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  • 1
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    Genotype sorting of two stably coexisting phytoplankton species in response to nutrient fluctuations (2020)
    In:  (Master thesis), Christian-Albrechts-Universität Kiel, Kiel, Germany, 44 pp
    Details
    Publication Date: 2020-07-21
    Keywords: Course of study: MSc Biological Oceanography
    Type: Thesis , NonPeerReviewed
    Format: text
    Location Call Number Limitation Availability
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    OceanRep: Thesis - not published by a publisher
  • 2
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    Season affects strength and direction of the interactive impacts of ocean warming and biotic stress in a coastal seaweed ecosystem (2020)
    ASLO (Association for the Sciences of Limnology and Oceanography) | Wiley
    Details
    Publication Date: 2023-02-08
    Description: The plea for using more “realistic,” community‐level, investigations to assess the ecological impacts of global change has recently intensified. Such experiments are typically more complex, longer, more expensive, and harder to interpret than simple organism‐level benchtop experiments. Are they worth the extra effort? Using outdoor mesocosms, we investigated the effects of ocean warming (OW) and acidification (OA), their combination (OAW), and their natural fluctuations on coastal communities of the western Baltic Sea during all four seasons. These communities are dominated by the perennial and canopy‐forming macrophyte Fucus vesiculosus—an important ecosystem engineer Baltic‐wide. We, additionally, assessed the direct response of organisms to temperature and pH in benchtop experiments, and examined how well organism‐level responses can predict community‐level responses to the dominant driver, OW. OW affected the mesocosm communities substantially stronger than acidification. OW provoked structural and functional shifts in the community that differed in strength and direction among seasons. The organism‐level response to OW matched well the community‐level response of a given species only under warm and cold thermal stress, that is, in summer and winter. In other seasons, shifts in biotic interactions masked the direct OW effects. The combination of direct OW effects and OW‐driven shifts of biotic interactions is likely to jeopardize the future of the habitat‐forming macroalga F. vesiculosus in the Baltic Sea. Furthermore, we conclude that seasonal mesocosm experiments are essential for our understanding of global change impact because they take into account the important fluctuations of abiotic and biotic pressures.
    Type: Article , PeerReviewed
    Format: text
    Location Call Number Limitation Availability
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 3
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    Maintenance of Intraspecific Diversity in Response to Species Competition and Nutrient Fluctuations (2022)
    MDPI
    Details
    Publication Date: 2024-02-07
    Description: Intraspecific diversity is a substantial part of biodiversity, yet little is known about its maintenance. Understanding mechanisms of intraspecific diversity shifts provides realistic detail about how phytoplankton communities evolve to new environmental conditions, a process especially important in times of climate change. Here, we aimed to identify factors that maintain genotype diversity and link the observed diversity change to measured phytoplankton morpho-functional traits Vmax and cell size of the species and genotypes. In an experimental setup, the two phytoplankton species Emiliania huxleyi and Chaetoceros affinis, each consisting of nine genotypes, were cultivated separately and together under different fluctuation and nutrient regimes. Their genotype composition was assessed after 49 and 91 days, and Shannon’s diversity index was calculated on the genotype level. We found that a higher intraspecific diversity can be maintained in the presence of a competitor, provided it has a substantial proportion to total biovolume. Both fluctuation and nutrient regime showed species-specific effects and especially structured genotype sorting of C. affinis. While we could relate species sorting with the measured traits, genotype diversity shifts could only be partly explained. The observed context dependency of genotype maintenance suggests that the evolutionary potential could be better understood, if studied in more natural settings including fluctuations and competition.
    Type: Article , PeerReviewed
    Format: text
    Location Call Number Limitation Availability
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 4
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    The circadian clock in Calanus finmarchicus – Relation to diel vertical migration (2016)
    In:  EPIC330 p.
    Details
    Publication Date: 2017-01-20
    Description: The marine copepod Calanus finmarchicus is an important key species in the Northern Atlantic due to his abundance and his position in the food web. It performs diel vertical migration (DVM), staying in deeper water layers during the day and ascending to the surface in the night. The exact trigger for the DVM is not known yet, but light seems to have an important influence on the position of C. finmarchicus. Some studies suggest an involvement of an endogenous rhythm, which controls the vertical position of C. finmarchicus throughout the day. In this work the DVM and respiration rate of C. finmarchicus were examined under natural simulated light conditions to identify possible circadian rhythms. Therefore, two laboratory experiments were performed with the CV-stage of C. finmarchicus under light/dark (LD) and constant darkness (DD) conditions. The position of C. finmarchicus in the DVM experiment showed a clear diurnal rhythm, with significant differences between day and night. The rhythm persisted in weaker form during constant darkness, indicating that an endogenous circadian clock is involved in the DVM. The results from the respiration experiment supported the assumption, revealing a rhythmicity in the oxygen uptake that also persisted under constant darkness. The light seemed to have in both experiments the role of a Zeitgeber that synchronises the circadian clock. For a final identification of the assumed clock a genetic analysis is necessary. However the experiments showed evidence that the DVM and the metabolic activity of C. finmarchicus are controlled by a circadian clock.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Thesis , notRev
    Format: application/pdf
    Location Call Number Limitation Availability
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    PAPER (OA)
  • 5
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    Experiment on impacts of ocean warming and biotic stress in a coastal seaweed ecosystem (2019)
    PANGAEA
    In:  Supplement to: Wahl, Martin; Werner, Franziska Julie; Buchholz, Björn; Raddatz, Stefanie; Graiff, Angelika; Matthiessen, Birte; Karsten, Ulf; Hiebenthal, Claas; Hamer, Jorin; Ito, Maysa; Gülzow, Elisa; Rilov, Gil; Guy-Haim, Tamar (2020): Season affects strength and direction of the interactive impacts of ocean warming and biotic stress in a coastal seaweed ecosystem. Limnology and Oceanography, 65(4), 807-827, https://doi.org/10.1002/lno.11350
    Details
    Publication Date: 2023-06-13
    Description: The plea for using more “realistic,” community‐level, investigations to assess the ecological impacts of global change has recently intensified. Such experiments are typically more complex, longer, more expensive, and harder to interpret than simple organism‐level benchtop experiments. Are they worth the extra effort? Using outdoor mesocosms, we investigated the effects of ocean warming (OW) and acidification (OA), their combination (OAW), and their natural fluctuations on coastal communities of the western Baltic Sea during all four seasons. These communities are dominated by the perennial and canopy‐forming macrophyte Fucus vesiculosus—an important ecosystem engineer Baltic‐wide. We, additionally, assessed the direct response of organisms to temperature and pH in benchtop experiments, and examined how well organism‐level responses can predict community‐level responses to the dominant driver, OW. OW affected the mesocosm communities substantially stronger than acidification. OW provoked structural and functional shifts in the community that differed in strength and direction among seasons. The organism‐level response to OW matched well the community‐level response of a given species only under warm and cold thermal stress, that is, in summer and winter. In other seasons, shifts in biotic interactions masked the direct OW effects. The combination of direct OW effects and OW‐driven shifts of biotic interactions is likely to jeopardize the future of the habitat‐forming macroalga F. vesiculosus in the Baltic Sea. Furthermore, we conclude that seasonal mesocosm experiments are essential for our understanding of global change impact because they take into account the important fluctuations of abiotic and biotic pressures.
    Keywords: BIOACID; Biological Impacts of Ocean Acidification
    Type: Dataset
    Format: application/zip, 13 datasets
    Location Call Number Limitation Availability
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    DATA PANGAEA
  • 6
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    Seasonal mesocosm community experiments with warming and acidification treatments in Kiel Outdoor Benthocosms (2019)
    PANGAEA
    Details
    Publication Date: 2023-06-13
    Description: Seasonal mesocosm community experiments: Four successive runs of ca 10 weeks in 12 outdoor mesocosms (ca 1400 L) with flow-through and a orthogonally crossed warming ("ambient" temperature vs warming by 5°C = "OW") and acidification ("ambient" CO2 vs increase by 700 µatm = "OA" and combined warming and acidification = "OWA" ) treatment. The tanks were started with the same community composition (Fucus vesiculosus; mesograzers Idotea spp., Gammarus spp., Littorina littorea; seastar Asteria rubens, filter feeders Balanus improvisus, Mytilus edulis); details in Wahl et al. 2015. Seasonal responses to the various treatments were (a) mean daily relative Fucus length growth of thallus tips (%), (b) relative Mytilus shell length growth (%), (c) mean daily relative growth of Balanus basal plate, (d-f) the relative population size changes of the three mesograzer species expressed as the log of final divided by initial abundances, (g) the relative survival of Asterias (%).
    Keywords: Abundance change; Asterias rubens, survival; Balanus improvisus, plate, growth rate; Experiment; Experimental treatment; Fucus vesiculosus, length, growth rate; Kiel-Outdoor-Benthocosms; KOB; MESO; Mesocosm experiment; Mytilus edulis, shell length, growth rate; Replicate; Season
    Type: Dataset
    Format: text/tab-separated-values, 528 data points
    Location Call Number Limitation Availability
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    DATA PANGAEA
  • 7
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    Bench-top experiment on response of Fucus photosynthesis (oxygen production) to light intensity (2019)
    PANGAEA
    Details
    Publication Date: 2024-01-26
    Description: Response of Fucus photosynthesis (oxygen production) to light intensity (PI-curve) assessed at 19.5°C and at 2 pH levels (8.2 and 7.75) for an irradiation range between 0 and 800 µmol cm-2 sec-1. The oxygen gradient across the diffusuve boundary layer was measured using microsensors and used to calculate the oxygen flux and deduce the oxygen production (nmol cm-2 sec-1).
    Keywords: Bench-top-experiment; Diffusion coefficient; Diffusive boundary layer; EXP; Experiment; Oxygen; Oxygen, flux, diffusive; Radiation, photosynthetically active; Species; Treatment; Treatment: temperature
    Type: Dataset
    Format: text/tab-separated-values, 156 data points
    Location Call Number Limitation Availability
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    DATA PANGAEA
  • 8
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    Bench-top experiment on Fucus responses to temperatures in thermobaths (2019)
    PANGAEA
    Details
    Publication Date: 2024-01-26
    Description: Fucus gross (GPP) and net (NPP) primary production, respiration (R) and metabolic balance (GPP/2R) responses to temperature in thermobaths: Temperature levels 5, 10, 15, 20, 22, 25°C; period Oct & Nov 2016; replication was 3.
    Keywords: Bench-top-experiment; DATE/TIME; EXP; Experiment; Experiment week; Gross primary production/Respiration rate ratio; Gross primary production of oxygen; Net primary production of oxygen; Replicate; Respiration rate, oxygen; Species; Treatment: temperature
    Type: Dataset
    Format: text/tab-separated-values, 423 data points
    Location Call Number Limitation Availability
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    DATA PANGAEA
  • 9
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    Bench-top experiment on Fucus oxygen production under different levels of acidification (2019)
    PANGAEA
    Details
    Publication Date: 2024-01-26
    Description: Fucus oxygen production (NPP) under different levels of acidification: pCO2 400, 900, 1400, 2400, 3900 µatm assessed by incubation; period Apr 2015; replication 6.
    Keywords: Bench-top-experiment; EXP; Experiment; Net primary production of oxygen; Replicate; Species; Treatment: pH
    Type: Dataset
    Format: text/tab-separated-values, 170 data points
    Location Call Number Limitation Availability
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    DATA PANGAEA
  • 10
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    Bench-top experiment on Fucus reproduction in response to temperature (2019)
    PANGAEA
    Details
    Publication Date: 2024-01-26
    Description: Fucus reproduction in response to temperature assessed as % change in conceptacles over the experimental duration of 5 weeks: Temperature levels 0, 5,10,15,20, 25°C; period Apr 2013, replucation 4; details and data in Graiff et al 2017.
    Keywords: Bench-top-experiment; Change; EXP; Experiment; Species; Treatment: temperature
    Type: Dataset
    Format: text/tab-separated-values, 94 data points
    Location Call Number Limitation Availability
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    DATA PANGAEA
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