Genetic diversity influences tolerance to climate change factors warming and acidification of Fucus vesiculosus L. (Phaeophyceae)

Climate change exposes brown algal Fucus vesiculosus populations to increasing temperature and pCO2, which may threaten individuals, in particular the early life-stages. Genetic diversity of F. vesiculosus populations is low in the Baltic compared to Atlantic populations. This might jeopardise their potential for adaptation to environmental changes. Here, we report on the responses of early life-stage F. vesiculosus to warming and acidification in a near-natural scenario maintaining natural and seasonal variation (Spring 2013 – 2014) of the Kiel Fjord in the Baltic Sea, Germany (54°27 ´N, 10°11 ´W). We assessed how stress sensitivity differed among sibling groups and how genetic diversity of germling populations affected their stress tolerance. Warming increased growth rates of Fucus germlings in spring and in early summer, but led to higher photoinhibition in spring and decreased their survival in summer. Acidification increased germlings’ growth in summer but otherwise showed much weaker effects than warming. During the colder seasons (autumn and winter), growth was slow while survival was high compared to spring and summer, all at ambient temperatures. A pronounced variation in stress response among genetically different sibling groups suggests a genotypic basis for this variation and thus a potential for adaptation for F. vesiculosus populations to future conditions. Corroborating this, survival in response to warming in populations with higher diversity was better than the mean survival of single sibling groups. We conclude that impacts on early life-stages depend on the combination of stressors and season, and that genetic variation is crucial for the tolerance to climate change stress. 

Anthropogenic global change exposes marine populations, inter alia, to increases in temperatures and pCO2 concentrations (IPCC 2013). The magnitude of these changes varies among geographic regions; in the Baltic Sea, warming and acidification are expected to increase up to 3-6 °C and to 1000 µatm respectively, by 2100 (Graham et al. 2008; Elken et al. 2015). 

Statistical Analysis

Growth rates (% d-1) and survival (%) values were analysed in a repeated-measures ANOVA for each cohort, where temperature, CO2 and time period were fixed factors and sibling group a random factor. Survival % values were arcsin transformed. The factor time period defined the repeated measures. Due to enhanced mortality in the high temperature treatments during late summer, for this period only the factor CO2 was analysed in a mixed model ANOVA with the fixed factor CO2 and the random factor sibling group.