Variable Oxygen Levels Lead to Variable Stoichiometry of Benthic Nutrient Fluxes in a Hypertrophic Estuary
"Harmful blooms of cyanobacteria may extend over long time spans due to self-sustaining mechanisms. We hypothesized that settled blooms may increase redox-dependent P release and unbalance the stoichiometry of benthic nutrient regeneration (NH4+:SiO2:PO43− ratios). We tested this hypothesis in the hypertrophic Curonian Lagoon, the largest in Europe. During summer, at peak chlorophyll and water temperatures, sediment cores were collected over 19 stations representing all the lagoon sedimentary environments. Sediment organic content, granulometry, aerobic respiration, and oxic[...]"
Source: Estuaries and Coasts
Authors: Marco Bartoli et al.
Quantifying Nitrous Oxide Cycling Regimes in the Eastern Tropical North Pacific Ocean With Isotopomer Analysis
"Nitrous oxide (N2O), a potent greenhouse gas, is produced disproportionately in marine oxygen deficient zones (ODZs). To quantify spatiotemporal variation in N2O cycling in an ODZ, we analyzed N2O concentration and isotopologues along a transect through the eastern tropical North Pacific (ETNP). At several stations along this transect, N2O concentrations reached a near surface maximum that exceeded prior measurements in this region, of up to 226.1 ± 20.5 nM at the coast. Above the σθ = 25.0 kg/m3 isopycnal, Keeling plot analysis revealed two sources[...]"
Source: AGU- Advanced Earth and Space Science
Author: Colette L. Kelly et al.
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Source partitioning of oxygen-consuming organic matter in the hypoxic zone of the Chesapeake Bay
"We surveyed the carbonate system along the main channel of the Chesapeake Bay in June 2016 to elucidate carbonate dynamics and the associated sources of oxygen‐consuming organic matter. Using a two endmember mixing calculation, chemical proxies, and stoichiometry, we demonstrated that in early summer, dissolved inorganic carbon (DIC) dynamics were controlled by aerobic respiration in the water column (43%), sulfate reduction in the sediment (39%), atmospheric CO2 invasion (13%), and CaCO3 dissolution (5%). A mass balance of the DIC concentration and its stable isotope suggested that the apparent δ13C of oxygen‐consuming[...]"
Source: Association for the Sciences of Limnology and Oceanography
Authors: Jianzhong Su et al.
Geoengineered Ocean Vertical Water Exchange Can Accelerate Global Deoxygenation
"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.
Meiofauna improve oxygenation and accelerate sulfide removal in the seasonally hypoxic seabed
"Oxygen depleted areas are widespread in the marine realm. Unlike macrofauna, meiofauna are abundant in hypoxic sediments. We studied to what extent meiofauna affect oxygen availability, sulfide removal and microbial communities. Meiofauna were extracted alive and added to intact sediments simulating abundance gradients previously reported in the area. [...]"
Source: Marine Environmental Research
Authors: Stefano Bonaglia et al.
Regulation of nitrous oxide production in low-oxygen waters off the coast of Peru
"Oxygen-deficient zones (ODZs) are major sites of net natural nitrous oxide (N2O) production and emissions. In order to understand changes in the magnitude of N2O production in response to global change, knowledge on the individual contributions of the major microbial pathways (nitrification and denitrification) to N2O production and their regulation is needed. In the ODZ in the coastal area off Peru, the sensitivity of N2O production to oxygen and organic matter was investigated using 15N tracer experiments in combination with quantitative PCR (qPCR) and microarray analysis of total and active functional genes targeting archaeal amoA and nirS as marker genes for nitrification and denitrification, respectively. [...]"
Authors: Claudia Frey et al.
The role of water masses in shaping the distribution of redox active compounds in the Eastern Tropical North Pacific oxygen deficient zone
and influencing low oxygen concentrations in the eastern Pacific Ocean
"Oceanic oxygen deficient zones (ODZs) influence global biogeochemical cycles in a variety of ways, most notably by acting as a sink for fixed nitrogen (Codispoti et al. 2001). Optimum multiparameter analysis of data from two cruises in the Eastern Tropical North Pacific (ETNP) was implemented to develop a water mass analysis for the large ODZ in this region. This analysis reveals that the most pronounced oxygen deficient conditions are within the 13°C water (13CW) mass, which is distributed via subsurface mesoscale features such as eddies branching from the California Undercurrent. [...]"
Source: Limnology and Oceanography
Authors: Zachary C. Evans et al.
Dinitrogen fixation across physico‐chemical gradients of the Eastern Tropical North Pacific oxygen deficient zone
"The Eastern Tropical North Pacific (ETNP) Ocean hosts one of the world's largest oceanic oxygen deficient zones (ODZs). Hotspots for reactive nitrogen (Nr) removal processes, ODZs generate conditions proposed to promote Nr inputs via dinitrogen (N2) fixation. In this study, we quantified N2 fixation rates by 15N‐tracer bioassay across oxygen, nutrient and light gradients within and adjacent to the ODZ. [...]"
Source: Global Biogeochemical Cycles
Authors: C.R. Selden et al.
Complete arsenic-based respiratory cycle in the marine microbial communities of pelagic oxygen-deficient zones
"Marine oxygen-deficient zones (ODZs) are naturally occurring midlayer oxygen-poor regions of the ocean, sandwiched between oxygenated surface and deep layers. In the absence of oxygen, microorganisms in ODZs use other compounds, such as oxidized forms of nitrogen and sulfur, as terminal electron acceptors. [...]"
Authors: Jaclyn K. Saunders et al.