BACTERIA AND HETEROTROPHIC MICROFLAGELLATE PRODUCTION IN THE SANTA-ROSA SOUND, FLORIDA

Bacterial and microflagellate biomass and production and grazing on ba cteria were compared weekly at a fixed station in Santa Rosa Sound, Fl orida, starting in February and ending in October. For both population s the weekly variation in biomass and production was as large as the s easonal variation. Cycles for biomass and production of these organism s 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 b acterial, experiments were conducted to examine bacterial growth rates in the absence of predators. This examination resulted in low bacteri al growth rates when biomass was high, and rapid growth rates typicall y occurred near minimum populations. Further analysis suggested that m icroflagellate predation was greater than bacterial production during minimum bacterial growth rates. With integration of production and gra zing rates over the study period, factors controlling bacterial growth were examined. Using this approach, 71% of the bacterial production w as grazed by < 8.0 mu m predators. The microflagellate biomass product ion was 41% of the grazing rate on bacteria. The total amount of bacte rial production assimilated into microflagellate biomass was 29%. Howe ver, 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.