Lipid and lignin/cutin compounds in Lake Baikal sediments over the last 37 kyr: implications for glacial-interglacial palaeoenvironmental change

A stratigraphic study of total organic carbon (TOC) concentration, carbon isotopic composition of total organic matter (TOM), lipids (n-alkanes, n-alkanols, n-alkanoic acids and sterols) and lignin/cutin compounds has been conducted for a Lake Baikal core (323-PCl) over the last glacial/interglacial. TOC concentrations (mg g(-1) dry sediment) are low (2-4) in the glacial sections, but high (10-29) in the interglacial ones. The concentrations of land plant-derived compounds such as n-C-14 to C-28 omega-hydroxyalkanoic acids, lignin phenols (p-hydroxyl, vanillyl and syringyl), total cutin acids, normalized to TOC in the interglacial, are 5-6 times higher than those in the glacial. Carbon isotopic compositions of TOM are -24 +/- 0.9parts per thousand. in the glacial, while they are -27 +/- 1.3parts per thousand. in the interglacial. The heavy isotope composition of TOM in the glacial might be due to a contribution from submerged plants and/or grasses. The light isotopic composition of TOM for the interglacial may be due to a contribution from both land plant- and phytoplankton (mainly diatom)-derived OM. Autochthonous organic carbon contents were estimated from the C/N ratio corrected for the effect of inorganic nitrogen and based on the assumption of C/N values of 8 for autochthonous and 25 for allochthonous OM. The estimation indicates that autochthonous OC comprises 74 +/- 6% of TOC for the glacial and 72 +/- 9% for the interglacial, respectively. Primary palaeoproductivity was estimated to be below 20 gC m(-2) y(-1) in the glacial (before 18 ka), but high (100-120 gC m(-2) y(-1)) in the interglacial (11-8 ka), which is 10-30% higher than the modern values. (C) 2004 Elsevier Ltd. All rights reserved.