Articles | Volume 14, issue 24
Biogeosciences, 14, 5693–5704, 2017
Biogeosciences, 14, 5693–5704, 2017

Research article 20 Dec 2017

Research article | 20 Dec 2017

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

Gabriella M. Weiss1, Eva Y. Pfannerstill1, Stefan Schouten1,2, Jaap S. Sinninghe Damsté1,2, and Marcel T. J. van der Meer1 Gabriella M. Weiss et al.
  • 1Department of Marine Microbiology and Biogeochemistry, NIOZ, Royal Netherlands Institute for Sea Research and Utrecht University, Den Burg, 1790 AB, the Netherlands
  • 2Department of Earth Sciences, Faculty of Geosciences, Utrecht University, Utrecht, the Netherlands

Abstract. Over the last decade, hydrogen isotopes of long-chain alkenones have been shown to be a promising proxy for reconstructing paleo sea surface salinity due to a strong hydrogen isotope fractionation response to salinity across different environmental conditions. However, to date, the decoupling of the effects of alkalinity and salinity, parameters that co-vary in the surface ocean, on hydrogen isotope fractionation of alkenones has not been assessed. Furthermore, as the alkenone-producing haptophyte, Emiliania huxleyi, is known to grow in large blooms under high light intensities, the effect of salinity on hydrogen isotope fractionation under these high irradiances is important to constrain before using δDC37 to reconstruct paleosalinity. Batch cultures of the marine haptophyte E. huxleyi strain CCMP 1516 were grown to investigate the hydrogen isotope fractionation response to salinity at high light intensity and independently assess the effects of salinity and alkalinity under low-light conditions. Our results suggest that alkalinity does not significantly influence hydrogen isotope fractionation of alkenones, but salinity does have a strong effect. Additionally, no significant difference was observed between the fractionation responses to salinity recorded in alkenones grown under both high- and low-light conditions. Comparison with previous studies suggests that the fractionation response to salinity in culture is similar under different environmental conditions, strengthening the use of hydrogen isotope fractionation as a paleosalinity proxy.

Short summary
Algal-derived compounds allow us to make assumptions about environmental conditions in the past. In order to better understand how organisms record environmental conditions, we grew microscopic marine algae at different light intensities, salinities, and alkalinities in a temperature-controlled environment. We determined how these environmental parameters affected specific algal-derived compounds, especially their relative deuterium content, which seems to be mainly affected by salinity.
Final-revised paper