The green alga, Scenedesnzus sp., killed by freeze-drying, was experimentally decomposed by microflora extracted from lake mud under aerobic conditions.The production of dissolved organic matter was about 7% as carbon and about 6% as nitrogen by the 30th day. These amounts probably were minimal.The dissolved organic product was fractionated between butanol and acidified water.One fraction was insolubilized when mixed with butanol, became suspended at the interface between the two solutions, and gave a white amorphous solid after vacumn drying. Its infllared spectrum showed it was proteinaceous; it contained more than 14 kinds of amino acids. The other was extracted with butanol and gave a dark brown viscous substance on drying.Aerobic microbial decomposition of Scenedesmus can be approximated to a first-order reaction during the first 30 days under laboratory conditions. Kinetic considerations of the decomposition pattern of the cell nitrogen and the production of dissolved organic nitrogen suggest that dead algal cell substance may be divided into labile and refractory constituents by their relative resistance to the action of bacteria. The dissolved organic nitrogenous material produced is composed of two major fractions:One is produced with the decomposition of algal cells ,and the other is probably excreted by bacteria through reassimilation of mincralizcd nitrogen, INTRODUCTIONDissolved organic matter (DOM ) in natural waters can function as organic substrates for heterotrophic metabolism, as a source of accessory growth factors, as antibiotics, and as complcxing agents for trace metals. Particulate aggregates of DOM may bc of direct importance in the nutrition of filter feeders.The composition of natural DOM is highly variable and little uudcrstood, but its sources are generally grouped into 1) excretion from phytoplankton, 2) dccomposition of phytoplankton, 3) cxcrction by animals, and 4) allochthonous drainage.Many studies concerning microbial clccomposition of dead plankton under laboratory conditions have dealt mainly with the regeneration of nu tricnts, ammonia, phosphatc, and silicate during the decomposition of dead plankton (e.g. Lewin 1961; Grill and Richards 1964; Skopintzev 1947 Skopintzev , 1949 Kamatani 1969) the changes of nitrogenous compounds (e.g. von Brand et al. 1937; von Brand and Rakestraw 1940, 1941; Botan ct al. 1960). However, few studies analyze the kinetics of microbial decomposition of dead plankton. Skopintzev obtained rate constants for the decomposition of the nitrogen componcnt in mixed plankton and Nitzschia and reported that the production of ammonia by the decomposition of plankton follows a first-order reaction. Grill and Richards studied the regeneration of phosphorus, nitrogen, and silicon from diatom cells and found phosphorus remineralization to consist of a first-order chain process from kinetic considerations.We have analyzed the patterns and kinetics of the decomposition of carbon and nitrogen from dead green algal cells under aerobic conditions and t...

No abstract

No abstract

No abstract

Vertical distribution of organic constituents, i .e . total organic carbon (TOC), extractable organic carbon with ethyl acetate (EOC), hydrocarbons, phytol, sterols, fatty acids and phenolic acids in Lake Vanda was studied to elucidate their features in relation to the stratification of lake water and the distribution of lake organisms . The concentrations of TOC, EOC and sterols increased with depth and attained the maximum values of 25 and 1 .5 mgC 1 -1 and 1 .4 µg 1-1 in the bottom, respectively, while those of fatty acids showed the maximum value of 61 µg 1-1 at a depth of 55 .4 m, along with the highest value of the ratio of unsaturated (uC16, uC 18 ) to saturated (C 16 , C 18 ) acids (8 .5) and with the highest carbon preference index (35) . Hydrocarbons were only found in the bottom layers (60 .4 and 65 .9 m) and bottom sediment . These results suggest strongly that the vertical distribution of lake organisms and their activity are quite different due to depth . In the bottom warm anoxic layers the degradation of organic materials must have occurred significantly and thus refractory organic materials should be concentrated .

No abstract

At the 60th day of anaerobic decomposition of dead cells of Scenedesmus sp. at 20C, the 30% of added algal cell carbon was transformed into dissolved organic carbon and 20% mineralized; 50% remained as particulate matter. On the other hand, 8% of the added algal cell nitrogen was transformed into dissolved organic nitrogen, 48% was mineralized, and 44% remained in particulate form. The dissolved organic compounds consisted mainly of lower fatty acids and yellowish acidic substances. Some proteinaceous material was found. Anaerobic decomposition patterns are compared with those under aerobic conditions and suggest the presence of relatively high concentrations of dissolved organic matter in anaerobic natural environments.

Phytol and stenols were studied for lake sediments from Syowa and Vestfold Oases in the Antarctic . Phytol and 6 stenols (cholesta-5,22-dien-3j3-ol, cholest-5-en-3j3-ol, 24-methylcholesta-5,22-dien-3j3-ol, 24 methylcholest-5-en-3j3-ol, 24-ethylcholesta-5,22-dien-3(3-ol and 24-ethylcholest-5-en-3j3-ol) were found, with concentrations ranging from 0.099 to 38 and 0.079 to 9.0µg g-' dry sediment, respectively. The dominant stenols are cholest-5-en-3a-ol, 24-methylcholest-5-en-3j3-ol and 24-ethylcholest-5-en-3j3-ol. These com pounds must be derived mainly from green and blue-green algae, diatoms and mosses. The relative abun dances of these stenols should reflect the difference of source organisms in the lakes and the surroundings.