Lipid Biomarker Isotopic Composition Changes during Early Diagenesis in Variable Biogeochemical Sediment Regimes - Implications for Carbon Cycling and Paleoceanography

University Of Georgia Research Foundation Inc, Athens GA

Investigators

Abstract

ABSTRACT OCE-0116786 Detailed chemical composition studies of the distribution of preserved lipid molecular markers (also termed molecular 'fossils' or 'fingerprints') in the sinking particulate matter of water columns and especially subsequently in sediments provides insight to our understanding of the inputs and processing of organic matter carbon in the ocean. Interpretation of the stable carbon isotopic composition (d 13C) of specific lipid molecular markers in aged sedimentary deposits has increasingly been suggested as a means of constraining past ocean and climate conditions and even reconstructing paleo atmospheric carbon dioxide mixing ratios (pCO2). The PI will measure isotopic d 13C fractionation effects on selected lipids using controlled laboratory experiments to simulate processes reflecting those undergone during natural diagenesis. This investigation will address the otherwise default assumption that diagenetic effects are negligible. Incubation experiments using target lipid biomarkers obtained from enriched 13C labeled algal cultures will be conducted in different biogeochemical regimes including: natural oxic and anoxic seawaters; simulated oxic vs. anoxic and cycled oxic/anoxic sediment-water interfaces; and in homogenized sediment cores with and without macrofauna. Compound specific isotopic analysis of biomarker 'molecular fossils' in sediments enhances understanding of the past conditions experienced by the marine organisms producing such molecules. Use of lipid biomarker information contained in natural archives such as deep sea sediments is key in reconstructing past climate change and helps answer fundamental questions such as how fast and how much can the planet's climate change.