ABSTRACT

Carbohydrate analysis of the sedimentary samples from Lake Suwa was conducted to ascertain the total amounts of carbohydrates present and their chemical nature, and to discuss the behavior of carbohydrates during the course of sedimentation. Total carbohydrate was determined in the range from 5.92 to 8.32mg/g dry sediment in the samples from the surface to 24cm depth of lake sediments. These values tended to decrease with depth. Lake sediments gave rhamnose, fucose, ribose, arabinose, xylose, mannose, galactose and glucose as the monosaccharide components when the sedimentary samples were treated with sulfuric acid. These monosaccharides were identified as benzoylhydrazones or acetyl derivatives. When alkali extracts of lake sediments were treated by gel filtration using sephadex G-25, low molecular weight carbohydrates and polysaccharide were separated. The polysaccharide, being major component of alkali extractable carbohydrate of lake sediment, was characterized by analyzing monosaccharide composition, degree of polymerization and type of glycosidic linkage between monosaccharide components. Results indicate that this polysaccharide of lake sediment is originated from diatoms living in this lake rather than from land vegetation. Monosaccharide composition of sedimentary samples from various depths was determined. Its vertical profile indicates that stabilities of monosaccharide components of sedimentary carbohydrate to microbiological attack increase in following order; glucose, galactose, fucose > mannose > ribose, rhamnose, arabinose. Vertical profile of low molecular weight carbohydrates indicates that the carbohydrates are intermediates during the decompositive processes of the polysaccharide in the sediment.