Photosynthetic rates in the surface waters of the Red Sea: the radiocarbon versus the non-isotopic dilution method

Abstract

Experiments carried out on board the research vessel FS 'Meteor' in the open waters of the Red Sea in July-August 1987 showed an apparent underestimation of primary production measured with the radiocarbon method. Short-term experiments with diluted water samples that estimated the growth rate of phytoplankton and the grazing rate of herbivorous microzooplankton provided the means to calculate the primary production. These values were compared with those measured simultaneously by means of the ( 14 C)bicarbonate uptake method. The comparison yielded a larger difference between both methods. The radiocarbon values amounted to a maximal possible average of only ~12% of the calculated ones.