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Chromium reduction and associated stable isotope fractionation restricted to anoxic shelf waters in the Peruvian Oxygen Minimum Zone

Abstract.

"The marine chromium (Cr) cycle is still insufficiently understood, in particular the mechanisms modulating the spatial distribution of dissolved stable Cr isotopes in seawater. Redox transformations between its main oxidation states, Cr(VI) and Cr(III), have been held accountable for the observed tight inverse logarithmic relationship between the dissolved Cr concentration [Cr] and its isotopic composition (δ53Cr), whereby isotopically light Cr(III) is removed in surface waters and oxygen minimum zones[...]"

 

Source: Science Direct
Authors: Philipp Nasemann et al.
DOI: https://doi.org/10.1016/j.gca.2020.06.027

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Benthic fluxes of oxygen and nutrients under the influence of macrobenthic fauna on the periphery of the intermittently hypoxic zone in the Baltic Sea

Abstract.

"Understanding the role of benthic organisms in marine sediments is becoming increasingly important with the growing problem of eutrophication of marine ecosystems around the world, including the Baltic Sea. Therefore, we have conducted a series of incubation experiments on sediment cores collected from sites characterized by varying oxygen conditions and measured the influx (uptake by sediment) of oxygen as well as the sediment–water exchange of phosphate, ammonia and silicate.[...]"

 

Source: Science Direct
Authors: Halina Kendzierska et al.
Doi: https://doi.org/10.1016/j.jembe.2020.151439

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Geoengineered Ocean Vertical Water Exchange Can Accelerate Global Deoxygenation

Abstract.

"Ocean deoxygenation is a threat to marine ecosystems. We evaluated the potential of two ocean intervention technologies, that is, “artificial downwelling (AD)” and “artificial upwelling (AU),” for remedying the expansion of Oxygen Deficient Zones (ODZs). The model‐based assessment simulated AD and AU implementations for 80 years along the eastern Pacific ODZ.[...]"

Source: Advancing Earth And Space Science 
Authors: Ellias Yuming Feng et al.
DOI: https://doi.org/10.1029/2020GL088263

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Ocean Carbon Uptake Under Aggressive Emission Mitigation

Abstract.

"Nearly every nation has signed the UNFCC Paris Agreement, committing to mitigate global anthropogenic carbon (Cant) emissions and limit global mean temperature increase to 1.5 °C. A consequence of emission mitigation is reduced efficiency of ocean Cant uptake, which is driven by mechanisms that have not been studied in detail. The historical pattern of continual increase in atmospheric CO2 has resulted in a proportional increase in Cant uptake. [...]"

Source: Biogeosciences
Authors: Sean Ridge and Galen McKinley
DOI: 10.5194/bg-2020-254

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Monitoring ocean biogeochemistry with autonomous platforms

Abstract.

"Human activities have altered the state of the ocean, leading to warming, acidification and deoxygenation. These changes impact ocean biogeochemistry and influence ecosystem functions and ocean health. The long-term global effects of these changes are difficult to predict using current satellite sensing and traditional in situ observation techniques. [...]"

Source: Nature Reviews Earth & Environment
Authors: Fei Chai et al.
DOI: 10.1038/s43017-020-0053-y

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Substrate regulation leads to differential responses of microbial ammonia-oxidizing communities to ocean warming

Abstract.

"In the context of continuously increasing anthropogenic nitrogen inputs, knowledge of how ammonia oxidation (AO) in the ocean responds to warming is crucial to predicting future changes in marine nitrogen biogeochemistry. Here, we show divergent thermal response patterns for marine AO across a wide onshore/offshore trophic gradient. [...]"

Source: Nature Communications
Authors: Zhen-Zhen Zheng et al.
DOI: 10.1038/s41467-020-17366-3

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Contrasting decadal trends of subsurface excess nitrate in the western and eastern North Atlantic Ocean

Abstract.

"Temporal variations in excess nitrate (DINxs) relative to dissolved inorganic phosphorus (DIP) were evaluated using datasets derived from repeated measurements along meridional and zonal transects in the upper (200–600 m) North Atlantic (NAtl) between the 1980s and 2010s. The analysis revealed that the DINxs trend in the western NAtl differed from that in the eastern NAtl. In the western NAtl, which has been subject to atmospheric nitrogen deposition (AND) from the USA, the subsurface DINxs concentrations have increased over the last 2 decades. [...]"

Source: Biogeosciences
Authors: Jin-Yu Terence Yang et al.
DOI: 10.5194/bg-17-3631-2020

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Atmospheric deposition of organic matter at a remote site in the central Mediterranean Sea: implications for the marine ecosystem

Abstract.

"Atmospheric fluxes of dissolved organic matter (DOM) were studied for the first time on the island of Lampedusa, a remote site in the central Mediterranean Sea (Med Sea), between 19 March 2015 and 1 April 2017. The main goals of this study were to quantify total atmospheric deposition of DOM in this area and to evaluate the impact of Saharan dust deposition on DOM dynamics in the surface waters of the Mediterranean Sea. Our data show high variability in DOM deposition rates without a clear seasonality and a dissolved organic carbon (DOC) input from the atmosphere of 120.7 mmol DOC m−2 yr−1. [...]"

Source: Biogeosciences
Authors: Yuri Galletti et al.
DOI: 10.5194/bg-17-3669-2020

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Emergent constraint on Arctic Ocean acidification in the twenty-first century

Abstract.

"The ongoing uptake of anthropogenic carbon by the ocean leads to ocean acidification, a process that results in a reduction in pH and in the saturation state of biogenic calcium carbonate minerals aragonite (Ωarag) and calcite (Ωcalc). Because of its naturally low Ωarag and Ωcalc (refs.), the Arctic Ocean is considered the region most susceptible to future acidification and associated ecosystem impacts. [...]"

Source: Nature
Authors: Jens Terhaar et al.
DOI: 10.1038/s41586-020-2360-3

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Twenty-first century ocean warming, acidification, deoxygenation, and upper-ocean nutrient and primary production decline from CMIP6 model projections

Abstract.

"Anthropogenic climate change is projected to lead to ocean warming, acidification, deoxygenation, reductions in near-surface nutrients, and changes to primary production, all of which are expected to affect marine ecosystems. Here we assess projections of these drivers of environmental change over the twenty-first century from Earth system models (ESMs) participating in the Coupled Model Intercomparison Project Phase 6 (CMIP6) that were forced under the CMIP6 Shared Socioeconomic Pathways (SSPs). [...]"

Source: Biogeosciences
Authors: Lester Kwiatkowski et al.
DOI: 10.5194/bg-17-3439-2020

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