SOME FACTORS WHICH INFLUENCE OXYGEN CONSUMPTION BY BACTERIA IN LAKE WATER

¹ From the Limnological Laboratory and the Department of Agricultural Bacteriology, University of Wisconsin

The rate of respiration of lake bacteria increases with temperature, the Q₁₀ from 8° to 25° C. being 2.1. Mixed microflora from Lake Mendota were found to consume from 21 to 43 x 10^-12 mgm. of oxygen per cell per hour at 25° C. Prolonged exposure at 37° C. is injurious to some of the bacteria.

The rate of respiration is independent of the oxygen concentration of the water within the examined range of 0.31 to 26.48 mgm./1. As the oxygen tension is reduced below 0.3 mgm./1. the rate of bacterial respiration decreases rapidly.

Both the character and the concentration of organic matter influence the rate of oxygen consumption by lake bacteria. The rate of respiration of "resting" cells increases as the concentration of glucose, asparagine and lactic acid is increased up to 100 to 1000 mgm./1.

About one-third of the organic matter in Lake Mendota water is readily oxidizable, the remainder being quite resistant to bacterial attack. The organic content of bottom deposits is less oxidizable than that of water, and the remains of plankton organisms are more readily oxidized by bacteria than the dissolved organic matter occurring in lake water.