TEMPERATURE REGULATION OF HETEROTROPHIC BACTERIOPLANKTON ABUNDANCE, PRODUCTION, AND SPECIFIC GROWTH-RATE IN CHESAPEAKE BAY

Heterotrophic bacterioplankton abundance, production, and specific growth rate in surface and bottom waters in north, mid-, and south Chesapeake Bay were studied monthly from February 1990 to November 1991. Seasonal variability of bacterial abundance, production, and specific growth rate across three study areas were all positively correlated with temperature except in summer, when temperature was > 20-degrees-C. The Q10 values for bacterial production and specific growth rate during nonsummer seasons (<20-degrees-C) ranged from 5.0 to 8.2 and 2.2 to 4.5. These relationships suggest that bacterial growth in Chesapeake Bay is seldom limited by in situ substrate supply but rather by temperature during nonsummer seasons. In summer, substrate supply might be important in regulating bacterial abundance and production. Spatial variability of bacterial abundance, production, and specific growth rate was temperature-dependent for both horizontal (north, mid-, and south bay) and vertical (surface and bottom water) distribution patterns. Large differences between surface and bottom waters in bacterial abundance, production, and specific growth rate were only observed in the midbay during summer. These differences might be due to the inhibition of bacterial activities by anoxia, whereas similarities at other times might be due to homogenization of the water-column temperature profile by mixing.