Effect of salinity on 2H/1H fractionation in lipids from continuous cultures of the coccolithophorid Emiliania huxleyi

Effects of alkalinity and salinity at low and high light intensity on hydrogen isotope fractionation of long-chain alkenones produced by <i>Emiliania huxleyi</i>

“…We note, however, that this experiment was performed with a nolonger-calcifying strain of E. huxleyi, and results might be different when haptophytes calcify since calcification may be impacted by alkalinity, which in turn could have consequences for other intracellular processes. At constant alkalinity over a range of salinity, we see a 2.6 ‰ change in fractionation per salinity unit, confirming that salinity does indeed have an effect on hydrogen isotope fractionation between alkenones and growth water (Schouten et al, 2006;Chivall et al, 2014;Sachs et al, 2016). Alkenones synthesized by haptophytes growing at different salinities under high light (600 µmol photos m −2 s −1 ) show a strong correlation between α C 37 values and salinity.…”

“…We performed a statistical comparison using ANCOVA between the different α C 37 -salinity relationships for previous E. huxleyi cultivation experiments (Schouten et al, 2006;Sachs et al, 2016; Table 2) and our experiments. Sachs et al (2016) report δD values for individual alkenones; thus, we used a weighted mean average of the δD C 37:3 and δD (2014), and the alkalinity-salinity experiment (Table 2).…”

“…Sachs et al (2016) report δD values for individual alkenones; thus, we used a weighted mean average of the δD C 37:3 and δD (2014), and the alkalinity-salinity experiment (Table 2). A possible explanation for the statistical difference between the α C 37 -salinity relationship of Sachs et al (2016) and the other three experiments could be due to the fact that the Sachs et al (2016) experiment was conducted using chemostats with a controlled growth rate, whereas, the other experiments were batch culture experiments in which growth rate varied. Growth rate has been shown to effect hydrogen isotope fractionation of alkenones (Schouten et al, 2006;Wolhowe et al, 2009;Sachs and Kawka et al, 2015), and, therefore, could account for the difference between reported fractionation responses to salinity.…”

“…With the exception of the high-light experiment, all other culture experiments with E. huxleyi being discussed here were grown at light intensities between 50 and 300 µmol photons m −2 s −1 (Schouten et al, 2006;Sachs et al, 2016; alkalinity-salinity experiment). The fact that the strong α C 37 -salinity response is also identified in E. huxleyi grown at high light conditions is important for understanding the influence of light and depth effects (i.e., Wolhowe et al, 2015) on the α C 37 of alkenones preserved in the sedimentary record.…”

“…In addition to the observed relationship between δD C 37 and δD H 2 O values, biological hydrogen isotope fractionation has been shown to decrease with increasing salinity, thereby amplifying the salinity-to-seawater δD relationship of alkenones grown in culture (Schouten et al, 2006;Wolhowe et al, 2009;Sachs et al, 2016). Therefore, δD C 37 has been proposed as an appropriate proxy for reconstructing SSS (Englebrecht and Sachs, 2005;Schouten et al, 2006).…”