@misc{SachseBillaultBowenetal.2012,
  author    = {Sachse, Dirk and Billault, Isabelle and Bowen, Gabriel J. and Chikaraishi, Yoshito and Dawson, Todd E. and Feakins, Sarah J. and Freeman, Katherine H. and Magill, Clayton R. and McInerney, Francesca A. and van der Meer, Marcel T. J. and Polissar, Pratigya and Robins, Richard J. and Sachs, Julian P. and Schmidt, Hanns-Ludwig and Sessions, Alex L. and White, James W. C. and West, Jason B. and Kahmen, Ansgar},
  title     = {Molecular Paleohydrology interpreting the Hydrogen- Isotopic Composition of Lipid Biomarkers from Photosynthesizing Organisms},
  series = {Annual review of earth and planetary sciences},
  volume    = {40},
  journal   = {Annual review of earth and planetary sciences},
  number    = {1},
  editor    = {Jeanloz, R},
  publisher = {Annual Reviews},
  address   = {Palo Alto},
  isbn      = {978-0-8243-2040-9},
  issn      = {0084-6597},
  doi       = {10.1146/annurev-earth-042711-105535},
  pages     = {221 -- 249},
  year      = {2012},
  abstract  = {Hydrogen-isotopic abundances of lipid biomarkers are emerging as important proxies in the study of ancient environments and ecosystems. A decade ago, pioneering studies made use of new analytical methods and demonstrated that the hydrogen-isotopic composition of individual lipids from aquatic and terrestrial organisms can be related to the composition of their growth (i.e., environmental) water. Subsequently, compound-specific deuterium/hydrogen (D/H) ratios of sedimentary biomarkers have been increasingly used as paleohydrological proxies over a range of geological timescales. Isotopic fractionation observed between hydrogen in environmental water and hydrogen in lipids, however, is sensitive to biochemical, physiological, and environmental influences on the composition of hydrogen available for biosynthesis in cells. Here we review the factors and processes that are known to influence the hydrogen-isotopic compositions of lipids-especially n-alkanes-from photosynthesizing organisms, and we provide a framework for interpreting their D/H ratios from ancient sediments and identify future research opportunities.},
  language  = {en}
}
@article{GarcinSchwabGleixneretal.2012,
  author    = {Garcin, Yannick and Schwab, Valerie F. and Gleixner, Gerd and Kahmen, Ansgar and Todou, Gilbert and Sene, Olivier and Onana, Jean-Michel and Achoundong, Gaston and Sachse, Dirk},
  title     = {Hydrogen isotope ratios of lacustrine sedimentary n-alkanes as proxies of tropical African hydrology insights from a calibration transect across Cameroon},
  series = {Geochimica et cosmochimica acta : journal of the Geochemical Society and the Meteoritical Society},
  volume    = {79},
  journal   = {Geochimica et cosmochimica acta : journal of the Geochemical Society and the Meteoritical Society},
  number    = {4},
  publisher = {Elsevier},
  address   = {Oxford},
  issn      = {0016-7037},
  doi       = {10.1016/j.gca.2011.11.039},
  pages     = {106 -- 126},
  year      = {2012},
  abstract  = {Hydrogen isotope values (delta D) of sedimentary aquatic and terrestrial lipid biomarkers, originating from algae, bacteria, and leaf wax, have been used to record isotopic properties of ancient source water (i.e., precipitation and/or lake water) in several mid-and high-latitude lacustrine environments. In the tropics, however, where both processes associated with isotope fractionation in the hydrologic system and vegetation strongly differ from those at higher latitudes, calibration studies for this proxy are not yet available. To close this gap of knowledge, we sampled surface sediments from 11 lakes in Cameroon to identify those hydro-climatological processes and physiological factors that determine the hydrogen isotopic composition of aquatic and terrestrial lipid biomarkers. Here we present a robust framework for the application of compound-specific hydrogen isotopes in tropical Africa. Our results show that the delta D values of the aquatic lipid biomarker n-C(17) alkane were not correlated with the delta D values of lake water. Carbon isotope measurements indicate that the n-C(17) alkane was derived from multiple source organisms that used different hydrogen pools for biosynthesis. We demonstrate that the delta D values of the n-C(29) alkane were correlated with the delta D values of surface water (i.e., river water and groundwater), which, on large spatial scales, reflect the isotopic composition of mean annual precipitation. Such a relationship has been observed at higher latitudes, supporting the robustness of the leaf-wax lipid delta D proxy on a hemispheric spatial scale. In contrast, the delta D values of the n-C(31) alkane did not show such a relationship but instead were correlated with the evaporative lake water delta D values. This result suggests distinct water sources for both leaf-wax lipids, most likely originating from two different groups of plants. These new findings have important implications for the interpretation of long-chain n-alkane delta D records from ancient lake sediments. In particular, a robust interpretation of palaeohydrological data requires knowledge of the vegetation in the catchment area as different plants may utilise different water sources. Our results also suggest that the combination of carbon and hydrogen isotopes does help to differentiate between the metabolic pathway and/or growth form of organisms and therefore, the source of hydrogen used during lipid biosynthesis.},
  language  = {en}
}