D/H ratios of environmental water recorded by D/H ratios of plant lipids

Isotope ratios of chemical components are powerful tools in the interpretation of palaeoenvironments, particularly carbonates from foraminiferans1,2, desert caliche3, and desert pavements4. Isotope ratios of plant cellulose are also indicators of environmental variables such as temperature and relative humidity5–7. Several workers have reported climatic fluctuations based on hydrogen and oxygen isotope ratios of cellulose from tree trunks8–10and peats11,12. Here I present measurements that demonstrate that for submerged aquatic plants δD values of lipids record D/H ratios of environmental water, whereas cellulose does not. I further demonstrate that δD values of lipids in conjunction with δ18O values of cellulose provide significant information on isotope ratios of environmental water.