Abstract
The microorganisms which colonize seawater incubated with mucilage from the kelps E. maxima or L. pallida show a clear succession. The media are 1st colonized by bacterial cocci followed by rods which are subsequently replaced by flagellates and ciliates whose combined biomass reaches some 6-10% of that of the bacteria. The maximal biomass of bacteria is achieved in 7-10 days incubation at 10.degree. C but is dependent both on the time of appearance and biomass of the flagellate and ciliate populations. Estimates for the rate of consumption of bacteria by flagellates of only 10 .mu.m3 body volume suggest that mineralization of bacteria by marine microflagellates may considerably exceed that in longer organisms at higher trophic levels.