Ecology of Heterotrophic Microflagellates. IV Quantitative Occurrence and Importance as Bacterial Consumers

Abstract

Heterotrophic nanoplankton flagellates and bacteria were quantified at regular intervals during a month in Limfjorden, Denmark. The number of flagellates averaged about 10 super(3) ml super(-1) and ranged from < 2 x 10 super(2) to about 3 x 10 super(3) ml super(-1). The composition of this fauna was dominated by choanoflagellates, non-pigmented chrysomonads and bicoecids. Bacteria occurred in concentrations ranging from 1.5 to 3 x 10 super(6) ml super(-1). Flagellate numbers followed bacterial numbers and the bacteria-flagellate system showed a cyclical behaviour with a frequency of about 16 d during the study period. Calculations based on laboratory data on the clearance of flagellates show that such organisms on the average filter 20% of the Limfjord water d super(-1) (range 12 to 67% d super(-1)).