PHOTOSYNTHETIC PARAMETERS AND EMPIRICAL MODELING OF PRIMARY PRODUCTION - A CASE-STUDY ON THE ANTARCTIC PENINSULA SHELF

Eight hundred photosynthesis-irradiance relationships were determined in the shelf waters adjacent to Palmer Station, Antarctica during the spring/summer periods of 1991-94. Biomass specific maximum photosynthe tic rate, P-max(B), and the light limited photosynthetic efficiency, a lpha(B), were poorly correlated to the physical forcing and nutrient r egimes at the sampling stations. The two photosynthetic parameters, ho wever, did strongly covary indicating the minimum irradiance required to saturate photosynthesis, I-k, was relatively constant in this highl y variable environment. The variability in I-k could partially be attr ibuted to both depth in the water column and time of the year, with th e highest values occurring for surface samples during the summer perio d of peak incident irradiance. Given this and the significant dependen ce of P-max on phytoplankton biomass, a simple empirical model for pri mary productivity was developed. An independent test of the model was performed on data collected in a mesoscale offshore grid and predicted primary production was found to be within 13% of measured values. Alt hough there are limitations to this approach (i.e. exclusion of diel p eriodicity in photosynthetic response), these results provide relative ly robust estimates of daily primary production for the Southern Ocean .