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  • Other Sources  (4)
  • 551.46  (4)
  • Hoboken, USA  (4)
  • American Chemical Society (ACS)
  • American Society of Hematology
  • Blackwell Publishing Ltd
  • Springer Nature
  • 2020-2022  (4)
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  • Other Sources  (4)
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  • 2020-2022  (4)
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  • 1
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    Growth response of calcifying marine epibionts to biogenic pH fluctuations and global ocean acidification scenarios (2021)
    John Wiley & Sons, Inc. | Hoboken, USA
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    Publication Date: 2021-06-27
    Description: In coastal marine environments, physical and biological forces can cause dynamic pH fluctuations from microscale (diffusive boundary layer [DBL]) up to ecosystem‐scale (benthic boundary layer [BBL]). In the face of ocean acidification (OA), such natural pH variations may modulate an organism's response to OA by providing temporal refugia. We investigated the effect of pH fluctuations, generated by the brown alga Fucus serratus' biological activity, on the calcifying epibionts Balanus improvisus and Electra pilosa under OA. For this, both epibionts were grown on inactive and biologically active surfaces and exposed to (1) constant pH scenarios under ambient (pH 8.1) or OA conditions (pH 7.7), or (2) oscillating pH scenarios mimicking BBL conditions at ambient (pH 7.7–8.6) or OA scenarios (pH 7.4–8.2). Furthermore, all treatment combinations were tested at 10°C and 15°C. Against our expectations, OA treatments did not affect epibiont growth under constant or fluctuating (BBL) pH conditions, indicating rather high robustness against predicted OA scenarios. Furthermore, epibiont growth was hampered and not fostered on active surfaces (fluctuating DBL conditions), indicating that fluctuating pH conditions of the DBL with elevated daytime pH do not necessarily provide temporal refugia from OA. In contrast, results indicate that factors other than pH may play larger roles for epibiont growth on macrophytes (e.g., surface characteristics, macrophyte antifouling defense, or dynamics of oxygen and nutrient concentrations). Warming enhanced epibiont growth rates significantly, independently of OA, indicating no synergistic effects of pH treatments and temperature within their natural temperature range.
    Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Keywords: 551.46 ; coastal marine environments ; calcifying marine epibionts
    Type: article
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    CITATION GEO-LEO
  • 2
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    Comparison of environmental tracers including organic micropollutants as groundwater exfiltration indicators into a small river of a karstic catchment (2021)
    John Wiley & Sons, Inc. | Hoboken, USA
    Details
    Publication Date: 2021-06-27
    Description: Understanding groundwater–surface water (GW–SW) interactions is vital for water management in karstic catchments due to its impact on water quality. The objective of this study was to evaluate and compare the applicability of seven environmental tracers to quantify and localize groundwater exfiltration into a small, human‐impacted karstic river system. Tracers were selected based on their emission source to the surface water either as (a) dissolved, predominantly geogenic compounds (radon‐222, sulphate and electrical conductivity) or (b) anthropogenic compounds (predominantly) originating from wastewater treatment plant (WWTP) effluents (carbamazepine, tramadol, sodium, chloride). Two contrasting sampling approaches were compared (a) assuming steady‐state flow conditions and (b) considering the travel time of the water parcels (Lagrangian sampling) through the catchment to account for diurnal changes in inflow from the WWTP. Spatial variability of the concentrations of all tracers indicated sections of preferential groundwater inflow. Lagrangian sampling techniques seem highly relevant for capturing dynamic concentration patterns of WWTP‐derived compounds. Quantification of GW inflow with the finite element model FINIFLUX, based on observed in‐stream Rn activities led to plausible fluxes along the investigated river reaches (0.265 m3 s−1), while observations of other natural or anthropogenic environmental tracers produced less plausible water fluxes. Important point sources of groundwater exfiltration can be ascribed to locations where the river crosses geological fault lines. This indicates that commonly applied concepts describing groundwater–surface water interactions assuming diffuse flow in porous media are difficult to transfer to karstic river systems whereas concepts from fractured aquifers may be more applicable. In general, this study helps selecting the best suited hydrological tracer for GW exfiltration and leads to a better understanding of processes controlling groundwater inflow into karstic river systems.
    Description: Karst aquifers represent an increased complexity when aiming to measure the interaction between groundwater and river water. Combining field‐based measurements on catchment scale and modelling, the applicability of ‘classical’ environmental groundwater tracers was compared to selected organic (micro)pollutants often considered as conservative and originally arising from a wastewater treatment plant. This study demonstrates that the choice of an appropriate tracer is crucial when either aiming to quantify groundwater exfiltration into karstic river systems, or indicating hydrological processes, applying (globally) omnipresent pollutants.
    Description: German Research Foundation (DFG) http://dx.doi.org/10.13039/501100001659
    Keywords: 551.46 ; carbamazepine ; groundwater inflow ; Lagrangian sampling ; radon ; wastewater treatment plant ; water quality
    Type: article
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  • 3
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    Automatic plankton image classification—Can capsules and filters help cope with data set shift? (2021)
    John Wiley & Sons, Inc. | Hoboken, USA
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    Publication Date: 2021-06-27
    Description: The general task of image classification seems to be solved due to the development of modern convolutional neural networks (CNNs). However, the high intraclass variability and interclass similarity of plankton images still prevents the practical identification of morphologically similar organisms. This prevails especially for rare organisms. Every CNN requires a vast amount of manually validated training images which renders it inefficient to train study‐specific classifiers. In most follow‐up studies, the plankton community is different from before and this data set shift (DSS) reduces the correct classification rates. A common solution is to discard all uncertain images and hope that the remains still resemble the true field situation. The intention of this North Sea Video Plankton Recorder (VPR) study is to assess if a combination of a Capsule Neural Network (CapsNet) with probability filters can improve the classification success in applications with DSS. Second, to provide a guideline how to customize automated CNN and CapsNet deep learning image analysis methods according to specific research objectives. In community analyses, our approach achieved a discard of uncertain predictions of only 5%. CapsNet and CNN reach similar precision scores, but the CapsNet has lower recall scores despite similar discard ratios. This is due to a higher discard ratio in rare classes. The recall advantage of the CNN decreases with increasing DSS. We present an alternative method to handle rare classes with a CNN achieving a mean recall of 96% by manually validating an average of 6.5% of the original images.
    Keywords: 551.46 ; North Sea ; plankton classification ; automated analyses
    Type: article
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  • 4
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    Long‐term intercomparison of two pCO2 instruments based on ship‐of‐opportunity measurements in a dynamic shelf sea environment (2021)
    John Wiley & Sons, Inc. | Hoboken, USA
    Details
    Publication Date: 2021-07-05
    Description: The partial pressure of carbon dioxide (pCO2) in surface seawater is an important biogeochemical variable because, together with the pCO2 in the atmosphere, it determines the direction of air–sea carbon dioxide exchange. Large‐scale observations of pCO2 are facilitated by Ships‐of‐Opportunity (SOOP‐CO2) equipped with underway measuring instruments. The need for expanding the observation capacity and the challenges involving the sustainability and maintenance of traditional equilibrator systems led the community toward developing simpler and more autonomous systems. Here we performed a comparison between a membrane‐based sensor and a showerhead equilibration sensor installed on two SOOP‐CO2 between 2013 and 2018. We identified time‐ and space‐adequate crossovers in the Skagerrak Strait, where the two ship routes often crossed. We found a mean total difference of 1.5 ± 10.6 μatm and a root mean square error of 11 μatm. The pCO2 values recorded by the two instruments showed a strong linear correlation with a coefficient of 0.91 and a slope of 1.07 (± 0.14), despite the dynamic nature of the environment and the difficulty of comparing measurements from two different vessels. The membrane‐based sensor was integrated with a FerryBox system on a ship with a high sampling frequency in the study area. We showed the strength of having a sensor‐based network with a high spatial coverage that can be validated against conventional SOOP‐CO2 methods. Proving the validity of membrane‐based sensors in coastal and continental shelf seas and using the higher frequency measurements they provide can enable a thorough characterization of pCO2 variability in these dynamic environments.
    Keywords: 551.46 ; surface seawater ; carbon dioxide ; partial pressure ; measurements
    Type: article
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