In situ photosynthetic quantum yield. Correspondence to hydrographic and optical variability within the Southern California Bight

Abstract

Time and space availability in the quantum yield was quantified for carbon fixation (φ) within the Southern California Bight for three weeks during summer 1988. the data were used to determine whether observed variabliity in φ could be empirically explained by independent parameter(s) routinely measured at sea. Most of the phytoplankton communities sampled were light-limited and thus operating a a maximum quantum yield (φmax). In situ φmax values were routinely 2- to 10-fold lower than the theoretical upper limit of 0.125 mol C μEin-1, varied more than 10-fold over the time and space scales of the study, did not routinely increase with decreasing light levels, and showed no correlation with any single or set of environmental variables measured. The unpredictable behaviour of φ resulted largely from variable correspondence between environmental parameters and the photosynthetic components of the quantum yield calculations. -from Authors