Ecological studies on bacteria in the sea and lake waters polluted with organic substances. IV. Determination of bacterial degradable organic matter in aquatic environments.

Abstract

Dissolved organic matter in sea waters polluted with organic matter to various extents was fractionated by ultrafiltration. It was found that the fraction of dissolved organic matter containing substances of molecular weight less than 10, 000 was easily utilized by bacteria when the water temperature was relatively high. The amounts of organic matter degradable by bacteria in lake water were estimated in water samples by measuring the changes in organic matter concentrations attributable to the bacterial growth during in situ incubation. Even in the case of polluted environments, the ratio of the amount of dissolved organic matter utilizable by bacteria to the total amount of dissolved organic matter was not very high. It is suggested that in polluted environments the fraction of utilizable dissolved organic matter is more quickly consumed by bacteria than in unpolluted environments. On the basis of the data obtained, an equation for estimating the utilization rate (α) of dissolved organic matter by bacteria was proposed as follows: α=X0|g•f(S0-S)|X-X0Applying this equation, the utilization rates of dissolved organic matter by bacteria in lake water was estimated with various water samples.