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Freshening increases the susceptibility to heat stress in intertidal mussels (Mytilus edulis) from the Arctic

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Temperatures in the Arctic are increasing at a faster pace than at lower latitudes resulting in range expansion of boreal species. In Greenland, the warming also drives accelerating melt of the Greenland Ice Sheet resulting in more meltwater entering Greenland fjords in summer. Our aim was to determine if increasing summer temperatures combined with lower salinity can induce the expression of stress-related proteins, for example, heat shock protein, in boreal intertidal mussels in Greenland, and whether low salinity reduces the upper thermal limit at which mortality occurs. We conducted a mortality experiment, using 12 different combinations of salinity and air temperature treatments during a simulated tidal regime, and quantified the change in mRNA levels of five stress-related genes (hsp24, hsp70, hsp90, sod and p38) in surviving mussels to discern the level of sublethal stress. Heat-induced mortality occurred in mussels exposed to an air temperature of 30°C and mortality was higher in treatments with lowered salinity (5 and 15‰), which confirms that low habitat salinity decreases the upper thermal limit of Mytilus edulis. The gene expression analysis supported the mortality results, with the highest gene expression found at combinations of high temperature and low salinity. Combined with seasonal measurements of intertidal temperatures in Greenland, we suggest heat stress occurs in low salinity intertidal area, and that further lowered salinity in coastal water due to increased run-off can make intertidal bivalves more susceptible to summer heat stress. This study thus provides an example of how different impacts of climate warming can work synergistically to stress marine organisms.

TidsskriftJournal of Animal Ecology
Sider (fra-til)1515-1524
Antal sider10
StatusUdgivet - jun. 2021

Bibliografisk note

Funding Information:
This study is a contribution to the ‘De‐icing Arctic Coasts’ project funded by DANCEA and ‘Face it’ funded by the EU H2020 Program (grant 869154). The authors thank Philippine Granger Joly de Boissel from the University of Prince Edward Island for sharing sequences used to design qPCR primers, and the Greenland Institute of Natural Resources for accommodation and fieldwork assistance. The travel to Greenland for M.B.N. and T.K.V. was supported by ‘William Demant Fonden’, ‘Familien Hede Nielsens Fond’ and ‘Selskabet for Arktisk Forskning og Teknologi (SAFT)’. J.T. was supported by the ‘The Independent Research Fund Denmark’ (case no. 7027‐00060B), the ‘Aage V. Jensens Fond’ and by a ‘Marie Sklodowska‐Curie Individual Fellowship (IF)’ under contract number 797387. J.G.S. acknowledge support from Aarhus Universitets Forskningsfond (Starting Grant: AUFF‐E‐2015‐FLS‐8‐72).

Publisher Copyright:
© 2021 The Authors. Journal of Animal Ecology published by John Wiley & Sons Ltd on behalf of British Ecological Society

Copyright 2021 Elsevier B.V., All rights reserved.

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