Sea freshening may drive the ecological impacts of emerging and existing invasive non-native species

James W.E. Dickey*, Ross N. Cuthbert, Gregor T. Steffen, Jaimie T.A. Dick, Elizabeta Briski

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)
12 Downloads (Pure)


Aim: The spread of invasive non-native species (INNS) will pose major threats to global biodiversity over the coming decades. However, predicting how key effects of climate change will influence the abilities of INNS to establish and exert ecological impact is a major challenge. One overlooked aspect of global change is the expected freshening of certain marine systems, which may interact with INNS and lead to drastic effects on community structure and stability. Location: Baltic Sea, Europe. Methods: Here, using three predatory amphipod crustaceans, we experimentally assessed how salinity reduction may affect the impacts of the emerging INNS, Pontogammarus maeoticus, relative to an existing INNS, Gammarus tigrinus and a trophically analogous native, Gammarus salinus. We quantified per capita impacts of the three species via the comparative functional response method (prey consumption over a range of prey densities) under a predicted seawater freshening scenario. We then combined amphipod functional responses with their life history traits to compare population-level relative impact potential (RIP) on prey of the three amphipod species across salinities. Results: Freshening substantially altered the predicted relative ecological impacts of both the INNS compared with the native. First, the functional responses of invasive P. maeoticus and G. tigrinus increased under freshening, while that of the native G. salinus decreased. Second, RIP became consistently higher for both the INNS compared to the native with increased freshening. Main conclusions: Our methods thus reveal potential for climate change via seawater freshening to drive large shifts in dominance and ecological impacts of INNS compared with natives. With the number of INNS introductions unlikely to saturate in the near future, we highlight the need to assess the impacts of potential future INNS, alongside established non-natives and native species, in combination with abiotic changes associated with climate change.

Original languageEnglish
Pages (from-to)144-156
JournalDiversity and Distributions
Issue number1
Early online date16 Nov 2020
Publication statusEarly online date - 16 Nov 2020

Bibliographical note

Funding Information:
JWED, JTAD and EB conceived the study, with JWED conducting the experiments, with assistance from GTS. JWED and RNC conducted statistical analyses, with JWED, RNC and JTAD preparing the initial manuscript. All authors provided valuable input to the development of the final manuscript and have given approval for publication. JWED was supported by Inland Fisheries Ireland (IFI), RNC by the Alexander von Humboldt Foundation and EB by the Alexander von Humboldt Sofja Kovalevskaja Award.

Publisher Copyright:
© 2020 The Authors. Diversity and Distributions published by John Wiley & Sons Ltd

Copyright 2020 Elsevier B.V., All rights reserved.


  • functional response
  • invasive non-native species
  • life history traits
  • Pontogammarus maeoticus
  • relative impact potential
  • sea freshening

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics


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