Microbiological Studies on Shallow Marine Areas―I.On the release of nutrient salts and organic acids from sediment to water layer

摘要

Laboratory experiments have been carried out to investigate the release of nutrient salts and soluble organic substance, from the sediments of shallow waters, by decomposition of organic matter, especially in view of the relation between the leaching of organic substances and the vicissitude of heterotrophic bacteria. The moist sediments of three different pearl oyster beds, which contained relatively a large amount of orgauic matter, were used for the preparation of sediment-water layer. And in the water layers, ammonia, phosphate, COD, total organic acids and viable count of aerobic or anaerobic bacteria were estimated. The change in pH and Eh of the waters was also determined. The results obtained from the experiments are as follows: 1. The leaching of ammonia, phosphate and organic acids from the sediments was noticed in each of the samples. In the sample in which much of the nutrient salts is released, the leaching of organic acid was also found to be large. 2. The quantity of organic acids in the waters increased gradually but the organic acid appeared to be decomposed and consumed by bacteria after the increase. The accumulation of organic acids in the water was larger in the anaerobic condition than in the aerobic, and the increase of bacterial population was inversely less in the anaerobic condition than in the aerobic. 3. In the sample in which organic acids are released relatively in abundance, the consumption rate of the organic acids was also rapid in comparison with that of others.