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Open Access Highly Accessed Research article

Importance of plasticity and local adaptation for coping with changing salinity in coastal areas: a test case with barnacles in the Baltic Sea

Anna-Lisa Wrange1*, Carl André1, Torbjörn Lundh2, Ulrika Lind3, Anders Blomberg3, Per J Jonsson1 and Jon N Havenhand1

Author Affiliations

1 Department of Biological and Environmental Sciences-Tjärnö, University of Gothenburg, S-45296 Strömstad, Sweden

2 Mathematical Sciences, Chalmers University of Technology and Mathematical Sciences, University of Gothenburg, Gothenburg, Sweden

3 Department of Chemistry and Molecular Biology, University of Gothenburg, Gothenburg, Sweden

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BMC Evolutionary Biology 2014, 14:156  doi:10.1186/1471-2148-14-156

Published: 19 July 2014

Abstract

Background

Salinity plays an important role in shaping coastal marine communities. Near-future climate predictions indicate that salinity will decrease in many shallow coastal areas due to increased precipitation; however, few studies have addressed this issue. The ability of ecosystems to cope with future changes will depend on species’ capacities to acclimatise or adapt to new environmental conditions. Here, we investigated the effects of a strong salinity gradient (the Baltic Sea system – Baltic, Kattegat, Skagerrak) on plasticity and adaptations in the euryhaline barnacle Balanus improvisus. We used a common-garden approach, where multiple batches of newly settled barnacles from each of three different geographical areas along the Skagerrak-Baltic salinity gradient were exposed to corresponding native salinities (6, 15 and 30 PSU), and phenotypic traits including mortality, growth, shell strength, condition index and reproductive maturity were recorded.

Results

We found that B. improvisus was highly euryhaline, but had highest growth and reproductive maturity at intermediate salinities. We also found that low salinity had negative effects on other fitness-related traits including initial growth and shell strength, although mortality was also lowest in low salinity. Overall, differences between populations in most measured traits were weak, indicating little local adaptation to salinity. Nonetheless, we observed some population-specific responses – notably that populations from high salinity grew stronger shells in their native salinity compared to the other populations, possibly indicating adaptation to differences in local predation pressure.

Conclusions

Our study shows that B. improvisus is an example of a true brackish-water species, and that plastic responses are more likely than evolutionary tracking in coping with future changes in coastal salinity.

Keywords:
Evolutionary change; Phenotypic plasticity; Baltic Sea; Crustacea; Common-garden experiment; Balanus (Amphibalanus) improvisus; Gompertz growth model