Abstract
Many aspects of the food web in the sea are ill understood: none more than the quantitative aspects of the heterotrophic activity of micro-organisms. Heterotrophic utilization of dissolved organic material by micro-organisms was recognized and discussed in principle by such workers as ZoBell, Waksman and Rakestraw in the thirties. There has been very little subsequent progress in understanding the details of the process, principally because of the lack of a suitable approach. Parsons and Strickland (1961) revived interest in this field when they introduced a simple radiochemical technique to follow the uptake of individual soluble organic compounds; subsequently Williams & Askew (1968) developed a method to measure the respiration of such compounds in sea-water samples.