Extensive Accumulation of Nitrous Oxide in the Oxygen Minimum Zone in the Bay of Bengal


"The production by microorganisms of nitrous oxide (N2O), a trace gas contributing to global warming and stratospheric ozone depletion, is enhanced around the oceanic oxygen minimum zones (OMZs). The production constitutes an important source of atmospheric N2O. Although an OMZ is found in the northern part of the eastern Indian Ocean, the Bay of Bengal (BoB), two earlier studies conducted during the later phase of winter monsoon (February) and spring intermonsoon (March–April) found quite different magnitudes of N2O accumulation. [...]".


Source: Wiley Online Library
Authors: Sakae Toyoda et al.

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Nitrite Oxidation Across the Full Oxygen Spectrum in the Ocean


"Fixed nitrogen limits primary productivity in most areas of the surface ocean. Nitrite oxidation is the main source of nitrate, the most abundant form of inorganic fixed nitrogen. Even though known as an aerobic process, nitrite oxidation is not always stimulated by increased oxygen concentration, and nitrite oxidation occurs in layers of oxygen minimum zones (OMZs) where oxygen is not detectable. Nitrite-oxidizing bacteria, known since their original isolation as aerobes, were also detected in these layers. Whether and how nitrite oxidation is occurring in the anoxic seawater is debated. [...]".


Source: Wiley Online Library 
Authors: Xin Sun et al.

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Hydroxylamine as a Potential Indicator of Nitrification in the Open Ocean


"Hydroxylamine (NH2OH), a short‐lived intermediate in the nitrogen cycle, is a potential precursor of nitrous oxide (N2O) in the ocean. However, measurements of NH2OH in the ocean are sparse. Here we present a data set of depth profiles of NH2OH from the equatorial Atlantic Ocean and the eastern tropical South Pacific and compare it to N2O, nitrate, and nitrite profiles under varying oxygen conditions. [...]"

Source: Geophysical Research Letters
Authors: Frederike Korth et al.
DOI: 10.1029/2018GL080466

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Coupling of oceanic carbon and nitrogen facilitates spatially resolved quantitative reconstruction of nitrate inventories


"Anthropogenic impacts are perturbing the global nitrogen cycle via warming effects and pollutant sources such as chemical fertilizers and burning of fossil fuels. Understanding controls on past nitrogen inventories might improve predictions for future global biogeochemical cycling. Here we show the quantitative reconstruction of deglacial bottom water nitrate concentrations from intermediate depths of the Peruvian upwelling region, using foraminiferal pore density. [...]"

Source: Nature Communications
Authors: Nicolaas Glock et al.
DOI: 10.1038/s41467-018-03647-5

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The hunt for the most-wanted chemolithoautotrophic spookmicrobes


"Microorganisms are the drivers of biogeochemical methane and nitrogen cycles. Essential roles of chemolithoautotrophic microorganisms in these cycles were predicted long before their identification. Dedicated enrichment procedures, metagenomics surveys and single-cell technologies have enabled the identification of several new groups of most-wanted spookmicrobes, including novel methoxydotrophic methanogens that produce methane from methylated coal compounds and acetoclastic ‘Candidatus Methanothrix paradoxum’, which is active in oxic soils. [...]"

Source: FEMS Microbiology Ecology
Authors: Michiel H in ‘t Zandt et al.
DOI: 10.1093/femsec/fiy064

New measurement technology helps to determine NO concentrations in the ocean

"Nitrogen monoxide (NO) belongs to the group of nitrogen oxides which are infamous as toxic emissions in urban agglomerations. But NO is also produced in nature and plays a role in the nitrogen cycle. However, from earth's largest ecosystem, the ocean, we have hardly any NO measurements."

Source: Science Daily

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Nitric oxide (NO) in the oxygen minimum zone off Peru


"Nitric oxide (NO) is a short-lived compound of the marine nitrogen cycle. However, measurements of NO in seawater are analytically challenging and our knowledge about its oceanic distribution is, therefore, rudimentary. NO was measured in the oxygen minimum zone (OMZ) of the eastern tropical South Pacific Ocean (ETSP) off Peru during R/V Meteor cruise M93 in February/March 2013. [...]"

Source: Deep Sea Research Part II: Topical Studies in Oceanography
Authors: Hannah E. Lutterbeck et al.
DOI: 10.1016/j.dsr2.2017.12.023

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Upwelling and isolation in oxygen-depleted anticyclonic modewater eddies and implications for nitrate cycling


"The temporal evolution of the physical and biogeochemical structure of an oxygen-depleted anticyclonic modewater eddy is investigated over a 2-month period using high-resolution glider and ship data. A weakly stratified eddy core (squared buoyancy frequency N2  ∼  0.1  ×  10−4 s−2) at shallow depth is identified with a horizontal extent of about 70 km and bounded by maxima in N2. The upper N2 maximum (3–5  ×  10−4 s−2) coincides with the mixed layer base and the lower N2 maximum (0.4  ×  10−4 s−2) is found at about 200 m depth in the eddy centre. The eddy core shows a constant slope in temperature/salinity (TS) characteristic over the 2 months, but an erosion of the core progressively narrows down the TS range. The eddy minimal oxygen concentrations decreased by about 5 µmol kg−1in 2 months, confirming earlier estimates of oxygen consumption rates in these eddies. [...]"


Source: Biogeosciences
Authors: Johannes Karstensen et al.
DOI: 10.5194/bg-14-2167-2017

Full article 


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