Abstract
To establish the technique of the fast repetition rate fluorometry (FRRF) for measuring primary production rate, we proposed the new method for obtaining the fluorescence value (Fm and F0) under the dark condition. The results indicated the validity of applying the Fm and F0 in deep water layer of lake with PAR=0 for their values under the dark condition, especially in the shallow lakes such as Lake Kasumigaura. To assess the validity of the FRRF technique, we compared estimates of primary production rates derived from fluorescence by means of FRRF with those measured using a 13C method under laboratory conditions. These comparisons indicate the high correlations between the FRRF and 13C techniques; however, the slopes of the regression lines were found to be <1.0 (FRRF < 13C). One of the reasons that FRRF underestimated the primary production rates as compared with the 13C method is likely the effect of the predominant algal species. Finally, we measured the primary production rates by using FRRF before/after algal bloom in 2012, and it is revealed that the water bloom does not absolutely have the linkage to the rate of primary production.
