Geochemical studies on the coastal lakes of Kamikoshiki Island in Kagoshima Prefecture, Japan. I. A preliminary report.

概要

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In the coastal region of Kamikoshiki Island in Kagoshima Prefecture of Japan, there are Lakes Namako-ike, Kai-ike, Kazaki-ike and Suguchi-ike. All four lakes are separated from the sea by a long gravel bar (Tomboro) called as "Nagamenohama." Although these lakes are thought to be formed in the same geological period (5-10×103yr BP), the ensuing geological succession has significantly differentiated their geochemical and biological situations. This study was undertaken to find out how these differences in ecological conditions reflect on the chemical composition of the underlying sediments. The sediment samples were collected with a grab sampler from the former three lakes. In Lake Kai-ike, particulates were collected from near the phototrophic "bacterial plate" peculiar to the lake. The stable carbon isotope ratio, δ13C, of the sedimentary organic matter was light (-25‰) for slightly saline Lake Kazaki-ike, while the values, around -22‰ for brackish Lake Kai-ike and Lake Namako-ike, were thought to indicate a higher contribution from authigenic marine biota. However, only slight differences were observed with regard to the major identifiable organic constituents examined, i. e., amino acids, carbohydrates and lipids (hydrocarbons, alcohols and fatty acids). The lipid compositions, influenced little by anthropogenic pollutants, were considered to represent a contribution primarily from the anaerobic bacterial community.
日本陸水学会の論文