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  • 2020-2024  (20)
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  • 1
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    Unknown
    Nitric oxide (NO) measurements from METEOR cruise M93 (2021)
    PANGAEA
    Details
    Publication Date: 2023-10-28
    Description: NO was measured in the oxygen minimum zone (OMZ) of the eastern tropical South Pacific Ocean (ETSP) off Peru during the R/V Meteor cruise M93 in February/March 2013. NO was measured at nine stations by taking discrete water samples at selected water depths between the surface and 327 m with a pump-CTD system. NO concentrations were determined with a chemiluminescence NO analyser connected to a stripping unit. For details see Lutterbeck et al., Deep-Sea Res. II, 156, 148-154, 2018.
    Keywords: Climate - Biogeochemistry Interactions in the Tropical Ocean; Date/Time of event; Depth, bottom/max; DEPTH, water; Error, relative; Event label; LATITUDE; LONGITUDE; M93; M93_347-3; M93_376-1; M93_378-1; M93_380-2; M93_391-10; M93_391-4; M93_399-4; M93_411-6; M93_441-2; M93_463-2; Meteor (1986); Nitric oxide; Nitric oxide, standard deviation; PCTD-RO; Pressure, water; PumpCTD/Rosette; Salinity; Sample code/label; SFB754; South Pacific Ocean; Station label; Temperature, water
    Type: Dataset
    Format: text/tab-separated-values, 1016 data points
    Location Call Number Limitation Availability
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    DATA PANGAEA
  • 2
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    Meridional and Cross-Shelf Variability of N2O and CH4 in the Eastern-South Atlantic (ESA) (2021)
    PANGAEA
    Details
    Publication Date: 2023-08-12
    Description: Upward transport and/or mixing of trace gas-enriched subsurface waters fosters the exchange of nitrous oxide (N2O) and methane (CH4) with the atmosphere in the Eastern-South Atlantic (ESA). To date, it is, however, unclear whether this source is maintained by local production or advection of trace-gas enriched water masses. So, the meridional and zonal variability of N2O and CH4 in the ESA were investigated to constrain the contributions of the major regional water masses to the overall budget of N2O and CH4. The fieldwork took place during the cruises M99 (July 31st - August 23rd, 2013) and M120 (October 17th - November 18th, 2015) onboard the R/V METEOR, which encompassed close-coastal and open ocean regions off Angola and Namibia. To investigate the regional concentration gradients of N2O and CH4 and corresponding sea-air fluxes, seven hydrographic sections (six zonal transects and one alongshore transect) were conducted between ~10°S and 26°S. Concentrations of dissolved N2O and CH4 in surface waters were continuously measured by using the Mobile Equilibrator Sensor System. To evaluate, the oceanic-atmospheric trace gas exchange, the atmospheric N2O and CH4 in ambient air were measured at several sporadic locations, with an inlet installed at 35 m height. The data were quality controlled by comparing with the data generated by NOAA in the nearest atmospheric sampling station (23.58° S, 15.03°E, Station NMB (Gobabeb, Namibia)). Also, to better understand the underlying patterns of the trace gas in the ESA, the vertical profiles were investigated by measuring discrete samples of N2O using the dynamic headspace method on M99. N2O and CH4 concentrations were also measured using a purge and trap system during M120 expedition.
    Keywords: Eastern Boundary Upwelling Syetms; Enhancing Prediction of Tropical Atlantic Climate and its Impact; Methane; nitrous oxide; PREFACE; SACUS/SACUS-II; Southwest African Coastal Upwelling System and Benguela Niños; trace gases
    Type: Dataset
    Format: application/zip, 4 datasets
    Location Call Number Limitation Availability
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    DATA PANGAEA
  • 3
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    Nitrous oxide production rates in the eastern tropical South Pacific during METEOR cruise M138 (2020)
    PANGAEA
    Details
    Publication Date: 2023-10-28
    Description: N2O production rates from ammonium, nitrite and nitrate and nitrate reduction rates and ammonium oxidation rates from the top 400 m water depth off the coast of Peru sampled from R/V Meteor during M138 in June 2017.
    Keywords: Ammonium; Ammonium, oxidation rate; Climate - Biogeochemistry Interactions in the Tropical Ocean; CTD/Rosette; CTD 013; CTD 018; CTD 036; CTD 044; CTD 063; CTD 069; CTD 076; CTD 085; CTD 099; CTD-RO; DATE/TIME; Density, sigma-theta (0); DEPTH, water; ELEVATION; Event label; LATITUDE; LONGITUDE; M138; M138_882-11; M138_883-15; M138_892-3; M138_894-4; M138_904-7; M138_906-7; M138_907-7; M138_912-1; M138_917-3; Meteor (1986); Nitrate; Nitrate, reduction rate; Nitrate and Nitrite; Nitrite; Nitrous oxide production; OMZ; Oxygen; Phosphate; Ratio; Salinity; Sample code/label; SFB754; Silicate; Standard deviation; Standard error; Temperature, water; Yield
    Type: Dataset
    Format: text/tab-separated-values, 474 data points
    Location Call Number Limitation Availability
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    DATA PANGAEA
  • 4
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    SFB754 Underway trace gases (2021)
    PANGAEA
    Details
    Publication Date: 2024-03-28
    Description: Continuous measurements of the climate-relevant trace gases carbon dioxide (CO2), nitrous oxide (N2O), and carbon monoxide (CO) in the surface ocean and overlying atmosphere were conducted during 9 SFB 754 cruises (see Table C14) spanning the North, South and equatorial Atlantic, as well as the South and equatorial Pacific. To this end, laser spectroscopy-based gas analyzers coupled to air-water equilibration chambers were used. For details of the analytical systems the reader is referred to the descriptions provided by Arévalo-Martínez et al. (2013) and Arévalo-Martínez et al. (2019). All trace gas measurements were quality-controlled to achieve the international standards for marine CO2 (Bender et al., 2002), N2O (Bange et al., 2019), and atmospheric CO (Zellweger et al., 2019; to date there is no accepted standard for seawater measurements). The final quality-controlled data is available through the Surface Ocean CO2 Atlas (SOCAT, https://www.socat.info/) and the Marine CH4-N2O database (MEMENTO, https://memento.geomar.de/) as well as on Pangaea
    Keywords: Climate - Biogeochemistry Interactions in the Tropical Ocean; SFB754
    Type: Dataset
    Format: 10 datasets
    Location Call Number Limitation Availability
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    DATA PANGAEA
  • 5
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    Nitrous oxide concentrations during CHINARE 36 cruise 2020 (2022)
    PANGAEA
    Details
    Publication Date: 2024-06-12
    Description: The data set comprises concentrations of dissolved N2O from seawater samples collected during the 36th Chinese Antarctic Research Expedition (36th CHINARE). The 36th CHINARE took place onboard the research vessel/icebreaker Xuelong 2 between the 3rd and 31st of January 2020 and focused on physical and biogeochemical surveys of the Ross Sea (Pacific sector of the Southern Ocean). Samples were collected by drawing water from 10 L Niskin bottles (installed on a standard CTD-Rosette) into brown borosilicate 20 mL vials, which were then sealed with rubber (butyl) stoppers and aluminium caps. Immediately after collection, samples were preserved by adding 0.05 mL of a saturated mercuric chloride solution. Samples were analyzed by means of a standard headspace method coupled to gas chromatography/electron capture detection. Details on the measurement equipment and data analysis can be found in Kock et al. (2016; see: www.biogeosciences.net/13/827/2016/).
    Keywords: Chinare36; Chinare36_A11-0-1; Chinare36_A11-0-10; Chinare36_A11-0-2; Chinare36_A11-0-3; Chinare36_A11-0-4; Chinare36_A11-0-5; Chinare36_A11-0-6; Chinare36_A11-0-7; Chinare36_A11-0-8; Chinare36_A11-0-9; Chinare36_A11-1-1; Chinare36_A11-1-10; Chinare36_A11-1-2; Chinare36_A11-1-3; Chinare36_A11-1-4; Chinare36_A11-1-5; Chinare36_A11-1-6; Chinare36_A11-1-7; Chinare36_A11-1-8; Chinare36_A11-1-9; Chinare36_A11-2-1; Chinare36_A11-2-10; Chinare36_A11-2-2; Chinare36_A11-2-3; Chinare36_A11-2-4; Chinare36_A11-2-5; Chinare36_A11-2-6; Chinare36_A11-2-7; Chinare36_A11-2-8; Chinare36_A11-2-9; Chinare36_A11-3-1; Chinare36_A11-3-10; Chinare36_A11-3-2; Chinare36_A11-3-3; Chinare36_A11-3-4; Chinare36_A11-3-5; Chinare36_A11-3-6; Chinare36_A11-3-7; Chinare36_A11-3-8; Chinare36_A11-4-1; Chinare36_A11-4-2; Chinare36_A11-4-3; Chinare36_A11-4-4; Chinare36_A11-4-6; Chinare36_A11-4-7; Chinare36_A11-4-8; Chinare36_A11-4-9; Chinare36_A3-10-1; Chinare36_A3-10-10; Chinare36_A3-10-11; Chinare36_A3-10-12; Chinare36_A3-10-13; Chinare36_A3-10-14; Chinare36_A3-10-2; Chinare36_A3-10-3; Chinare36_A3-10-4; Chinare36_A3-10-5; Chinare36_A3-10-6; Chinare36_A3-10-7; Chinare36_A3-10-8; Chinare36_A3-10-9; Chinare36_A3-5-1; Chinare36_A3-5-10; Chinare36_A3-5-11; Chinare36_A3-5-2; Chinare36_A3-5-3; Chinare36_A3-5-4; Chinare36_A3-5-5; Chinare36_A3-5-6; Chinare36_A3-5-7; Chinare36_A3-5-8; Chinare36_A3-5-9; Chinare36_A3-9-1; Chinare36_A3-9-10; Chinare36_A3-9-12; Chinare36_A3-9-13; Chinare36_A3-9-14; Chinare36_A3-9-2; Chinare36_A3-9-3; Chinare36_A3-9-4; Chinare36_A3-9-5; Chinare36_A3-9-6; Chinare36_A3-9-7; Chinare36_A3-9-8; Chinare36_A3-9-9; Chinare36_A4-3-1; Chinare36_A4-3-2; Chinare36_A4-3-3; Chinare36_A4-3-4; Chinare36_A4-3-6; Chinare36_A4-3-7; Chinare36_A4-3-8; Chinare36_A4-3-9; Chinare36_R1-1-1; Chinare36_R1-1-2; Chinare36_R1-1-3; Chinare36_R1-1-4; Chinare36_R1-1-6; Chinare36_R1-1-7; Chinare36_R1-1-8; Chinare36_R1-1-9; Chinare36_R1-2-1; Chinare36_R1-2-10; Chinare36_R1-2-2; Chinare36_R1-2-3; Chinare36_R1-2-4; Chinare36_R1-2-5; Chinare36_R1-2-6; Chinare36_R1-2-7; Chinare36_R1-2-8; Chinare36_R1-2-9; Chinare36_R1-3-1; Chinare36_R1-3-10; Chinare36_R1-3-2; Chinare36_R1-3-3; Chinare36_R1-3-4; Chinare36_R1-3-5; Chinare36_R1-3-6; Chinare36_R1-3-7; Chinare36_R1-3-8; Chinare36_R1-3-9; Chinare36_R1-4-1; Chinare36_R1-4-2; Chinare36_R1-4-3; Chinare36_R1-4-4; Chinare36_R1-4-5; Chinare36_R1-4-6; Chinare36_R1-4-7; Chinare36_R1-4-8; Chinare36_R1-4-9; Chinare36_R1-5-1; Chinare36_R1-5-2; Chinare36_R1-5-3; Chinare36_R1-5-5; Chinare36_R1-5-6; Chinare36_R1-5-8; Chinare36_R1-5-9; Chinare36_R1-6-1; Chinare36_R1-6-2; Chinare36_R1-6-3; Chinare36_R1-6-4; Chinare36_R1-6-5; Chinare36_R1-6-6; Chinare36_R1-6-7; Chinare36_R1-6-8; Chinare36_R1-6-9; Chinare36_R1-7-1; Chinare36_R1-7-2; Chinare36_R1-7-3; Chinare36_R1-7-4; Chinare36_R1-7-5; Chinare36_R1-7-6; Chinare36_R1-7-7; Chinare36_R1-7-8; Chinare36_R1-8-1; Chinare36_R1-8-2; Chinare36_R1-8-3; Chinare36_R1-8-4; Chinare36_R1-8-5; Chinare36_R1-8-6; Chinare36_R1-8-8; Chinare36_R1-8-9; Chinare36_RA1-0-1; Chinare36_RA1-0-10; Chinare36_RA1-0-11; Chinare36_RA1-0-12; Chinare36_RA1-0-13; Chinare36_RA1-0-2; Chinare36_RA1-0-3; Chinare36_RA1-0-4; Chinare36_RA1-0-5; Chinare36_RA1-0-6; Chinare36_RA1-0-7; Chinare36_RA1-0-8; Chinare36_RA1-0-9; Chinare36_RA1-1-1; Chinare36_RA1-1-10; Chinare36_RA1-1-11; Chinare36_RA1-1-12; Chinare36_RA1-1-13; Chinare36_RA1-1-2; Chinare36_RA1-1-3; Chinare36_RA1-1-4; Chinare36_RA1-1-5; Chinare36_RA1-1-6; Chinare36_RA1-1-7; Chinare36_RA1-1-8; Chinare36_RA1-1-9; Chinare36_RA1-2-1; Chinare36_RA1-2-10; Chinare36_RA1-2-11; Chinare36_RA1-2-12; Chinare36_RA1-2-13; Chinare36_RA1-2-2; Chinare36_RA1-2-3; Chinare36_RA1-2-4; Chinare36_RA1-2-5; Chinare36_RA1-2-6; Chinare36_RA1-2-7; Chinare36_RA1-2-8; Chinare36_RA1-2-9; Chinare36_RA1-3-1; Chinare36_RA1-3-10; Chinare36_RA1-3-11; Chinare36_RA1-3-12; Chinare36_RA1-3-13; Chinare36_RA1-3-2; Chinare36_RA1-3-3; Chinare36_RA1-3-4; Chinare36_RA1-3-5; Chinare36_RA1-3-6; Chinare36_RA1-3-7; Chinare36_RA1-3-8; Chinare36_RA1-3-9; Chinare36_RA1-4-3; Chinare36_RA1-4-4; Chinare36_RA1-4-5; Chinare36_RA1-4-6; Chinare36_RA1-4-7; Chinare36_RA1-4-8; Chinare36_RA1-4-9; Chinare36_RA1-5-1; Chinare36_RA1-5-10; Chinare36_RA1-5-11; Chinare36_RA1-5-12; Chinare36_RA1-5-13; Chinare36_RA1-5-14; Chinare36_RA1-5-2; Chinare36_RA1-5-3; Chinare36_RA1-5-4; Chinare36_RA1-5-5; Chinare36_RA1-5-6; Chinare36_RA1-5-7; Chinare36_RA1-5-8; Chinare36_RA1-5-9; Chinare36_RA1-6-1; Chinare36_RA1-6-10; Chinare36_RA1-6-11; Chinare36_RA1-6-12; Chinare36_RA1-6-13; Chinare36_RA1-6-14; Chinare36_RA1-6-2; Chinare36_RA1-6-3; Chinare36_RA1-6-4; Chinare36_RA1-6-5; Chinare36_RA1-6-6; Chinare36_RA1-6-7; Chinare36_RA1-6-8; Chinare36_RA1-6-9; Chinare36_RA1-7-1; Chinare36_RA1-7-10; Chinare36_RA1-7-11; Chinare36_RA1-7-12; Chinare36_RA1-7-13; Chinare36_RA1-7-14; Chinare36_RA1-7-3; Chinare36_RA1-7-4; Chinare36_RA1-7-5; Chinare36_RA1-7-6; Chinare36_RA1-7-7; Chinare36_RA1-7-8; Chinare36_RA1-7-9; Chinare36_RA2-1-1; Chinare36_RA2-1-10; Chinare36_RA2-1-11; Chinare36_RA2-1-2; Chinare36_RA2-1-3; Chinare36_RA2-1-4; Chinare36_RA2-1-5; Chinare36_RA2-1-6; Chinare36_RA2-1-7; Chinare36_RA2-1-8; Chinare36_RA2-1-9; Chinare36_RA2-2-1; Chinare36_RA2-2-10; Chinare36_RA2-2-11; Chinare36_RA2-2-12; Chinare36_RA2-2-13; Chinare36_RA2-2-2; Chinare36_RA2-2-3; Chinare36_RA2-2-4; Chinare36_RA2-2-5; Chinare36_RA2-2-6; Chinare36_RA2-2-7; Chinare36_RA2-2-8; Chinare36_RA2-2-9; Chinare36_RA2-3-1; Chinare36_RA2-3-10; Chinare36_RA2-3-11; Chinare36_RA2-3-2; Chinare36_RA2-3-3; Chinare36_RA2-3-4; Chinare36_RA2-3-5; Chinare36_RA2-3-6; Chinare36_RA2-3-7; Chinare36_RA2-3-8; Chinare36_RA2-3-9; Chinare36_RA2-5-1; Chinare36_RA2-5-10; Chinare36_RA2-5-11; Chinare36_RA2-5-12; Chinare36_RA2-5-13; Chinare36_RA2-5-14; Chinare36_RA2-5-2; Chinare36_RA2-5-3; Chinare36_RA2-5-4; Chinare36_RA2-5-5; Chinare36_RA2-5-6; Chinare36_RA2-5-7; Chinare36_RA2-5-8; Chinare36_RA2-5-9; Chinare36_RA2-6-1; Chinare36_RA2-6-10; Chinare36_RA2-6-11; Chinare36_RA2-6-12; Chinare36_RA2-6-13; Chinare36_RA2-6-14; Chinare36_RA2-6-2; Chinare36_RA2-6-3; Chinare36_RA2-6-4; Chinare36_RA2-6-5; Chinare36_RA2-6-6; Chinare36_RA2-6-7; Chinare36_RA2-6-8; Chinare36_RA2-6-9; Chinare36_RA2-7-1; Chinare36_RA2-7-10; Chinare36_RA2-7-11; Chinare36_RA2-7-12; Chinare36_RA2-7-13; Chinare36_RA2-7-14; Chinare36_RA2-7-2; Chinare36_RA2-7-3; Chinare36_RA2-7-4; Chinare36_RA2-7-5; Chinare36_RA2-7-6; Chinare36_RA2-7-7; Chinare36_RA2-7-8; Chinare36_RA2-7-9; Chinare36_RA3-2-1; Chinare36_RA3-2-2; Chinare36_RA3-2-3; Chinare36_RA3-2-4; Chinare36_RA3-2-5; Chinare36_RA3-2-6; Chinare36_RA3-2-7; Chinare36_RA3-2-8; Chinare36_RA3-2-9; Chinare36_RA3-3-1; Chinare36_RA3-3-10; Chinare36_RA3-3-11; Chinare36_RA3-3-12; Chinare36_RA3-3-2; Chinare36_RA3-3-3; Chinare36_RA3-3-4; Chinare36_RA3-3-5; Chinare36_RA3-3-6; Chinare36_RA3-3-7; Chinare36_RA3-3-8; Chinare36_RA3-3-9; Chinare36_RA3-4-1; Chinare36_RA3-4-10; Chinare36_RA3-4-11; Chinare36_RA3-4-2; Chinare36_RA3-4-3; Chinare36_RA3-4-4; Chinare36_RA3-4-5; Chinare36_RA3-4-6; Chinare36_RA3-4-7; Chinare36_RA3-4-8; Chinare36_RA3-4-9; Chinare36_RA3-5-1; Chinare36_RA3-5-10; Chinare36_RA3-5-11; Chinare36_RA3-5-12; Chinare36_RA3-5-13; Chinare36_RA3-5-2; Chinare36_RA3-5-3; Chinare36_RA3-5-4; Chinare36_RA3-5-5; Chinare36_RA3-5-6; Chinare36_RA3-5-7; Chinare36_RA3-5-8; Chinare36_RA3-5-9; Chinare36_RA3-6-1; Chinare36_RA3-6-10; Chinare36_RA3-6-11; Chinare36_RA3-6-12; Chinare36_RA3-6-13; Chinare36_RA3-6-2; Chinare36_RA3-6-3; Chinare36_RA3-6-4; Chinare36_RA3-6-5; Chinare36_RA3-6-6; Chinare36_RA3-6-7; Chinare36_RA3-6-8; Chinare36_RA3-6-9; Chinare36_RA3-7-10; Chinare36_RA3-7-11; Chinare36_RA3-7-12; Chinare36_RA3-7-13; Chinare36_RA3-7-14; Chinare36_RA3-7-2; Chinare36_RA3-7-3; Chinare36_RA3-7-4; Chinare36_RA3-7-5; Chinare36_RA3-7-6; Chinare36_RA3-7-7; Chinare36_RA3-7-8; Chinare36_RA3-7-9; DATE/TIME; Density, sigma, in situ; DEPTH, water; Event label; Greenhouse gases; LATITUDE; LONGITUDE; nitrous oxide; Nitrous oxide; Nitrous oxide, dissolved; Salinity; Southern Ocean; Temperature, water;
    Type: Dataset
    Format: text/tab-separated-values, 2460 data points
    Location Call Number Limitation Availability
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    DATA PANGAEA
  • 6
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    Nitrous oxide and hydroxylamine measurements in the Southwest Indian Ocean (2020)
    Elsevier
    Details
    Publication Date: 2023-09-19
    Description: Highlights: • Enhanced surface N2O saturations were found between 5°S and 10°S in the SWIO. • The SWIO was a rather weak source of N2O to the atmosphere. • A distinct N2O maximum was found at about 1000 m. • The distributions of NH2OH in the water column were highly variable. • Nitrification was the major formation pathway of N2O in the SWIO. The southwestern basin of the Indian Ocean (SWIO) remains a rather under-sampled region with regard to nitrogen-cycle processes. Here we present the results of extensive nitrous oxide (N2O) measurements as well as the first reported open ocean measurements of hydroxylamine (NH2OH). Enhanced N2O sea-to-air fluxes were found in the zonal band between 5°S and 10°S as a result of wind-driven upwelling, and N2O depth profiles showed supersaturation throughout the water column with a distinct maximum at about 1000 m. Excess N2O (ΔN2O) was found to be positively correlated with apparent oxygen utilization (AOU) and nitrate. Although the water column distribution of NH2OH was highly variable, combined analysis with N2O and nutrient data allows us to argue for nitrification as the major formation pathway of N2O in the SWIO.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
    Format: text
    Location Call Number Limitation Availability
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 7
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    Ideas and perspectives: A strategic assessment of methane and nitrous oxide measurements in the marine environment (2020)
    Copernicus Publications (EGU)
    Details
    Publication Date: 2023-02-08
    Description: In the current era of rapid climate change, accurate characterization of climate-relevant gas dynamics-namely production, consumption, and net emissions-is required for all biomes, especially those ecosystems most susceptible to the impact of change. Marine environments include regions that act as net sources or sinks for numerous climateactive trace gases including methane (CH4) and nitrous oxide (N2O). The temporal and spatial distributions of CH4 and N2O are controlled by the interaction of complex biogeochemical and physical processes. To evaluate and quantify how these mechanisms affect marine CH4 and N2O cycling requires a combination of traditional scientific disciplines including oceanography, microbiology, and numerical modeling. Fundamental to these efforts is ensuring that the datasets produced by independent scientists are comparable and interoperable. Equally critical is transparent communication within the research community about the technical improvements required to increase our collective understanding of marine CH4 and N2O. A workshop sponsored by Ocean Carbon and Biogeochemistry (OCB) was organized to enhance dialogue and collaborations pertaining to marine CH4 and N2O. Here, we summarize the outcomes from the workshop to describe the challenges and opportunities for near-future CH4 and N2O research in the marine environment.
    Type: Article , PeerReviewed
    Format: text
    Format: video
    Location Call Number Limitation Availability
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 8
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    Regulation of nitrous oxide production in low-oxygen waters off the coast of Peru (2020)
    Copernicus Publications (EGU)
    Details
    Publication Date: 2023-02-08
    Description: 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. Denitrification was responsible for the highest N2O production with a mean of 8.7 nmol L−1 d−1 but up to 118±27.8 nmol L−1 d−1 just below the oxic–anoxic interface. The highest N2O production from ammonium oxidation (AO) of 0.16±0.003 nmol L−1 d−1 occurred in the upper oxycline at O2 concentrations of 10–30 µmol L−1 which coincided with the highest archaeal amoA transcripts/genes. Hybrid N2O formation (i.e., N2O with one N atom from NH+4 and the other from other substrates such as NO−2) was the dominant species, comprising 70 %–85 % of total produced N2O from NH+4, regardless of the ammonium oxidation rate or O2 concentrations. Oxygen responses of N2O production varied with substrate, but production and yields were generally highest below 10 µmol L−1 O2. Particulate organic matter additions increased N2O production by denitrification up to 5-fold, suggesting increased N2O production during times of high particulate organic matter export. High N2O yields of 2.1 % from AO were measured, but the overall contribution by AO to N2O production was still an order of magnitude lower than that of denitrification. Hence, these findings show that denitrification is the most important N2O production process in low-oxygen conditions fueled by organic carbon supply, which implies a positive feedback of the total oceanic N2O sources in response to increasing oceanic deoxygenation.
    Type: Article , PeerReviewed
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    Carbon monoxide cycling in the Ria Formosa Lagoon (southern Portugal) during summer 2021 (2023)
    Copernicus Publications (EGU)
    Details
    Publication Date: 2024-01-10
    Description: Carbon monoxide (CO) is an atmospheric trace gas that plays a crucial role in the oxidizing capacity of the Earth’s atmosphere. Moreover, it functions as an indirect greenhouse gas, influencing the lifetimes of potent greenhouse gases such as methane. Albeit being an overall source of atmospheric CO, the role of coastal regions in the marine cycling of CO and how its budget can be affected by anthropogenic activities, remain uncertain. Here, we present the first measurements of dissolved CO in the Ria Formosa Lagoon, an anthropogenically influenced system in southern Portugal. The dissolved CO concentrations in the surface layer ranged from 0.16 to 3.1 nmol L−1 with an average concentration of 0.75 ± 0.57 nmol L−1. The CO saturation ratio ranged from 1.7 to 32.2, indicating that the lagoon acted as a source of CO to the atmosphere in May 2021. The estimated average sea-to-air flux density was 1.53 μmol m−2 d−1, mainly fueled by CO photochemical production. Microbial consumption accounted for 83 % of the CO production, suggesting that the resulting CO emissions to the atmosphere were modulated by microbial consumption in the surface waters of the Ria Formosa Lagoon. The results from an irradiation experiment with aquaculture effluent water indicated that aquaculture facilities in the Ria Formosa Lagoon seem to be a negligible source of atmospheric CO.
    Type: Article , NonPeerReviewed , info:eu-repo/semantics/article
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    High Diazotrophic Diversity but Low N2 Fixation Activity in the Northern Benguela Upwelling System Confirming the Enigma of Nitrogen Fixation in Oxygen Minimum Zone Waters (2022)
    Frontiers
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    Publication Date: 2024-02-07
    Description: Oxygen minimum zones (OMZs) have been suggested as a suitable niche for the oxygen-sensitive process of biological fixation of dinitrogen (N2) gas. However, most N2 fixation rates reported from such waters are low. This low N2 fixation activity has been proposed to result from the unusual community of N2 fixers, in which cyanobacteria were typically underrepresented. The Northern Benguela Upwelling System (North BUS) is part of one of the most productive marine ecosystems and hosts a well-developed OMZ. Although previous observations indicated low to absent N2 fixation rates, the community composition of diazotrophs needed to understand the North BUS has not been described. Here, we present a first detailed analysis of the diazotrophic diversity in the North BUS OMZ and the Angola tropical zone (ATZ), based on genetic data and isotope speciation. Consistent with a previous study, we detected a slight N deficit in the OMZ, but isotope data did not indicate any active or past N2 fixation. The diazotroph community in the North BUS was dominated by non-cyanobacterial microbes clustering with members of gamma-proteobacteria, as is typical for other OMZ regions. However, we found a strikingly high diversity of Cluster III diazotrophs not yet described in other OMZs. In contrast to previous observations, we could also identify cyanobacteria of the clades Trichodesmium sp., UCYN-A and Cyanothece sp., in surface waters connected to or above the OMZ, which were potentially active as shown by the presence of genes and transcripts of the key functional marker gene for N2 fixation, nifH. While the detection of diazotrophs and the absence of active N2 fixation (based on isotopic speciation) are consistent with other OMZ observations, the detected regional variation in the diversity and presence of cyanobacteria indicate that we still are far from understanding the role of diazotrophs in OMZs, which, however, is relevant for understanding the N cycle in OMZ waters, as well for predicting the future development of OMZ biogeochemistry in a changing ocean.
    Type: Article , PeerReviewed
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