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  • Elsevier  (3)
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  • 1
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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
  • 2
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    Spatial distribution of microplastics in sediments and surface waters of the southern North Sea (2019)
    Elsevier
    In:  Environmental Pollution, 252 . pp. 1719-1729.
    Details
    Publication Date: 2021-01-08
    Description: Microplastic pollution within the marine environment is of pressing concern globally. Accordingly, spatial monitoring of microplastic concentrations, composition and size distribution may help to identify sources and entry pathways, and hence allow initiating focused mitigation. Spatial distribution patterns of microplastics were investigated in two compartments of the southern North Sea by collecting sublittoral sediment and surface water samples from 24 stations. Large microplastics (500−5000 μm) were detected visually and identified using attenuated total reflection (ATR) Fourier transform infrared (FTIR) spectroscopy. The remaining sample was digested enzymatically, concentrated onto filters and analyzed for small microplastics (11−500 μm) using Focal Plane Array (FPA) FTIR imaging. Microplastics were detected in all samples with concentrations ranging between 2.8 and 1188.8 particles kg−1 for sediments and 0.1–245.4 particles m−3 for surface waters. On average 98% of microplastics were 〈100 μm in sediments and 86% in surface waters. The most prevalent polymer types in both compartments were polypropylene, acrylates/polyurethane/varnish, and polyamide. However, polymer composition differed significantly between sediment and surface water samples as well as between the Frisian Islands and the English Channel sites. These results show that microplastics are not evenly distributed, in neither location nor size, which is illuminating regarding the development of monitoring protocols.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/j.envpol.2019.06.093
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 3
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    Facilitation of intraguild prey by its intraguild predator in a three-species Lotka–Volterra model (2014)
    Elsevier
    In:  EPIC3Theoretical Population Biology, Elsevier, 92, pp. 55-61, ISSN: 0040-5809
    Details
    Publication Date: 2018-02-16
    Description: Explaining the coexistence of multiple species in the competition and predation theatre has proven a great challenge. Traditional intraguild predation (IGP) models have only relatively small regions of stable coexistence of all species. Here, we investigate potential additional mechanisms that extend these regions of stable coexistence. We used a 3-species Lotka–Volterra system to which we added an interaction term to model a unidirectional facilitative relationship between the two predators in the IGP. In this modelling study the IG predator was able to precondition a part of the common resource by an instantaneous manipulation, which resulted in the immobilization of the resource species. This mechanism of immobilization facilitated the resource uptake by the IG prey and thus increased its growth rates even in the presence of the common predator. The facilitative relationship of the IG prey by the IG predator produced a stable coexistence of both predators even though the IG prey was an inferior competitor for a common resource, which cannot be attained with the traditional IGP models. Furthermore, our model predicted a 3-species stable coexistence even at high enrichment where no coexistence was found in the basic IGP model. Thus, we showed that diversity of resource traits could significantly alter emergent community patterns via shifts in exploitative competition of IGP-related predators. The described mechanism could potentially lead to a higher efficiency in exploitation of common resources and thus promote higher diversity in a real community.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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