A simplified14C method for grazing measurements on natural planktonic populations

Abstract

The method used consists of adding highly radioactive material (40 μCi/1 NaH14CO3) to sea water with its natural concentrations of zoo- and phytoplankton, incubating this water in the light, separating zoo- from phytoplankton after 1 h or at the most 2 h and measuring the radioactivity of both. Under such conditions, the concentration of the tracer in phytoplankton can be simplified as a linear function of time, and that of the zooplankton as a parabolic function of time. This simplification leads to an overestimation of grazing of at most 2-3%. Comparisons with the Coulter Counter method are given and discussed. © 1978 Biologischen Anstalt Helgoland.