Research Product

Bacterial and microflagellate biomass and production and grazing on bacteria were compared weekly at a fixed station in Santa Rosa Sound, Florida, starting in February and ending in October. For both populations the weekly variation in biomass and production was as large as the seasonal variation. Cycles for biomass and production of these organisms were generally out of phase, rendering it difficult to estimate the net grazing of bacteria by microflagellates at individual time points. For evaluation of factors that control the fate of carbon cycled by bacterial, experiments were conducted to examine bacterial growth rates in the absence of predators. This examination resulted in low bacterial growth rates when biomass was high, and rapid growth rates typically occurred near minimum populations. Further analysis suggested that microflagellate predation was greater than bacterial production during minimum bacterial growth rates. With integration of production and grazing rates over the study period, factors controlling bacterial growth were examined. Using this approach, 71% of the bacterial production was grazed by <8.0 µm predators. The microflagellate biomass production was 41% of the grazing rate on bacteria. The total amount of bacterial production assimilated into microflagellate biomass was 29%. However, based on the variations in biomass and activity of the microbial assemblages, it appears that substrate and predation exert alternating control on bacterial abundance and production.