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  • 2015-2019  (22)
  • 1995-1999  (57)
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  • 1
    Online Resource
    Online Resource
    Mechanismen biochemischer Temperaturanpassung : ein Vergleich der Enzymeigenschaften bei Crustaceen aus verschiedenen Klimazonen (2017)
    Kiel : Inst. für Meereskunde
    Details Availability
    Keywords: Hochschulschrift ; Krebstiere ; Temperaturanpassung
    Type of Medium: Online Resource
    Pages: Online-Ressource (95 Seiten, 3,2 MB) , Diagramme
    Series Statement: Berichte aus dem Institut für Meereskunde an der Christian-Albrechts-Universität Kiel 226
    URL: https://oceanrep.geomar.de/25780/
    URL: http://dx.doi.org/10.3289/ifm_ber_226
    DOI: 10.3289/ifm_ber_226
    Language: German
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    GEOMAR CATALOGUE
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  • 2
    Online Resource
    Online Resource
    Zur Lebensweise des antarktischen und des nordischen Krills Euphausia superba und Meganyctiphanes norvegica : vergleichende Untersuchungen der Häutungsphysiologie und des Wachstums im Freiland und Labor = On the way of life of the antarctic and the northern krill Euphausia superba and Meganyctiphanes norvegica : comparative Investigations of Moult Physiology and Growth in the Field and the Laboratory (2017)
    Kiel : Inst. für Meereskunde
    Details Availability
    Keywords: Hochschulschrift
    Type of Medium: Online Resource
    Pages: Online-Ressource (255 Seiten, 5 MB) , Illustrationen, Diagramme
    Series Statement: Berichte aus dem Institut für Meereskunde an der Christian-Albrechts-Universität Kiel 185
    URL: https://oceanrep.geomar.de/25789/
    URL: http://dx.doi.org/10.3289/ifm_ber_185
    DOI: 10.3289/ifm_ber_185
    Language: German
    Note: Zusammenfassung in deutscher und englischer Sprache
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    GEOMAR CATALOGUE
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  • 3
    Electronic Resource
    Electronic Resource
    A laboratory study on digestive processes in the Antarctic krill, Euphausia superba, with special regard to chitinolytic enzymes (1999)
    Springer
    Polar biology 21 (1999), S. 295-304 
    Details
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Feeding experiments of 9, 14 and 20 days duration were carried out on the Antarctic krill, Euphausia superba. Two groups were fed with the chitinous diatom Cyclotella cryptica and the non-chitinous green algae Dunaliella bioculata, respectively. A control group remained unfed. The time courses of the activities of endo- and exochitinase in the stomach and the midgut gland were compared with those of the digestive enzymes protease, cellulase (1,4-β-d-glucanase) and laminarinase (1,3-β-d-glucanase). Specific activities of all enzymes were higher in the stomach than in the midgut gland. Characteristic time courses of activity were evident after 4 days. In starved animals, enzyme activities decreased to a minimum after 4 days and recovered within 14 days to initial values. In the stomach, the activities of endo- and exochitinase increased when krill were fed on Cyclotella. For animals fed with Dunaliella, activities stayed constant or decreased slightly. The results confirm chitinases as digestive enzymes and, therefore, the capability of krill to utilize various food sources.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003000050365
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    Paper (German National Licenses)
    Fulltext
  • 4
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    Ammonium excretion and oxygen respiration of tropical copepods and euphausiids exposed to oxygen minimum zone conditions (2016)
    Copernicus Publications (EGU)
    In:  Biogeosciences (BG), 13 (8). pp. 2241-2255.
    Details
    Publication Date: 2019-09-23
    Description: Calanoid copepods and euphausiids are key components of marine zooplankton communities worldwide. Most euphausiids and several copepod species perform diel vertical migrations (DVMs) that contribute to the export of particulate and dissolved matter to midwater depths. In vast areas of the global ocean, and in particular in the eastern tropical Atlantic and Pacific, the daytime distribution depth of many migrating organisms corresponds to the core of the oxygen minimum zone (OMZ). At depth, the animals experience reduced temperature and oxygen partial pressure (pO2) and an increased carbon dioxide partial pressure (pCO2) compared to their near-surface nighttime habitat. Although it is well known that low oxygen levels can inhibit respiratory activity, the respiration response of tropical copepods and euphausiids to relevant pCO2, pO2 and temperature conditions remains poorly parameterized. Further, the regulation of ammonium excretion at OMZ conditions is generally not well understood. It was recently estimated that DVM-mediated ammonium supply considerably fuels bacterial anaerobic ammonium oxidation – a major loss process for fixed nitrogen in the ocean. These estimates were based on the implicit assumption that hypoxia or anoxia in combination with hypercapnia (elevated pCO2) does not result in a downregulation of ammonium excretion. Here we show that exposure to OMZ conditions can result in strong depression of respiration and ammonium excretion in calanoid copepods and euphausiids from the Eastern Tropical North Atlantic and the Eastern Tropical South Pacific. These physiological responses need to be taken into account when estimating DVM-mediated fluxes of carbon and nitrogen into OMZs.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.5194/bg-13-2241-2016
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 5
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    Zooplankton in Kongsfjorden (1996–2016) in Relation to Climate Change (2019)
    Nature Research
    In:  In: The Ecosystem of Kongsfjorden, Svalbard. Nature Research, Cham, Switzerland, pp. 229-300. ISBN 978-3-319-46423-7
    Details
    Publication Date: 2020-01-13
    Description: Zooplankton in Kongsfjorden, Svalbard, is shaped by irregular advection of seawater from the West Spitsbergen Current as well as input of freshwater of glacial and riverine origin. The zooplankton community reflects contributions of Arctic vs. Atlantic water masses in the fjord, and is changing with increasing temperature and declining sea ice. Here, we review zooplankton studies from Kongsfjorden, and present new data from a 20-year time series (1996–2016) of zooplankton abundance/biomass in the fjord based on annual surveys during summer. During the last decade, the marine environment of the West Spitsbergen Shelf and adjacent fjords has undergone changes with increasing temperatures and volume of inflowing Atlantic Water and declining sea ice. Annual monitoring of mesozooplankton since 1996 has shown high seasonal, spatial, and inter-annual variation in species abundance and biomass, and in the proportion of Atlantic and Arctic species. Inter-annual variations in species composition and abundance demonstrate fluctuating patterns related to changes in hydrography. “Warm years” in Kongsfjorden were characterized by higher abundances of Atlantic species, such as Calanus finmarchicus, Oithona atlantica, Thysanoessa longicaudata and Themisto abyssorum. Other krill species, particularly Thysanoessa inermis and to a lesser extent T. longicaudata, increased in abundance during the warming period in 2006–2007, mainly in the inner basin. “Cold years”, on the other hand, were characterized by higher abundance of Themisto libellula. There was no clear impact, however, of changes in environmental factors on the abundance or biomass of the Arctic species Calanus glacialis suggesting that the changes in environmental conditions have not reached critical levels for this species. The long-term zooplankton data demonstrate that some Atlantic species have become more abundant in the Kongsfjorden’s pelagic realm, suggesting that they may benefit from increasing temperature, and also that the total biomass of zooplankton has increased in the fjord implying potentially higher secondary production.
    Type: Book chapter , NonPeerReviewed
    Format: text
    DOI: 10.1007/978-3-319-46425-1_7
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    OceanRep: Book chapter
  • 6
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    Ammonium excretion and respiration rate of tropical copepods and euphausiids measured during METEOR cruise M93, M97 and Maria S. Merian cruise MSM22 (2015)
    PANGAEA
    In:  Supplement to: Kiko, Rainer; Hauss, Helena; Buchholz, Friedrich; Melzner, Frank (2016): Ammonium excretion and oxygen respiration of tropical copepods and euphausiids exposed to oxygen minimum zone conditions. Biogeosciences, 13(8), 2241-2255, https://doi.org/10.5194/bg-13-2241-2016
    Details
    Publication Date: 2023-10-28
    Description: Respiration and ammonium excretion rates at different oxygen partial pressure were measured for calanoid copepods and euphausiids from the Eastern Tropical South Pacific and the Eastern Tropical North Atlantic. All specimens used for experiments were caught in the upper 400 m of the water column and only animals appearing unharmed and fit were used for experiments. Specimens were sorted, identified and transferred into aquaria with filtered, well-oxygenated seawater immediately after the catch and maintained for 1 to 13 hours prior to physiological experiments at the respective experimental temperature. Maintenance and physiological experiments were conducted in darkness in temperature-controlled incubators at 11, 13 or 23 degree C (±1). Before and during experiments, animals were not fed. Respiration and ammonium excretion rate measurements (both in µmol h-1 gDW-1) at varying oxygen concentrations were conducted in 12 to 60 mL gas-tight glass bottles. These were equipped with oxygen microsensors (ø 3 mm, PreSens Precision Sensing GmbH, Regensburg, Germany) attached to the inner wall of the bottles to monitor oxygen concentrations non-invasively. Read-out of oxygen concentrations was conducted using multi-channel fiber optic oxygen transmitters (Oxy-4 and Oxy-10 mini, PreSens Precision Sensing GmbH, Regensburg, Germany) that were connected via optical fibers to the outside of the bottles directly above the oxygen microsensor spots. Measurements were started at pre-adjusted oxygen and carbon dioxide levels. For this, seawater stocks with adjusted pO2 and pCO2 were prepared by equilibrating 3 to 4 L of filtered (0.2 µm filter Whatman GFF filter) and UV - sterilized (Aqua Cristal UV C 5 Watt, JBL GmbH & Co. KG, Neuhofen, Germany) water with premixed gases (certified gas mixtures from Air Liquide) for 4 hours at the respective experimental temperature. pCO2 levels were chosen to mimic the environmental pCO2 in the ETSP OMZ or the ETNA OMZ. Experimental runs were conducted with 11 to 15 trial incubations (1 or 2 animals per incubation bottle and three different treatment levels) and three animal-free control incubations (one per experimental treatment). During each run, experimental treatments comprised 100% air saturation as well as one reduced air saturation level with and without CO2. Oxygen concentrations in the incubation bottles were recorded every 5 min using the fiber-optic microsensor system and data recording for respiration rate determination was started immediately after all animals were transferred. Respiration rates were calculated from the slope of oxygen decrease over selected time intervals. Chosen time intervals were 20 to 105 min long. No respiration rate was calculated for the first 20 to 60 min after animal transfer to avoid the impact of enhanced activity of the animal or changes in the bottle water temperature during initial handling on the respiration rates and oxygen readings. Respiration rates were obtained over a maximum of 16 hours incubation time and slopes were linear at normoxia to mild hypoxia. Respiration rates in animal-free control bottles were used to correct for microbial activity. These rates were 〈 2% of animal respiration rates at normoxia. Samples for the measurement of ammonium concentrations were taken after 2 to 10 hours incubation time. Ammonium concentration was determined fluorimetrically (Holmes et al., 1999). Ammonium excretion was calculated as the concentration difference between incubation and animal-free control bottles. Some specimens died during the respiration and excretion rate measurements, as indicated by a cessation of respiration. No excretion rate measurements were conducted in this case, but the oxygen level at which the animal died was noted.
    Keywords: Climate - Biogeochemistry Interactions in the Tropical Ocean; SFB754
    Type: Dataset
    Format: application/zip, 2 datasets
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  • 7
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    Near-bottom zooplankton aggregations in Kongsfjorden with link to images from the optical zooplankton sensor MOKI (2015)
    PANGAEA
    In:  Supplement to: Hirche, Hans-Juergen; Laudien, Jürgen; Buchholz, Friedrich (2015): Near-bottom zooplankton aggregations in Kongsfjorden: implications for pelago-benthic coupling. Polar Biology, https://doi.org/10.1007/s00300-015-1799-4
    Details
    Publication Date: 2024-03-01
    Description: Near-bottom zooplankton communities have rarely been studied despite numerous reports of high zooplankton concentrations, probably due to methodological constraints. In Kongsfjorden, Svalbard, the near-bottom layer was studied for the first time by combining daytime deployments of a remotely operated vehicle (ROV), the optical zooplankton sensor moored on-sight key species investigation (MOKI), and Tucker trawl sampling. ROV data from the fjord entrance and the inner fjord showed high near-bottom abundances of euphausiids with a mean concentration of 17.3 ± 3.5 n/100 m**3. With the MOKI system, we observed varying numbers of euphausiids, amphipods, chaetognaths, and copepods on the seafloor at six stations. Light-induced zooplankton swarms reached densities in the order of 90,000 (euphausiids), 120,000 (amphipods), and 470,000 ind/m**3 (chaetognaths), whereas older copepodids of Calanus hyperboreus and C. glacialis did not respond to light. They were abundant at the seafloor and 5 m above and showed maximum abundance of 65,000 ind/m**3. Tucker trawl data provided an overview of the seasonal vertical distribution of euphausiids. The most abundant species Thysanoessa inermis reached near-bottom concentrations of 270 ind/m**3. Regional distribution was neither related to depth nor to location in the fjord. The taxa observed were all part of the pelagic community. Our observations suggest the presence of near-bottom macrozooplankton also in other regions and challenge the current view of bentho-pelagic coupling. Neglecting this community may cause severe underestimates of the stock of elagic zooplankton, especially predatory species, which link secondary production with higher trophic levels.
    Keywords: AWI_BPP; Bentho-Pelagic Processes @ AWI; DATE/TIME; DEPTH, water; File name; File size; Kongsfjorden, Spitsbergen, Arctic; Latitude of event; Longitude of event; M1; M1_NearBlomstrand; M2; M2_NearKongsbreen; M3; M3_Kongsfjordneset; M4; M4_CrossNyAlesund; M5; M5_Juttaholmen; M6; M6_Midtholmen; MOKI; Moored onsight keyspecies investigation; Moored onsight keyspecies investigation (MOKI); Optional event label; Uniform resource locator/link to image
    Type: Dataset
    Format: text/tab-separated-values, 666 data points
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    DATA PANGAEA
  • 8
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    Physical oceanography of a profile from Kongsfjorden, Svalbard in 2013 (2015)
    PANGAEA
    In:  Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven
    Details
    Publication Date: 2024-03-01
    Keywords: AWI_BPP; Bentho-Pelagic Processes @ AWI; CTD, handheld; DEPTH, water; Fluorescence, chlorophyll; hCTD; Kongsfjorden_2013_P1; Kongsfjorden, Spitsbergen, Arctic; Profile 1; Salinity; STD/CTD model SD204, SAIV A/S, Bergen, Norway; Temperature, water
    Type: Dataset
    Format: text/tab-separated-values, 174 data points
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    DATA PANGAEA
  • 9
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    Balance of production and respiration in German Bight planktonic communities (1997)
    In:  EPIC3KUSTOS - TRANSWATT Meeting, Hamburg, 1997
    Details
    Publication Date: 2017-02-13
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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    PAPER (OA)
  • 10
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    Distribution and abundance of euphausiids and pelagic amphipods in Kongsfjorden, Isfjorden and Rijpfjorden (Svalbard) and changes in their relative importance as key prey in a warming marine ecosystem (2016)
    SPRINGER
    In:  EPIC3Polar Biology, SPRINGER, 39, pp. 1765-1784, ISSN: 0722-4060
    Details
    Publication Date: 2017-01-27
    Description: Euphausiid (krill) and amphipod dynamics were studied during 2006–2011 by use of plankton nets in Kongsfjorden (79�N) and adjacent waters, also including limited sampling in Isfjorden (78�N) and Rijpfjorden (80�N). The objectives of the study were to assess how variations in physical characteristics across fjord systems affect the distribution and abundance of euphausiids and amphipods and the potential for these macrozooplankton species to reproduce in these waters. The abundances of euphausiids and amphipods were higher in Kongsfjorden than in Rijpfjorden and Isfjorden, and the highest abundances were observed at the innermost stations of Kongsfjorden, where Thysanoessa inermis and Themisto libellula dominated. The Atlantic species Thysanoessa longicaudata, Meganyctiphanes norvegica and Themisto abyssorum dominated at the outside Kongsfjorden. Inter-annual and seasonal variability in abundances of euphausiids and amphipods were evident. The presence of ripe euphausiids outside Kongsfjorden indicates that they may reproduce in these areas. Mature individuals of T. abyssorum were recorded mainly outside Kongsfjorden, whereas no mature or ripe T. libellula were present in both the inner and outer parts of this fjord. If the warming trend persists, as seen during the last decade, this would favour the Atlantic/boreal euphausiid species, while Arctic species, such as the amphipod T. libellula, may decline. Euphausiids and amphipods are major food of capelin (Mallotus villosus) and polar cod (Boreogadus saida), respectively, in this region, and changes in prey abundance will likely have an impact on the feeding dynamics of these important fish species.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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