The effect of temperature and salinity on the stable hydrogen isotopic composition of long chain alkenones produced by Emiliania huxleyi and Gephyrocapsa oceanica

S. Schouten (1) , J. Ossebaar (1) , K. Schreiber (2) , M. V. M. Kienhuis (1) , G. Langer (2) , J. Bijma (2)

1 Department of Marine Biogeochemistry and Toxicology
2 Department of Bentho-pelagic processes

Two haptophyte algae, Emiliania huxleyi and Gephyrocapsa oceanica, were cultured at different temperatures and salinities to investigate the impact of these factors on the hydrogen isotopic composition of long chain alkenones synthesized by these algae. Results showed that alkenones synthesized by G. oceanica were on average depleted in D by 30 per mil compared to those of E. huxleyi when grown under similar conditions. The fractionation factor, ?_{alkenones-H2O}, ranged from 0.760 to 0.815 for E. huxleyi and from 0.741 to 0.788 for G. oceanica. There was no significant correlation of ?_{alkenones-H2O} with temperature but a positive linear correlation was observed between ?_{alkenones-H2O} and salinity with ~3 per mil change in fractionation per salinity unit. This suggests that salinity can have a substantial impact on the stable hydrogen isotopic composition of long chain alkenones in natural environments and, vice versa, that ?D can possibly be used as a proxy to estimate paleosalinity.

Domaines: Cosmologie et astrophysique extra-galactique [astro-ph.CO]; Astrophysique [astro-ph]; Interfaces continentales, environnement; Océan, Atmosphère; Sciences de la Terre

S. Schouten, J. Ossebaar, K. Schreiber, M. V. M. Kienhuis, G. Langer, et al.. The effect of temperature and salinity on the stable hydrogen isotopic composition of long chain alkenones produced by Emiliania huxleyi and Gephyrocapsa oceanica. Biogeosciences Discussions, 2005, 2 (6), pp.1681-1695. ⟨hal-00297824⟩