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

Read the full article here.

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

Read the full article here.

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

Read the full article here.

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