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  • 1
    facet.materialart.
    Unknown
    In:  , 2 pp.
    Publication Date: 2019-02-27
    Description: 18/2/2019-24/2/2019
    Type: Report , NonPeerReviewed
    Format: text
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  • 2
    Publication Date: 2019-05-04
    Description: Two 7-day mesocosm experiments were conducted in October 2012 at the Instituto Nacional de Desenvolvimento das Pescas (INDP), Mindelo, Cape Verde. Surface water was collected at night before the start of the respective experiment with RV Islândia south of São Vicente (16°44.4'N, 25°09.4'W) and transported to shore using four 600L food safe intermediate bulk containers. Sixteen mesocosm bags were distributed in four flow-through water baths and shaded with blue, transparent lids to approximately 20% of surface irradiation. Mesocosm bags were filled from the containers by gravity, using a submerged hose to minimize bubbles. The accurate volume inside the individual bags was calculated after addition of 1.5 mmol silicate and measuring the resulting silicate concentration. The volume ranged from 105.5 to 145 L. The experimental manipulation comprised addition of different amounts of inorganic N and P. In the first experiment, the P supply was changed at constant N supply in thirteen of the sixteen units, while in the second experiment the N supply was changed at constant P supply in twelve of the sixteen units. In addition to this, “cornerpoints” were chosen that were repeated during both experiments. Four cornerpoints should have been repeated, but setting the nutrient levels in one mesocosm was not succesfull and therefore this mesocosm also was set at the center point conditions. Experimental treatments were evenly distributed between the four water baths. Initial sampling of the mesocosms on day 1 of each run was conducted between 9:45 and 11:30. After nutrient manipulation, sampling was conducted on a daily basis between 09:00 and 10:30 for days 2 to 8.
    Type: Dataset
    Format: text/tab-separated-values, 586 data points
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  • 3
    Publication Date: 2019-02-12
    Type: Dataset
    Format: text/tab-separated-values, 1800 data points
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  • 4
    Publication Date: 2019-02-12
    Type: Dataset
    Format: text/tab-separated-values, 427 data points
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  • 5
    Publication Date: 2019-05-04
    Type: Dataset
    Format: text/tab-separated-values, 6236 data points
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  • 6
    Publication Date: 2019-05-04
    Description: Two 7-day mesocosm experiments were conducted in October 2012 at the Instituto Nacional de Desenvolvimento das Pescas (INDP), Mindelo, Cape Verde. Surface water was collected at night before the start of the respective experiment with RV Islândia south of São Vicente (16°44.4'N, 25°09.4'W) and transported to shore using four 600L food safe intermediate bulk containers. Sixteen mesocosm bags were distributed in four flow-through water baths and shaded with blue, transparent lids to approximately 20% of surface irradiation. Mesocosm bags were filled from the containers by gravity, using a submerged hose to minimize bubbles. The accurate volume inside the individual bags was calculated after addition of 1.5 mmol silicate and measuring the resulting silicate concentration. The volume ranged from 105.5 to 145 L. The experimental manipulation comprised addition of different amounts of inorganic N and P. In the first experiment, the P supply was changed at constant N supply in thirteen of the sixteen units, while in the second experiment the N supply was changed at constant P supply in twelve of the sixteen units. In addition to this, “cornerpoints” were chosen that were repeated during both experiments. Four cornerpoints should have been repeated, but setting the nutrient levels in one mesocosm was not succesfull and therefore this mesocosm also was set at the center point conditions. Experimental treatments were evenly distributed between the four water baths. Initial sampling of the mesocosms on day 1 of each run was conducted between 9:45 and 11:30. After nutrient manipulation, sampling was conducted on a daily basis between 09:00 and 10:30 for days 2 to 8.
    Type: Dataset
    Format: text/tab-separated-values, 858 data points
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  • 7
    Publication Date: 2017-06-15
    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 could fuel bacterial anaerobic ammonium oxidation – a major loss process for fixed nitrogen in the ocean considerably. These estimates were based on the implicit assumption that hypoxia or anoxia in combination with hypercapnia (elevated pCO2) does not result in a down-regulation of ammonium excretion. We exposed calanoid copepods from the Eastern Tropical North Atlantic (ETNA; Undinula vulgaris and Pleuromamma abdominalis) and euphausiids from the Eastern Tropical South Pacific (ETSP; Euphausia mucronata) andthe ETNA (Euphausia gibboides) to different temperatures, carbon dioxide and oxygen levels to study their survival, respiration and excretion rates at these conditions. An increase in temperature by 10°C led to an approximately 2-fold increase of the respiration and excretion rates of U.vulgaris (Q10, respiration=1.4; Q10,NH4-excretion=1.6), P. abdominalis (Q10, respiration=2.0; Q10,NH4-excretion=2.4) and E. gibboides (Q10, respiration=2.0; Q10,NH4-excretion=2.4; E. mucronata not tested). Exposure to differing carbon dioxide levels had no overall significant impact on the respiration or excretion rates. Species from the ETNA were less tolerant to low oxygen levels than E. mucronata from the ETSP, which survived exposure to anoxia at 13°C. Respiration and excretion rates were reduced upon exposure to low oxygen levels, albeit at different species-specific levels. Reduction of the excretion and respiration rates in ETNA species occurred at a pO2 of 0.6 (P. abdominalis) and 2.4 kPa (U. vulgaris and E.gibboides) at OMZ temperatures. Such low oxygen levels are normally not encountered by these species in the ETNA. E. mucronata however regularly migrates into the strongly hypoxic to anoxic core of the ETSP OMZ. Exposure to low oxygen levels led to a strong reduction of respiration and ammonium excretion in E. mucronata (pcrit respiration=0.6, pcrit NH4excretion=0.73). A drastic reduction of respiratory activity was also observed by other authors for euphausiids, squat lobsters and calanoid copepods, but was not yet accounted for when calculating DVM-mediated active fluxes into the ETSP OMZ. Current estimates of DVM-mediated active export of carbon and nitrogen into the ETSP OMZ are therefore likely too high and future efforts to calculate these export rates should take the physiological responses of migratory species to OMZ conditions into account.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , NonPeerReviewed
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  • 8
    facet.materialart.
    Unknown
    In:  (Diploma thesis), Christian-Albrechts-Universität, Kiel, 88 pp
    Publication Date: 2012-02-23
    Type: Thesis , NonPeerReviewed
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  • 9
    Publication Date: 2018-12-11
    Description: Baltic sprat (Sprattus sprattus balticus, Schneider 1908) is a key species in the Baltic Sea ecosystem, where it is the most abundant planktivorous fish. In the present study, we applied the daily egg production method (DEPM) for the years 1999–2008 to estimate the size of the stock component reproducing in the Bornholm Basin, a major spawning ground for sprat and cod. This is the first study assessing this stock with a fishery independent egg production method for a consecutive time series of ten years. DEPM stock size estimates were compared with those obtained by a multi species virtual population analysis for the same stock component and results from an acoustic survey. In general, the results obtained by the DEPM were in the same order of magnitude compared to the other methods and most similar to the acoustic estimate. However, in some years differences between methods were substantial. With respect to previous egg production methods to assess Baltic sprat stock components our approach takes several aspects into account which were ignored before, e.g. effect of ambient temperature range on sprat egg stage duration and mortality and interannual variability of adult stock parameters. Since the accurate determination of the daily spawning fraction bears major uncertainties, different scenarios were tested for this parameter. Least deviation compared to the other assessment methods was obtained when using a daily female spawning fraction of 24%, which corresponds well to values described in literature. The applicability of the DEPM to Baltic sprat was clearly demonstrated. Thus, it can serve as valuable tool for the estimation of Baltic sprat stock sizes independent of data obtained from commercial fisheries.
    Type: Article , PeerReviewed
    Format: text
    Format: text
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  • 10
    Publication Date: 2019-02-12
    Type: Dataset
    Format: text/tab-separated-values, 1274 data points
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