Laboratory microbial degradation (14.2 yr.) of a freshwater submerged plant yielded a polymeric residue, from which humic acid-like and kerogen-like colored materials were isolated. In order to evaluate the submerged plantderived organic matter as one possible contributor to the sedimentary organic matter, chemical analyses (lipids, amino acids and saccharides) of the whole-plant residue and the kerogen-like material were examined. The kerogen-like material was further characterized by alkaline permanganate oxidation and vacuum pyrolysis. The oxidation products as well as the pyrolysate hydrocarbons of the kerogen-like material exhibited a qualitative similarity to the natural kerogens from freshwater lacustrine sediments. However, the long-chain prevalence in fatty acid and alcohol composition and the high cellulose content of the kerogen-like material suggested that the kerogen-like material should have originated from surface material of the plant. The chemical composition of this material, showed an obvious difference from the kerogen of sediment from Lake Haruna, where the submerged plant was collected. The difference was interpreted to indicate a large contribution of the planktonic organic matter to the formation of natural kerogen in lacustrine sediments.