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  • 1
    Publikationsdatum: 2015-09-17
    Beschreibung: During two independent cruises in the north-eastern tropical Atlantic Ocean, we applied two different approaches to investigate the impact of diazotrophy on nitrogen stable isotope signatures in nitrate and particulate organic nitrogen (PON) of the food-web constituents. The first approach, used during the Poseidon cruise 348 in the Mauritanian upwelling, investigated the long-term influence of diazotrophy on the natural abundance of 15N-NO-3 and PON. The second approach, adopted during the Cape Verde field cruise, applied stable isotope tracer addition experiments. These served to determine the instantaneous transfer of diazotrophic N to the higher trophic level. Both approaches showed that N2 fixation was compatible with the pattern and the magnitude of the isotopic depletion of dissolved NO-3 during the Mauritanian upwelling cruise, as well as PON in zooplankton and phytoplankton during the Cape Verde cruises. An N-budget using 15N incorporation rates and diazotrophic N2 fixation rates showed that 6 % of the daily N2 fixation was potentially taken up by the mesozooplankton community. Direct grazing accounted for 56 % of gross mesozooplanktonic N incorporation, while 46 % occurred due to channelling through the microbial loop.
    Materialart: Article , PeerReviewed
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 2
    Publikationsdatum: 2014-03-25
    Beschreibung: During two simultaneous cruises in the Central Baltic Sea in July 2007 we applied a 15N tracer addition approach to assess the impact of cyanobacterial N2 fixation on mesozooplankton production in the Central Baltic Sea. We determined rates of diazotrophic 15N2 fixation, as well as uptake of diazotrophic derived 15N by mesozooplankton species. Diazotrophic 15N2 fixation rates were low representing pre-bloom situations. A first order estimate using a two source mixing model of natural δ15N-PON abundance revealed that diazotrophic fixed N contributed to 27 ± 8% to mesozooplankton biomass. Additionally, the application of stable isotope tracer showed that fixed 15N was detectable in the mesozooplankton fraction within 1 h after the onset of the incubation. On a daily basis, 5% up to 100% of newly fixed 15N and 14% of cyanobacteria standing stock were incorporated by mesozooplankton species in our experimental set-ups. By applying size fractionating experiments and the usage of different control treatments, we calculated that the majority of 15N transfer (67%) was mediated by the release of nitrogenous compounds and their channelling through the microbial loop towards the mesozooplankton community. Moreover, direct grazing on filamentous cyanobacteria accounted for 33% of gross 15N incorporation. Grazing in the experiments seemed to be largely influenced by cyanobacterial species dominating the community and by the abundance of Cladoceran species like Evadne. Overall, N2 fixing cyanobacteria are ecological more important as instantaneous sources of nitrogen for higher trophic levels of the Baltic Sea food web than previously assumed.
    Materialart: Article , PeerReviewed
    Format: text
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 3
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    Unbekannt
    Institut für Geowissenschaften der Christian-Albrechts-Universität Kiel
    In:  Berichte - Reports / Institut für Geowissenschaften, Christian-Albrechts-Universität zu Kiel, 23 . Institut für Geowissenschaften der Christian-Albrechts-Universität Kiel, Kiel, Germany, 99 pp.
    Publikationsdatum: 2020-08-03
    Materialart: Report , NonPeerReviewed
    Format: text
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 4
  • 5
    Publikationsdatum: 2022-04-01
    Beschreibung: The mean trophic position (TP) of mesozooplankton largely determines how much mass and energy is available for higher trophic levels like fish. Unfortunately, the ratio of herbivores to carnivores in mesozooplankton is difficult to identify in field samples. Here, we investigated changes in the mean TP of mesozooplankton in a highly dynamic environment encompassing four distinct habitats in the southern South China Sea: the Mekong River plume, coastal upwelling region, shelf waters, and offshore oceanic waters. We used a set of variables derived from bulk and amino acid nitrogen stable isotopes from particulate organic matter and four mesozooplankton size fractions to identify changes in the nitrogen source and TP of mesozooplankton across these habitats. We found clear indications of a shift in N sources for biological production from nitrate in near‐coastal waters with shallow mixed layer depths toward an increase in diazotroph‐N inputs in oceanic waters with deep mixed layer depths where diazotrophs shaped the phytoplankton community. The N source shift was accompanied by a lengthening of the food chain (increase in the TP). This may provide further support for the connection between diazotrophy and the indirect routing of N through the marine food web. Our combined bulk and amino acid δ15N approach also allowed us to estimate the trophic enrichment (TE) of mesozooplankton across the entire regional ecosystem. When put in the context of literature values, a high TE of 5.1‰ suggested a link between ecosystem heterogeneity and the less efficient transfer of mass and energy across trophic levels.
    Beschreibung: Plain Language Summary: Zooplankton are one of the central pillars of the marine food web and form an important link between the production of organic matter by phytoplankton and biomass at higher trophic levels (e.g., fish). Of particular interest are mesozooplankton (0.2–20 mm in size), which encompass a diverse assemblage of animals utilizing a range of feeding strategies, including herbivory, omnivory, and carnivory. Since mass and energy are lost with each trophic step, their prevailing feeding strategy determines the availability of mass and energy to the upper food web. The exact relationship between carnivores and herbivores in mesozooplankton has so far only been studied with complex experiments or in homogenous environments. We have now resolved zooplankton feeding relationships in a highly dynamic marine environment. Specifically, we used stable nitrogen isotopes in amino acids and bulk organic matter in combination with a habitat‐delineating method for phytoplankton to directly determine the ratio of carnivores to herbivores in zooplankton from dynamic habitats in the South China Sea. The mass and energy transfer across trophic levels is less efficient in such variable marine environments compared to stable open ocean systems. These findings represent a big step toward understanding the dynamics of planktonic food webs in general.
    Beschreibung: Key Points: Trophic structure of mesozooplankton is regulated by similar environmental factors such as phytoplankton assemblages. Diazotrophy and nutrient availability correlated with enhanced mesozooplankton carnivory in a complex tropical marine ecosystem. Mass and energy transfer across trophic levels of planktonic food webs are less efficient in spatially and temporally variable ecosystems.
    Beschreibung: Deutsche Forschungsgemeinschaft (DFG) http://dx.doi.org/10.13039/501100001659
    Beschreibung: National Foundation for Science and Technology Development (NAFOSTED) http://dx.doi.org/10.13039/100007224
    Beschreibung: National Aeronautics and Space Administration (NASA) http://dx.doi.org/10.13039/100000104
    Beschreibung: Schmidt Ocean Institute
    Beschreibung: National Science Foundation (NSF) http://dx.doi.org/10.13039/100000001
    Beschreibung: https://doi.org/10.5061/dryad.bk3j9kdbv
    Schlagwort(e): ddc:577.7
    Sprache: Englisch
    Materialart: doc-type:article
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 6
    Publikationsdatum: 2019-09-18
    Beschreibung: Increasing sea surface temperatures (SST) and blooms of lipid‐poor, filamentous cyanobacteria can change mesozooplankton metabolism and foraging strategies in marine systems. Lipid shortage and imbalanced diet may challenge the build‐up of energy pools of lipids and proteins, and access to essential fatty acids (FAs) and amino acids (AAs) by copepods. The impact of cyanobacterial blooms on individual energy pools was assessed for key species temperate Temora longicornis and boreal Pseudo‐/Paracalanus spp. that dominated field mesozooplankton communities isolated by sea‐sonal stratification in the central Baltic Sea during the hot and the cold summer. We looked at (a) total lipid and protein levels, (b) FA trophic markers and AA composition, and (c) compound‐specific stable carbon isotopes (δ13C) in bulk mesozooplankton and in a subset of parameters in particulate organic matter. Despite lipid‐poor cyanobacterial blooms, the key species were largely able to cover both energy pools, yet a tendency of lipid reduction was observed in surface animals. Omni‐ and car‐nivory feeding modes, FA trophic makers, and δ13C patterns in essential compounds emphasized that cyanobacterial FAs and AAs have been incorporated into meso‐zooplankton mainly via feeding on mixo‐ and heterotrophic (dino‐) flagellates and detrital complexes during summer. Foraging for essential highly unsaturated FAs from (dino‐) flagellates may have caused night migration of Pseudo‐/Paracalanus spp. from the deep subhalocline waters into the upper waters. Only in the hot summer (SST〉19.0°C) was T. longicornis submerged in the colder subthermocline water (~4°C). Thus, the continuous warming trend and simultaneous feeding can eventually lead to competition on the preferred diet by key copepod species below the thermocline in stratified systems. A comparison of δ13C patterns of essential AAs in surface meso‐zooplankton across sub‐basins of low and high cyanobacterial biomasses revealed the potential of δ13C‐AA isoscapes for studies of commercial fish feeding trails across the Baltic Sea food webs.
    Repository-Name: EPIC Alfred Wegener Institut
    Materialart: Article , isiRev
    Format: application/pdf
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 7
    Publikationsdatum: 2023-05-12
    Schlagwort(e): BIOACID; Biological Impacts of Ocean Acidification; Carbon, organic, particulate; Carbon, organic, particulate, standard deviation; Carbon fixation rate; Carbon fixation rate, per particulate organic carbon; Carbon fixation rate, standard deviation; Carlo Erba EA 1108 + Thermo Finnigan Delta S mass-spectrometer; DATE/TIME; Incubation duration; MarsXpress (CEM); Microscopy; Nitrogen, organic, particulate; Nitrogen, organic, particulate, standard deviation; Nitrogen fixation rate; Nitrogen fixation rate, per particulate organic carbon; Nitrogen fixation rate, standard deviation; Nodularia spumigena; Nodularia spumigena, standard deviation; Phosphorus, organic, particulate; Salinity; Standard deviation; Temperature, technical; Treatment
    Materialart: Dataset
    Format: text/tab-separated-values, 240 data points
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 8
    Publikationsdatum: 2024-04-25
    Beschreibung: This dataset contains abiotic and biotic data from sediment samples from four sites in the northwestern Weddell Sea. Data are provided for sediment pigments (chlorophyll a and phaeopigment content through fluorometry), total organic carbon (TOC), total nitrogen (TN), stable isotope values of carbon and nitrogen (δ13C, δ15N) and grain size (silt&clay 〈 32 µm, very fine sand 63–125 µm, fine sand 125–250 µm, medium sand 250–500 µm, coarse sand 500–1000 µm, larger coarse sand 〉 1000 µm). A minimum of three replicate samples (cores) were collected using a MUC10 multicorer. All sediment cores were subsampled with a 10-ml syringe (inner diameter 1 cm). Subsamples were sliced in 1-cm steps down to 5 cm depth. The same sampling and measurements as for PS 96 were carried out (see below "Related to". Prior to TOC and δ13C analysis sediment samples were acidified to eliminate inorganic carbon. Detailed methods are described in Säring et al. (2022), except for stable isotopes: Flash combustion in a Flash 2000 (Thermo) elemental analyser to a Delta V advantage (Thermo) isotope ratio masspectrometer. δ values are reported relative to atmospheric N2 (δ15N) and Vienna PeeDee Belemnite (δ13C). Reference materials for stable isotope analysis: IAEA-N1, IAEA-N2, IAEA-N3, NBS 22, IAEA-CH-3 and IAEA-CH-6; calibration material: Acetanilide (Merck). The analytical precision for both stable isotope ratios was 〈±0.2‰. Cores with the label -e (Environment) were only used to collect the above data. Environmental, fauna and benthic boundary flux data were collected from cores with the label -i (Incubation). This data table is part of studies analyzing the role of environmental parameters for meio- and macrofaunal community compositions and polychaete community distribution patterns (see "Supplement to", "Related to" and "Further details" below).
    Schlagwort(e): Antarctic; Carbon, organic, total; Chlorophyll a; Chlorophyll a per unit sediment mass; Core; Cruise/expedition; Date/Time of event; Depth, bottom/max; DEPTH, sediment/rock; Depth, top/min; Elevation of event; Event label; Flash combustion in a Flash 2000 (Thermo) elemental analyzer; Fluorometry; Gear; Grain Size; Grain size, Mastersizer 3000, Malvern Instrument Inc.; Latitude of event; Longitude of event; MUC; MultiCorer; Nitrogen, total; Operation number; organic matter; phaeopigments; Phaeopigments per unit sediment mass; pigments; Polarstern; Priority Programme 1158 Antarctic Research with Comparable Investigations in Arctic Sea Ice Areas; PS118; PS118_12-3; PS118_12-5; PS118_12-6; PS118_38-2; PS118_38-3; PS118_6-2; PS118_6-3; PS118_6-4; PS118_8-4; PS118_8-5; PS118_8-6; PS118_8-7; PS118_8-8; sediment; Size fraction 〈 0.063 mm, mud, silt+clay; Size fraction 〉 1 mm, gravel; Size fraction 0.125-0.063 mm, 3.0-4.0 phi, very fine sand; Size fraction 0.250-0.125 mm, 2.0-3.0 phi, fine sand; Size fraction 0.500-0.250 mm, 1.0-2.0 phi, medium sand; Size fraction 1.000-0.500 mm, 0.0-1.0 phi, coarse sand; Southern Ocean; SPP1158; stable carbon isotopes; Station label; total nitrogen (TN); total organic carbon (TOC); Weddell Sea; δ13C, total organic carbon; δ15N, bulk sediment
    Materialart: Dataset
    Format: text/tab-separated-values, 2119 data points
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 9
    Publikationsdatum: 2024-04-23
    Beschreibung: The Amazon River is known as a region of intense biochemical reactivity. As a result of increased anthropogenic impacts in its catchment (e.g. population growth, agriculture, and deforestation), The Amazon River is undergoing fundamental changes. The RV METEOR cruise M174 (doi:10.1594/PANGAEA.935041) aimed to provide an integrated overview of nitrogen cycling processes in areas influenced by the Amazon River, which is crucial to estimate the ecosystem's health and productivity. During this cruise, six stations were visited to explore the significance of denitrification as a dominant pathway in the watercolumn of the Amazon and Pará estuaries. This dataset presents the stable isotopic composition of nitrate (d15N- d18O-NO3), as well as d2H and d18O of ambient water.
    Schlagwort(e): According to Böttcher & Schmiedinger (2021); According to Sigman et al. (2001) and Weigand et al. (2016); Amazon; Amazon estuary; Amazon River; Calculated; CTD, Sea-Bird, SBE 911plus; CTD/Rosette; CTD-RO; d15N; d18O; d2H; Date/Time of event; Event label; Latitude of event; Longitude of event; M174; M174_10-2; M174_12-2; M174_13-3; M174_14-2; M174_17-16; M174_9-2; Meteor (1986); Methods of Seawater Analysis, 3rd edition (Grasshoff et al., 1999); nitrate; Nitrate; Nitrate, standard deviation; Salinity; South Atlantic Ocean; Stable isotopes; Temperature, water; water; δ15N, nitrate; δ15N, nitrate, standard deviation; δ18O, nitrate; δ18O, nitrate, standard deviation; δ18O, water; δ18O, water, standard deviation
    Materialart: Dataset
    Format: text/tab-separated-values, 60 data points
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 10
    Publikationsdatum: 2024-04-25
    Beschreibung: This dataset contains biotic and abiotic data from water-column samples taken with Niskin bottles mounted on the CTD rosette from 14 sites in the Weddell Sea (mostly South-Eastern). Data are provided for water-column pigments (chlorophyll a and phaeopigment content through fluorometry), total carbon (TC) and nitrogen (TN) and stable isotope values of carbon and nitrogen (δ13C, δ15N) from the chlorophyll maximum (Cmax, defined as the water depth with maximum fluorescence detected during in-situ profiles) and close to the sea bottom. Water was filtered onto glass fiber filters (GF/C for pigments, combusted GF/F for C and N analyses) and stored at -80°C prior to analysis. Detailed methods are described in Säring et al. (submitted) except for stable isotopes: Flash combustion in a Flash 2000 (Thermo) elemental analyser to a Delta V advantage (Thermo) isotope ratio masspectrometer. δ values are reported relative to atmospheric N₂ (δ15N) and Vienna PeeDee Belemnite (δ13C). Reference materials for stable isotope analysis: IAEA-N1, IAEA-N2, IAEA-N3, NBS 22, IAEA-CH-3 and IAEA-CH-6; calibration material: Acetanilide (Merck). The analytical precision for both stable isotope ratios was 〈±0.2‰. Samples were not acidified to avoid loss of material. We assumed low inorganic carbon content in the water column for our analyses. This data table is part of a larger study analysing the role of environmental parameters for meio- and macrofaunal community composition (see Related to below).
    Schlagwort(e): Antarctica; ANT-XXXI/2 FROSN; Carbon, total; Chlorophyll a; chlorophyll bottom; chlorophyll maximum; Cruise/expedition; CTD/Rosette; CTD-RO; Date/Time of event; DEPTH, water; Elevation of event; Event label; Flash combustion in a Flash 2000 (Thermo) elemental analyser to a Delta V advantage (Thermo) isotope ratio masspectrometer; Flash combustion in a Flash 2000 (Thermo) elemental analyzer; Fluorometry; Gear; Latitude of event; Longitude of event; Nitrogen, total; phaeopigments; Phaeopigments; pigments; Polarstern; Priority Programme 1158 Antarctic Research with Comparable Investigations in Arctic Sea Ice Areas; PS96; PS96/001-1; PS96/005-2; PS96/010-7; PS96/017-1; PS96/026-13; PS96/027-1; PS96/037-2; PS96/048-1; PS96/059-1; PS96/061-2; PS96/072-2; PS96/090-3; PS96/104-1; PS96/115-1; Sample type; Southern Ocean; SPP1158; Stable isotope; Station label; Total Carbon; total nitrogen; water column; Weddell Sea; δ13C; δ15N
    Materialart: Dataset
    Format: text/tab-separated-values, 235 data points
    Standort Signatur Einschränkungen Verfügbarkeit
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