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Characterizing niche differentiation among marine consumers with amino acid δ13C fingerprinting
  • Thomas Larsen,
  • Thomas Hansen,
  • Jan Dierking
Thomas Larsen
Max Planck Institute for the Science of Human History
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Thomas Hansen
GEOMAR Helmholtz Centre for Ocean Research Kiel
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Jan Dierking
GEOMAR Helmholtz Centre for Ocean Research Kiel
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Abstract

Marine food webs are highly compartmentalized and characterizing the trophic niches among consumers is important for predicting how impact from human activities affect the structuring and functioning of marine food webs. Biomarkers such as bulk stable isotopes have proven to be powerful tools to elucidate trophic niches, but they may lack in resolution, particularly when spatio-temporal variability in a system is high. To close this gap, we investigated whether carbon isotope (δ13C) patterns of essential amino acids (EAAs), also termed δ13AA fingerprints, can characterize niche differentiation in a highly dynamic marine system. We tested the ability of δ13AA fingerprints to differentiate trophic niches among six functional groups and ten individual species in the Baltic Sea. We also tested whether fingerprints of the common zooplanktivorous fishes, herring and sprat, differ among four Baltic Sea regions with different biochemical conditions and phytoplankton assemblages. Additionally, we investigated how these results compared to bulk C and N isotope data for the same sample set. We found significantly different δ13AA fingerprints among all six functional groups. Species differentiation was in comparison less distinct, due to partial convergence of the species’ fingerprints within functional groups. Herring and sprat displayed region specific δ13AA fingerprints indicating that this approach could be used as a migratory marker. Bulk isotope data had a lower power to differentiate between trophic niches, but may provide more easily interpretable information about relative trophic position than the fingerprints. We conclude that δ13AA fingerprinting has a strong potential to advance our understanding of ecological niches, and trophic linkages from producers to higher trophic levels in dynamic marine systems. Given how management practices of marine resources and habitats are reshaping the structure and function of marine food webs, implementing new and powerful tracer methods are urgently needed to improve the knowledge base for policy makers.

Peer review status:ACCEPTED

26 Feb 2020Submitted to Ecology and Evolution
28 Feb 2020Submission Checks Completed
28 Feb 2020Assigned to Editor
03 Mar 2020Reviewer(s) Assigned
25 Mar 2020Review(s) Completed, Editorial Evaluation Pending
30 Mar 2020Editorial Decision: Revise Minor
24 May 20201st Revision Received
26 May 2020Submission Checks Completed
26 May 2020Assigned to Editor
26 May 2020Review(s) Completed, Editorial Evaluation Pending
02 Jun 2020Editorial Decision: Accept