Distinction between Bacterial and Algal Utilization of Soluble Substances in the Sea

SUMMARY: The presence of numerous bacteria and diatoms attached to the sand grains of a littoral beach have been shown by fluorescence microscopy. Bacteria and diatoms were found in a viable condition to depths exceeding 10 cm. The rate of uptake of 14C-acetate was measured over the range 10–5000 μg./l. and the results analysed by Michaelis-Menten kinetics. By the use of autoradiography it was shown that the bacteria alone were responsible for the uptake of 3H-acetate. It is concluded that algal heterotrophy is negligible in sea waters.