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Saderne V.,Leibniz Institute of Marine Science | Saderne V.,Netherlands Institute for Sea Research | Fietzek P.,CONTROS Systems & Solutions GmbH | Herman P.M.J.,Netherlands Institute for Sea Research
PLoS ONE | Year: 2013

The impact of ocean acidification on benthic habitats is a major preoccupation of the scientific community. However, the natural variability of pCO2 and pH in those habitats remains understudied, especially in temperate areas. In this study we investigated temporal variations of the carbonate system in nearshore macrophyte meadows of the western Baltic Sea. These are key benthic ecosystems, providing spawning and nursery areas as well as food to numerous commercially important species. In situ pCO2, pH (total scale), salinity and PAR irradiance were measured with a continuous recording sensor package dropped in a shallow macrophyte meadow (Eckernförde bay, western Baltic Sea) during three different weeks in July (pCO2 and PAR only), August and September 2011.The mean (± SD) pCO2 in July was 383±117 μatm. The mean (± SD) pCO2 and pHtot in August were 239±20 μatm and 8.22±0.1, respectively. The mean (± SD) pCO2 and pHtot in September were 1082±711 μatm and 7.83±0.40, respectively. Daily variations of pCO2 due to photosynthesis and respiration (difference between daily maximum and minimum) were of the same order of magnitude: 281±88 μatm, 219±89 μatm and 1488±574 μatm in July, August and September respectively. The observed variations of pCO2 were explained through a statistical model considering wind direction and speed together with PAR irradiance. At a time scale of days to weeks, local upwelling of elevated pCO2 water masses with offshore winds drives the variation. Within days, primary production is responsible. The results demonstrate the high variability of the carbonate system in nearshore macrophyte meadows depending on meteorology and biological activities. We highlight the need to incorporate these variations in future pCO2 scenarios and experimental designs for nearshore habitats. © 2013 Saderne et al. Source


Schmidt M.,Leibniz Institute of Marine Science | Linke P.,Leibniz Institute of Marine Science | Esser D.,CONTROS Systems & Solutions GmbH
Marine Technology Society Journal | Year: 2013

Recently developed methane sensors, based on infrared (IR) absorption technology, were successfully utilized for subsea methane release measurements. Long-term investigation of methane emissions (fluid flux determination) from natural methane seeps in the Hikurangi Margin offshore New Zealand were performed by using seafloor lander technology. Small centimeter-sized seep areas could be sampled at the seafloor by video-guided lander deployment. In situ sensor measurements of dissolved methane in seawater could be correlated with methane concentrations measured in discrete water samples after lander recovery. High backscatter flares determined by lander-based Acoustic Doppler Current Profiler (ADCP) measurement indicate bubble release from the seafloor. Highest methane concentrations determined by the IR sensor coincided with periods of high ADCP backscatter signals. The high fluid release cannot be correlated with tidal changes only. However, this correlation is possible with variability in spatial bubble release, sudden outbursts, and tidal changes in more quiescent seepage phases. A recently developed IR sensor (2,000 m depth-rated) with a detection limit for methane of about 1 ppm showed good linearity in the tested concentration range and an acceptable equilibration time of 10 min. The sensor was successfully operated offshore Santa Barbara by a small work-class ROV at a natural methane seep (Farrar Seep). High background methane concentration of 50 nmol L-1 was observed in the coastal water, which increases up to 560 nmol L-1 in dissolved methane plumes south of the seepage area. ROV- and lander-based sensor deployments have proven the applicability of IR sensor technology for the determination of subsea methane release rates and plume distribution. The wide concentration range, low detection limit, and its robust detection unit enable this technology for both subsea leak detection and oceanographic trace gas investigations. Source


Becker M.,University of Kiel | Becker M.,Leibniz Institute of Marine Science | Andersen N.,Leibniz Laboratory for Radiometric Dating and Stable Isotope Research | Fiedler B.,Leibniz Institute of Marine Science | And 5 more authors.
Limnology and Oceanography: Methods | Year: 2012

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 CO 2 (fCO 2) 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 fCO 2 and the stable carbon isotope ratio of DIC [δ 13C(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 CO 2 monitoring system and isotope ratio mass spectrometric analysis of individual water samples. Agreement within ΔfCO 2 = 0.35 μatm for atmospheric and ΔfCO 2 = 2.5 μatm and Δδ 13C(DIC) = 0.33‰ for seawater measurements have been achieved. Whereas "calibration-free" fCO 2 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 fCO 2, equilibrium δ 13C(CO 2), δ 13C(DIC), and pO 2 aboard moving research vessels, thus making possible corresponding measurements with high spatial and temporal resolution. © 2012, by the American Society of Limnology and Oceanography, Inc. Source


Schmidt M.,Leibniz Institute of Marine Science | Linke P.,Leibniz Institute of Marine Science | Sommer S.,Leibniz Institute of Marine Science | Esser D.,CONTROS Systems & Solutions GmbH | Cherednichenko S.,Leibniz Institute of Marine Science
Marine Technology Society Journal | Year: 2016

During RV Poseidon cruise POS469 (May 2014), the distribution of pCO2 in the near field of submarine volcanic gas flares in shallow water depths down to 50 m below sea level was continuously monitored using three different and independent methodologies. In situ nondispersive infrared (NDIR) spectrometry, pH measurements, and onboard membrane inlet mass spectrometry (MIMS) were used to determine the fate of rising CO2 bubbles and the dissolved CO2 plume patterns in a 300 × 400-m working area. The In situ sensor carrier platform, a towed video-controlled water sampling rosette, equipped with CTD sensors, guaranteed excellent ground truthing of seafloor characteristics and bubble discharge. Sensor data and near-seafloor observations indicated that the gas bubbles (<9 mm in diameter, >97 vol.% of CO2) dissolved very rapidly within the first 10 m above seafloor. Bottom water masses enriched with pCO2 (up to 1,100 μatm) show low pH values (up to 7.80) and tend to spread rather downslope west than following the measured weak current in SSE-SSW direction. The 3-D evaluation of pCO2plume is a valuable tool to back-trace the origin of CO2 leakage when compared with local current regimes, water column CTD data, and seafloor bathymetry. Seep sites offshore Panarea can be used for studying CO2 leakage behavior and testing measuring strategies in shallow waters. Moreover, this area is a naturally designed laboratory to improve existing physicochemical and oceanographic transport models for subsea CO2 leakage. © 2015 Marine Technology Society Inc. All Rights reserved. Source


Fiedler B.,Leibniz Institute of Marine Science | Fietzek P.,Leibniz Institute of Marine Science | Fietzek P.,CONTROS Systems & Solutions GmbH | Vieira N.,Instituto Nacional Of Desenvolvimento Das Pescas | And 3 more authors.
Journal of Atmospheric and Oceanic Technology | Year: 2013

In recent years, profiling floats, which form the basis of the successful international Argo observatory, are also being considered as platforms for marine biogeochemical research. This study showcases the utility of floats as a novel tool for combined gas measurements of CO2 partial pressure (pCO2) and O2. These float prototypes were equipped with a small-sized and submersible pCO2 sensor and an optode O2 sensor for highresolution measurements in the surface ocean layer. Four consecutive deployments were carried out during November 2010 and June 2011 near the Cape Verde Ocean Observatory (CVOO) in the eastern tropical North Atlantic. The profiling float performed upcasts every 31 h while measuring pCO2, O2, salinity, temperature, and hydrostatic pressure in the upper 200 m of the water column. To maintain accuracy, regular pCO2 sensor zeroings at depth and surface, as well as optode measurements in air, were performed for each profile. Through the application of data processing procedures (e.g., time-lag correction), accuracies of floatborne pCO2 measurements were greatly improved (10-15 μatm for the water column and 5 matm for surface measurements). O2 measurements yielded an accuracy of 2 μmol kg-1. First results of this pilot study show the possibility of using profiling floats as a platform for detailed and unattended observations of the marine carbon and oxygen cycle dynamics. © 2013 American Meteorological Society. Source

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