LIPID-COMPOSITION OF WATER AND SURFACE SEDIMENTS IN TAKAPOTO-ATOLL LAGOON (FRENCH-POLYNESIA)

Dissolved, particulate and sedimentary lipid compounds were analyzed i n samples collected in May 1988 at three sites in the lagoon of the cl osed atoll of Takapoto (Tuamotu archipelago, French Polynesia). The st udy provides background information dealing with water quality and the nature and concentration of lipids. Nonaromatic hydrocarbons and fatt y acids were isolated from lipids and analyzed by gas chromatography/m ass spectrometry. Non-aromatic hydrocarbon concentrations did not exce ed 1000 ng 1(-1) in water, and 2300 ng g-1 in surface sediments and ar e among the lowest encountered in pristine marine environments. No not iceable petroleum pollution was evidenced in the lagoon. Nevertheless, traces of petroleum-derived compounds were detected at the central si te for both surface and deep water. Total fatty acid concentrations va ried in the range 6.3-14.4 mug l-1 for the particulate phase and in th e range 0.5-3.2 mug l-1 for the dissolved phase. The molecular fingerp rints of fatty acids and hdyrocarbons evidenced a predominant algal, a nd to a lesser extent microbial, origin of the organic matter present in water and sediments. Mono- and poly-unsaturated fatty acids, which are essential components for animal metabolism, were identified in not iceable amounts in suspended matter (1.8-4.6 mug l-1), and at highly v ariable levels in the dissolved phase (0.08-1.21 mug l-1).