to El Niño Southern Oscillation (ENSO) remains poorly understood in oxygen minimum zones (OMZ). The Mexican Pacific upwelling system supports high productivity and a permanent OMZ. Here, the spatiotemporal distribution of the prokaryotic community and nitrogen-cycling genes was investigated along a repeated transect subjected to varying oceanographic conditions associated with La Niña in 2018 and El Niño in 2019. [...]".

Source: Wiley Online Library 
Authors: Silvia Pajares et al.
DOI: https://doi.org/10.1111/1462-2920.16362

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Abstract.

"A new box model is employed to simulate the oxygen-dependent cycling of nutrients in the Peruvian oxygen minimum zone (OMZ). Model results and data for the present state of the OMZ indicate that dissolved iron is the limiting nutrient for primary production and is provided by the release of dissolved ferrous iron from shelf and slope sediments. Most of the removal of reactive nitrogen occurs by anaerobic oxidation of ammonium where ammonium is delivered by aerobic organic nitrogen degradation. Model experiments simulating the effects of ocean deoxygenation and warming show that the productivity of the Peruvian OMZ will increase due to the enhanced release of dissolved iron from shelf and slope sediments. A positive feedback loop rooted in the oxygen-dependent benthic iron release amplifies, both, the productivity rise and oxygen decline in ambient bottom waters. [...]". 

Source: Biogeochemistry

Authors: Klaus Wallmann et al.

DOI: https://doi.org/10.1007/s10533-022-00908-w 

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Abstract.

"The effects of bottom water oxygen concentration on sediment oxygen uptake, oxygen penetration depth, nitrate and ammonium fluxes, anammox, denitrification, dissimilatory nitrate reduction to ammonium, nitrification, and mineralization were investigated off the Changjiang estuary and its adjacent East China Sea, by combining a seasonal comparison[...]"

Source: ASLO- Association for the Sciences Limnology and Oceanography
Authors: Guodong Song et al.
DOI: https://doi.org/10.1002/lno.11630

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Abstract.

"The budget of reactive nitrogen (Nr; oxidized and reduced inorganic and organic forms of nitrogen) has at least doubled since the preindustrial era due to human activities. Excess Nr causes significant detrimental effects on many terrestrial and aquatic ecosystems; less is known about the impact on the open ocean. Nr deposition may already rival biological N2 fixation quantitatively and will likely continue to rise.[...]"

Source: Annual Review of Earth and Planetary Sciences
Authors: Katye E. Altieri et al.
DOI: https://doi.org/10.1146/annurev-earth-083120-052147

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Abstract.

"In this study, we investigate the role of sedimentary N cycling in the southern North Sea. We present a budget of ammonification, nitrification and sedimentary NO−3 consumption and denitrification in contrasting sediment types of the German Bight (southern North Sea), including novel net ammonification rates. [...]"

Source: Biogeosciences
Authors: Alexander Bratek et al.
DOI: 10.5194/bg-17-2839-2020

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Abstract.

"Biological dinitrogen (N₂) fixation, the reduction of atmospheric N₂ to ammonia, is important for maintaining the fertility of the oceans by providing biologically useful nitrogen to support primary organic matter production (i.e., carbon dioxide fixation). N₂ fixation offsets the removal of combined nitrogen by microbial denitrification and anaerobic ammonium oxidation (anammox) and export to the deep sea. For several decades, there has been a lack of consensus as to whether losses of N through microbial removal pathways are balanced by biological nitrogen fixation, along with other inputs such as atmospheric nitrogen deposition and terrestrial runoff. [...]"

Source: Science
Authors: Jonathan P. Zehr1 and Douglas G. Capone
DOI: 10.1126/science.aay9514

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"Every year, the Mississippi River dumps around 1.4 million metric tons of nitrogen into the Gulf of Mexico, much of it runoff from agricultural fertilizer. This nitrogen can lead to algal blooms, which in turn deplete oxygen concentrations in the water, creating hypoxic dead zones. The nitrogen cycle is a phenomenon environmental scientists would really like to understand better. “As humans, we do put a lot of reactive nitrogen compounds into the ocean, especially in coastal regions, by…river runoff,” said Katharina Kitzinger of the Max Planck Institute for Marine Microbiology in Bremen, Germany. “It’s really crucial to understand how microbes turn over this excess nitrogen that we put into the environment. [...]”"

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Abstract.

"Anoxic marine zones (AMZs), also known as ‘oxygen‐deficient zones’, contribute to the loss of fixed nitrogen from the ocean by anaerobic microbial processes. While these microbial processes associated with the nitrogen cycle have been extensively studied, those linked to the carbon cycle in AMZs have received much less attention, particularly the autotrophic carbon fixation —a crucial component of the carbon cycle. [...]"

Source: Environmental Microbiology Reports
Authors: Paula Ruiz‐Fernández et al.
DOI: 10.1111/1758-2229.12837

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Abstract.

"Predicting the effects of invasive ecosystem engineering species in new bioregions has proved elusive. In part this is because separating biological effects from purely physical mechanisms has been little studied and yet could help predict potentially damaging bioinvasions. Here we tested the effects of a large bio-engineering fanworm Sabella spallanzanii (Sabella) versus worm-like structures (mimics) on gas and nutrient fluxes in a marine soft bottom sediment. [...]"

Source: Scientific Reports
Authors: L. W. Tait et al.
DOI: 10.1038/s41598-020-58557-8

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