An organic Geochemical analysis of Terrestrial biomarkers in a transect of the Great Barrier Reef Lagoon

Abstract

Organic geochemical analyses of benthic sediments from a Northern Queensland coastal transect indicate that most terrestrial organic material is confined to near-shore sediments (<10 km offshore). Traces of higher plant material reach the inner fringes of the Great Barrier Reef, as indicated by the presence of pentacyclic triterpenoid alcohols (PTA) in near-reef sediments. A likely source of these alcohols is mangroves. PTA and long-chain normal alkanes appear to be the most reliable of the lipid biomarker classes analysed in assessing the distribution of terrestrial organic matter along the transect. Other terrestrial biomarker classes (sterols, normal fatty acids and fatty alcohols) present in the sediment do not show good correlation with distance from the land. This is believed to be due to the additional input of these biomarkers from planktonic sources.