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  • Elsevier  (2)
  • Schweizerbart  (2)
  • Nature Publishing Group  (1)
  • 1
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    Plankton responses to ocean acidification: The role of nutrient limitation (2018)
    Elsevier
    In:  Progress in Oceanography, 165 . pp. 11-18.
    Details
    Publication Date: 2021-02-08
    Description: Highlights: • Ocean acidification increases phytoplankton standing stock. • This increase is more pronounced in smaller-sized taxa. • Primary consumers reac differently depending on nutrient availability. • Bacteria and micro-heterotrophs benefited under limiting conditions. • In general, heterotrophs are negatively affected at nutrient replete periods. Abstract: In situ mesocosm experiments on the effect of ocean acidification (OA) are an important tool for investigating potential OA-induced changes in natural plankton communities. In this study we combined results from various in-situ mesocosm studies in two different ocean regions (Arctic and temperate waters) to reveal general patterns of plankton community shifts in response to OA and how these changes are modulated by inorganic nutrient availability. Overall, simulated OA caused an increase in phytoplankton standing stock, which was more pronounced in smaller-sized taxa. This effect on primary producers was channelled differently into heterotroph primary consumers depending on the inorganic nutrient availability. Under limiting conditions, bacteria and micro-heterotrophs benefited with inconsistent responses of larger heterotrophs. During nutrient replete periods, heterotrophs were in general negatively affected, although there was an increase of some mesozooplankton developmental stages (i.e. copepodites). We hypothesize that changes in phytoplankton size distribution and community composition could be responsible for these food web responses.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/j.pocean.2018.04.006
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 2
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    Dietary and seasonal variability in trophic relations at the base of the North Sea pelagic food web revealed by stable isotope and fatty acid analysis (2018)
    Elsevier
    In:  Journal of Sea Research, 141 . pp. 61-70.
    Details
    Publication Date: 2021-02-08
    Description: A two-dimensional biomarker approach including fatty acids and stable isotopes of seston and copepods was applied to examine how the variability at the base of the food web affects trophic interactions between primary producers and copepod consumers over a sampling period of two years. We investigated how the composition of the seston affected feeding behaviour by analysing the fatty acid and stable isotope signals of the copepods Calanus helgolandicus, Acartia spp., Centropages spp. and Temora longicornis at Helgoland Roads, North Sea. Our results indicate that the relative contributions of autotrophic and heterotrophic fractions in the seston determined the stable isotope signal of the seston and hence the δ15N of copepods. Our findings show that the combination of stable isotope and fatty acid analyses provides an ideal tool to address the complexity of trophic relations in planktonic food-webs and to define relative trophic position and feeding preferences of e.g. copepods. Defining accurate baselines from bulk seston samples containing a mixture of auto- and heterotroph protist communities still remains a challenge when defining lower food-web dynamics in natural plankton communities
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/j.seares.2018.08.004
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 3
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    In situ experimental evidence of the fate of a phytodetritus pulse at the abyssal sea floor (2003)
    Nature Publishing Group
    In:  Nature, 424 . pp. 763-765.
    Details
    Publication Date: 2017-03-07
    Description: More than 50% of the Earth' s surface is sea floor below 3,000 m of water. Most of this major reservoir in the global carbon cycle and final repository for anthropogenic wastes is characterized by severe food limitation. Phytodetritus is the major food source for abyssal benthic communities, and a large fraction of the annual food load can arrive in pulses within a few days1, 2. Owing to logistical constraints, the available data concerning the fate of such a pulse are scattered3, 4 and often contradictory5, 6, 7, 8, 9, 10, hampering global carbon modelling and anthropogenic impact assessments. We quantified (over a period of 2.5 to 23 days) the response of an abyssal benthic community to a phytodetritus pulse, on the basis of 11 in situ experiments. Here we report that, in contrast to previous hypotheses5, 6, 7, 8, 9, 10, 11, the sediment community oxygen consumption doubled immediately, and that macrofauna were very important for initial carbon degradation. The retarded response of bacteria and Foraminifera, the restriction of microbial carbon degradation to the sediment surface, and the low total carbon turnover distinguish abyssal from continental-slope ‘deep-sea’ sediments.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1038/nature01799
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 4
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    Seasonality and diversity patterns of microphytobenthos in a mesotrophic lake (2006)
    Schweizerbart
    In:  Archiv für Hydrobiologie, 167 (1-4). pp. 447-465.
    Details
    Publication Date: 2019-02-27
    Description: Investigations on the littoral microphytobenthos populations of lakes are very rare. Based on new sampling techniques, allowing the undisturbed sampling of sublittoral sediments, we present information on limnic microphytobenthos populations of the Schöhsee in Northern Germany (10° 26′ E, 54° 13′ N). Investigations on microphytobenthic communities at a sandy and a muddy site provided new insights into the community structure and seasonal variations of limnic benthic microalgae. The microphytobenthos was characterised by low chlorophyll-a contents (0.16 μg cm−2 to 0.74 μg cm−2) and low cell numbers (25 cells cm−2 to 266 cells cm−2). Both sites showed similar patterns in terms of algal biomass and seasonality; no site-specific characteristics were observed. The productivity of the sediment microflora in the Schöhsee was low and most likely related to the mesotrophic lake character and to reduced light conditions in the near-shore sublittoral. The algal communities at both sites showed high diversity, distinct seasonality and succession patterns with shifts in community composition in spring, summer and autumn. The community was dominated by Fragilaria spp., Navicula spp., Nitzschia spp., and Stauroneis spp. in spring shifting to a Stauroneis spp.-dominated community in summer. In autumn the populations were dominated by Navicula spp., Nitzschia spp., and Stauroneis spp. Overall, the taxonomic composition showed a dominance of prostrate diatoms, whereas cyanobacteria, green algae and erect diatoms occurred rarely and with low abundance. Thus, the sediment microflora of the Schöhsee can be characterized as a flat, two-dimensional community.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1127/0003-9136/2006/0167-0447
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 5
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    Spectral fingerprinting for specific algal groups on sediments in situ: a new sensor (2006)
    Schweizerbart
    In:  Archiv für Hydrobiologie, 167 (1-4). pp. 575-592.
    Details
    Publication Date: 2019-07-03
    Description: Currently it is still extremely difficult to adequately sample populations of microalgae on sediments for large-scale biomass determination. We have now devised a prototype of a new benthic sensor (BenthoFluor) for the quantitative and qualitative assessment of microphytobenthos populations in situ. This sensor enables a high spatial and temporal resolution and a rapid evaluation of the community structure and distribution. These determinations are based on the concept that five spectral excitation ranges can be used to differentiate groups of microalgae, in situ, within a few seconds. In addition, because sediments contain a lot of yellow substances, which can affect the fluorescence and optical differentiation of the algae, the device was equipped with a UV-LED for yellow substances correction. The device was calibrated against HPLC with cultures and tested in the field. Our real-time approach can be used to monitor algal assemblage composition on sediments and is an ideal tool for investigations on the large-scale spatial and temporal variation of algal populations in sediments. Apart from the differentiation of algal populations, the BenthoFluor allows instantaneous monitoring of the chlorophyll concentrations and determination of which algae are responsible for this on the uppermost surface of sediments in the field and in experimental set-ups.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1127/0003-9136/2006/0167-0575
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    OceanRep: Article in a Scientific Journal - peer-reviewed
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