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  • 1
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    Springer
    In:  EPIC3Building Bridges at the Science-Stakeholder Interface, Building Bridges at the Science-Stakeholder Interface, Springer, 133 p., pp. 73-78, ISBN: 978-3-319-75919-7
    Publication Date: 2019-08-15
    Repository Name: EPIC Alfred Wegener Institut
    Type: Inbook , peerRev , info:eu-repo/semantics/other
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  • 2
    Publication Date: 2022-01-31
    Description: Gelatinous zooplankton (Cnidaria, Ctenophora, and Urochordata, namely, Thaliacea) are ubiquitous members of plankton communities linking primary production to higher trophic levels and the deep ocean by serving as food and transferring “jelly‐carbon” (jelly‐C) upon bloom collapse. Global biomass within the upper 200 m reaches 0.038 Pg C, which, with a 2–12 months life span, serves as the lower limit for annual jelly‐C production. Using over 90,000 data points from 1934 to 2011 from the Jellyfish Database Initiative as an indication of global biomass (JeDI: http://jedi.nceas.ucsb.edu, http://www.bco‐dmo.org/dataset/526852), upper ocean jelly‐C biomass and production estimates, organism vertical migration, jelly‐C sinking rates, and water column temperature profiles from GLODAPv2, we quantitatively estimate jelly‐C transfer efficiency based on Longhurst Provinces. From the upper 200 m production estimate of 0.038 Pg C year−1, 59–72% reaches 500 m, 46–54% reaches 1,000 m, 43–48% reaches 2,000 m, 32–40% reaches 3,000 m, and 25–33% reaches 4,500 m. This translates into ~0.03, 0.02, 0.01, and 0.01 Pg C year−1, transferred down to 500, 1,000, 2,000, and 4,500 m, respectively. Jelly‐C fluxes and transfer efficiencies can occasionally exceed phytodetrital‐based sediment trap estimates in localized open ocean and continental shelves areas under large gelatinous blooms or jelly‐C mass deposition events, but this remains ephemeral and transient in nature. This transfer of fast and permanently exported carbon reaching the ocean interior via jelly‐C constitutes an important component of the global biological soft‐tissue pump, and should be addressed in ocean biogeochemical models, in particular, at the local and regional scale.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
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  • 3
    Publication Date: 2022-01-31
    Description: The enactment of the Water Framework Directive (WFD) initiated scientific efforts to develop reliable methods for comparing prevailing lake conditions against reference (or nonimpaired) states, using the state of a set biological elements. Drawing a distinction between impaired and natural conditions can be a challenging exercise. Another important aspect is to ensure that water quality assessment is comparable among the different Member States. In this context, the present paper offers a constructive critique of the practices followed during the WFD implementation in Greece by pinpointing methodological weaknesses and knowledge gaps that undermine our ability to classify the ecological quality of Greek lakes. One of the pillars of WDF is a valid lake typology that sets ecological standards transcending geographic regions and national boundaries. The national typology of Greek lakes has failed to take into account essential components. WFD compliance assessments based on the descriptions of phytoplankton communities are oversimplified and as such should be revisited. Exclusion of most chroococcal species from the analysis of cyanobacteria biovolume in Greek lakes/reservoirs and most reservoirs in Spain, Portugal, and Cyprus is not consistent with the distribution of those taxa in lakes. Similarly, the total biovolume reference values and the indices used in classification schemes reflect misunderstandings of WFD core principles. This hampers the comparability of ecological status across Europe and leads to quality standards that are too relaxed to provide an efficient target for the protection of Greek/transboundary lakes such as the ancient Lake Megali Prespa.
    Type: Article , PeerReviewed
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  • 4
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    Springer
    In:  EPIC3Marine Anthropogenic Litter, Marine Anthropogenic Litter, Berlin, Springer, 447 p., pp. 201-227, ISBN: 978-3-319-16510-3
    Publication Date: 2023-06-21
    Description: Microplastics in aquatic ecosystems and especially in the marine environment represent a pollution of increasing scientific and societal concern, thus, meanwhile a substantial number of studies on microplastics exist. Although first steps towards a standardisation of methodologies used for the detection and identification of microplastics in environmental samples are made, the comparability of data on microplastics is currently hampered by a huge variety of different methodologies which result in the generation of data of extremely different quality and resolution. This chapter reviews the methodology presently used for assessing the concentration of microplastics in the marine environment with focus on the most convenient techniques and approaches. After an overview of non-selective sampling approaches, sample processing and treatment in the laboratory, the reader is introduced to the currently applied techniques for the identification and quantification of microplastics. The subsequent case study on microplastics in sediment samples from the North Sea measured with focal plane array (FPA)-based micro-Fourier transform infrared (micro-FTIR) spectroscopy shows that only 1.4 % of the particles visually resembling microplastics were of synthetic polymer origin. This finding emphasizes the importance of verifying the synthetic polymer origin of potential microplastics. Thus, a burning issue concerning current microplastic research is the generation of standards that allow for the assessment of reliable data on concentrations of microscopic plastic particles and the involved polymers with analytical laboratory techniques such as micro-FTIR or micro-Raman spectroscopy.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Inbook , peerRev
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  • 5
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    AGU (American Geophysical Union)
    In:  Journal of Geophysical Research: Biogeosciences, 114 . G00D03.
    Publication Date: 2018-02-06
    Description: Lake Tahoe is an ultra-oligotrophic subalpine lake that is renowned for its clarity. The region experiences little cloud cover and is one of the most UV transparent lakes in the world. As such, it is an ideal environment to study the role of UV radiation in aquatic ecosystems. Long-term trends in Secchi depths showed that water transparency to visible light has decreased in recent decades, but limited data are available on the UV transparency of the lake. Here we examine how ultraviolet radiation varies relative to longer-wavelength photosynthetically active radiation (PAR, 400-700 nm, visible wavelengths) horizontally along inshore-offshore transects in the lake and vertically within the water column as well as temporally throughout 2007. UV transparency was more variable than PAR transparency horizontally across the lake and throughout the year. Seasonal patterns of Secchi transparency differed from both UV and PAR, indicating that different substances may be responsible for controlling transparency to UV, PAR, and Secchi. In surface waters, UVA (380 nm) often attenuated more slowly than PAR, a pattern visible in only exceptionally transparent waters with very low dissolved organic carbon. On many sampling dates, UV transparency decreased progressively with depth suggesting surface photobleaching, reductions in particulate matter, increasing chlorophyll a, or some combination of these increased during summer months. Combining these patterns of UV transparency with data on visible light provides a more comprehensive understanding of ecosystem structure, function, and effects of environmental change in highly transparent alpine and subalpine lakes such as Tahoe.
    Type: Article , PeerReviewed
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  • 6
    Publication Date: 2022-03-09
    Description: The seasonal and interannual variability of chlorophyll in the Gulf of Mexico open waters is studied using a three‐dimensional coupled physical‐biogeochemical model. A 5 years hindcast driven by realistic open‐boundary conditions, atmospheric forcings, and freshwater discharges from rivers is performed. The use of recent in situ observations allowed an in‐depth evaluation of the model nutrient and chlorophyll seasonal distributions, including the chlorophyll vertical structure. We find that different chlorophyll patterns of temporal variability coexist in the deep basin which thereby cannot be considered as a homogeneous region with respect to chlorophyll dynamics. A partitioning of the Gulf of Mexico open waters based on the winter chlorophyll concentration increase is then proposed. This partition is basically explained by the amount of nutrients injected into the euphotic layer which is highly constrained by the dynamic of the winter mixed layer. The seasonal and interannual variability appears to be affected by the variability of atmospheric fluxes and mesoscale dynamics (Loop Current eddies in particular). Finally, estimates of primary production in the deep basin are provided.
    Type: Article , PeerReviewed
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  • 7
    Publication Date: 2018-02-06
    Description: During the SAMUM field campaign in southern Morocco in May and June 2006 density currents generated by evaporative cooling after convective precipitation were frequently observed at the Sahara side of the Atlas Mountain chain. The associated strong surface cold-air outflow during such events has been observed to lead to dust mobilization in the foothills. Here a regional model system is used to simulate a density current case on 3 June 2006 and the subsequent dust emission. The model studies are performed with different parameterization schemes for convection, and with different horizontal model grid resolutions to examine to which extent the model system can be used for reproducing dust emissions in this region. The effect of increasing the horizontal model grid resolution from 14 km to 2.8 km on the strength on the density currents and thus on dust emission is smaller than the differences due to different convection parameterization schemes in this case study. While the results in reproducing the observed density current at the Atlas Mountain varied with different convection parameterizations, the most realistic representation of the density current is obtained at 2.8 km grid resolution at which no parameterization of deep convection is needed.
    Type: Article , PeerReviewed
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  • 8
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    Chinese Mechanical Engineering Society | Springer
    In:  Chinese Journal of Mechanical Engineering, 29 (5). pp. 863-870.
    Publication Date: 2020-07-27
    Description: Seafloor massive sulfide(SMS) deposits which consist of Au, Ag, Cu, and other metal elements, have been a target of commercial mining in recent decades. The demand for established and reliable commercial mining system for SMS deposits is increasing within the marine mining industry. The current status and progress of mining technology and equipment for SMS deposits are introduced. First, the mining technology and other recent developments of SMS deposits are comprehensively explained and analyzed. The seafloor production tools manufactured by Nautilus Minerals and similar mining tools from Japan for SMS deposits are compared and discussed in turn. Second, SMS deposit mining technology research being conducted in China is described, and a new SMS deposits mining tool is designed according to the environmental requirement. Finally, some new trends of mining technology of SMS deposits are summarized and analyzed. All of these conclusions and results have reference value and guiding significance for the research of SMS deposit mining in China.
    Type: Article , PeerReviewed
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  • 9
    Publication Date: 2018-03-09
    Description: Jamaica Bay, NY, is a highly urbanized estuary within the boroughs of New York City conspicuously lacking published information on dissolved trace metal concentrations. The current study examines the distribution and cycling of trace metals in that embayment with data gathered during cruises in November 2004, April 2005, and June 2006. Most of the metal distributions (Fe, Zn, Co, Ag, Cu, Pb, Ni) in the water column are explained by the input of substantial volumes of treated wastewater effluent. However, several lines of evidence suggest that submarine groundwater discharge (SGD) is also an important source of dissolved Fe, Zn, Co, Ni, and isotopically distinct stable Pb ratios (206Pb, 207Pb, 208Pb) in the Bay. Conversely, the recirculated seawater component of SGD is an apparent sink for dissolved Mo. This study provides the first measurements of dissolved trace metals in the Jamaica Bay water column and subterranean estuary and provides evidence for trace metal input due to SGD.
    Type: Article , PeerReviewed
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  • 10
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    AGU (American Geophysical Union)
    In:  Journal of Geophysical Research: Solid Earth, 113 (C7). C07007.
    Publication Date: 2019-07-25
    Description: The main physical and biological processes that control the seasonal cycle of the plankton dynamics over the Western Black Sea were explored by means of a three‐dimensional, 7‐compartment, on‐line coupled biophysical model that was developed for this study. Adopting high frequency forcing in terms of air‐sea interaction and Danube river inputs, we performed a simulation of the coupled model during the 2002–2003 period. A series of 8‐day Chl‐a SeaWiFS images provided a validation tool that guided us, along with available in situ measurements, to the improvement of model parameterizations and the calibration of the biological parameters. The simulation of the seasonal phytoplankton variability over the entire Western Black Sea, extending from the highly eutrophic river influenced area to the open sea area, was a major challenge that made necessary the representation of both the spatial and time variability of several processes. Despite the model simplicity, the simulated Chl‐a patterns presented a good agreement as compared to the SeaWiFS and in situ data. During winter, phytoplankton in coastal areas was shown to be limited by light availability, primarily due to the increased particulate matter concentrations, as a result of resuspension from the sediment and the increased river loads. During summer, the primary production was mostly sustained by riverine nutrients and regeneration processes and thus was strongly linked to the evolution of the Danube plume. The limiting nutrients showed deviations from the observed concentrations, indicating the necessity for a more realistic phytoplankton growth model.
    Type: Article , PeerReviewed
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