Oxygen production and carbon fixation in oligotrophic coastal bays and the relationship with gross and net primary production

Planktonic primary production and respiration in 2 coastal oligotrophic sites of the Northwest Mediterranean Sea were examined. Primary production was quantified using 3 methods (light and dark changes in dissolved O-2, O-18-labeling and C-14 uptake technique) using in situ bottle incubations. Gross primary production (GPP) based on the O-2 light-dark technique was not significantly different from that using the O-18-labeling technique, indicating that the former technique provides accurate estimates of GPP in these environments. Respiration in the dark was not significantly different frorn respiration in the light. Total C-14 uptake (including the dissolved and particulate organic carbon fractions) during the whole duration of the light period approached GPP and consequently overestimated net primary production