Characterization of particulate organic matter in Mediterranean sea-surface films and underlying water by flash pyrolysis and gas chromatographic analyses

Abstract

Sea-surface films and the corresponding 20 cm subsurface waters were sampled during four cruises in the Western Mediterranean and in the Northern Adriatic Sea. The composition of the particulate material was determined by a combination of several methods: analysis of total organic carbon and proteins, gas chromatographic analysis of fatty acids and non-aromatic hydrocarbons, and by flash pyrolysis-mass spectrometry (Py-MS). Enrichment factors in the sea-surface films were: 1.4–6.1 for organic carbon; 1–17.7 for proteins; 2.1–47.5 for total carbohydrates; 4.4–45 for total lipids. The relative values of proteins and carbohydrates, for four pairs of microlayer and subsurface water samples, were discussed from their scores on two significant discriminant functions derived from pyrolysis mass spectral data. Details of the chemical structure of the surface film/underlying water pair were derived from complementary analyses of particulate organic matter by Py-MS and GC. It was shown that the fatty acids originating from autochtonous biological productivity were dominant in the sea-surface film. Unsaturated compounds were however depleted in the microlayer.