Between‐ and within‐population variations in thermal reaction norms of the coccolithophore Emiliania huxleyi

Abstract

Thermal reaction norms for growth rates of six Emiliania huxleyi isolates originating from the central Atlantic (Azores, Portugal) and five isolates from the coastal North Atlantic (Bergen, Norway) were assessed. We used the template mode of variation model to decompose variations in growth rates into modes of biological interest: vertical shift, horizontal shift, and generalist-specialist variation. In line with the actual habitat conditions, isolates from Bergen (Bergen population) grew well at lower temperatures, and isolates from the Azores (Azores population) performed better at higher temperatures. The optimum growth temperature of the Azores population was significantly higher than that of the Bergen population. Neutral genetic differentiation was found between populations by microsatellite analysis. These findings indicate that E. huxleyi populations are adapted to local temperature regimes. Next to between-population variation, we also found variation within populations. Genotype-by-environment interactions resulted in the most pronounced phenotypic differences when isolates were exposed to temperatures outside the range they naturally encounter. Variation in thermal reaction norms between and within populations emphasizes the importance of using more than one isolate when studying the consequences of global change on marine phytoplankton. Phenotypic plasticity and standing genetic variation will be important in determining the potential of natural E. huxleyi populations to cope with global climate change.

High levels of solar radiation offset impacts of ocean acidification on calcifying and non-calcifying strains of Emiliania huxleyi

“…As discussed above, calcification should account for this discrepancy. On the other hand, these 2 strains were isolated from different regions, therefore their temperature reaction norms should be different (Zhang et al 2014). Although we grew these 2 species at the same temperature level for the purpose of comparison, our results can hardly reflect their responses to OA in their natural habitat (Sett et al 2014).…”

A Model Simulation of the Adaptive Evolution through Mutation of the Coccolithophore Emiliania huxleyi Based on a Published Laboratory Study

“…The coccolithophore E. huxleyi is widely distributed over the global ocean (e.g., Hagino et al, 2011), viable over a temperature range from 4 to 28 • C (e.g., Watabe and Wilbur, 1966;Fielding, 2013), with maximum growth rates in the temperature range 18-25 • C (Watabe and Wilbur, 1966;Zhang et al, 2014). In general, growth rates increase with temperature, with clear differences between Arctic and Atlantic strains (Daniels et al, 2014;Zhang et al, 2014).…”

“…Y. Zhang, U. Riebesell, and T. Reusch provided their growth rate vs. temperature data and fitted thermal response functions from Zhang et al (2014). The author wishes to thank the two reviewers for their constructive and helpful comments, which improved the manuscript immeasurably.…”

“…In general, growth rates increase with temperature, with clear differences between Arctic and Atlantic strains (Daniels et al, 2014;Zhang et al, 2014). Zhang et al developed thermal reaction norms (TRNs) for six E. huxleyi isolates originating from the central Atlantic near the Azores, Portugal (38 • 34 ′ N; monthly SST range 16-22 • C), and five isolates originating from coastal waters near Bergen, Norway (60 • 18'N; monthly SST range 6-16 • C), all kept at 15 • C in culture.…”

A niche comparison of <i>Emiliania huxleyi</i> and <i>Gephyrocapsa oceanica</i> and potential effects of climate change

“…light and temperature inhibition and limitation) both tem- Rhodes et al, 1995;van Rijssel and Gieskes, 2002;Helm et al, 2007;Zhang et al, 2014) at a much narrower experimental range (10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20) • C), the upper and lower limits for E. huxleyi growth were added into the equation with a general transform of T = (T t − 2) × (30 − T t ), where T t is the temperature of an incubation. To accurately express the onset of high 30 temperature inhibition, the transform was further modified with a square root transform to give T = (T t − 2) × (30 − T t ).…”