OBSERVATIONS ON HETEROTROPHIC ACTIVITY IN THE EASTERN TROPICAL PACIFIC1

Abstract

The kinetics of substrate uptake by heterotrophic microbial populations was examined at three depths over a broad area of the eastern tropical Pacific Ocean. Ten different 14 C‐labeled compounds were used as substrates. In many cases uptake data could not be used in the conventional manner to determine the kinetic constants because of either extremely low levels of uptake or extreme variability in uptake from one substrate concentration to another. Neither occurrence of usable uptake patterns nor the level of uptake at the 100 µ g C liter −1 level of added substrate appeared to correlate with specific in situ variations in descriptive parameters. A strong correlation was observed between the uptake of proline (100 µg C liter −1 ) and the concentration of viable bacteria as determined by plate counts.