Microbiological Studies on Shallow Marine Areas―V On the distribution of the sulfate-reducing bacteria and sulfur bacterial groups in oxygen-deficient or anoxic bottom layer of bay in summer

摘要

In connection with the formation of oxygen-deficient or anoxic layer, thedistribution of bacterial groups which produce or oxidize the sulfides and some oceanographic factors in their environment were investigated in summer 1968 and 1969 at Omura Bay, west coast of Kyushu. Phytoplankton blooms which had increased in early summer appeared to sink down from the middle layer to the bottom while consuming dissolved oxygen because of the oxidative decomposition of planktonic matter by heterotrophic bacteria. In general, dissolved oxygen and both Eh and pH values remarkably decreased in bottom water below a depth of about 16m. Sulfate-reducing bacteria and aerobic or anaerobic thiobacilli most of which seemed to be facultative autotrophic were commonly found in bottom water, while photosynthetic sulfur-and nonsulfur bacteria were variable in their distribution. It appeared that bacteria were relatively active in bottom and that thiobacilli might participate partly in the consumption of dissolved oxygen due to the biochemical oxidation of reduced sulfur compounds. A schematic diagram on some chemical characters of sea water and distribution of bacterial groups in the bay was presented.