Toby K. Westberry^1,2 and David A. Siegel¹

       ¹Institute for Computational Earth System Science, University of California, Santa Barbara, ²Interdepartmental Program in Marine Science, University of California, Santa Barbara,

Abstract.   Solar stimulated phytoplankton fluorescence yields have been used as an instantaneous, non-intrusive means of assessing phytoplankton biomass and rates of primary production.  The quantum yields for carbon assimilation, F_c and solar stimulated fluorescence, F_f, quantify photochemical energy flow through the phytoplankton component of the marine  ecosystem.  Data collected as part of the Bermuda Bio-Optics Project (BBOP; 1992-1997) allows us to accurately characterize the variability these and other biogeochemically relevant parameters and allows us to construct a photon budget for the Sargasso Sea.  In addition, knowledge of F_c/F_f and the volume flux of fluoresced radiation enables determinations of primary production to be obtained.  As part of this analysis, the method of Kiefer et al. (1989) for computing naturally fluoresced radiation is validated using a full spectral, radiative transfer model.  Preliminary results from BBOP give fluorescence quantum yields similar to previous studies varying from 1 to 5%, while the ratio of  F_c/F_f varies from ~ 0 to 5 atoms carbon fixed per quanta fluoresced.  Only weak statistical relationships were found among the quantum yields and other physical and photo-physiological variables, though a seasonal cycle is evident.  No obvious predictive relationships have yet been described by the data.  We will address the coupling of the quantum yield parameters and their significance for the prediction of primary production rates.