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Diverse Marinimicrobia bacteria may mediate coupled biogeochemical cycles along eco-thermodynamic gradients

Abstract.

"Microbial communities drive biogeochemical cycles through networks of metabolite exchange that are structured along energetic gradients. As energy yields become limiting, these networks favor co-metabolic interactions to maximize energy disequilibria. Here we apply single-cell genomics, metagenomics, and metatranscriptomics to study bacterial populations of the abundant “microbial dark matter” phylum Marinimicrobia along defined energy gradients. [...]"

Source: Nature Communications
Authors: Alyse K. Hawley et al.
DOI: 10.1038/s41467-017-01376-9

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Nitrogen losses in sediments of the East China Sea: Spatiotemporal variations, controlling factors and environmental implications

Abstract.

"Global reactive nitrogen (N) has increased dramatically in coastal marine ecosystems over the past decades and caused numerous eco-environmental problems. Coastal marine sediment plays a critical role in N losses via denitrification and anaerobic ammonium oxidation (anammox) and release of nitrous oxide (N2O). However, both the magnitude and contributions of denitrification, anammox, and N2O production in sediments still remain unclear, causing uncertainty in defining the N budget for coastal marine ecosystems. [...]"

Source: Biogeosciences
Authors: Xianbiao Lin et al.
DOI: 10.1002/2017JG004036

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Methane fluxes from coastal sediments are enhanced by macrofauna

Abstract.

"Methane and nitrous oxide are potent greenhouse gases (GHGs) that contribute to climate change. Coastal sediments are important GHG producers, but the contribution of macrofauna (benthic invertebrates larger than 1 mm) inhabiting them is currently unknown. Through a combination of trace gas, isotope, and molecular analyses, we studied the direct and indirect contribution of two macrofaunal groups, polychaetes and bivalves, to methane and nitrous oxide fluxes from coastal sediments. [...]"

Source: Scientific Reports
Authors: Stefano Bonaglia et al.
DOI: 10.1038/s41598-017-13263-w

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Rapid nitrous oxide cycling in the suboxic ocean

Abstract.

"Nitrous oxide (N2O) is a powerful greenhouse gas and a major cause of stratospheric ozone depletion, yet its sources and sinks remain poorly quantified in the oceans. We used isotope tracers to directly measure N2O reduction rates in the eastern tropical North Pacific. Because of incomplete denitrification, N2O cycling rates are an order of magnitude higher than predicted by current models in suboxic regions, and the spatial distribution suggests strong dependence on both organic carbon and dissolved oxygen concentrations. Furthermore, N2O turnover is 20 times higher than the net atmospheric efflux. The rapid rate of this cycling coupled to an expected expansion of suboxic ocean waters implies future increases in N2O emissions. [...]"

Source: Science (2015)
Authors: Andrew R. Babbin, Daniele Bianchi, Amal Jayakumar, Bess B. Ward
DOI:10.1126/science.aaa8380

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Dependence of nitrite oxidation on nitrite and oxygen in low-oxygen seawater

Abstract.

"Nitrite oxidation is an essential step in transformations of fixed nitrogen. The physiology of nitrite oxidizing bacteria (NOB) implies that the rates of nitrite oxidation should be controlled by concentration of their substrate, nitrite, and the terminal electron acceptor, oxygen. The sensitivities of nitrite oxidation to oxygen and nitrite concentrations were investigated using 15N tracer incubations in the Eastern Tropical North Pacific. Nitrite stimulated nitrite oxidation under low in situ nitrite conditions, following Michaelis-Menten kinetics, indicating that nitrite was the limiting substrate. [...]

Source: Geophysical Reasearch Letters
Authors: Xin Sun, Qixing Ji, Amal Jayakumar, Bess B. Ward
DOI: 10.1002/2017GL074355

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Oceanic nitrogen cycling and N2O flux perturbations in the Anthropocene

Abstract.

"There is currently no consensus on how humans are affecting the marine nitrogen (N) cycle, which limits marine biological production and CO2 uptake. Anthropogenic changes in ocean warming, deoxygenation, and atmospheric N deposition can all individually affect the marine N cycle and the oceanic production of the greenhouse gas nitrous oxide (N2O). However, the combined effect of these perturbations on marine N cycling, ocean productivity, and marine N2O production is poorly understood. Here we use an Earth system model of intermediate complexity to investigate the combined effects of estimated 21st century CO2 atmospheric forcing and atmospheric N deposition.  [...]"

Source: Global Biogeochemical Cycles
Authors: A. Landolfi, C. Somes, W. Koeve, L. M. Zamora, A. Oschlies
DOI: 10.1002/2017GB005633

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Low oxygen eddies in the eastern tropical North Atlantic: Implications for N2O cycling

Abstract.

"Nitrous oxide (N2O) is a climate relevant trace gas, and its production in the ocean generally increases under suboxic conditions. The Atlantic Ocean is well ventilated, and unlike the major oxygen minimum zones (OMZ) of the Pacific and Indian Oceans, dissolved oxygen and N2O concentrations in the Atlantic OMZ are relatively high and low, respectively. [...]"

Source: Scientific Reports
Authors: D. S. Grundle et al.
DOI: 10.1038/s41598-017-04745-y

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