ABSTRACT: Control of bacterial growth and abundance in the plankton of Loch Ness, a deep, oligotrophic lake in northern Scotland, UK, was studied over a 12 mo period. Bacterial intrinsic growth rates and grazing loss rates were estimated from dilution experiments. Growth limitation due to resource availability was determined from nutrient addition experiments. Measured bacterial intrinsic growth rates ranged from zero to 0.69 d^-1, these low growth rates being typical of oligotrophic lakes. Bacterial growth rate was stimulated on different occasions by addition of an organic carbon substrate or by addition of mineral nutrients; however, during summer stratification bacterial growth was principally limited by phosphorus availability. Bacterial growth rate fluctuated irregularly, apparently influenced by the influx of resources from the catchment and hence by rainfall patterns. Bacterial growth rarely responded to increased incubation temperature. Although bacterial growth in Loch Ness was generally slow, new bacterial production was removed quite efficiently by grazers and bacterial densities showed only little fluctuation. Heterotrophic nanoflagellates were sometimes an important component of the bacterivore community, but other grazers such as cladocerans also appeared to play an important role in Loch Ness.

KEY WORDS: Bacterial growth · Bacterivory · Nutrients · Temperature · Loch Ness

Published in AME Vol. 15, No. 1 (1998) on May 22
ISSN: 0948-3055. Copyright © Inter-Research, Oldendorf/Luhe, 1998