PRODUCTION AND TURNOVER RATES OF FATTY-ACIDS IN MARINE PARTICULATE MATTER THROUGH PHYTOPLANKTON PHOTOSYNTHESIS

A combined C-13 and gas chromatography-mass spectrometry (C-13-GC-MS) method was applied for the determination of the fatty acid composition of photosynthetic products of phytoplankton. The accuracy of the estimation of C-13 abundance by GC-MS was ascertained by analyzing C-13-enriched authentic specimens. The production rates of 17 fatty acids was determined in the regional upwelling and non-upwelling area around Hachijo Island, Japan. Although 14:0, 16:0 and 16:1 were the main components of the photosynthetically produced fatty acids at both stations, a marked difference in the proportion of 16:1 was found between the two stations, probably reflecting the difference in the dominant phytoplankton species. The ratio of unsaturated fatty acids to saturated fatty acids in the photosynthetic products was high in the upwelling area. The calculated turnover rate of each fatty acid through phytoplankton photosynthesis varied widely. Polyunsaturated fatty acids showed higher turnover rates, whereas low turnover rates were noticed in odd carbon number acids (iso 15:0, anteiso 15:0, 15:0 and 17:0) and 18:1 (n-7), which have been reported to originate from bacteria. The weighted average values of the turnover rates of all fatty acids determined in this study were 0.021 and 0.087 h-1 for the non-upwelling and the regional upwelling area, respectively.