Particulate and dissolved lipids in sea water

Abstract

Dissolved and particulate lipid extracts were collected at a number of locations in the Gulf of Mexico, the Scotia Sea, and in and near the Cariaco Trench. Lipid material was defined as those organic compounds extractable with chloroform. The lipids of sea water were a very complex mixture of compounds. Lipids constituted ~4% of the dissolved organic carbon and ~20% of the particulate organic carbon. All concentrations of lipids measured were extremely low and apparently of biogenic origin. Lipid content was estimated both gravimetrically and gas chromatographically. Compounds in the extracts were identified by a combination of authentic standards, gas chromatography-mass spectrometry, and high resolution mass spectrometry. The major constituents (10-100 ng/l) of the analyzable dissolved lipids were n-alkanes, pristane, phytane, and alkyl esters of fatty acids. Minor components ([less than or equal to] 5 ng/l) included olefins and/or cycloalkanes, an indane, a few aromatics, short-chained acids, and possibly a lactone and an alcohol. The major constituents of the analyzable particulate lipids were also n-alkanes, pristane, phytane, and the alkyl fatty acid esters. Often olefins, alkylated benzenes, quinones, and the unresolved G.C. material were significant components of the particulate lipids. Minor components of the particulate lipids included ketones, phenols, an indane, benzoates, aromatics, and possibly derivatives of inositol, dioxane, and pyran. Both phases had compounds that were unique and many compounds that were similar. Seasonal, diurnal, vertical, and areal variations were observed in lipid content. The dissolved lipids were less variable than the particulate lipids. The lipid content of particulate organic carbon decreased with depth. Lipid concentrations reflected variations in routine oceanographic parameters such as salinity and temperature and the aperiodicity of sources. Anoxic conditions appeared to preserve lipid materials in the particulate phase. N-alkanes may have two sources (marine and terrestrial) superimposed on a low fairly constant background of hydrocarbons caused by low level chronic oil pollution in the Gulf of Mexico...