A device for the in situ measurement of zooplankton food selection, grazing and respiration rates

Summary

A new device is described for the in situ measurement of the grazing and respiratory activity of the natural zooplankton community. the natural zooplankton is concentrated by a sieving mechanism. A control which is free of zooplankton is segregated simultaneously. All steps are carried out under in situ conditions. After an exposure of four hours at the sampling depth parameters of zooplankton activity can be determined by comparisons with an initial sample. Phytoplankton counts allow estimates of specific grazing rates and of relative grazing efficiencies. Respiration rates can be determined by comparisons of oxygen concentrations between initial and terminal samples. the device can be used in eutrophic and mesotrophic lakes during the vegetational period.