Autotrophic and bacterial production: Fractionation of plankton populations by differential filtration of samples from the English channel

The relationship between release of organic substances by phytoplankton and their utilization by heterotrophic bacteria has been measured by means of differential filtration in parallel Steemann Nielsen and Parsons and Strickland incubations. In Southampton Waters (UK), between March and September, the values for bacterial production measured in the above manner varied between 1 and 30%, the total primary production being taken as 100%. Even when low bacterial production occurs during the light period of incubation, a significant increase takes place during the following dark period. Thus, a close correlation between primary algal and the resultant bacterial production can be demonstrated. Quantitative data on bacterial production may be obtained from the conventional productivity experiments by simple double filtration.