Bound lipid biomarkers in sediments from El Junco Lake, Galapagos Islands

Solvent extracted sediments from El Junco Lake, Galapagos were sequentially hydrolyzed with base and acid. Some of the "bound'' lipids thus generated were not detected among the "free'' lipids obtained from the initial solvent extract of the freeze dried sediment. These include alpha-hydroxy acids, beta-hydroxy acids, methyl beta-hydroxy acids and cutin acids. Other bound lipids differed from the free lipids in their chain length, such as alkanols, sterols, omega-hydroxy acids and (omega-1)-hydroxy acids. A suite of biomarkers with unique ions of m/z 341 were identified in the acid hydrolysates that are most likely C-40 cyclic biomarkers derived from the L race of Botryococcus braunii. Free lipids and their isotopic composition are likely to be sufficient for the purpose of paleoenvironmental reconstructions, and therefore base or acid hydrolysis of solvent extracted sediment is not necessary. Nevertheless, the additional lipid biomarkers liberated by base and acid hydrolysis can provide information on microbial inputs to the sediment. (C) 2014 Elsevier Ltd. All rights reserved.