| Summary: | The functional and physiological responses of the boreo-arctic species Semibalanus balanoides and the warmer-water Elminius modestus were investigated under current and future pH and temperature treatments. Metabolic rates were measured after 30 d exposure to determine how the two species cope physiologically under the combined stress of ocean warming and acidification. Survival and growth rate were measured over the 30 d exposure to highlight any energetic costs of metabolic maintenance. The survivorship data were then ran through an age-structured population model, to predict the future impact of climate change on the recruitment of local S. balanoides and E. modestus populations. The study found that the non-native E. modestus can maintain its metabolic processes by diverting energy from growth in order to survive. However, the native species S. balanoides finds its aerobic scope significantly reduced at pH 7.7, as they cannot divert any more energy from growth, leading to mortality. The model supports this, demonstrating that under chronic pH and temperature stress, E. modestus’ recruitment will be largely unaffected, whereas S. balanoides recruitment is substantially reduced with temperature leading to extirpation by the year 2055.
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