MULTISCALE VARIABILITY IN BACTERIOPLANKTON ABUNDANCE, PRODUCTION, ANDSPECIFIC GROWTH-RATE IN A TEMPERATE SALT-MARSH TIDAL CREEK

Heterotrophic bacterioplankton abundance, production, and specific gro wth rate in a salt-marsh tidal creek were measured weekly from April 1 991 to September 1992. During the same period, tidal and diel sampling studies were performed in May, June, and October 1998 and May and Aug ust 1992. Seasonal variability of bacterial abundance, production, and specific growth rate was regulated by temperature during nonsummer se asons when temperature was < 20 degrees C. During summer, bacterial va riables were not limited by temperature. Daily variability of bacteria l abundance, production, and specific growth rate was regulated intera ctively by tidal mixing, substrate supply, and temperature over severa l tidal cycles. Higher bacterial abundance, production, and specific g rowth rate observed at low tide indicated that bacterial growth rate i n the tidal creek was higher than in the adjacent river waters. This p attern might be due to larger nutrient fluxes originating in the tidal creek. Occasionally, the tidal effect was overridden by temperature d uring study periods when temperature changed dramatically over several tidal cycles. Bacterial diel patterns in production and specific grow th rate in the tidal creek occurred only when day-night temperature di fferences exceeded 10 degrees C, with maximal values during daytime. S hort-term temperature manipulation experiments suggested that diel pat terns in bacterial production and specific growth rate were probably c aused by temperature, not light intensity. Thus, temperature regulated both seasonal and diel variations in bacterial production.