BACTERIAL-GROWTH AND LOSSES DUE TO BACTERIVORY IN A MESOTROPHIC LAKE

Bacterial secondary production and rates of bacterivory were determine d from samples collected from mesotrophic Lake Arlington. Bacterial pr oduction and losses were determined by comparing the growth of natural bacterial assemblages in the presence of predators (unfiltered sample s) to growth in the absence of predators (water filtered through 1.0 m um porosity filters). Growth rates of heterotrophic nanoflagellates (H NF) were estimated from growth in the absence of predators (water filt ered through 5.0 mum porosity filters). Bacterial growth rates ranged between 0.002 and 0.069 h-1, and averaged 0.026 h-1. HNF grew at rates ranging between 0.003 and 0.107 h-1 and averaged 0.028 h-1. Grazing r ates ranged between 0.002 and 0.043 h-1, and averaged 0.018 h-1. The a nnual average rate of bacterial biomass synthesis was 3.2 mug C l-1 h- 1 and approximately 69% of this production was grazed. Temporal change s in growth and grazing rates suggest a tightly coupled predator-prey linkage in this lake.