Improved end-member characterisation of modern organic matter pools in theOhrid Basin (Albania, Macedonia) and evaluation of new palaeoenvironmentalproxies

[摘要] We present elemental, lipid biomarker and, in the supplement,compound-specific isotope (δ¹³C, δ²H) data for soils and leaf litter collected in thecatchment of Lake Ohrid (Albania, Macedonia), as well as macrophytes,particulate organic matter and sediments from the lake itself. Lake Ohridprovides an outstanding archive of continental environmental change of atleast 1.2 million years and the purpose of our study is to ground truth organicgeochemical proxies that we developed in order to study past changes in theterrestrial biome. We show that soils dominate the lipid signal of the lakesediments rather than the vegetation or aquatic biomass. There is a strongimprint of suberin monomers on the composition of total lipid extracts andchain-length distributions of n-alkanoic acids, n-alcohols, ω-hydroxyacids and α, ω-dicarboxylic acids. Our end-member surveyidentifies that ratios of mid-chain length suberin-derived to long-chainlength cuticular-derived alkyl compounds as well as their average chainlength distributions can be used as new molecular proxies of organic mattersources to the lake. We tested these for the 8.2 ka event, a pronounced andwidespread Holocene climate fluctuation. In SE Europe climate became drierand cooler in response to the event, as is clearly recognisable in thecarbonate and organic carbon records of Lake Ohrid sediments. Our newproxies indicate biome modification in response to hydrological changes,identifying two phases of increased soil organic matter (OM) supply, first from soils withmoderately degraded OM and then from more degraded soils. Our studydemonstrates that geochemical fingerprinting of terrestrial OM should focuson the main lipid sources, rather than the living biomass. Both can exhibitclimate-controlled variability, but are generally not identical.

[学科分类] 地球化学与岩石