Neutral sugars as biomarkers in the particulate organic matter of a French Mediterranean river

Neutral sugars (arabinose, glucose, galactose, fucose, mannose, rhamnose, xylose and lyxose) in riverine POM and adjacent soil samples were analysed by gas chromatography over a period of 18 months in a small Mediterranean river basin. Total neutral sugars or TCHO, and individual neutral sugar abundance were highly variable, with TCHO yields varying from 0.04 to 94 mgTCHO/100 mgOC and concentrations from 0.04 to 78 μg/l. The most abundant neutral sugars were arabinose (ARA) in riverine POM and fucose (FUC) in soil samples. Temporal fluctuations in relative neutral sugar abundance (wt.%) and ratios indicated a mainly allochthonous and transformed POM source during autumn and winter while the dry season (from Dec-97 to Jul-98) was characterised by a fresher, phytoplanktonic component. Comparison of %FUC+RHA, %GLU, %GLU+GAL and (FUC+RHA)/(ARA+XYL) ratios with other parameters such as chlorophyll a and lignin-phenols enhanced the conclusions concerning the neutral sugar sources (terrestrial and phytoplanktonic) of riverine POM.