Decreasing δ13C and δ15N values in four coastal species at different trophic levels indicate a fundamental food-web shift in the southern North and Baltic Seas between 1988 and 2016

  • Anna-Marie Corman
  • Philipp SchwemmerEmail author
  • Moritz Mercker
  • Harald Asmus
  • Heinz Rüdel
  • Roland Klein
  • Markus Boner
  • Sabine Hofem
  • Jan Koschorreck
  • Stefan Garthe


Marine ecosystems are exposed to increasing human pressures and climatic change worldwide. It has therefore become essential to describe ecosystem statuses with respect to multinational protection schemes, often necessitating long-term monitoring programmes. Changes in the food-web structure, which can be monitored via stable isotope measurements, represent an important descriptor of the status of marine ecosystems. We investigated long-term changes (29 years) in isotopic values (δ13C and δ15N) in four indicative organisms at different trophic levels in the southern North and Baltic Seas: bladderwrack (Fucus vesiculosus), blue mussel (Mytilus ssp.), eelpout (Zoarces viviparus), and herring gull (Larus argentatus). Time series analyses using generalised additive models revealed largely consistent declines in δ13C and δ15N throughout all trophic levels of the coastal food web at all study sites, indicating a clear change in these coastal regions from 1988 to 2016. There were no clear long-term patterns in egg biometrics for herring gulls, except for a consistent increase in eggshell thickness. The declines in stable isotope values were in line with the results of previous long-term studies of single higher-trophic-level species, which suggested that the noted changes were mainly caused by altered foraging patterns of the studied species. The current results demonstrate that declines in δ13C and δ15N have occurred throughout the whole food web, not just in particular species. We discuss the possible reasons for the decrease in stable isotope values, including decreasing eutrophication and an increase in terrestrial carbon sources.


Fucus vesiculosus Larus argentatus Mytilus ssp. Stable isotope Time series analysis Zoarces viviparus 



S. Furness provided language support.

Funding information

This study was funded by the German Federal Environmental Agency (UBA).

Supplementary material

10661_2018_6827_MOESM1_ESM.docx (29 kb)
ESM 1 (DOCX 28 kb)


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Copyright information

© Springer International Publishing AG, part of Springer Nature 2018

Authors and Affiliations

  • Anna-Marie Corman
    • 1
  • Philipp Schwemmer
    • 1
    Email author
  • Moritz Mercker
    • 2
  • Harald Asmus
    • 3
  • Heinz Rüdel
    • 4
  • Roland Klein
    • 5
  • Markus Boner
    • 6
  • Sabine Hofem
    • 6
  • Jan Koschorreck
    • 7
  • Stefan Garthe
    • 1
  1. 1.Research & Technology Centre (FTZ)Kiel UniversityBüsumGermany
  2. 2.BIONUM Büro für BiostatistikHamburgGermany
  3. 3.Alfred Wegener InstituteList/SyltGermany
  4. 4.Fraunhofer Institute for Molecular Biology and Applied Ecology IMESchmallenbergGermany
  5. 5.Insitute of BiogeographyUniversity of TrierTrierGermany
  6. 6.Agroisolab GmbHJülichGermany
  7. 7.Federal Environmental AgencyBerlinGermany

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