Temperature response curves of Emiliania huxleyi during laboratory experiments

At the end of the two year incubation of a subantarctic E. huxleyi culture (2015-11-20 to 2017-12-01), a temperature response experiment was performed using the Now (Day 747) and Future (Day 725) populations. Now and Future populations were grown in triplicate 28 ml Nalgene Oak Ridge-style centrifuge tubes (Sigma) in Now or Future medium, respectively. The tubes were held in an aluminium temperature gradient block similar to Thomas et al. (1963), that was heated at one end and cooled at the other using water maintained at constant temperature by refrigerated circulators (Julabo GmbH). The temperature regime resulted in a range of 10 temperatures along the length of the block from 6.2°C at one end to 16.5°C at the other, with a range within replicates at each temperature of 0.1 – 0.2°C. The block was lit from below which achieved a light level of 62 +/- 7 μmol m⁻² s⁻¹ at the bottom of the tubes in a 12 hour: 12 hour light: dark cycle. To ensure uniform light each replicate was manually rotated through the row holes at the set temperature during the incubation period. Measurements of in vivo chl-a were made daily and growth rates calculated from the least squares regression of the natural logarithm of in vivo fluorescence, versus time.