Bio-optical studies during the JGOFS-equatorial Pacific program: a contribution to the knowledge of the equatorial system

Bio-optical studies, pursued in the equatorial Pacific area during the International Joint Global Ocean Flux Study program, contributed to a better knowledge of this oceanic system. Besides the classical estimation of biogeochemical “core parameters” via optical measurements (e.g., Chl a concentration, particulate matter concentration, etc.), several original bio-optical studies included the estimation of the contributions from the various particulate pools and, within the algal pool, from the various phytoplanktonic communities, to the inherent optical properties (attenuation, scattering, absorption) and to stimulated Chl a fluorescence. New insights also were gained concerning the variations in these properties associated with the diel cycle, tropical instability waves, and Kelvin waves. Such studies are critical to improving the interpretation of the spatial and temporal variability of optical properties in terms of biogeochemical quantities. In addition, studies of diel variations of light attenuation by particles, of sun-stimulated fluorescence Chl a, and of the photophysiological parameters of phytoplankton to be used in bio-optical models, all contributed to a better assessment of primary production rates in the equatorial Pacific.