Marine N2O emissions from nitrification [...] constrained by modern observations and projected in multi-millennial global warming simula
"Nitrous oxide (N2O) is a potent greenhouse gas (GHG) and ozone destructing agent, yet, global estimates of N2O emissions are uncertain. Marine N2O stems from nitrification and denitrification processes which depend on organic matter cycling and dissolved oxygen (O2). We introduce N2O as an obligate intermediate product of denitrification and as an O2-dependent byproduct from nitrification in the Bern3D ocean model. [...]"
Source: Global Biogeochemical Cycles
Authors: G. Battaglia, F. Joos
Diverse Marinimicrobia bacteria may mediate coupled biogeochemical cycles along eco-thermodynamic gradients
"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.
A dynamic microbial community with high functional redundancy inhabits the cold, oxic subseafloor aquifer
"The rock-hosted subseafloor crustal aquifer harbors a reservoir of microbial life that may influence global marine biogeochemical cycles. Here we utilized metagenomic libraries of crustal fluid samples from North Pond, located on the flanks of the Mid-Atlantic Ridge, a site with cold, oxic subseafloor fluid circulation within the upper basement to query microbial diversity. [...]"
Source: The ISME Journal
Authors: Benjamin J. Tully et al.
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Impacts of El Niño events on the Peruvian upwelling system productivity
"Every 2–7 years, El Niño events trigger a strong decrease in phytoplankton productivity off Peru, which profoundly alters the environmental landscape and trophic chain of the marine ecosystem. Here we use a regional coupled physical-biogeochemical model to study the dynamical processes involved in the productivity changes during El Nino, with a focus on the strongest events of the 1958–2008 period. Model evaluation using satellite and in situ observations shows that the model reproduces the surface and subsurface interannual physical and biogeochemical variability. [...]"
Source: Journal of Geophysical Research: Oceans
Authors: D. Espinoza-Morriberón
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Spatial Patterns of Groundwater Biogeochemical Reactivity in an Intertidal Beach Aquifer
"Beach aquifers host a dynamic and reactive mixing zone between fresh and saline groundwater of contrasting origin and composition. Seawater, driven up the beachface by waves and tides, infiltrates into the aquifer and meets the seaward-discharging fresh groundwater, creating and maintaining a reactive intertidal circulation cell. Within the cell, land-derived nutrients delivered by fresh groundwater are transformed or attenuated. We investigated this process by collecting porewater samples from multi-level wells along a shore-perpendicular transect on a beach near Cape Henlopen, Delaware and analyzing solute and particulate concentrations. [...]"
Authors: Kyra H. Kim
Widespread seawater circulation in 18–22 Ma oceanic crust: Impact on heat flow and sediment geochemistry
"On the basis of heat-flow measurements, seismic mapping, and sediment pore-water analysis, we demonstrate widespread and efficient ventilation of the 18–22 Ma oceanic crust of the northeast equatorial Pacific Ocean. Recharge and discharge appear to be associated with basement outcrops, including seamounts and north-south–trending faults, along which sediment cover thins out and volcanic rocks are exposed. Low-temperature hydrothermal circulation through the volcanic crust leads to the reduction of heat flow through overlying sediments, with measured heat-flow values that are well below those expected from conductive cooling curves for lithosphere of this age. [...]"
Authors: Thomas Kuhn et al.
The onset of widespread marine red beds and the evolution of ferruginous oceans
"Banded iron formations were a prevalent feature of marine sedimentation ~3.8–1.8 billion years ago and they provide key evidence for ferruginous oceans. The disappearance of banded iron formations at ~1.8 billion years ago was traditionally taken as evidence for the demise of ferruginous oceans, but recent geochemical studies show that ferruginous conditions persisted throughout the later Precambrian, and were even a feature of Phanerozoic ocean anoxic events. [...]"
Source: Nature Communications
Authors: Haijun Song et al.
Ecological Energetic Perspectives on Responses of Nitrogen-Transforming Chemolithoautotrophic Microbiota to Changes in the Marine Environment
"Transformation and mobilization of bioessential elements in the biosphere, lithosphere, atmosphere and hydrosphere constitute the Earth's biogeochemical cycles, which are driven mainly by microorganisms through their energy and material metabolic processes. Without microbial energy harvesting from sources of light and inorganic chemical bonds for autotrophic fixation of inorganic carbon, there would not be sustainable ecosystems in the vast ocean. Although ecological energetics (eco-energetics) has been emphasized as a core aspect of ecosystem analyses and microorganisms largely control the flow of matter and energy in marine ecosystems, marine microbial communities are rarely studied from the eco-energetic perspective. [...]"
Source: Frontiers in Microbiology
Authors: Hongyue Dang and Chen-Tung A. Chen
Eutrophication-Driven Deoxygenation in the Coastal Ocean
"Human activities, especially increased nutrient loads that set in motion a cascading chain of events related to eutrophication, accelerate development of hypoxia (lower oxygen concentration) in many areas of the world’s coastal ocean. Climate changes and extreme weather events may modify hypoxia. Organismal and fisheries effects are at the heart of the coastal hypoxia issue, but more subtle regime shifts and trophic interactions are also cause for concern. The chemical milieu associated with declining dissolved oxygen concentrations affects the biogeochemical cycling of oxygen, carbon, nitrogen, phosphorus, silica, trace metals, and sulfide as observed in water column processes, shifts in sediment biogeochemistry, and increases in carbon, nitrogen, and sulfur, as well as shifts in their stable isotopes, in recently accumulated sediments."
Source: Oceanography Volume 27 (2014)
Authors: Nancy N. Rabalais et al.