A lipid molecular marker assessment of sediments from the Northern Gulf of Mexico before and after the passage of Hurricane Lili

Abstract

A characterization study of lipid molecular markers was undertaken to identify the provenance of organic matter in surface sediments from the Louisiana Shelf, west of the Atchafalaya River before and after the passage of Hurricane Lili (a category 2 storm) in October 2002. During both sampling periods, terrestrially derived organic matter, as revealed by long chain n-alkanes, terrestrial aquatic hydrocarbon ratio (TAR HC) and β-sitosterol, was a predominant component of the organic matter, supporting earlier studies. A petroleum derived unresolved complex mixture (UCM) was detected at each station during both sampling events and displayed no statistically significant difference between inshore and offshore stations. The absence of any relationship between the UCM and the bulk radiocarbon isotopic compositions suggests that petroleum derived organic matter does not significantly control the ages of the sedimentary organic carbon (>2000 years). In addition, sterols, linear, mono- and polyunsaturated fatty acids (FAs) from multiple organic matter sources, including diatoms, dinoflagellates and zooplankton, were also detected at each site. These compounds indicated the sources of organic matter for pre- and post-hurricane samples were similar overall. Surface area-normalized concentrations of n-alkanes and bacterially derived FAs for the pre- and post-hurricane sediments were statistically different between events whereas other parameters such as total sterol and FA concentrations were not.