Annual Cycle of Bacterial Specific Biovolumes in Howe Sound, a Canadian West Coast Fjord Sound

Abstract

The mean specific biovolumes (biovolume cell −1 ) of the bacterioplankton within a 250-m-deep water column in Howe Sound, British Columbia, were determined for the period of 4 September 1984 to 23 October 1985. These bacteria had an annual cycle in mean specific biovolume; they were small (ca. 0.058 μm 3 ) in mid-winter, larger in spring (ca. 0.076 μm 3 ), larger again in summer (up to 0.102 μm 3 ), and largest (ca. 0.133 μm 3 ) in early fall (immediately after the decrease in phytoplankton production). The mean specific biovolumes changed coincidently through the water column with time, although the larger bacterioplankton tended to occur in the surface and deepest water. Although the mean specific biovolumes correlated better with in situ temperature ( r = 0.65, a = 0.01) than with in situ chlorophyll a concentration ( r = 0.34, a = 0.25), modeling experiments with batch cultures of the dinoflagellate Prorocentrum minimum (Pavillard) and the green alga Dunaliella tertiolecta (Butcher) indicated that the biomass and physiological condition of the phytoplankters may be more important than temperature in determining these bacterial specific biovolumes.