The estimation of extracellular release by phytoplankton and heterotrophic activity of aquatic bacteria.

The actual extracellular release of organic matter by algae was determined in water samples in which the heterotrophic activity of bacteria was inhibited by gentamycin. Gentamycin rapidly and efficiently inhibited the activity of aquatic bacteria without affecting phytoplankton metabolism. Aquatic bacteria utilized the products of algal extracellular release. The amount of algal photosynthetic products metabolized by bacteria can be taken as a measure of their heterotrophic activity in waters.