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Food source diversity, trophic plasticity, and omnivory enhance the stability of a shallow benthic food web from a high-Arctic fjord exposed to freshwater inputs

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  • Guillaume Bridier, Universite de Bretagne Occidentale
  • ,
  • Frédéric Olivier, Sorbonne Université
  • ,
  • Laurent Chauvaud, Universite de Bretagne Occidentale
  • ,
  • Mikael K. Sejr
  • Jacques Grall, Universite de Bretagne Occidentale

Under climate change, many Arctic coastal ecosystems receive increasing amounts of freshwater, with ecological consequences that remain poorly understood. In this study, we investigated how freshwater inputs may affect the small-scale structure of benthic food webs in a low-production high-Arctic fjord (Young Sound, NE Greenland). We seasonally sampled benthic invertebrates from two stations receiving contrasting freshwater inputs: an inner station exposed to turbid and nutrient-depleted freshwater flows and an outer station exposed to lower terrestrial influences. Benthic food web structure was described using a stable isotope approach (δ13C and δ15N), Bayesian models, and community-wide metrics. The results revealed the spatially and temporally homogeneous structure of the benthic food web, characterized by high trophic diversity (i.e., a wide community isotopic niche). Such temporal stability and spatial homogeneity mirrors the high degree of trophic plasticity and omnivory of benthic consumers that allows the maintenance of several carbon pathways through the food web despite different food availability. Furthermore, potential large inputs of shelf organic matter together with local benthic primary production (i.e., macroalgae and presumably microphytobenthos) may considerably increase the stability of the benthic food web by providing alternative food sources to locally runoff-impacted pelagic primary production. Future studies should assess beyond which threshold limit a larger increase in freshwater inputs might cancel out these stability factors and lead to marked changes in Arctic benthic ecosystems.

Original languageEnglish
JournalLimnology and Oceanography
Pages (from-to)S259-S272
Publication statusPublished - Jan 2021

Bibliographical note

Funding Information:
A big thanks to Egon Randa Frandsen, Jakob Thyrring, Mie Sichlau Winding, Carl Isaksen, Mel Murphy, Erwan Amice, and Jean‐Manuel Warnet for their contributions in the field, collecting samples for stable isotope analyses. We are greatly indebted to the MarineBasis progamme and the Zackenberg/Daneborg staff for their support in the field. Thanks to Jean‐Marie Munaron for his help on laboratory analyses. Friendly thanks to Jérôme Jourde, Michel Le Duff, Vincent Le Garrec, Gabin Droual, Carolin Uhlir, Anne‐Helene Tandberg, and Natalia Shunatova for their teaching on species identification. We are grateful to Loïc Michel and Nathan McTigue for their advice and assistance with Bayesian analyses. Warm thanks to Tarik Meziane for his comments on the manuscript. This work was a part of the PhD project of Guillaume Bridier and co‐funded by the “Allocation de Recherche Doctorale” from the Brittany Regional Council and the Université de Bretagne Occidentale/LIA BeBEST. Additional funding was provided by the Institut Polaire Français Paul‐Emile Victor (IPEV – PRIVARC project), the European H2020 INTAROS program, the Agence Nationale de la Recherche (ANR GAAP), the Fondation UBO (FAC 2018) and the Observatoire Marin de l'IUEM (UMS3113). Part of the data included in this manuscript was provided by the MarineBasis programme. We warmly thank the two anonymous reviewers for their extensive constructive comments which greatly improved this manuscript. This study is an international collaboration between the BeBEST International Laboratory (UBO, UQAR, CNRS, and MNHN) and the Aarhus University.

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© 2021 Association for the Sciences of Limnology and Oceanography

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