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  • American Society of Limnology and Oceanography  (7)
  • AtlantOS  (4)
  • ASLO (Association for the Sciences of Limnology and Oceanography)  (3)
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  • 1
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    Toward continuous monitoring of seawater 13CO2/12CO2 isotope ratio and pCO2: Performance of cavity ringdown spectroscopy and gas matrix effects (2010)
    American Society of Limnology and Oceanography
    In:  Limnology and Oceanography: Methods, 8 . pp. 539-551.
    Details
    Publication Date: 2019-09-23
    Description: The potential of a continuous wave cavity ringdown spectrometer for monitoring the isotope ratio 13CO2/12CO2 and the partial pressure pCO2 of CO2 dissolved in water was thoroughly analyzed by quantitative measurements. Running calibration gas standards under typical operation conditions, a relative accuracy of D(d13C[CO2]) = ±0.1‰ with 120 min averaging time has been demonstrated. Absolute uncertainties were determined to be D(d13C[CO2]) = ±0.2‰ and D(xCO2) = ±0.5 ppmv. No principle problems were encountered when using the instrument in combination with a water-air equilibration setup. By contrast, when performing measurements of CO2 in gas matrices with a composition different from that of ambient air, pressure broadening linewidth effects induced significant errors in both d13C(CO2) and xCO2 values. These effects, which compromise the accessible accuracy in environmental studies, can be quantitatively taken into account by using a spectroscopically based correction procedure. Relying on linewidth analysis, the instrument was shown to be capable of continuous and simultaneous measurement of d13C(CO2), pCO2, as well as water content and O2 supersaturation, and thus holds the potential for online monitoring of these quantities aboard research vessels.
    Type: Article , PeerReviewed
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  • 2
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    Using cavity ringdown spectroscopy for continuous monitoring of δ13C(CO2) and ƒCO2 in the surface ocean (2012)
    American Society of Limnology and Oceanography
    In:  Limnology and Oceanography: Methods, 10 . pp. 752-766.
    Details
    Publication Date: 2019-09-23
    Description: The role of the global surface ocean as a source and sink for atmospheric carbon dioxide and the flux strengths between the ocean and the atmosphere can be quantified by measuring the fugacity of CO2 (ƒCO2) as well as the dissolved inorganic carbon (DIC) concentration and its isotopic composition in surface seawater. In this work, the potential of continuous wave cavity ringdown spectroscopy (cw-CRDS) for autonomous underway measurements of ƒCO2 and the stable carbon isotope ratio of DIC [δ13C(DIC)] is explored. For the first time, by using a conventional air-sea equilibrator setup, both quantities were continuously and simultaneously recorded during a field deployment on two research cruises following meridional transects across the Atlantic Ocean (Bremerhaven, Germany–Punta Arenas, Chile). Data are compared against reference measurements by an established underway CO2 monitoring system and isotope ratio mass spectrometric analysis of individual water samples. Agreement within ΔƒCO2 = 0.35 μatm for atmospheric and ΔƒCO2 = 2.5 μatm and Δδ13C(DIC) =0.33‰ for seawater measurements have been achieved. Whereas “calibration-free” ƒCO2 monitoring is feasible, the measurement of accurate isotope ratios relies on running reference standards on a daily basis. Overall, the installed CRDS/equilibrator system was shown to be capable of reliable online monitoring of ƒCO2, equilibrium δ13C(CO2), δ13C(DIC), and pO2 aboard moving research vessels, thus making possible corresponding measurements with high spatial and temporal resolution.
    Type: Article , PeerReviewed
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  • 3
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    Redfield ratios revisited: Removing the biasing effect of anthropogenic CO2 (2001)
    ASLO (Association for the Sciences of Limnology and Oceanography)
    In:  Limnology and Oceanography, 46 . pp. 964-970.
    Details
    Publication Date: 2014-01-30
    Description: Redfield ratios of remineralization are calculated based on chemical data analysis on isopycnal surfaces. The concentrations of dissolved inorganic carbon used in this study were corrected for the anthropogenic CO2 content as estimated with a back-calculation technique. The corrections increased the apparent carbon remineralization by 25-30%, thus proving important for the reliable estimation of Redfield carbon ratios in the presence of anthropogenic CO2. Best estimates from this study largely confirm the more recently published Redfield ratios of remineralization. The following results were obtained for the latitude range 3-41°N along 20-29°W in the Northeast Atlantic Ocean: Corg: P ratio = 123 ± 10; Corg : N ratio = 7.2 ± 0.8; -O2 :Corg ratio = 1.34 ± 0.06; -O2 : P ratio = 165 ± 15; N: P ratio = 17.5 ± 2.0. These ratios are in close agreement with the average composition of phytoplankton and represent respiration of organic matter consisting on average of 52% protein, 36% polysaccharide, and 12% lipid.
    Type: Article , PeerReviewed
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  • 4
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    Evaluation of a lifetime-based optode to measure oxygen in aquatic systems (2006)
    American Society of Limnology and Oceanography
    In:  Limnology and Oceanography: Methods, 4 . pp. 7-17.
    Details
    Publication Date: 2019-09-23
    Description: In this article, we evaluate the performance of a commercially available lifetime-based optode and compare it with data obtained by other methods. We performed a set of 10 different tests, including targeted laboratory evaluations and field studies, covering a wide range of situations from shallow coastal waters and wastewater treatment plants to abyssal depths. Our principal conclusion is that, owing to high accuracy (± 2 µM), long-term stability (more than 20 months), lack of pressure hysteresis, and limited cross-sensitivity, this method is overall more suitable for oxygen monitoring than other methods.
    Type: Article , PeerReviewed
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  • 5
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    A novel electrochemical calibration setup for oxygen sensors and its use for the stability assessment of Aanderaa optodes (2012)
    American Society of Limnology and Oceanography
    In:  Limnology and Oceanography: Methods, 10 . pp. 921-933.
    Details
    Publication Date: 2019-09-23
    Description: We present a laboratory calibration setup for the individual multi-point calibration of oxygen sensors. It is based on the electrochemical generation of oxygen in an electrolytic carrier solution. Under thorough control of the conditions, i.e., temperature, carrier solution flow rate, and electrolytic current, the amount of oxygen is strictly given by Faraday's laws and can be controlled to within ± 0.5 μmol L–1 (2 SD). Whereas Winkler samples can be taken for referencing with a reproducibility between triplicates of 0.8 μmol L–1 (2 SD), the calibration setup can provide a Winkler-free way of referencing with an accuracy of ± 1.2 μmol L–1 (2 SD). Thus calibrated oxygen optodes have been deployed in the Southern Ocean and the Eastern Tropical Atlantic both in profiling and underway mode and confirm the validity of the laboratory calibrations to within few μmol L–1. In two cases, the optodes drifted between deployments, which was easily identified using the calibration setup. The electrochemical calibration setup may thus facilitate accurate oxygen measurements on a large scale, and its small size makes it possible to configure as a mobile, sea-going, Winkler-free system for oxygen sensor calibrations.
    Type: Article , PeerReviewed
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  • 6
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    Spectrophotometric pH measurement in the ocean: Requirements, design, and testing of an autonomous charge-coupled device detector system (2004)
    American Society of Limnology and Oceanography
    In:  Limnology and Oceanography: Methods, 2 . pp. 126-136.
    Details
    Publication Date: 2018-08-14
    Description: A newly designed system for high quality discrete spectrophotometric measurements of pHT using a low-cost CCD detector is described. Considerations and requirements for the choice of spectrophotometers with a CCD detector instead of scanning spectrophotometers with photomultiplier detector are elucidated. The presented system is evaluated in the laboratory for system accuracy and short-term precision and at-sea for long-term precision and at-sea capability. Derived system characteristics are a (1s) short-term precision of ± 0.0012 pH units and a (1s) long-term precision at-sea of ± 0.0032 pH units based on Certified Reference Materials (CRM). Such long-term precision is equivalent to a deviation of ± 1.1 to 2.2 µmol kg-1 in total dissolved inorganic carbon (TCO2) and ± 1.4 to 2.1 µmol kg-1 in total alkalinity (TA), depending on temperature and the TCO2/TA ratio. Over-determination of the CO2 system (TCO2, TA, pHT) from surface-to-deep water profiles support the accuracy and precision assessment in comparison to earlier data. With careful design and testing low-cost CCD spectrophotometers can be used for high accuracy pH-measurements.
    Type: Article , PeerReviewed
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  • 7
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    Time response of oxygen optodes on profiling platforms and its dependence on flow speed and temperature (2014)
    American Society of Limnology and Oceanography
    In:  Limnology and Oceanography: Methods, 12 . pp. 617-636.
    Details
    Publication Date: 2019-09-23
    Description: The time response behavior of Aanderaa optodes model 3830, 4330, and 4330F, as well as a Sea-Bird SBE63 optode and a JFE Alec Co. Rinko dissolved oxygen sensor was analyzed both in the laboratory and in the field. The main factor for the time response is the dynamic regime, i.e., the water flow around the sensor that influences the boundary layer’s dynamics. Response times can be drastically reduced if the sensors are pumped. Laboratory experiments under different dynamic conditions showed a close to linear relation between response time and temperature. Application of a diffusion model including a stagnant boundary layer revealed that molecular diffusion determines the temperature behavior, and that the boundary layer thickness was temperature independent. Moreover, field experiments matched the laboratory findings, with the profiling speed and mode of attachment being of prime importance. The time response was characterized for typical deployments on shipboard CTDs, gliders, and floats, and tools are presented to predict the response time as well as to quantify the effect on the data for a given water mass profile. Finally, the problem of inverse filtering optode data to recover some of the information lost by their time response is addressed.
    Type: Article , PeerReviewed
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  • 8
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    OceanSITES Innovation Report (2019)
    AtlantOS
    In:  AtlantOS Deliverable, D3.17 . AtlantOS, 24 pp.
    Details
    Publication Date: 2021-05-19
    Description: Innovation and improvement report on the extension of capabilities to measure emerging EOVs including metagenomics across different observational platforms with links to MicroB3 best practice.
    Type: Report , NonPeerReviewed , info:eu-repo/semantics/book
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  • 9
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    Particulate matter flux interception in oceanic mesoscale eddies by the polychaete Poeobius sp. (2018)
    ASLO (Association for the Sciences of Limnology and Oceanography) | Wiley
    In:  Limnology and Oceanography, 63 (5). pp. 2093-2109.
    Details
    Publication Date: 2021-05-19
    Description: Gelatinous zooplankton hold key functions in the ocean and have been shown to significantly influence the transport of organic carbon to the deep sea. We discovered a gelatinous, flux‐feeding polychaete of the genus Poeobius in very high abundances in a mesoscale eddy in the tropical Atlantic Ocean, where it co‐occurred with extremely low particle concentrations. Subsequent analysis of an extensive in situ imaging dataset revealed that Poeobius sp. occurred sporadically between 5°S–20°N and 16°W–46°W in the upper 1000 m. Abundances were significantly elevated and the depth distribution compressed in anticyclonic modewater eddies (ACMEs). In two ACMEs, high Poeobius sp. abundances were associated with strongly reduced particle concentrations and fluxes in the layers directly below the polychaete. We discuss possible reasons for the elevated abundances of Poeobius sp. in ACMEs and provide estimations showing that a single zooplankton species can completely intercept the downward particle flux by feeding with their mucous nets, thereby substantially altering the biogeochemical setting within the eddy.
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  • 10
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    Validation of sensor and instrumentation innovations (2018)
    AtlantOS
    In:  AtlantOS Deliverable, D6.3 . AtlantOS, 60 pp.
    Details
    Publication Date: 2021-05-19
    Description: Validated prototypes of new and enhanced biogeochemical and biological sensors and instruments. Validation will be undertaken in the laboratory, in test scenarios, and by deployment in operational conditions
    Type: Report , NonPeerReviewed , info:eu-repo/semantics/book
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