The succession of microheterotrophs and phytoplankton within the microbial loop in Oslofjorden, May-October 1984

The relative proportions of autotrophs, heterotrophic protozoa and bacteria were studied by epifluorescence microscopy at three depths in Oslofjorden Cell volume estimates allowed direct comparison of groups. Analyses of size frequency showed heterotrophic dinoflagellates to be an important member of the microbial loop In the period August-September the ratio of autotrophs/heterotrophic protozoa/bacteria varied little in spite of relatively large variations in several environmental factors, indicating a robust regulation within the microbial loop. Most typical of this period were low levels of inorganic nutrients The period of stable ratios was longest in the upper depth and decreased downwards