NEUTRAL MONOSACCHARIDES FROM A HYPERSALINE TROPICAL ENVIRONMENT - APPLICATIONS TO THE CHARACTERIZATION OF MODERN AND ANCIENT ECOSYSTEMS

Surficial and buried sediment samples from a hypersaline lagoon-sabkha system (Abu Dhabi, United Arab Emirates) were analysed for carbohydra tes (as neutral monosaccharides) to distinguish and characterise vario us types of recent and ancient tropical ecosystems on a molecular leve l. The samples consisted of surficial and buried microbial mats, lagoo nal sediments containing seagrass (Halodule uninervis), and mangrove ( Avicennia marina) paleosoils and handpicked mangrove leaves, ranging i n age from contemporary to ca. 6000 yr BP. Analysis of quantitative ne utral monosaccharide data by multivariate techniques shows that variou s groups can be distinguished: intact vascular plant material (mangrov e leaf) contains high amounts of arabinose and glucose and hardly any partially methylated monosaccharides, whereas microbial mats in genera l and lagoonal seagrass sediments show high contributions of fucose, r ibose, mannose, galactose, and partially methylated monosaccharides. M oreover, surficial microbial mats consisting of filamentous cyanobacte ria (Microcoleus chtonoplastes, Lyngbya aestuarii) can be distinguishe d from other mats and sediments containing coccoid cyanobacteria (Ento physalis major) and/or fermenting, sulphate reducing, and methanogenic bacteria on the basis of high contributions of specific groups of par tially methylated monosaccharides and other ''minor'' saccharides. The neutral monosaccharides present in mangrove paleosoils are for a subs tantial part derived from microorganisms.