Tracing carbon flow and trophic structure of a coastal Arctic marine food web using highly branched isoprenoids and carbon, nitrogen and sulfur stable isotopes

Rémi Amiraux, C.j. Mundy, Marie Pierrejean, Andrea Niemi, Kevin J. Hedges, Thomas A. Brown, Jens K. Ehn, Kyle H. Elliott, Steven H. Ferguson, Aaron T. Fisk, Grant Gilchrist, Les N. Harris, Katrin Iken, Kevin B. Jacobs, Kelsey F. Johnson, Z.a. Kuzyk, Audrey Limoges, Tracey N. Loewen, Oliver P. Love, Cory J.d. MatthewsWesley R. Ogloff, Bruno Rosenberg, Janne E. Søreide, Cortney A. Watt, David J. Yurkowski

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Abstract

Climate-driven alterations of the marine environment are most rapid in Arctic and subarctic regions, including Hudson Bay in northern Canada, where declining sea ice, warming surface waters and ocean acidification are occurring at alarming rates. These changes are altering primary production patterns that will ultimately cascade up through the food web. Here, we investigated (i) the vertical trophic structure of the Southampton Island marine ecosystem in northern Hudson Bay, (ii) the contribution of benthic and pelagic-derived prey to the higher trophic level species, and (iii) the relative contribution of ice algae and phytoplankton derived carbon in sustaining this ecosystem. For this purpose, we measured bulk stable carbon, nitrogen and sulfur isotope ratios as well as highly branched isoprenoids in samples belonging to 149 taxa, including invertebrates, fishes, seabirds and marine mammals. We found that the benthic invertebrates occupied 4 trophic levels and that the overall trophic system went up to an average trophic position of 4.8. The average δ34S signature of pelagic organisms indicated that they exploit both benthic and pelagic food sources, suggesting there are many interconnections between these compartments in this coastal area. The relatively high sympagic carbon dependence of Arctic marine mammals (53.3 ± 22.2 %) through their consumption of benthic invertebrate prey, confirms the important role of the benthic subweb for sustaining higher trophic level consumers in the coastal pelagic environment. Therefore, a potential decrease in the productivity of ice algae could lead to a profound alteration of the benthic food web and a cascading effect on this Arctic ecosystem
Original languageEnglish
Article number109938
Number of pages12
JournalEcological Indicators
Volume147
Early online date31 Jan 2023
DOIs
Publication statusPublished - 1 Mar 2023

Keywords

  • Subarctic
  • Hudson Bay
  • Southampton Island
  • Stable isotopes
  • HBIs
  • Carbon Flux
  • Trophic Interactions
  • Fishes
  • Invertebrates
  • Marine mammals

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