Variation of content of lipid classes, sterols and fatty acids in gonads and digestive glands of Scrobicularia plana in relation to environment pollution levels.

Lipids are central for energy metabolism and their fate in bivalves is closely linked to environmental conditions and gametogenic cycle. In order to assess the pollution impact on lipid metabolism of bivalves, storage and structure lipids from samples of Scrobicularia plana were studied. These samples were collected during sexual maturity both from estuaries considered contaminated (Goyen and Blavet) and from a reference site (Bay of St Brieuc) for comparison. Lipids were extracted from the gonads and the digestive glands and further separated by column chromatography. Fatty acids and sterols were then analyzed by gas chromatography-mass spectrometry. Correlations were shown between dioxin-like compounds (Eq-TCDD) and triacyglycerol levels (TAG). In the same way, glycolipids and contamination by polycyclic aromatic hydrocarbons (PAH) and pollutants with estrogenic activity seem to be closely related. In a second time, lipid indices (ratio between storage and structure lipids) were evaluated. Whereas these indices are often used in fish to assess habitat quality with regards to differential anthropogenic pressure, the ratio TAG/sterols was not here significantly influenced by the site of origin of S. plana. Intersite fluctuations of the ratio TAG/phospholipids also remained very limited. This could be explained by the limited contamination level in studied sites but also by a contrasted response from organisms in different taxa (bivalves vs. fish). Environmental pollution is not the only factor able to induce changes in lipid classes. The trophic wealth seemed to be different between the reference site and contaminated estuaries, the total organic carbon content being higher in muddy estuarine sediments.