A field technique for the determination of zooplankton grazing on natural bacterioplankton

SUMMARY. 1. A method for the determination of zooplankton community grazing rates on natural populations of bacteria is described.
2. Undisturbed zooplankton samples were incubated with ³H-thymidine-labelled bac teriioplankton, and animals and their food subsequently separated by size.
3. Prehandling of zooplankton by concentration before incubation reduce the grazing rates by a factor ranging from three to four.
4. Time series experiments showed that appropriate incubation periods ranged from 40 min at 14°C to 60 min at 10°C.
5. Spatial variability in the zooplankton was the main source of the overall standard error. This was considerably reduced by using composite samples.