海洋性硝酸化成細菌に関する研究-VII

Abstract

Wakasa Bay and its offshore being picked out as the object of investigation in the offshore region, the distribution of marine nitrifying bacteria and the role played by them in the region were examined. The results obtained are as follows; 1. Marine nitrifying bacteria always occur in the sea water as well as in the bottom muds but the bacterial counts are very low, i.e. 100-102 cells/l and ca. 101 cells/g or less, respectively. Contrary to Maizuru Bay, most of nitrification in the offshore region might be carried out in the sea water rather than in the bottom muds, because estimated total number of the bacteria in the former is far larger than those in the latter. 2. In the sea water ammonia and nitrite concentrations always are very low, the concentration of soluble organic nitrogen compounds is always comparatively high and also nitrate concentration always is very low in euphotic zone but comparatively high in disphotic and aphotic zones. The facts might suggest that nitrate is a low concentration in euphotic zone because it is rapidly consumed by phytoplankton, but it is accumulated comparatively much in disphotic and aphotic zones because it is scarcely consumed by them, being formed by oxidizing ammonia. 3. A part of the nitrate which has been accumulated in disphotic and aphotic zones might be brought to euphotic zone by the vertical mixture such as eddy diffusion and the distribution of these nitrogen compounds seems to balance under the condition mentioned above.